School Science Lessons
Topic19
2024-06-16
Food, household items, cooking
(topic19)
Contents
19.6.0 Cola
19.4.1 Colloids in food
19.4.2 Electrophoresis, food dyes, marking pen ink, (Experiments)
19.4.3 Elements in food, (Experiments)
19.4.4 Fish oils
19.2.0 Food allergies and intolerances, "hyperactive"
19.1.0 Household chemicals
19.4.5 Margarine
19.4.6 Olive oil
19.4.7 Phthalic acid, Phthalates
19.5.0 Tests
19.1.0 Household chemicals
19.1.01 Household chemicals, chemicals in the home.
19.1.1 Acid-base indicators in the home
19.1.2 Acidulated water
19.1.3 Cooking fats
19.1.4 Emulsifying agents
19.1.5 Food acids, acids in foods
19.1.6 Leavening agents
19.1.7 Polyhydric alcohols
19.1.8 Sequestrants
19.1.9 Wheat and flour
Experiments
19.1.10 Dipsticks to test the vitamin C, ascorbic acid, content of food
19.2.9.1 Make jelly with fresh pineapple and tinned pineapple
19.1.11 pH of solid acids
19.1.12 Prepare baking powder
19.1.14 Prepare self-leavened flour, "self-raising flour"
19.1.15 Prepare vinegar from wine
19.1.16 Solid acids, add sodium carbonate
19.1.17 Solid acids, solubility
19.1.18 Use flour to clean brass and copper
19.1.19 Use flour to make glue
19.1.20 Use flour to make papier-mâché
19.1.21 Use flour to make play dough
19.1.22 Table salt and rock salt
19.1.23 Water retention agents
19.5.0 Tests
19.1.32 Tests for borax / turmeric adulteration of food
19.5.8 Tests for glucose
19.5.1 Tests for ketones
19.5.2 Tests for nitrates / nitrites with dipsticks
19.5.3 Tests for sulfites
19.5.4 Tests for tartaric acid
19.5.5 Tests for urine
19.5.6 Tests with multiple reagent strips
19.5.7 Tests for water
19.5.8 Tests for glucose
19.1.24 Tests for glucose, Clinitest tablet
19.1.25 Tests for glucose, Clinistix strip
19.1.26 Tests for glucose, blood glucose
19.1.26 Tests for glucose concentration, ferricyanide test
19.1.28 Tests for glucose, Nelson-Somogyi test
19.1.29 Tests for glucose, glucose oxidase test
19.1.30 Tests for glucose, glycosylated haemoglobin test
19.1.31 Tests for glucose, urine test
19.1.33 Tests for glucose, urine test, Diastix strip
19.2.0 Food allergies and intolerances, "hyperactive"
19.2.01 Food allergies and intolerances, "hyperactive"
19.2.1 Amine intolerance
19.2.2 Aspartame sweetener
19.2.3 Gluten intolerance
19.2.4 Lactose intolerance, lactose tolerance
19.2.5 Monosodium glutamate intolerance
19.2.6 Phenylalanine sweetener
19.2.7 Salicylate intolerance
19.6.0 Cola
19.6.1 Cola label
19.6.2 Cola contents
19.6.3 Cola, Diet or Light contents
19.6.4 Cola uses
19.6.5 Cola light
19.1.01 Household chemicals, chemicals in the home.
Acids are used give tartness to foods, or to alter the acidity of the medium, i.e. to lower the pH in canned products, to prevent the crystallization of jams and jellies.
Bases are used as ingredients of baking powders used in pastry production, and in powders for effervescent beverages.
Improving agents includes chemical compounds that enhance the quality criteria of foods, e.g. flavour and consistency, and substances used for polishing and glazing confectionery products.
19.1.1 Acid-base indicators in the home:
Use grape juice or red cabbage juice for acid-base indicators.
Note the sour tastes of fruit and vinegar and the taste of baking soda.
Grape juice turns red in acid lemonade and blue in alkaline dishwater.
Use flower pigments as pH indicators.
19.1.2 Acidulated water
Acidulated water is water that has been made slightly acidic by the addition of an acid substance such as lemon juice or vinegar (about one teaspoon to half a litre of water).
Peeled fruit and vegetables such as apples, pears, celeriac, globe artichokes and salsify are immersed in acidulated water to prevent them from discolouring.
It can also be used for cooking.
Cauliflower will be snowy white if boiled in acidulated water.
19.1.3 Cooking fats
Shortening is solid, white fat made from hydrogenated vegetable oil.
Solid fats derived from coconuts are quite saturated.
Lard is the rendered fat from pig abdomen.
Deep frying requires fats / oils with heat tolerant properties, e.g. corn oil and peanut oils, but not butter, margarine, lard and olive oil.
19.1.4 Emulsifying agents
Emulsifying (surface active) agents, "food soaps" (E433-444) are used to stabilize emulsions of oil and water components in foods.
19.1.5 Food acids, acids in foods
Ethanoic acid, acetic acid, vinegar
Benzoic acid, in cranberries, prunes and plums
Butyric acid, in decomposition of butter, rancid butter
Caffeotannic acid, no such compound, in tannin from coffee berries, mainly chlorogenic acid, C16H18O9, an antioxidant ester
Citric acid, C6H8O7, in citrus fruits, lemon, orange, cocoa, pepper, rhubarb
Tannic acid in tea
Tartaric acid in grapes, pineapples, potatoes, carrots.
19.1.6 Leavening agents
Leavening is foaming in batters and dough to make the final product lighter and softer to eat.
1. Mechanical leavening agents includes whisking cream or egg whites to make air foams for sponge cakes, batters and meringues.
Also, beating white sugar with butter, creaming, is used to make cookies.
2. Chemical leavening agents are usually baking powder (a mixture), and baking soda (sodium bicarbonate, sodium hydrogencarbonate) that react with acidic ingredients to form carbon dioxide bubbles in the mixture.
Acidic ingredients may include buttermilk, chocolate, cream of tartar (potassium bitartrate), fruit preserves, lemon juice, molasses, monocalcium phosphate, sodium aluminium phosphate, sodium aluminium sulfate, sour milk, vinegar, yoghurt.
Cream of tartar is the most common ingredient in baking powder mixtures.
However, "double acting" baking powder may use monocalcium phosphate and sodium aluminium sulfate to slow the release of carbon dioxide.
The best combination of a leavening agent with an acidic ingredient cannot be decided in the chemistry laboratory, because different combinations affect speed of carbon dioxide release, flavour development, surface browning, texture, moisture content and palatability.
So the best combination must be decided by cooks and people who pay for and consume the end products.
3. Biological leavening agents include generation of carbon dioxide by yeast fermentation for production of fermented food.
Bakers' yeast Saccharomyces cerevisiae from the brewing industry is used to make bread and cakes.
Baking yeast is in two forms, compressed yeast cake and active dry yeast.
The "brewer's yeast" sold in health food stores for nutritional purposes is not an active yeast so is not a leavening agent.
Lactobacillus bacteria (over 120 species), is used to make cheese, chote, cider, kimchi, pickles, sauerkraut, silage, sourdough bread, wine, yoghurt.
Natural yeasts and strains of lactobacillus, both from the air, vary in their characteristics in different places so local products, e.g. beer and baked products, may have their own eating characteristics and taste.
19.1.7 Polyhydric alcohols
Polyhydric alcohols are used as a humectant to keep from drying.
They may also be sweet, e.g. sugarless chewing gum may contain mannitol (E421) sorbitol (E420) and glycerol (E422), and have the same calorific value as cane sugar, 16.5 kj / g.
Examples: Dulcitol, Galactinol, Glycerol, myo-Inositol, d-Mannitol, Pinitol (monomethyl ether), Quebrachitol, Quercitol, d-Sorbitol
19.1.8 Sequestrants
Sequestrants, sequestering agents, either removes an ion or makes it ineffective by forming a complex with it, e.g. a chelate complex.
An example is the sequestration of Ca2+ ions in water softening.
A sequestrant binds with metal ions to prevent them from catalysing chemical reactions that spoil preserved food.
Metals such as copper, iron and nickel get into food from processing machinery or because of chemical reactions with the container.
The sequestrant citric acid acts as a synergist (increases the effect) for antioxidants.
Sequestrants are used in shortenings, mayonnaise, lard, margarine, cheese.
19.1.9. Wheat and flour
1. Bread and noodle wheat
Bread and noodle wheat are the dominant types of wheat planted throughout Australia.
They fall into classifications that have different receivable standards.
From APH (Australian Prime Hard), with high quality requirements through to FEED, which has limited quality requirements.
Queensland conditions are conducive to the production of high quality grain and the breeding and development of new varieties reflects these conditions.
