School Science Lessons
Topic 19 Household chemicals, acids in the home, composition of food
2009-09-18
Please send comments to: J.Elfick@uq.edu.au
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Table of contents
19.1.0 Household chemicals
19.1.1.0 Acids in the home
19.2.0 Composition of food, vitamins, minerals
19.3.6 Food preservation (See topic 19a)
19.4.0 Food chemistry
19.4.4 Shopping chemistry
19.3.0 Cooking ( See topic 19b)
19.3.5 Microwave cooking
19.4.1 Checklist of household chemicals
19.4.2 Kitchen hints
19.4.2.1 Stain removal
19.5.0 Fabrics in the home
19.5.1 Natural and synthetic fabrics
19.6.0 Hardware, laundry, painting, cleaning, preserving
19.7.0 Beauty and skin care products
19.8.0 Common measure
19.1.0 Household chemicals
19.1.0.1 Sequestrants
19.1.0.2 Stabilizers and thickeners
19.1.0.3 Emulsifying (surface active) agents
19.1.0.4 Polyhydric alcohols
4.38 Calorific value of fuel
19.1.0.5 Water retention agents
19.1.0.6 Acidulated water
19.4.1 Checklist of chemicals in the home
19.4.2 Kitchen hints
2.35 Carbon dioxide in the home
19.1.6 Baking powder
19.1.7 Prepare carbon dioxide, sodium hydrogen carbonate with buttermilk, sour milk, vinegar, fruit juice
19.1.8 Prepare self-leavened flour, "self-raising flour"
19.1.8.1 Plain flour and self-raising flour
19.1.9 Prepare baking powder
19.1.16 Table salt and rock salt
19.1.17 Cooking fats
11.3.3 Triple scale wine hydrometer
6.6.18 Alcoholic fermentation
19.1.20 Dipsticks to test the vitamin C, ascorbic acid, content of food
19.1.20.1 Tests for metallic copper
19.1.20.4 Tests for glucose, urine test
19.1.20.4.1 Tests for ketones
19.1.20.5 Multiple reagent strips
19.1.20.6 Tests for nitrates / nitrites with dipsticks
19.1.22.7 Tests for sulfites
19.1.20.8 Tests for tartaric acid
19.1.20.9 Tests for adulteration of food by borax with turmeric paper
19.1.20.12 Tests for urine
19.1.20.13 Tests for water
19.1.1.0 Acids in the home
19.1.1 Solid acids, solubility
19.1.2 Solid acids, pH
19.1.3 Solid acids, add sodium carbonate
12.3.1 Taste of acids, solid acids in the home
19.1.5 Acid-base indicators
19.2.0 Composition of food
19.2.0.1 Colloids in food
4.2.1 Make yoghurt (activity for primary grade 4 students, about 9 years old)
4.2.2 Make sauerkraut (activity for primary grade 4 students, about 9 years old)
7.8.0 Colloids, sols, emulsions, gels, aerosols, foams, types of colloids
7.8.3.2.1 Gels in the home kitchen
9.127 Elements in foods
19.4.2.2 Food allergies and intolerance
19.2.1.0 Fats in our food
19.2.1.1 Fats in animals and plants
19.2.1.1a Electrophoresis of food dyes and coloured marking pen ink
19.2.1.1.1 The cis and trans forms of linoleic acid
19.2.1.2 Classification of fats
19.2.1.3 Hydrogenation, cis-trans fatty acids
19.2.1.4 Rancidity
19.2.1.5 Heat fats
19.2.1.6 Antioxidants, antioxidant phenols, vitamin E, beta-carotene
19.2.1.7 Cholesterol
19.2.1.8 Omega-3 fatty acids
19.2.1.9 Free radicals
19.2.1.10 Margarine
19.4.3 Margarine label
19.2.1.11 Coconut oil
19.2.1.12 Fish oils
19.2.1.13 Ice-cream
19.1.1.14 Chocolate
16.3.3.1 Waxes
19.2.9 Pectin in jelly and jam
19.2.9.1 Jelly using fresh pineapple and tinned pineapple
19.2.10 Egg white, albumen, and egg yolk
19.2.10.2 Eggs in a cake mix
19.2.11 Yeast, fermentation, brewing, whisky, fish sauce
19.2.12 Salad dressing and mayonnaise emulsions
19.2.13 Prepare fruit salts
19.2.14 Food colouring liquids and detergent
19.2.15 Heat starch, glycemic index
19.2.17 Glycoalkaloids, avoid bruised or green potatoes
19.2.18 Extract iron, Fe, from breakfast cereal
19.2.21 Fish smell
19.2.22 Laundry starch
19.2.22.1 Wheat starch and gluten
19.2.23 Milk
19.2.24 Butter
19.2.26 Custard
19.2.27 Garlic
19.4.2.3 Caffeine, extraction with supercritical carbon dioxide
19.2.28 Tests for harmful substances in cigarette smoke
19.2.29 Toxic effect of common drugs on Daphnia
19.2.30 Tests for chewing gum quality by comparing bubbles