Flour milled from Australian Prime Hard wheat is used to produce high-protein, Chinese-style, yellow, alkaline noodles and Japanese Ramen noodles of superior brightness, colour and eating quality.
Australian Prime Hard flour is also suitable for the production of high-protein, high-volume breads and wanton dumpling skins.
Australian Prime Hard can be blended with lower-protein wheat to produce flours suitable for a wide range of baked products.
2. Durum wheat (Triticum durum)
Durum wheat is used in the production of pasta products, where the main requirement is grain of high protein, preferably more than 13% and a minimum of 11.5 %.
Grain appearance is also important, because downgrading can occur due to black point, weather damage and mottling.
Acceptable levels of black points are as follows: ADR1 3%, ADR2 5% and ADR3 20%.
3. Soft wheat
Soft wheat represents two distinct types.
The Soft Biscuit type (9 to 105% protein), is suitable for the biscuit industry, and the Soft Noodle type (9 to 11.5% protein), is suitable for the manufacture of cakes, pastry and white salted noodles.
Soft Biscuit types are best grown using irrigation and suitable crop management to achieve target protein levels.
Capped domestic market volumes exist so growers should seek pre-plant contracts.
4. Feed wheat
Feed wheat is generally high yielding varieties that have quality limitations for use in flour and noodle production.
5. Forage wheat
Forage wheat is commonly the winter type and have the major advantage of adaptability to a wide range of sowing times.
The winter habit delays maturity in early sowing, thus extending the period of vegetative growth.
Maturity varies once vernalization requirements have been met.
In Australia, winter wheat is usually sown in late March or early April.
Effects of grain defects on end-product quality
1. Black point
Excessive levels may result in "specky" semolina or discoloured bran, wheat germ and divide flours (pastry flour).
The end products are often visually unattractive, especially with durum products, e.g. pasta.
2. Sprouting (low falling number)
The finished product is affected by high levels of alpha amylase in the flour, which causes "key holing" in bread, fragile noodles, discoloured biscuits and cakes.
Sprouting has a small impact on pasta except at FN (falling numbers) < 200 seconds.
3. Frost damage
Frost damage can cause low failing number, reduced flour yield, increased grain hardness and very poor baking performance for bread, biscuits and breakfast cereals.
4. Excessive screenings
Excessive screenings causes reduced grain and flour yield (so loss of profitability), but has little effect on end product quality, other than excluding excess screenings caused by frost and heat stress damage.
Samples tested with high screenings have poor baking quality.
This may be attributed to heat stress damage during grain filling, which was also believed to be responsible for the high screenings.
4. Low density
Reduced grain and flour yield (loss of profitability), has little effect on end-product quality, excluding low density due to frost and heat stress damage.
5. Heat damage
For heat damage due to drying at temperatures above 600oC, the flour produced from this grain is of poor baking quality and baked products are often unsaleable.
In Australia, winter wheat is usually sown in late March or early April.
19.1.10 Dipsticks to test the vitamin C, ascorbic acid, content of food
1. Use dipsticks to measure vitamin C content in fruit juices.
You may find more than in the original fruit, because the processor adds the minimum to replace any vitamin naturally present that has not survived processing and storage.
2. Test the effect of boiling vitamin C in water.
3. Test the effect of cooking at different pH values by adding sodium carbonate of soda.
4. Test the effect of boiling in the absence of oxygen.
If blend vegetables and measure vitamin C content before and after, you will find a large increase, because the boiling extracts the soluble vitamin from the food.
5. Test your urine and establish how much you excrete after taking a dose (1 -2 g) over a period of one day?
Measure the volume of urine and the concentration of vitamin C.
Plot the amount of the original vitamin remaining, and the rate of excretion during the day.
19.1.11 pH of solid acids
Divide the solution in one test-tube into three portions in three different test-tubes.
Test the first solution with litmus paper.
Add drops of methyl orange solution to the second solution.
Add drops of phenolphthalein solution to the third solution.
19.1.12 Prepare baking powder
Baking powder is a chemical leavening agent and sponging agent.
To prepare 10 g of baking powder, weigh 3 g of sodium hydrogencarbonate, 2 g of starch and 0.7 g of calcium phosphate.
Mix them with 5.3 g of sodium dihydrogen phosphate in a small beaker.
Weigh flour and the prepared sponging agent in the ratio of 50 to 1, and mix them thoroughly to make 20 g of self-leavened flour.
Add 15 mL water to the prepared self-leavened flour and knead the dough.
Lay aside the dough for 5-10 minutes (leaven dough) and then make the dough into spongy, delicious steamed bread by steaming for 15-20 minutes.
19.1.14 Prepare self-leavened flour, "self-raising flour"
Plain flour and self-raising flour
"Plain flour" is "wheat flour" made from the endosperm "kernels" of wheat grains by grinding and sifting.
"Self-raising flour" contains plain flour and baking soda, sodium hydrogencarbonate.
Experiment
In the kitchen, to test whether flour is plain flour or self-raising flour, place a little on your tongue.
1. If you feel a tingle, this indicates that the flour is self-raising flour.
2. Use self-leavened flour to make steamed bread.
Mix the flour with water without addition of any baking soda.
Knead the dough and let it stand for 10 to 15 minutes.
This kind of flour is made by blending a small quantity of chemical sponging agent, also called baking powder, with ordinary flour.
The sponging agent contains 20 to 40% of sodium hydrogencarbonate, and 35 to 50% of acidic substances such as sodium dihydrogen phosphate, potassium hydrogen tartrate and aluminium potassium sulfate (potassium alum, Al2(SO4)3.K2(SO4).24H2O) and filling agents, e.g. starch and aliphatic acids.
Sodium hydrogencarbonate reacts with acidic substances to produce carbon dioxide, while the acidic substances decompose the carbonate to lower the basicity of finished products.
The filling agents are used to prevent the flour from moisture absorption, agglomeration and loss of effects.
They can also regulate the forming rate of gas or make the bubbles be evenly produced.
When water is added to self-leavened flour, the hydrolysis of sodium hydrogencarbonate shows basicity, while hydrolysis of sodium dihydrogen phosphate shows acidity.
The reaction results in release of carbon dioxide.
The heat decomposes sodium hydrogencarbonate to make spongy steamed bread.
19.1.15 Prepare vinegar from wine
1. Acetobacter cerevisiae is Gram stain negative, has ellipsoidal to rod-shaped cells occurring singly, in pairs, or short chains to form colonies that are beige to brown, round to wavy.
Its grows the substrates glucose, ethanol, organic acids, and glycerol.
It is an obligate aerobe so it requires oxygen.
It is often found on spoiled and unspoiled fruit and can be isolated from beer.
It is a spoilage organism converting ethanol to acetic acid.
It is sensitive to very low pH, but can grow at wine pH and survive low oxygen level.
Its optimum temperature is 20-25oC.
It can withstand ethanol levels as high as 15%.
Acetic acid bacteria derive their energy from the oxidation of ethanol to acetic acid during respiration.
C2H5OH + O2 --> CH3COOH + H2O.
2. Live vinegar, or vinegar culture, contains the acetobacter bacteria, which converts alcohol to acetic acid and produces the "mother", (mothery, mother-of-vinegar) a gelatinous slime of yeast and acetic acid bacteria that eventually forms on the surface of the wine vinegar mixture.
This smooth, leathery, greyish film becomes quite thick and heavy.
It should not be disturbed.
It often becomes heavy enough to fall and is succeeded by another formation.
If the "mother" falls, remove and discard it.
An acid test will indicate when all of the alcohol is converted to vinegar.
Wine making suppliers sell acid test kits and acetobacter as "mother" or vinegar culture.
Some of the vinegar can be withdrawn and pasteurized for use while the remaining unpasteurized vinegar containing the living bacteria may be used as a culture to start another batch.
So a piece of the "mother" is not necessary to start a new batch of vinegar making.
Some people add diluted wine to the culture every 4 to 8 weeks, depending on the temperature and when most of the alcohol is converted to vinegar as determined by an acid test.
Adding more alcohol to the culture keeps it alive, prevents spoilage and increases the quality of vinegar.
3. Acetic acid (ethanoic acid) is a weak acid, only about 1% dissociates in water, pH of 2-3, so it can be used for cooking, preserving foods, salad dressings, with cooked fish, a cleaning aid and treating stings from marine animals.
CH3COOH (aq) <--> CH3COO- (aq) + H+ (aq).
4. Pasteurizing kills vinegar bacteria and prevents the formation of the "mother", which could lead to spoilage.
Pasteurized vinegar keeps indefinitely if tightly capped and stored in a dark place at room temperature, but above high temperature cause a loss of acidity, flavour and aroma.
If unpasteurized vinegar is exposed to oxygen without alcohol present, bacteria can convert the vinegar to carbon dioxide and water.
5. When first made, vinegar has a strong, sharp taste, but it becomes mellow with age when esters form as in wine.
If undisturbed, suspended solids fall to leave clear and bright vinegar that can be siphoned off into sanitized bottles with plastic caps.
Avoid stored vinegar contact with metal or air.
The quality of vinegar improves for up to two years and then gradually declines.
6. In Japan, the polished rice vinegar komesu and the unpolished rice vinegar kurosu are traditional seasonings that are made through saccharification of rice, alcohol fermentation, and oxidation of ethanol to acetic acid.
An alcoholic liquid with vinegar, called moromi, is fermented in covered containers to prevent bacterial contamination.
A crepe pellicle of acetic acid bacteria, Acetobacter genera, covers the moromi surface and the fermentation is allowed to continue for about a month.
Experiments
See:4.2.6 Prepare vinegar with Acetobacter aceti
1. To prepare vinegar from wine, use 10-11% alcohol wine, although dilute the alcohol to 5.0 to 7% alcohol containing less than 10% alcohol is subject to spoilage.
The alcohol concentration should not inhibit the activity of the bacteria that transform the wine.
The vinegar process may not get started with over 12.5% alcohol or if the wine was treated with sulfur.
Wine should contain no excess sugar, because it increases the chance of spoilage and the formation of a slime-like substance in the vinegar.
The wine does not have to be clear before it is combined with the vinegar culture, because vinegar clears as it ages.
Vinegar is a mixture of at least 5% acetic acid, if it is sold, with water and flavouring and colouring chemicals depending on the method of production, e.g. balsamic vinegar, apple vinegar, brown vinegar and white vinegar.
2. The simplest method to prepare vinegar is to leave an open, 3/4 filled bottle of wine in a dark place, at 24-29oC, for 6-8 weeks.
Cover with netting to allow access to air, but to keep away vinegar flies.
3. Use 2 measures of dry wine (11 to 12% alcohol), 1 measure of water (boiled 15 minutes and allowed to cool), 1 measure of vinegar culture with active bacteria.
Some wines contain sulfites or preservatives that could kill the vinegar bacteria.
4. For a steady supply of vinegar, use a 5 litre wide mouth glass or stainless steel container (not plastic), whose capacity is at least a gallon and pour one litre of wine and 200 mL of vinegar into it.
Remove the cover for a half hour every day.
In a couple of weeks, the madre (mother), a viscous starter, will have settled to the bottom of the jug, while the vinegar above it will be ready for use.
Add more wine as you remove vinegar to keep the level in the jug constant.
19.1.16 Solid acids, add sodium carbonate
See diagram: 9.154: Limewater test for carbon dioxide.
Add a little solid sodium carbonate to a sample of each acid solution.
Note what happens in each case.
Pass gases from the reaction through limewater.
Shake the test-tube so that the gas mixes with the limewater.
The milky precipitate shows that carbon dioxide forms when acids react with sodium carbonate.
19.1.17 Solid acids, solubility
| Citric acid.
| Tartaric acid.
| Boric acid. |
Shake different solid acids in separate test-tubes half filled with water.
Which of the acids are the most soluble and the least soluble in water?
19.1.18 Use flour to clean brass and copper.
Mix equal parts flour and salt, and add one teaspoon white vinegar to make a paste.
Spread a thick layer on the brass and let dry.
Rinse and wipe off paste.
19.1.19 Use flour to make glue.
Mix flour and water to a pancake batter consistency for use on paper, light-weight fabric, and cardboard.
19.1.20 Use flour to make papier-mâché.
Mix one cup flour with two thirds cup water in a medium size bowl to a thick glue consistency.
To thicken, add more flour.
Cut newspaper strips approximately 2 to 4 cm in width.
Dip each strip into the paste, gently pull it between your fingers to remove excess paste, and apply it to any object (an empty bottle, carton, or canister).
Repeat until surface you want to cover (clay, cartons, bottles, or any disposable container makes a good base).
Continue until the base is completely covered.
Let dry, then decorate with poster paint.
After the paint dries, coat with shellac.
19.1.21 Use flour to make play dough.
Add five drops food colouring to two cups water.
Then add two cups flour, one cup salt, one teaspoon cream of tartar, and two tablespoons vegetable oil.
Mix well.
Cook and stir over medium heat for three minutes (or until the mixture holds together).
Turn onto board or cookie sheet and kneed to proper consistency.
Store in an airtight container.
19.1.22 Table salt and rock salt
Experiments
1. Common salt is sodium chloride crystals.
Common salt, rock salt, comes from the naturally occurring mineral of sodium chloride called halite.
It is often found as cubic crystals and associated with gypsum in Triassic rocks.
Sea salt is extracted from evaporated sea water.
Table salt may be made from rock salt or naturally evaporated sea salt and contain iodine (iodized salt) anti-caking agents, e.g. anti-caking agent (554) and potassium iodate.
Kosher salt is a coarse salt with large crystals used for drawing blood from meat.
Pickling salt is a fine grained salt used for pickling and it contains no additives, e.g. anti-caking agents.
Grey sea salt, "Sel gris", is unprocessed, and has minerals from the sea.
Indian black salt, kala namak, has a brown black in colour and a smoky, sulfur flavour.
Rock salt is a grey colour, contains minerals and impurities, and is used in ice cream machines and for melting ice and snow on the roads using brine and sea sand.
2. Table salt may be "iodized" by the addition of potassium iodide or potassium iodate.
About 0.01% potassium iodide in table salt is added as a nutrient for the thyroid hormone thyroxine for those on an iodine deficient diet, which leads to goitre.
However, the iodide will oxidize in air to iodine that is lost through evaporation.
Thiosulfate was formerly used as a stabilizer, but now it is normally glucose, dextrose.
Because alkaline conditions prevent oxidation, bases such as sodium bicarbonate or phosphates may also be added.
Potassium iodate may be used to avoid these problems.
3. Atmospheric moisture may cause the cubic crystals of sodium chloride to stick together and the salt does not flow.
This problem can be solved by using about 0.5% drying agents, e.g. carbonates (E501-4) and sodium aluminium silicate (E554).
Another method is to change the shape (habit) of the cubic salt crystals to a form that does not provide large flat surfaces to pack together.
Salt normally crystallizes as cubes, because the octahedral faces of the crystal consisting of either all Na+ or all Cl- grow faster than the cubic faces with alternating Na+ and Cl-.
If an impurity is absorbed onto the surface of the fast growing octahedral faces, e.g. urea, the reverse happens, and octahedral crystals form instead of cubes.
So more than 13 ppm potassium ferrocyanide K4Fe(CN)6.3H2O), (E536), is added to table salt.
This compound is quite safe, however, to avoid using the word "cyanide" on labels, the compound may be referred to as "yellow prussiate of potash" or the IUPAC name "hexacyanoferrate".
Experiments
4. Sprinkling salt on water causes the surface to contract momentarily towards the crystals, while with pepper, the opposite tends to happen.
* Examine the label on a contained of table salt and note the contents in addition to sodium chloride.
* Prepare a freezing mixture and measure its temperature.
A mixture of ice and sodium chloride, freezing mixture, has temperature -20oC.
The salt lowers the melting point of ice.
The salted ice is still at 0oC, but above its new melting point. so it melts.
19.1.23Water retention agents
Water retention agents, e.g. polyphosphates (E450-452) are used in processing poultry, fish and mammalian meats to bind water and minimize "drip".
Phosphates are also used in soft drinks.
However, excessive intake of phosphates from processed food may harm bone growth in children.
19.1.24 Tests for glucose, Clinitest tablet
Clinitest tablet is a form of Benedict's test for glucose
Add 10 drops of water to five drops of urine and add one Clinitest tablet.
The solution effervesces then boils without heating with a Bunsen burner, because the Clinitest tablet contains sodium hydroxide and citric acid besides Benedict's reagent.
If the solution turns blue the test is negative.
If the solution turns green to orange or an orange flash, the test is positive.
This oxidation method to measure blood glucose is based on the reducing properties of glucose.
Glucose will reduce cupric salts to cuprous salts it a hot alkaline solution and the quantity of cuprous salts produced is proportional to the glucose concentration.
Oxidation methods to measure blood sugar give results higher than other methods, because they also measure reduction of some non-glucose substances.
19.1.25 Tests for glucose, Clinistix strip
Test for glucose, test for (+) glucose in urine, indicator substance o-toluidine "Clinistix" strip is impregnated with the enzymes glucose oxidase and peroxidase, and a chromogen system, the indicator substance o-toluidine.