10.5.5 Steam distillation to find water and fat content of food
19.3.0 Cooking
19.3.1 Taste, smell, flavour
19.3.2 Anatomy and physiology of meat
19.3.3 Boiling, test the cooking water of boiled vegetables.
19.3.3.1 Mashed potato, pommes purée
19.3.4 Baking and retention of nutrients
19.3.4.1 Tests for dextrins in toast
19.3.4.2 Browning reactions of fruits and vegetables
19.3.4.2.1 Tests for lemon juice effect on apple browning
19.3.4.3 Non-enzymatic browning, caramelization
19.3.4.4 Non-enzymatic browning, the Maillard reaction
19.3.4.5 Roasting meat
19.3.4.6 Meat treatments, marinades, salting meat, marbled beef
19.3.5 Microwave cooking
19.1.0 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.
19.1.0.1 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.
19.1.0.2 Stabilizers and thickeners are added to improve the texture and blends of foods, e.g. carrageenan (E407, from seaweed used in icings, frozen desserts, salad dressing, whipped cream, confectionery, and cheeses.
19.1.0.3 Emulsifying (surface active) agents, "food soaps" (E433-444) are used to stabilize emulsions of oil and water components in foods.
19.1.0.4 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.
19.1.0.5 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.
19.1.0.6 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, for instance, will be snowy white if boiled in acidulated water.
19.1.1 Solid acids, solubility
See appendix A: Citric acid | See appendix A: (+)Tartaric acid | See appendix A: Trioxyboric (III) 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?
19.1.2 Solid acids, pH
See: Acid-base indicators
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.
19.1.3 Solid acids, add sodium carbonate
See appendix: Sodium carbonate | See diagram: 3.34.9: 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.
19.1.5 Acid-base indicators
5.53.01 pH and acid-base indicators | See appendix: Sodium hydrogen carbonate, baking soda
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.
19.1.6 Baking powder
See: 13.7.7: Prepare carbon dioxide by heating hydrogen carbonates | See appendix: Cream of tartar
Formerly, bakers added sodium bicarbonate and sour milk, lactic acid, to bread dough to make bread rise as carbon dioxide gas bubbles formed during baking. Later dry cream of tartar from the wine industry was substituted for sour milk to make a dry mixture. Later, calcium acid phosphate. CaHPO4, was substituted for cream of tartar. Nowadays corn starch or rice flour is added to keep the mixture dry. Baking powder is a mixture of sodium bicarbonate with cream of tartar, tartaric acid, acid phosphate or sodium aluminium phosphate or any combination of these without any farinaceous (wheat) substance, so it can be labelled "gluten free". It must yield >10% of carbon dioxide and may contain permitted colouring substance. Baking powder contains compounds called food aerators, to be added to dough to make it rise during cooking as bubbles of carbon dioxide gas form. Baking powder can be used as a substitute for yeast which is used in sour dough.
Baking powder contains:
1. A leavening agent as a sources of carbon dioxide (dry solids): baking soda (sodium bicarbonate, sodium hydrogen carbonate, NaHCO3) or ammonium hydrogen carbonate,
2. Acidic substances to form acids when water is added: 1. cream of tartar (potassium hydrogen tartrate, acid tartrate)
3. Phosphates to replace cream of tartar
3.1. Acid phosphates, e.g. calcium hydrogen phosphate (calcium acid phosphate, CaHPO4) sodium dihydrogen phosphate V (sodium dihydrogen orthophosphate, sodium orthophosphate NaH2PO4.2H2O)
3.2 Phosphate aerators, e.g. food additive E450 Diphosphates (Sodium and potassium phosphates) food additive E541 Sodium aluminium phosphate, basic (emulsifier, acidity regulator) 3. Rice flour or corn flour to keep the mixture dry.
If baking powder contains 36% phosphate aerators it could contain about 10% aluminium. Baking powder must be stored dry. Mix the leavening agent baking soda, sodium bicarbonate, with acidic ingredients to make it work in cooking. However, baking powder contains baking soda and a powdered acid, so it can work without other acidic ingredients.
19.1.7 Prepare carbon dioxide, sodium hydrogen carbonate with buttermilk, sour milk, vinegar, fruit juice
See appendix: Sodium hydrogen carbonate, baking soda
Add acid buttermilk or sour unpasteurized milk or vinegar or fruit juice to sodium hydrogen carbonate. The reaction forms carbon dioxide.
19.1.8 Prepare self-leavened flour, "self-raising flour"
See appendix: Sodium dihydrogen phosphate V | See appendix: Potassium hydrogen tartrate | See appendix: Aluminium potassium sulfate (potassium alum)
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 hydrogen carbonate, 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 such as starch and aliphatic acids. Sodium hydrogen carbonate 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 hydrogen carbonate shows basicity, while hydrolysis of sodium dihydrogen phosphate shows acidity. The reaction results in release of carbon dioxide. The heat decomposes sodium hydrogen carbonate to make spongy steamed bread.
19.1.8.1 Plain flour and self-raising flour
See appendix: Baking soda
"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 hydrogen carbonate.
In the kitchen, to test whether flour is plain flour or self-raising flour, place a little on your tongue. If you feel a tingle, this indicates that the flour is self-raising flour.
19.1.9 Prepare baking powder
See appendix: Baking powder
To prepare 10 g of chemical sponging agent, baking powder, weigh 3 g of sodium hydrogen carbonate, 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 commercial 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.
19.1.16 Table salt and rock salt
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".
4. Sprinkling salt on water causes the surface to contract momentarily towards the crystals, while with pepper, the opposite tends to happen.
4.1 Examine the label on a contained of table salt and note the contents in addition to sodium chloride.
4.2 Make 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.
19.1.17 Cooking fats
Shortening is solid, white fat made from hydrogenated vegetable oil. Copha is a solid fat derived from coconuts and is quite saturated. Lard is the rendered fat from pig abdomen. Deep frying requires fats / oils with heat tolerant properties, e.g. corn and peanut oils but not butter, margarine, lard and olive oil.
19.1.20 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.
19.1.20.1 Tests for metallic copper
1. Copper in water,
2. Copper in ice confectionery, Sensitivity: 10-5000 mg / L 3. Legal limits for food (mg / kg).
19.1.20.4 Tests for glucose, urine test
See 9.141: Tests for reducing sugars, Benedict's test for reducing sugars
See diagram 16.13.4.7: Schiff base, azomethine
See diagram 16.8.0: o-toluidine
Artificial urine samples
Sample 1. Dissolve 1g albumin, 3g sodium chloride and 5g urea in 1 litre of water.
Sample 2. Dissolve 1g 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.
1. Clinitext tablet, a form of Benedict's test
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.
2. Clinistix strip
It 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.
3. Diastix strip
It 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.
4. 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.
4. Glucose reduces yellow ferricyanide to colourless ferrocyanide in a hot alkaline solution. The decrease of yellow colour is proportional to the glucose concentration.
5. 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”.
6. 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+
7. 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 beta 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.
19.1.20.4.1 Tests for ketones
See 16.5.1.1: 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 red-brown 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.
19.1.20.5 Multiple reagent strips
It is a firm plastic strip to which are affixed several separate reagent areas. Sugar, 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 semiquantitative test will be really useful.
Glucose: It makes use of the same principle as described above for the Diastix strip. The final colour ranging from green to brown.
Bilirubin: It is based on the coupling of bilirubin with diazotized dichloronaniline in a strongly acid medium. The colour ranges through various shades of tan.
Ketone: 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.
Specific gravity: 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.
pH: 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: 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.
Uroblilinogen: This test is based on a modified Ehrlich reaction, in which p-dimethyl amino benzaldehyde in conjunction with a colour enhancer reacts with urobilinogen in a strongly acid medium to produce a pink red colour.
19.1.20.6 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.
19.1.20.8 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
19.1.20.9 Tests for adulteration of food by borax with tumeric paper
Use turmeric paper
19.1.20.12 Tests for urine
Dipsticks
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
19.1.20.13 Tests for water
pH, free chlorine and total chlorine, chlorine / chloramine, ammonia (NH3 / NH4+) nitrite and nitrate, oxygen.