The o-toluidine is oxidized to a blue-green substance (Schiff base), with varying shades of colour, which is then compared with the standard chart provided in the kit to report the approximate level of glucose present in the urine.
Compared to Benedict's test, which detects the total sugar present in urine, the strip test detects semi-quantitatively the amount of glucose present in urine.
Dip the reagent area of the "Clinistix" strip in fresh urine for two seconds.
Gently tap the edge of the strip against the side of the urine container to remove excess urine.
Compare the test area closely with a colour chart exactly 30 seconds after dipping the strip in the urine.
Hold the strip close to the colour chart and match carefully.
19.1.26 Tests for glucose, blood glucose
Glucose tolerance test
After fasting, blood glucose is measured then the patient drinks 50 g of glucose dissolved in 100 mL of water.
Samples of urine are collected periodically, e.g. every half hour for two hours.
Fasting blood glucose is about 80 to 120 mg / 100 mL and after two hours blood glucose should be < 120 mg / 100 mL.
If blood glucose exceeds 150 mg / mL (and fasting blood glucose was > 120 mg / 100 mL) the diagnosis is diabetes mellitus.
Glucose does not pass into the urine unless blood glucose is up to 180 mg / 100 mL, the renal threshold.
19.1.26 Tests for glucose concentration, ferricyanide test
Glucose reduces yellow ferricyanide to colourless ferrocyanide in a hot alkaline solution.
The decrease of yellow colour is proportional to the glucose concentration.
19.1.28 Tests for glucose, Nelson-Somogyi test
The reducing sugars when heated with alkaline copper tartrate reduce the copper from the cupric to cuprous state and thus cuprous oxide is formed.
When cuprous oxide is treated with arsenomolybdic acid, the reduction of molybdic acid to molybdenum blue takes place.
The blue colour developed is compared with a set of standards in a colorimeter at 620 nm.
Non-glucose reducing substances can be removed to produce a protein-free filtrate by use of acids to precipitate proteins from the sample thus removing interference with colour reactions, turbidity and foaming, e.g. the zinc sulfate-barium hydroxide method of Nelson-Somogyi is said to give the closest value of "true glucose".
19.1.29 Tests for glucose, glucose oxidase test
Enzyme methods for measurement of blood glucose are quite specific for glucose only, e.g. the enzymes glucose oxidase and hexokinase.
Glucose oxidase catalyses the oxidation of glucose to gluconic acid and hydrogen peroxide.
glucose + O2 --> gluconic acid + H2O2
Hexokinase catalyses the phosphorylation of glucose in the presence of ATP.
Glucose-6-phosphate forms and is converted to 6-phosphogluconate by a second enzyme, glucose-6-phosphate dehydrogenase.
Then the NADPH can be measured.
glucose + ATP --> G-6-P + ADP
G-6-P + NADP --> 6-phosphogluconate + NADPH + H+.
19.1.30 Tests for glucose, glycosylated haemoglobin test
If blood glucose level is high for some time, haemoglobin becomes glycosylated, i.e. the glucose molecule binds covalently to the last valine group of the β chain and stays there for the about 120 days the life of the red blood cell.
Measurement of blood glucose level is only a measure of the patient blood glucose level at the time of sampling, but measurement of glycosylated haemoglobin shows the blood glucose level for the preceding months.
19.1.31 Tests for glucose, urine test
A pre-mixed synthetic urine called "Quick Fix" may be available.
Prepare artificial urine samples
Sample 1. Dissolve 1g serum albumin, 3g sodium chloride and 5g urea in 1 litre of water.
Sample 2. Dissolve 1g serum albumin, 3g sodium chloride and 1g glucose in 1 litre of water.
Test the artificial urine samples for colour, odour, turbidity (clear or cloudy) PH (universal indicator) protein (more cloudy in hot water) glucose ("Clinistix").
The tests for reducing sugars gives no values for fructose, galactose, or the non-reducing disaccharides, sucrose and lactose, but maltose does react.
The tests are used measure the hydrolysis of sucrose to glucose, (invertase or H+), the formation of glucose in germinating seeds, for glucose in urine and indirectly blood glucose.
The commonly used Benedict's test measures total reducing substance and does not accurately measure the amount of glucose present in the blood, because of the presence of non-glucose reducing substances, e.g. glutathione, uric acid, ascorbic acid, and creatinine.
19.1.32 Tests for borax / turmeric adulteration of food
Borax or boric acid adulteration
Detect borax or boric acid adulteration in chopped and squeezed meat by adding concentrated hydrochloric acid, then dip turmeric paper into the filtered solution.
The turmeric paper turns bright cherry-red colour
Add a drop of ammonia solution to the coloured turmeric paper, which turns dark green to black to show the presence of boric acid in the meat.
Turmeric adulteration
Add borax to solution to solutions of food, e.g. ground rhubarb root or mustard made from Sinapsis alba, to detect adulteration with turmeric to improve the colour of the product.
The addition of borax causes a deep brown colour to detect the adulteration.
19.1.33 Tests for glucose, urine test, Diastix strip
"Diastix" strip has an area impregnated with the above enzymes together with potassium iodide and a blue background dye.
The oxygen liberated in the final reaction binds with the dye to produce a series of colour changes 30 seconds after wetting the strip with urine.
19.2.01 Food allergies and intolerances, "hyperactive"
1. Some people can be sensitive to the effects of natural food chemicals.
Although the body becomes accustomed to small amounts of these substances in the daily diet, eating too much of certain foods or a sudden change of diet or infection, can alter the body's reaction.
The tastier a food is, the richer it is likely to be in natural chemicals, e.g. chocolate and mint.
Small amounts of natural chemicals present in a food, e.g. chocolate, may not be enough to cause a reaction by itself.
However, the chocolate may cause a reaction, because a chemical may be common to many different foods.
So a reaction occurs when the threshold is finally exceeded by eating the chocolate.
Organic foods may contain fewer traces of pesticides and other agricultural chemicals, but they contain the same natural pesticides and preservatives in the skin.
2. Food additives
People who are sensitive to natural food chemicals are usually also sensitive to food additives, e.g. preservatives to keep foods fresh and colourings to make foods look more attractive.
If you need to avoid these additives, check the labels.
3. Food intolerance, hyperactive
A food intolerance is any reaction to food not caused by the immune system, as in a food allergy.
The particular food can be identified only by excluding the suspect food from the diet, then later reintroducing it to see if the intolerance occurs again.
So there is no scientific test for "food intolerance".
Reactions to food chemicals are called intolerances.
They irritate different parts of the body causing headaches, mouth ulcers, stomach pains and bowel irritation.
Children may become "hyperactive" after eating a rich meal or coloured, flavoured and preserved foods or drinks during a children's birthday party.
However, sucrose sugar by itself does not cause hyperactivity in children.
In sensitive people, natural chemicals may build up to cause recurrent symptoms.
They should avoid spicy foods and processed foods.
4. Food allergy
A food allergy is an adverse reaction to a generally harmless substance within a food, triggered by the immune system.
It is caused by antibodies to food proteins from particular foods, e.g. milk, eggs, wheat, peanuts or fish.
A food allergy may cause itching mouth, vomiting and cramps.
People sensitive to natural food chemicals are usually also sensitive to one or more of the common food additives.
Egg allergy to proteins in the white and yolk of eggs are more common in very young children although adults seem to have more yolk allergy than children.
5. Oil allergy
Margarine and oils may be preserved to stop them going rancid, but cold pressed oils are not preserved, e.g. cold pressed coconut oil.
Sunflower and safflower oils sometimes contain antioxidants.
Margarine is sometimes preserved fat reduced ("light").
Spreads are usually preserved.
Heavily flavoured fats and oils, e.g. olive oil, corn oil, peanut oil, sesame oil, walnut oil, almond oil, all contain moderate to high levels of natural chemicals.
Cow or goat milk, cream and butter are all very low in natural chemical content.
6. Starch allergy
Refined rice products and wheaten cornflour (gluten powder, wheat starch), are the lowest in natural chemicals, though some people prefer whole grain and wholemeal products.
Potato products may contain preservatives (220 to 228), or antioxidants if cooked in oil.
7. Sugar allergy, hyperactivity
Refined sugar in moderation usually causes no adverse effects.
Avoid all sweets with colours and flavours other than vanilla.
Most dried fruits are preserved with sulfite that may cause asthma attacks.
Sun dried fruits without preservative have a very high natural chemical content.
19.2.1 Amine intolerance
Amines come from protein breakdown or fermentation.
Large amounts are present in cheese, chocolate, wines, beer, yeast extracts and fish products.
They are also found in certain fruits and vegetables, e.g. bananas, avocados, tomatoes and broad beans.
You also make tiny amounts of some amines in your own body, e.g. Adrenaline, (Epinephrine).
Amines increase with ripening in fruits that go soft, e.g. banana and avocado.
Highly sensitive people should wash fruits and vegetables thoroughly before eating, thickly peel pears and potatoes and discard the outer leaves of lettuce.
Yoghurt may have some amines.
Cheeses contain varying amounts of natural amines and MSG.
The tastier the cheese, the higher its chemical content is likely to be.
Soy milk and fresh products like tofu and tofu ice cream all have a low natural chemical content and so usually causes no chemical intolerance problems unless the person is allergic to soy bean proteins.
However, fermented products like soy sauce, tempeh and miso are rich in natural amines and MSG.
Browning meat, grilling or charring will increase natural amine levels, which make them more tasty.
Fresh meats, poultry, seafood, and eggs are all low in natural chemicals.
However, amines can form as a result of a protein breakdown in aged, overcooked and processed meats.
Pork, chicken skin, canned or frozen fish, liver, kidney and other offal contain high amine levels.
Purchase and eat raw meat within two days.
Processed meats are rich in amines, and may be preserved with nitrites, e.g. ham, bacon, corned beef.
Fish products, especially those that are salted, smoked, pickled or dried, are rich in amines and other natural chemicals.
19.2.2 Aspartame sweetener
Aspartame, HOOCCH2CH(NH2)CONHCH(CH2C6H5)COOCH3, N-(L-α-Aspartyl)-L-phenylalanine methyl ester.
Aspartame is the name for the artificial, non-carbohydrate sweetener, aspartyl-phenylalanine-1-methyl ester, i.e. the methyl ester of the dipeptide of the amino acids aspartic acid and phenylalanine D-forms and L-forms, which are enantiomers (mirror image molecules), of each other.
Aspartic acid, 2-aminobutanedioic acid, HOOCCH2CH(NH2)COOH, also called aspartate, the name of its anion, is one of the 20 natural proteinogenic amino acids, which are the building blocks of proteins.
The amount of aspartame in an average can of diet cola is about 0.06%.
Aspartame is 160 times sweeter than sugar, sucrose with E number (additives code) E951.
It is a common sweetener in prepared foods, particularly soft drinks.
Aspartame is one of the sugar substitutes used by diabetics.
Products containing aspartame usually have a warning label that they contain phenylalanine, in compliance with US FDA guidelines.
Aspartame breaks down into its constituent amino acids when heated in the presence of water and acids.
So it is unsuitable for use in baking, but is commonly in diet soft drinks or to sweeten coffee and tea.
A soft drink is a drink that contains no alcohol.
While aspartame, like other peptides, has a caloric value of 4 kilocalories per gram, the quantity of aspartame needed to produce a sweet taste is so small as to make its caloric contribution negligible, which makes it a popular sweetener for those trying to avoid calories from sugar.
Some authorities suggest that aspartame is a risky chemical food additive, and its use during pregnancy and by children is one of the greatest modern tragedies in human history.
Aspartame is synthesized from the two amino acids L-aspartic acid and L-phenylalanine, which are bonded by methanol.
Aspartame breaks down easily and loses its sweetness when heated.
Toxic levels of aspartame in the blood may result in mental retardation, altered brain function and behaviour changes in humans and cause side effects including dizziness, headaches and menstrual problems.
Since the FDA approved aspartame for consumption in 1981, some researchers have suggested that a rise in brain tumour rates in the United States may be at least partially related to the increasing availability and consumption of aspartame and phenylalanine.
Each sachet of the sweetener "Equal" contains dextrose C6H12O6, Aspartame, acesulfame potassium C4H4KNO4S, starch, (C6H10O5)n corn starch, silicon dioxide anti-caking agent SiO2, maltodextrin (D-glucose units), C6nH(10n+2)O (5n+1), and flavouring.
The tablet form may also contain α-Lactose monohydrate, C12H22O11.H2O.
From the label: "1 EQUAL sachet is as sweet as 2 teaspoons of sugar (approximately 8 g), but it contains 1 /8 of the Calories of sugar for the same level of sweetness" EQUAL contains per 0.045 g tablet, Energy 0.6 kJ, Protein 0.01g, Fat, (Total) 0 g, Fat (Saturated) 0 g, Carbohydrates 0.02 g, Sugars 0.02 g, Sodium 0.3 mg.
19.2.3 Gluten intolerance
Wheat may be a problem for people who cannot tolerate gluten.
Coeliac disease is an allergy to gluten.
Bread making flour may be preserved with sulfite, but most disappears during cooking.
Baking powder may be labelled "gluten free".
19.2.4 Lactose intolerance, lactose tolerance
Lactose intolerance is a problem for people who cannot tolerate lactose, (milk sugar).
Refined sugar in moderation usually causes no adverse effects.
The milk sugar lactose is digested by lactase enzyme produced in the intestines.
It is essential for babies, so being not needed in adults its production in the body generally declines with age after the age of 5 years.
In a person with lactose intolerance the lactose is attacked by bacteria in the large intestine to produce bloating gases and diarrhoea.
However, some adults can still produce lactase, because of a mutation in the DNA that controls the lactase gene.
The mutation is common in Northern Europeans and has occurred independently in East Africa and Saudi Arabia in other populations dependent on milk producing animals.
The same mutation may be quite common in the world.
19.2.5 Monosodium glutamate intolerance
See diagram 16.3.6.0.1: Monosodium glutamate.
MSG, monosodium glutamate, sodium hydrogen glutamate, is the monosodium salt of glutamic acid, a natural amino acid and a building block of all proteins.
It is found naturally in most foods.
It is as an additive to increase the flavour of soups, sauces, Asian cooking and snack foods.
Umami is the savoury taste of glutamates, monosodium glutamate.
Excess MSG, often in Asian soup liquids, causes unpleasant "wooden tongue" feelings.
MSG is banned in prepared baby food.
It is produced by fermentation of sugars produced by acid hydrolysis of molasses or tapioca, using the bacterium Corynebacterium glutanicum.
However, the MSG used to prepare cheap street foods may be adulterated.
19.2.6 Phenylalanine sweetener
Phenylalanine has the systematic name: (S)-2-Amino-3-phenyl-propanoic acid, chemical formula C9H11NO2, C6H5CH2CH(NH2)COOH.
So phenylalanine is classed as a phenylketonic.
The α-amino acid phenylalanine exists in two forms, the D-form and L-form, which are enantiomers, i.e. mirror image molecules, of each other.
L-phenylalanine (LPA), is an electrically neutral amino acid, one of the twenty common amino acids used to biochemically form proteins, coded for by DNA.
Its enantiomer, D-phenylalanine (DPA), can be synthesized artificially.
L-phenylalanine is in living organisms, including the human body, where it is an essential amino acid.
The synthesized mix DL-phenylalanine (DLPA), which is a combination of the D-forms and L-forms, is as a nutritional supplement.
Some authorities suggest that the amino acid DL-phenylalanine should be used with caution if you are pregnant or diabetic, if you have high blood pressure or suffer anxiety attacks.
Phenylalanine is part of the composition of aspartame, a common sweetener found in prepared foods (particularly soft drinks, and gum).
Phenylketonuria (PKU), is an inherited human genetic disorder of people without the ability to metabolize phenylalanine that occurs in about 1 in 15 000 births, but 1 in 4 500 births among the Irish.
Due to phenylketonuria, products containing aspartame usually have a warning label that they contain phenylalanine, in compliance with USA FDA guidelines.
Phenylalanine, a natural amino acid found in many foods, is deleterious only to sufferers of the genetic disorder phenylketonuria.
19.2.7 Salicylate intolerance
Salicylates are in medicine for painkilling, anti-inflammatory action and as preservatives in processed foods.
Salicylates include salicylic acid and sodium salicylates.
Salicylates usually do not cause harm to healthy adults, but aspirin may be harmful to children and to elderly people.
Other salicylate painkillers include extract of the bark of the willow tree (Salix alba vulgaris), and oil from meadow sweet, (Spirea ulmaria).
Other naturally occurring salicylates are in many fruits and vegetables in very small amounts.
Aspirin, analgesic, acetylsalicylic acid (2-acetyloxybenzoic acid), is made in factories from salicylic acid, HOC6H4COOH, 1-hydroxybenzoic acid.
Methyl salicylate oil of wintergreen (Gaultheria procumbens), as a liniment for sore muscles.
Phenyl salicylates (salol), are in sunscreens and as a stabilizer in plastics.
Salicylanilide, a compound of salicylic acid and aniline derivatives, is as an antiseptic in soap.