19.1.22.7 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.
19.2.0.1 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.
19.2.1.0 Fats in our food
See diagram 19.2.1: Glycerol, triglyceride, cis and trans, oleic acid, stearic acid, linoleic acid
Fats, oils and some waxes are the naturally occurring esters of long, straight chain carboxylic acids. These esters are the materials from which soaps are made. At room temperature, fats are solid or semi-solid and oils are liquids alcohol + organic acid ---> ester + water glycerol + fatty acid ---> fats or oils + water All fats form from glycerol, glycerine, propan-1,2,3-triol, CH2OHCHOHCH2OH. The fatty acid part of the fat differs 1. in the length of the chain, which controls the molecular mass, and 2. the number and position of the double bonds, unsaturation. The 3 main groups of fatty acids are 1. saturated fatty acids, e.g. stearic acid 2. the straight chain unsaturated fatty acids, e.g. oleic acid, and 3. the polyunsaturated fatty acids, e.g. linoleic acid. The normal saturated fatty acids have the general formula CH3(CH2)nCOOH, where n is usually an even number from 2 to 24, e.g. stearic acid (n=16) lauric acid (n=10). Milk contains short chain fatty acids, n < 10. The building block for fatty acids is the acetate ion, CH3COO-. The most important unsaturated fatty acids have 18 carbon atoms with one double bond in the middle of the chain, called mono-unsaturated fatty acids. Polyunsaturated fatty acids have more double bonds between the middle double bond and the carboxyl group, COOH. Atoms can rotate about single bonds but not about double bonds, so two arrangements are possible called "cis" and "trans". Most double bonds in natural fats and oils are cis, e.g. oleic acid in olive oil. Fatty acids with the cis double bond do not pack together easily so have a low melting point of double bond containing material (i.e. oils). Substances made up of shorter chains also melt at lower temperatures. Chemists describe polyunsaturaed fatty acids as having more than one cis-methylene interrupted double bond.
19.2.1.1 Fats in animals and plants
Fats and oils are used to store, transport and utilize the fatty acids that an organism requires for its metabolic processes. Energy storage in animals: fat 38 kj /g, carbohydrates 17 kj /g, protein 23 kj /g. Fats store water and when metabolized in the body to produce energy, they also produce water, e.g. fatty hump of the camel. Plants, fungi, yeasts and bacteria, can synthesize both fats and their component fatty acids. Animals can synthesize most of their fatty acid needs, but they prefer to ingest plant foods and modify them to their own needs. Only plants can synthesize linoleic and linolenic acids, but animals can increase the chain length and further increase unsaturation, e.g. fish oils, that are rich in unsaturated acids.
Saturated fatty acids are predominantly present in fats which are solid at room temperature, for example, milk, butter and animal fats. Saturated fats may raise the level of "bad" cholesterol leading to hardening of the arteries, high blood pressure, heart disease and strokes. Animals produce mainly saturated fats because their fats also have a structural support function and must not be too fluid. Some animals can maintain a high temperature through internal heating, insulation and behaviour. Unsaturated fatty acids may be mono-unsaturated or polyunsaturated. Mono-unsaturated fatty acids, e.g. oleic acid, are found in most animal and plant fats and oils, especially olive oil. Unsaturated fatty acids occur mainly in oils. Most fats and oils contain a mixture of saturated and unsaturated fatty acids but in widely varying proportions. An intake of fat in the diet is essential as some fatty acids are required for important functions in the body. Fat soluble vitamins A, D, E and K must also be provided by food containing fat. A fat free diet is not only difficult to prepare but is also very unpalatable.
The so-called "bad cholesterol" is the LDL (low density lipoprotein) cholesterol used to build body cells but excess can form plaque on the walls of arteries to the heart and brain causing atherosclerosis. The so-called "good cholesterol" is HDL (high density lipoprotein) cholesterol produced in the liver and intestines that removes excess cholesterol from atherosclerosis plaques and my protect from heart attack. Electrophoresis is used to separate the LDL fraction of total cholesterol to measure the HDL and LDL levels and determine the risk factors for coronary heart disease.