Most fruits and many vegetables contain natural salicylates, and some also have high amine levels.
Salicylates have a natural preservative action and are concentrated near any surface of fruits and vegetables.
Levels of salicylates are higher in unripe fruits and decrease with ripening.
In many cases these natural chemicals are concentrated near the skin and you can avoid them by peeling, e.g. potatoes and pears.
Natural chemical content also varies with ripeness.
Salicylates are highest in unripe fruit, and decrease with ripening.
Flavoured or fruit yoghurt may also contain salicylates.
Spicy processed meats can also contain salicylates or MSG, e.g. salami, seasoned meats, meat pies, sausages and sausage rolls, frankfurters, meat pastes and extracts.
19.4.1 Colloids in foods
Most foods and their components of lipids, proteins and carbohydrates are colloidal, e.g. milk consists of fat particles dispersed in water.
Margarine is an emulsion of water, flavours, colours, and vitamins in a semi-solid fat.
Mayonnaise is oil, vinegar and egg yolk.
Blood, enzymes, muscle tissue, bone skin and hair all involve colloids.
Lotions, creams and ointments are mostly emulsions of oils dispersed in water or vice versa.
Emulsions are one form of colloids.
Other examples of colloids are paints, rubbers, oils, pigments, plastics, gels, starches, air pollution and clouds.
19.4.2 Electrophoresis, food dyes, marking pen ink
See diagram 19.2.1.1a: Electrophoresis.
Electrophoresis is the movement of molecules in a solution under constant electric charge.
Electrophoresis is the movement of colloidal particles in a fluid caused by an electric field.
If a solution contains different sized molecules with different charges, the molecules can be separated, because they move at differnt speeds under constant electric charge.
Electrophoresis can used to separate different proteins in solution.
Gel electrophoresis is used to sort molecules based on their size and charge.
An electric field is applied to make molecules move through an agar gel to make negatively charged molecules move towards the positive terminal and positively charged molecules move towards the negative terminal.
Larger molecules move slower than smaller molecules leaving the different sized molecules as bands the gel.
Experiments
1. Cut the sides of a 10 cm × 5 cm flat bottom plastic container down to 3 cm height, e.g. a margarine container.
Fold a piece of aluminium foil over one short end of the container to cover both the outside end and extend to the bottom of the container.
Do the same at the other end of the container.
2. Make a comb from a piece of flat thick plastic, e.g. the lid of an ice cream container for a thin comb or a Styrofoam meat tray for a thick comb.
The comb must fits neatly into the width of the plastic container.
It has two lips that hang over the sides of the plastic container tub to keep the comb in place.
However, the teeth of the comb should not touch the bottom of the plastic container.
Cut 6 teeth in the comb.
Each tooth should be 5 mm wide and 15 mm long.
3. Prepare a 0.1% bicarbonate buffer by dissolving 0.2 g of sodium bicarbonate in 200 mL of water.
Mix 1g of agar in 100 mL of the 0.1% bicarbonate buffer and heat to boiling in a microwave oven.
Heat for 30 seconds then 10 second pulses until it boils.
Leave to cool to hand temperature.
4. Make 1 cm diameter spots of vegetable food dyes, e.g. cochineal or ink from coloured marker pens on filter paper.
5. Prepare a 1% agar gel solution by dissolving 1 g of agar in 100 mL in bicarbonate buffer solution.
Fill the plastic container with agar gel to a depth of 1 cm.
Insert the comb so that the top of the agar solution is just below the top of the teeth of the comb.
Fix the comb 2 cm from one end of the plastic container.
Leave the gel to set undisturbed for 15 minutes.
When the gel is set, carefully remove the comb.
6. Cut out 3 mm × 4 mm rectangular pieces of the colour spots and insert them into the wells formed from the teeth of the comb.
Pour 100 mL of bicarbonate buffer solution into the plastic contained to completely cover the gel.
Some colour from the paper rectangles may diffuse into the buffer solution, but this will not affect the colours diffusing through the gel.
7. Connect the gel to five 9-volt batteries connected in series with wire leads and alligator clips.
Connect the end of the tank with the samples to the negative terminal of the battery.
If fewer batteries are used the samples will take longer to run and may diffuse into the gel.
Leave the circuit connected for 45 minutes until separation of samples occurs.
19.4.3 Elements in food
See diagram 3.2.98: Find nitrogen in foods.
1. Collect small pieces of different foods together, such as cheese, bread, flour, sugar, leaves, maize.
Collect small pieces of different foods together, such as cheese, bread, flour, sugar, leaves, maize.
Heat a piece of each, about the size of a rice grain, on a tin lid or metal bottle top.
Hold the lid with tongs.
Black carbon is always left on the lid.
2. Heat small amounts of food with copper oxide in a small test-tube.
Copper oxide releases oxygen to the food.
Test the gas in the test-tube with limewater by withdrawing a little gas in a teat pipette and bubbling the gas through the limewater.
The limewater turns milky indicating the presence of carbon dioxide.
Also, water is condensed on the cooler parts of the tube.
3. Put a small amount of crushed food in a test-tube and add three times that volume of soda lime.
Mix the substances thoroughly then heat the test-tube.
Use your hand to fan gases from the mouth of the test-tube towards you to smell ammonia at the mouth of the tube.
Test the gases with wet blue and red litmus paper.
The red litmus paper turns blue.
If the food gives off ammonia gas, the nitrogen in the ammonia must have come from the food.
4. Mix separately cane sugar, vegetable oil and egg white with soda lime, then heat the mixtures.
Note any smell of ammonia at the mouth of the test-tube containing the egg white.
The nitrogen in the ammonia came from the protein in the egg white.
5. Heat a mixture of 0.5 cm of sucrose and 1.0 cm of concentrated sulfuric acid gently for 2 seconds and then leave to stand.
Note the vigorous reaction and the colour change from white sugar to black carbon.
C12H22O11 + (H2SO4 catalyst) --> 12C + 11H2O.
19.5.1 Tests for ketones
See 16.5.01: Ethyl acetoacetonate (ethyl 3-oxobutanoate).
1. Add drops of 10% ferric chloride to 5 mL of urine.
Ferric phosphate forms, but dissolves in excess ferric chloride.
The solution turns brown-red if acetoacetic acid is present.
2. Rotheras's test, Acetest, Ketostix uses nitroprusside to detect acetone acetoacetic acid, and beta-hydroxybutyric acid, (BHB, not an acetone), by colour change from pink to purple in acetoacetate.
Ketostix detects acetoacetate, but not BHB nor acetone.
Sodium nitroprusside dihydrate, Sodium nitroferricyanide, Na2[Fe(CN)5NO].2H2O.
19.5.2 Tests for nitrates / nitrites with dipsticks
Sensitivity for nitrate = 10-500 mg / L.
Sensitivity for nitrite = 1 -50 mg / L.
Interference from nitrite removed by adding aminosulfonic acid so separate nitrite strip not needed.
1. The tests for oxides of nitrogen in air.
Sensitivity 1 mL of NO2 / m3 of air.
2. The tests for nitrite in saliva, average 7 mg / L, except after foods with high nitrate level, e.g. celery, beets, where you obtain elevated levels for 24 hours.
3. The tests for nitrate / nitrite in fermented raw meat, e.g. salami, legal limit 500 mg / kg, nitrate, Cured meat (corned beef) legal limit 125 mg / kg, nitrite, Canned ham, legal limit 50 mg / kg, nitrite.
4. The tests for nitrite in vegetable, e.g. Conventional carrots 40-100 mg / kg, Organically grown carrots 200-400 mg / kg, Fresh spinach 5 mg / kg, if refrigerated for two weeks 300 mg / kg.
5. The tests for denitrification in waterlogged soils, soil + nitrate + glucose ---> N2O, Sensitivity: nitrate 10-500 mg / L nitrite 1-50 mg / L
Nitrates and nitrites (E249-253) occur naturally in many vegetables.
Additional nitrite can be derived from nitrate by bacterial activity in the gut.
19.5.3 Tests for sulfites
1. Tests for air pollution
Sensitivity: 5 mL (13 Mg) of SO2 / m3 air
2. Tests for sulfite preservatives
Legal limits: Fruit juices 115 mg / L, concentrated 600 mg / kg, Gelatine 1000 mg / kg, Dehydrated carrots 1000 mg / kg, Cheese 300 mg / kg, Sausages 500 mg / kg, Wine 300 mg / kg, Sensitivity: 10-500 mg / L.
19.5.4 Tests for tartaric acid
Grape juice and wine (added acetic acid ensures total tartrate is measured) Less than 1 g / L indicates very poor quality.
Sensitivity: 0.5-10 g / L.
19.5.5 Tests for urine
Reagent dipsticks ("Dip-stix") can be used to test for the following chemicals in a fresh urine sample: blood, protein, glucose, ketones, nitrite, N-acetyl-B-glucosaminidase, bilirubin, robilinogen.
19.5.6 Tests with multiple reagent strips
It is a firm plastic strip to which are affixed several separate reagent areas.
Sugar, serum albumin, urobilinogen and bilirubin are the four biochemical substances tested in a random urine sample.
Although the heat and acetic acid test detects the presence of proteins such as albumin, only a semi-quantitative test will be really useful.
19.5.7 Tests for water
Tests for pH, free chlorine and total chlorine, chlorine / chloramine, ammonia (NH3 / NH4+) nitrite and nitrate, oxygen.
19.6.1 Cola label
Kola nut (Cola nitida), Sterculiaceae.
Experiment
Check for the following information on a drink-can with the example information included below:
1. Name: "Normal name" or name modified by words, e.g. "lite", "diet", "no sugar".
If trade mark, shown as ™ or (registered trademark)
Volume, e.g. 375 mL (drink-can), 1.25 L (big plastic bottle)
"Refund at collection depot"
Bar code for item and price
Best before date (see base of can or neck of bottle)
"Store in a cool place"
Consumer information: (Telephone number)
Batch number, e.g. 965DB2
2. This drink contains: Carbonated water, Flavour, Colour (150d), Food acid (338, 330), Sweeteners (951, 950), Preservative (211), Caffeine, Phenylalanine
3. Nutrition information: Servings per package, e.g. 5, Serving size: e.g. 375 mL
4. Average quantity per 100 mL.
19.6.2 Cola contents
Kola nut (Cola nitida), Sterculiaceae.
Energy 180 kJ, 43 Calories, Protein 0 g, Fat 0 g, Fat, saturated 0 g, Carbohydrate 10.6 g, Sugars 10.6 g, Sodium 10.0 mg
"Soft drink" Contains: Carbonated water, Sugar, Colour (150d), Food acid, (338), Flavour, Caffeine.
Although flavourings are not listed, in 1993 a report listed the original flavourings as lime juice, vanilla, orange, lemon, nutmeg, cassia, coriander and neroli.
However, the composition of the modern product is still a secret.
Recently, in Australia, traditional Coca-Cola packets have the large sign: No Sugar.
19.6.3 Cola, Diet or Light contents
Energy 1.5 kJ, 0.4 Calories, Protein 0.05 g, Fat 0, Fat of which saturates 0, Carbohydrate 0.1, Carbohydrates of which Sugars 0, Sodium 15 g.
Soft drink Contains: Carbonated water, Flavour, Colour (150d) Food acid, (338, 330) Sweeteners (951, 950) Preservative (211)
19.6.4 Cola uses
"Cola-Mentos Fountain Kit", Mentos + cola, (toy product)
1. Clean a burned saucepan by pouring cola into it and boiling to remove the staining.
2. Make a modern photograph look like an old sepia tone photograph.
Lightly brush the photograph with cola and dry quickly.
Do not wet it too much or it will buckle.
Treat photocopied black and white pictures in the same way to make "antique" prints.
Treat photocopied maps in the same way and put them in antique style frames.
3. If you dye your hair and the result is too intense, flat cola will help to lighten it.
4. Soak old coins in cola to give them a brilliant shine for collections and decorative items.
5. Pour cola into a kettle and leave it there all day to remove lime scale and leave it clean inside.
6. Pour a can of cola into the toilet to clean it with the acid in the cola.
7. Make an excellent barbecue sauce by mixing cola and ketchup, half and half.
Coat chicken or meat with it before cooking.
8. Flat cola makes a good hair conditioner so pour it over your hair, rinse and dry.
9. Put cola into flat wide dishes in the garden to remove slugs, which are attracted by the sweet smell so that once they fall in, they cannot get out.
10. Loosen rusty bolts by soaking a rag in cola, and wrapping it around the bolt, then leave for a few hours so make the bolt easier to move.
11. Clean jewellery in cola by brushing with a toothbrush and rinsing well, but do not use on jewellery containing gemstones.
12. Flat cola helps to settle upset stomachs, but fresh, fizzy cola may irritate them.
You can take the fizz out of cola by adding sugar.
19.6.5 Cola light
Sugar free, carbonated water, caramel, colour, sodium cyclamate and acesulfame-k and aspartame, phosphoric acid and citric acid, caffeine and other flavourings,
preservative, phenylketourics, contains phenylalanine, Energy 0.18 kcal, all aluminium can.
Experiment
Observe the labels on soft drink (non-alcoholic drink), bottles and the labels printed on cans of the regular drink, diet or light drink, drink with special flavours, e.g. vanilla flavour.
19.2.9.1 Make jelly with fresh pineapple and tinned pineapple
Experiment
Fresh pineapple contains a powerful proteolytic enzyme called bromelase, but in tinned pineapple it is inactivated.
So a pineapple garnish for ham, gammon, should be made of fresh pineapple.
Fresh pineapple interferes with setting gelatine and whipped egg whites, because the enzyme is active.
Bilirubin test
It is based on the coupling of bilirubin with diazotized dichloronaniline in a strongly acid medium.
The colour ranges through various shades of tan.
Glucose test
It makes use of the same principle as described above for the strip.
The final colour ranging from green to brown.
Ketone test
It is based on Rothera's reaction principle and on the development of colours, ranging from buff pink for a negative reading to purple when acetoacetate reacts with nitroprusside.
It also detects acetone, but not beta-hydroxybutyrate.
pH test
This test is based on the double indicator principle that gives a broad range of colours covering the entire urinary pH range.
Colours range from orange through yellow and green to blue.
Proteins test
The test area of the reagent strip is impregnated with an indicator, tetrabromophenol blue, buffered to pH 3.0.
At this pH it is yellow in the absence of protein.
Protein forms a complex with the dye turning the colour of the dye to green or bluish green.
The colour is compared with the colour chart provided, which indicates the approximate protein concentration.
It is based on the protein error of the pH indicator.
At a constant pH, the presence of protein leads to the development of any green colour.
Colours range from yellow for "negative" through yellow green and green to green blue for "positive" reactions.
Specific gravity (relative density) test
In the presence of an indicator, the polyelectrolytes present in urine give colours ranging from deep blue-green in urine of low ionic concentration
through green to yellow-green in urine of increasing ionic concentration.
Urobilinogen test
Ehrlich's benzaldehyde reaction is a test for urobilinogen in the urine.
Dissolve 2 g of dimethyl-p-aminobenzaldehyde in 100 mL of 5% hydrochloric acid and add this reagent to urine.
A red colour in the cold indicates the presence of an excessive amount of urobilinogen.
19.4.7 Phthalic acid, Phthalates
Phthalic acid C8H6O4, C6H4(CO2H)2, benzene-1,2-dicarboxylic acid, formerly derived from naphthalene, aromatic dicarboxylic acid, has many isomers.
Made by oxidation reaction using naphthalene + potassium permanganate or potassium dichromate.
Phthalic anhydride, C8H4O3, C6H4(CO)2O, benzene-1,2-dicarboxylic anhydride, phthalandione, Toxic, strong skin irritant, used to produce phthalic esters, chemical plasticisers, plastics from vinyl chloride, large scale production to make plasticisers.
Phthalates
Phthalates, C6H4(COOR1)(COOR2) are esters of phthalic acid, [C6H4(COOH)2].
Phthalates are used as chemical plasticizers and to make polymers and alkyd resins, and to soften polyvinyl chloride (PVC).
They are used to make shower curtains, PVC piping and inflatable products.
Alkyd resins are usually made from glycerol and phthalate anhydride for paint, car parts, electric switches and insulators, electronic components and television parts.
Phthalates are not chemically bound to the plastics they are added to, so they may be continuously released to the air as plastics harden over time.
So their use is being phased out in some countries, because of concern about possible risk to foetuses and young children.
Phthalates include the following:
Bisphenol-A (BPA), Epoxy resin polymer
| DPB, dibutyl phthalate | DNOP, di-n-octyl phthalate | DiNP di-isononyl phthalate | DEP, diethyl phthalate | BBzP, benzyl butyl phthalate | Di-isononyl phthalate | DEHP, di-2-ethylhexyl phthalate | DiDp, diisodecyl phthalate | DnHP, i-n-hexyl phthalate | DnOP, di-n-octyl phthalate | Dimethyl phthalate, DMP, (C2H3O2)C6H4, insecticide.
See diagram16.13.8.