Polyunsaturated fatty acids, e.g. linoleic acid, linolenic acid, are found mainly in vegetable oils. Polyunsaturated fats are essential to animals as building blocks and for controlling the cholesterol content of the blood. Plants produce mainly unsaturated oils which allow them to withstand extremes of temperature because their fats or oils are fluid at low temperatures. Polyunsaturated fats lower "bad" cholesterol but also lower "good" cholesterol. Polyunsaturated fats are found in margarine, vegetable oils and seed oils. Some research claims that polyunsaturated fats may be are oxidized into "free radicals" which contribute to the development of some cancers and accelerate ageing.
Mono-unsaturated fats are the "good" fats and should make up most of the fats in a diet, up to about 30% of a diet.
Saturated fat in the diet can raise the level of blood cholesterol to increase the risk of heart disease from atherosclerosis, fatty plaques on the walls of blood vessels.
Unsaturated fat can form free radicals by lipid peroxidation, leading to cancer and accelerated ageing. So both saturated and unsaturated fat can have health hazards!
Oleic acid has been found to increase good cholesterol and lower bad cholesterol. Proponents of olive oil claim that in countries where oleic acid is the principle fat in the diet the people have the lowest incidence of heart disease and strokes and the longest life span and that only olive oil is high in mono-unsaturated fats and low in both polyunsaturated and saturated fats. However, it seems that people living in different countries where the components of fats in their diets are almost identical may have very different rates of the incidence of cancer, so perhaps other factors are involved.
19.2.1.1a Electrophoresis of food dyes and coloured marking pen ink
See diagram 19.2.1.1a: Electrophoresis
Electrophoresis is the movement of colloidal particles in a fluid caused by an electric field.
1. 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 on the gel.
2. Cut the sides of a 10 cm X 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.
3. 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 which 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.
4. Make a 0.1% bicarbonate buffer by dissolving 0.2g 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.
3. Make 1 cm diameter spots of vegetable food dyes, e.g. cochineal or ink from coloured marker pens on filter paper. .
4. Make a 1% agar gel solution by dissolving 1f 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.
5. Cut out 3 mm X 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.
6. 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.
19.2.1.1.1 The cis and trans forms of linoleic acid
See diagram 19.2.1: cis and trans, linoleic acid
In the cis configuration, the four hydrogen atoms adjacent to the double bonds occur on the same side of the carbon axis. In the trans configuration, the four hydrogen atoms adjacent to the double bonds occur on alternate sides of the main carbon axis with two on one side and two on the other. The more stable trans configuration may be produced from the cis configuration during partial hydrogenation of polyunsaturated vegetable oils to improve their texture. However, trans fatty acids tend to raise the level of low density lipoproteins (bad LDLs) and lower the level of high density lipoproteins (good HDLs) resulting in changes in cholesterol levels that may increase the risk of the heart disease atherosclerosis. So mono-unsaturated, unhydrogenated oils, e.g. olive oil, are preferable to the trans fatty acids in french fries, chips, and donuts. The first double bond is on carbon #6, counting from left to right so this is an omega-6 fatty acid, typical of the unsaturated fatty acids in plant oils and seeds. However, fish oils contain omega-3 fatty acids, i.e. the first double bond in on carbon #3.
19.2.1.2 Classification of fats
1. Saponification value from hydrolysis of a fats into component fatty acids, as their anions or soaps, and glycerol. Saponification value = number of milligrams of potassium hydroxide to saponify one gram of fat (or oil). It is a measure of the average chain length, molecular mass of the fatty acids. Fat and saponification value: Coconut oil 250-260, Butter 245-255, Lard (pig fat) 193-200, Peanut oil, 185-195, Linseed oil, 189-196.
2. Iodine value measures the number of double bonds in the fat. Iodine reacts with the double bond. Iodine value is the number of grams of iodine that react with 100 g of fat or oil. Fats with low iodine values are saturated. Fats with high iodine values are polyunsaturated. Fat and iodine value: Coconut oil 8-10, Butter 26-45, Lard 46-66, Peanut oil 83-98, Linseed oil 170-204.
3. Acid value measures how much glycerides in the fat or oil have been decomposed to free acid. This regulated by food standards codes.
4. Peroxide value measures the oxygen taken up by the oil to form peroxides and is a measure of freshness of the oil. This regulated by food standards codes.
5. Oxygen uptake. If polyunsaturated fats are incubated at 60oC, they gain weight from oxygen uptake.
19.2.1.3 Hydrogenation, cis-trans fatty acids
3[CH2O(CO)(CH2)7CH==CH(CH2)7CH3] + 3H2 --->3[CH2O(CO)(CH2)16CH]
glyceryl trioleate + hydrogen (nickel catalyst) + heat ---> glyceryl tristearate
Hydrogenation means to add hydrogen to a molecule. Unsaturated fats can be saturated by adding hydrogen to the double bonds with a nickel catalyst. Hydrogenation converts a substance with the properties of a liquid vegetable oil into a substance with the properties of a solid animal fat, e.g. linoleic and oleic acids turn into stearic acid. Margarine is made from pure vegetable oils but the manufacturing process may cause some hydrogenation of unsaturated fatty acids. Processed oils such as shortenings may contain a high proportion of fats changed by hydrogenation. In nature, most unsaturated fatty acids are cis fatty acids, i.e. the hydrogen atoms are on the same side of the double carbon bond. In trans fatty acids the two hydrogen atoms are on opposite sides of the double bond. Trans double bonds can occur in nature as the result of fermentation in grazing animals so people eat them in the form of meat and dairy products. Trans double bonds are also formed during the hydrogenation of vegetable or fish oils, e.g. French fries (fried potato chips) donuts, and other snack foods are high in trans fatty acids. Manufacturers may hydrogenate polyunsaturated oils to help foods to stay fresh or to obtain a solid fat product, e.g. margarine. Trans fatty acids, i.e. hydrogenated fats, tend to raise total blood cholesterol levels, and raise LDL bad cholesterol and lower HDL good cholesterol.
In some countries, governments have required fast-food companies to commit to reducing trans fats in their cooking and listing trans fat content on labelling. Some companies have claimed that consumers do not like the taste of products if all trans fats are eliminated. However, apparently, if only a small proportion of trans fats are used, taste is not a problem. In other countries, trans fats in cooking have been banned altogether by legislation.
19.2.1.4 Rancidity
Oxygen in the air oxidizes unsaturated fats adjacent to the double bond to produce smaller easily evaporated volatile compounds with a rancid smell. Most of the fatty acids in butter are C16 -C18 but shorter chain fatty acids are also present. The acid from rancid butter is 1,3-butadiene: CH2=CH-CH=CH2, a butane with two double bonds, bivinyl. butyric acid: C3H7COOH. Cheeses made from milk with more short chain fatty acids have a stronger smell. Margarine rarely becomes rancid because the longer chain fatty acids must first be broken before the short chain, rancid smelling compounds form. Commercial fats and oils have added antioxidants to prevent rancid compounds from forming. The same short chain acids in rancid butter are present in human perspiration
19.2.1.5 Heat fats
Smoke point is the temperature at which a fat breaks down into visible gaseous products and thin wisps of bluish smoke begin to rise from the surface. Smoke point, smoking point, falls with the continued use for cooking because the oil or fat decomposes and the free fatty acids have a lower smoke point. So the higher the initial smoke point, the longer the fat is usable before it starts to smoke. Smoke point of an oil or fat is an important piece of information for consumers and should be listed on food labels. Flash point is the higher temperature when bursts of flame start. Ignition temperature, is the higher temperature at which the entire surface of the frying medium becomes covered with flame. P/S ratio is the ratio of polyunsaturated fatty acids to the saturated fatty acids present. Although heating may not change the P/S ratio of polyunsaturated oils, it causes the formation of oxidized compounds, which tend to destroy the vitamin E content and make oils unpalatable. Changes in the peroxide value of oils after heating reveal how heating oxidizes oils. Olive oil is mainly mono-unsaturated oleic acid is the most stable cooking oil because it also contains a steroid stabilizer. So it needs no refining, preservatives or refrigeration. 1. Safflower oil: Approx. smoke point: 246oC Approx. P/S ratio: 6.0 2. Sunflower oil: Approx. smoke point: 229oC Approx. P/S ratio: 4.7 3. Maize oil: Approx. smoke point: 229oC Approx. P/S ratio: 3.1 4. Peanut oil: Approx. smoke point: 246oC Approx. P/S ratio: 1.9 (e) Soybean oil: Approx. smoke point: 256oC Approx. P/S ratio: 3.7 (f) Olive oil: Approx. smoke point: 204oC Approx. P/S ratio: 0.5
19.2.1.6 Antioxidant phenols, antioxidants, vitamin E, beta-carotene
See diagram 19.2.1.6: Antioxidants, BHT, BHA, TBHQ, Propyl gallate, Vitamin E