The Danger of Phthalates by Dr Ameeta Gajjar
"Fitness First Australia" Sept / Oct 2013
See diagram 16.3.5.1: Plastics recycling code.
Phthalates are industrial compounds added to different kinds of plastics to make them softer and more durable.
They have found their way into everything from food containers and toys to vinyl flooring, shoes and even cosmetics and shampoos.
Since phthalates are not bonded within the product they are used in, they can leach out and be absorbed orally from food and drinks, through the skin, via inhalation and even medical injection procedures.
We are only just waking up to the adverse impact of phthalates on our health.
As more links between phthalates and medical problems are established, there is increasing feeling that phthalates could be responsible for one of the great silent health pandemics of our time.
While some phthalates such as DEHP are now banned for certain products, they could still be having an effect as they degrade slowly.
Even very small amounts of phthalates have been shown to interact with other toxins and have cumulative effects.
The common phthalates are DEHP (cheap to use), DBP, DIDP and DINP.
DEHP was banned in Australia in 2011 for certain products, including children's toys (less than 36 months of age), and eating utensils, if the concentration of DEHP exceeded 1 percent.
So DEHP can still be present, quite legally in minute amounts in many plastic products.
DEHP, di-2-ethylhexyl phthalate, [dioctyl phthalate, DOP], C6H4(C8H17COO)2, most common phthalate plasticizer.
DBP, dibutyl phthalate, C16H22O4, banned in cosmetics in EU, suspected endocrine disruptor.
DiNP di-isononyl phthalate, C26H42O4, EU restriction.
Why you should be concerned
Phthalates have been linked to various medical problems.
1. Cancer
Phthalates have been found to mimic our hormones and with other environmental pollutants, are known as "endocrine disrupting chemicals."
Studies have shown a link between breast cancer and phthalate exposure.
2. Obesity
Metabolic syndrome and insulin resistance associations have been found between urinary phthalates and increased waist circumference and insulin resistance in US males and adolescents.
3. Allergies /Asthma
Studies have found an association between allergies in children and phthalates.
There was also an association with asthma.
Other symptoms from phthalates exposure include low birth weight in infants, abnormal foetal development and behavioural and /or l earning difficulties.
How to avoid phthalates
Avoid plastic containers and bottles with the recycling codes 1, 3, 6 or 7.
If they have no number, avoid those by checking the bottom of the product for the number in a triangle.
These are the typical plastics to avoid:
Recycling code 1 are PET (polyethylene terephthalate): Found in water bottles, soft drink bottles.
Recycling code 3 are PVC (polyvinyl chloride): Found in cling film, food packaging, cooking oil bottles and toys.
Recycling code 6 are PS (polystyrene) Found in disposable plates /cups / trays, egg cartons and takeaway containers.
Recycling code 7 are PC (polycarbonate) and others.
Found in baby bottles, large water containers.
Practical tips on reducing your phthalate exposure
1. Reduce use of plastic water bottles - use glass or stainless steel bottles instead.
2. Do not heat foods and drinks in plastic in microwave ovens, particularly baby bottles.
3. Avoid plastic cookware - opt for Pyrex or ceramic containers, especially for heating and storing.
4. Buy natural, certified organic cosmetics and personal care products, (nearly 900 chemicals used in cosmetics are known to be toxic, including phthalates, SLS and parabens).
5. Open the car windows!
The "new car smell" is partly from phthalates, with their concentration getting worse when the car gets hot.
6. Choose safer plastic toys, (some are labelled "phthalate free"), or avoid plastic toys.
19.4.6 Olive oil
Olive oil is composed mainly of triglycerides, composed of a mixture of three fatty acids, and small quantities of free fatty acids (FFA), glycerol, phosphatides, pigments, flavour compounds, and sterols.
The major fatty acids in olive oil triglycerides are:
Oleic acid, monounsaturated omega-9 fatty acid, 55 to 83% of olive oil.
Linoleic acid, polyunsaturated omega-6 fatty acid, 3.5 to 21% of olive oil.
Palmitic acid, saturated fatty acid, 7.5 to 20% of olive oil.
Stearic acid, saturated fatty acid, 0.5 to 5% of olive oil.
Linolenic acid, alpha-linolenic acid, polyunsaturated omega-3 fatty acid, 0 to 1.5% of olive oil.
Olive oil contains more oleic acid and less linoleic and linolenic acids than other vegetable oils, so it is more monounsaturated than polyunsaturated fatty acids.
So olive oil is more resistant to oxidation, because if more double bonds in a fatty acid, it is more unstable and easily broken down by heat and light.
Olive oil is the most stable cooking oil, because it also contains a steroid stabilizer, so it needs no refining, preservatives or refrigeration.
Some people do not fry in olive oil, because of the low smoke point, 165-190oC, but olive oils produce less toxic aldehydes than other cooking oils and can be used safely for frying for up to 10 times.
Olive oil contains no preservatives, but keeps much longer than other edible oils, particularly if kept in an air-tight container and away from heat and light.
However, olive oil kept in a refrigerator becomes thick and cloudy.
Olive oil: smoke point: 204oC, P/S ratio: 0.5
Trade names:
1. "Olive oil", is usually a refined or blended oil with acid content less than 3.3%.
2. "Virgin Olive oil" is a premium oil with excellent aroma and flavour, maximum acid content 1.5-2.0 %, for cooking and salad dressing (3 parts olive oil, 1 part vinegar or lemon juice).
3. "ExtraVirgin Olive Oil", best quality edible oil, maximum acid content 1.0 %.
19.4.4 Fish oils
Fish oils, ω-3, containing eicosapentaenic acid, EPA and docosahexaenoic acid, DHA, are taken as supplements to lower total serum triglycerides and maintain healthy levels of cholesterol.
19.4.5 Margarine
See 16.3.3.2: Diacetyl, butanedione.
An example of a legal definition of table margarine is that it is a mixture of edible fats, oils and water, prepared in the form of a water in oil emulsion containing < 16% water, < 4% salt and > 8.5 mg of vitamin A and > 55 g of vitamin D per kilogram.
The P: S ratio is the ratio of polyunsaturated fat to saturated fat.
A "heart-healthy" margarine should have a P: S ratio > 2: 1.
The term "polyunsaturated" is permitted where the proportion of cis-methylene interrupted polyunsaturated fatty acids in the margarine is > 49%, the proportion of saturated fatty acids < 20% of the total fatty acids, and the P/S ratio > 2: 1.
The total cholesterol content must appear on the packet as mg / 100 g.
The remaining 40% of the fatty acids can be mono-unsaturated, e.g. oleic acid.
A softer margarine that requires constant refrigeration has a P/S ratio 3: 1.
Table margarine may contain antioxidants, flavouring, e.g. flavour of butter from 3-hydroxy-2-butanone and diacetyl (2, 3-butanedione, dimethylglyoxal, C4H6O2), and vegetable colouring, e.g. usually carotene, a source of vitamin A, and which gives the colour to butter.
Previously, margarine contained coconut oil, but producers changed to soybean oil, because of concern about the high content of saturated fats in coconut oil.
However, new margarine-like products contain coconut oil, along with non-genetically modified and naturally cholesterol-free vegetable oils, but not palm oil, e.g. "Nuttelex".
Margarine label
Information from the label on a 250 g packet of an Australian "Original, Cholesterol free spread" margarine.
Ingredient list: Vegetable oils, water salt, skim milk powder and whey powder, emulsifiers (soybean lecithin, 471), food acid (citric) colour (β-carotene), vitamin A and D, flavour.
Keep refrigerated.
Contains 70% fats and oils.
No artificial colours.
Virtually free of trans fatty acids.
Contains soy and milk as indicated in bold type.
Margarine label
Experiment - Margarine label
Observe the label of a packet of margarine bought in your local store.
Note list the list of ingredients and compare it to the list below.
Table 4.3.0 Margarine label
Nutrient Quantity per 5 g serve Quantity per 100 g
Energy 130 kj 2 620 kj
Protein < 1 g < 1 g
Fat, total 3.5 g 70 g
Saturated fatty acids 0.9 g 17 g
Trans fatty acids 0.03 g 0.63 g
Polyunsaturated fatty acids 0.9 g 17.0 g
ω-3 fatty acids 0.25 g 5 g
ALA 0.25 g 5 g
Mono-unsaturated fatty acids 1.7 g 34 g
Cholesterol nil nil
Carbohydrate < 1 g < 1 g
Sugars < 1 g < 1 g
Sodium 49 mg 790 mg
Vitamin A 50 g, ** 7% RDI) 1 000 g
Vitamin D 0.5 g (** 5% RDI) 10 g
Potassium 1 mg 14 mg
** RDI, Recommended dietary intake (Australia / New Zealand)