Antioxidants are preservatives for fatty products and oils that are themselves oxidized instead of the added substance. Antioxidants inhibits oxidation or reaction with oxygen. They are soluble in oil and cheap to produce. They prevent the occurrence of oxidation, i.e. rancidity. Vitamin C (ascorbic acid E300-301) is an antioxidants for water-soluble products. The fat soluble antioxidant butylated hydroxy anisole (BHA) E320 is added to edible oil and fat products in some countries. However, the antioxidant butylated hydroxy toluene (BHT) E321 is not usually added to foods but it is used in polythene film used to wrap food. It is added to petrol, lubrication products and rubber. Some antioxidant esters allowed in edible oils, margarine, table spread, salad oils include mono-tert-butylhydroquinone (TBHQ) and propyl gallate, propyl, octyl and dodecyl of gallic acid (3,4,5-trihvdroxvbenzoic acid, E310-312}
Antioxidants are related to the "natural" antioxidant, vitamin E, alpha-tocopherol and have similar properties. Vitamin E occurs in vegetable oils, e.g. wheat germ oil. It prevents the oxidation of unsaturated fatty acids in cell membranes and removes toxins. Lack of vitamin E may cause liver damage and infertility. The amount of vitamin E needed in the human diet depends on the amount of polyunsaturated fat consumed. However, excess vitamin A is harmful, as with any fat soluble vitamin.
Red wine is said to contain polyphenol and anthrocyanidin anti-oxidants and the anti-oxidant reservatol. Antioxidants in green tea may be at a concentration of  21 mg of total polyphenols per 100 mL.
19.2.1.7 Cholesterol
See diagram 19.2.1.7: Steroids
High cholesterol levels in the blood indicate the potential for atherosclerosis and coronary heart disease. Cholesterol is a fat-like molecule, an alcohol, base of all steroids, e.g. sex hormones, bile acids, vitamin D and cortisone. Cholesterol is not a fat but a steroidal alcohol. It has 27 carbon atoms so it is not a terpene. It is essential for the blood and cell membranes and is found in all the cells of the body. It is produced in the liver and also comes from foods of animal origin. Cholesterol in the blood becomes coated with a phospholipid protein envelope called lipoprotein in a high density (HDL) and low density (LDL) form. LDL carries cholesterol. Special receptors on the cells favour use of LDL. In countries where people eat large amounts of meat and dairy products their diets are high in cholesterol and saturated fats and so the mortality rate from heart disease is high. In countries where diets are low in cholesterol and rich in the polyunsaturated fats found in vegetable oils and fish, the death rate from coronary disease is lower. Vegetable oils contain the phytosterols instead of cholesterol. Isolation of ergosterol used to be employed as evidence proving the addition of vegetable oil to animal products. Atherosclerosis occurs when excess LDL cholesterol circulates in the blood, accumulates in the inner walls of the arteries to the heart and brain, and reacts with other substances to form a plaque that can clog those arteries. A blood clot can form to block a narrowed artery and can cause a heart attack or stroke. So the levels of HDL cholesterol and LDL cholesterol in the blood are measured to evaluate the risk of heart attack. A level < 130 mg/dL is optimal for most people. As high LDL level reflects an increased risk of heart disease LDL cholesterol is called "bad" cholesterol. Up to one fourth of blood cholesterol is carried by high density lipoprotein (HDL). It is called "good" cholesterol because it may protect against heart attack. by carrying cholesterol away from the arteries and back to the liver, to be excreted from the body. What is called LPG cholesterol is a genetic variation of plasma LDL that may cause fatty deposits in arteries. People with heart disease, diabetes or who are obese are likely to have high triglycerides level, high LDL cholesterol level and a low HDL cholesterol level. Triglyceride levels < 150 mg/dL are normal. Most people can raise their HDL (good cholesterol) levels by exercising, not smoking and staying at a healthy weight.
LDL cholesterol of less than 100 mg/dL is the optimal level. A LDL level more than 130 mg/dL reflects an increased risk of heart disease. That is why LDL cholesterol is often called "bad" cholesterol. Lpa is a genetic variation of plasma LDL. A high level of Lpa is an important risk factor for developing fatty deposits in arteries prematurely. The way an increased Lpa contributes to disease is not understood. The lesions in artery walls contain substances that may interact with Lpa leading to the build up of fatty deposits. People with high triglycerides often have a high total cholesterol, a high LDL cholesterol and a low HDL cholesterol level. Many people with heart disease also have high triglyceride levels. People with diabetes or who are obese are also likely to have high triglycerides. Triglyceride levels of less than 150 mg/dL are normal; levels from 150-199 are borderline high. Levels that are borderline high or high (200 mg/dL to 499 mg/dL) may need treatment in some people. Triglyceride levels of 500 mg/dL or above are very high. Doctors need to treat high triglycerides in people who also have high LDL cholesterol levels.
19.2.1.8 Omega-3 fatty acids
Omega-3 is a family of polyunsaturated fatty acids. The parent omega-3-alpha linolenic acid (ALA) is obtained from the diet and is polyunsaturated with 8 carbon atoms and 3 double bonds. The long chain omega-3 fatty acids eicosapentaenoic acid, EPA, and docosahexaenoic acid, DHA, can be synthesized from dietary ALA, but in seems that EPA and DHA should be obtained from the diet containing oily fish and fish oil as well as fortified bread and fruit juice. ALA, EPA and DHA are important role for structural membrane lipids, in nerve tissue and the retina beside a wide range of functions in cells and tissues.
19.2.1.9 Free radicals
A free radical is a molecule carrying an impaired electron. Free radicals are extremely reactive. As free radicals take an electron from the other molecules, they convert these molecules into free radicals or breakdown or alter their chemical structure. Free radicals can damage proteins, sugars, fatty acids and nucleic acids that combine and accumulate as "age pigment". The main free radicals are superoxide radical (SOR) hydroxyl radical (OHR) hydroperoxyl radical (HPR) alkoxyl radical (AR) peroxyl radical (PR) and nitric oxide radical (NOR) Other molecules that are not free radicals, but act much like them, are singlet oxygen, hydrogen peroxide (H2O2) and hypochlorous acid (HOCl). The free radicals and non-free radical mimics are called "oxidants" or "reactive oxygen species" (ROS). Free radicals live for only a few seconds because of their extreme reactivity. Free radical damage includes ageing, cancer, heart/artery disease, hypertension, Alzheimer's disease, ageing immune deficiency, cataracts, diabetes, inflammatory disease, and just ageing. Free radicals and oxidants are produced by normal physiological processes and by enzymes that detoxify pollutants. Monosaturated fats, cholesterol, and saturated fats are subject to free radical but polyunsaturated fatty acids are most susceptible. In humans the first line of antioxidant defence are the antioxidant enzymes, e.g. glutathione peroxidase (GPX) and tripeptide glutathione (GSH) help destroy SOR, H2O2 and lipid peroxides. Vitamins C and E, and mineral selenium have a major antioxidant role, besides various drugs. Vitamin C may be the most important nutrient antioxidant. Vitamin E is the chief fat-soluble antioxidant, and occurs in all membranes. Alpha-lipoic acid (ALA) is a quasi-vitamin anti-oxidant. It can be made by the body, but also absorbed from diet or supplements.
19.2.1.10 Margarine
See 19.4.3: Margarine label | See 16.3.9: Diacetyl, 2,3-butanedione
Information from a margarine label 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 mu g of vitamin D per kilogram. 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 as mg/100 g must appear on the packet. 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) vegetable colouring, e.g. usually carotene, a source of vitamin A, and which gives the colour to butter. Previously margarine contained coconut oil but produces changed to soybean oil because of concern about the high content of saturated fats in coconut oil.
19.2.1.11 Coconut oil
See 17.0: New ways to make coconut oil
Proponents of including coconut oil in the diet claim that In the United States, the commercial interests of the US domestic fats and oils industry and soybean growers were successful at driving down usage of coconut oil by pointing to the high concentration of saturated fats in coconut oil. During concern over increased rates of heart disease the edible oil industry's response at that time was to claim that it was only the saturated fat in the hydrogenated oils which was causing the problem. Not being domestically grown in the US, coconut oil and palm oil industries were not able to defend themselves. However, the proponents for coconut oil say it is rich in short and medium chain fatty acids. Desiccated coconut is about 69% coconut fat. and coconut milk is about 24% fat. About 50% of coconut fat is lauric acid which has antibacterial, antiviral and antiprotozoal functions in food. Also, another one medium chain fatty acid, capric acid, has been added to the list of coconut's antimicrobial components. It is claimed that natural coconut fat in the diet leads to a normalization of body lipids, protects against alcohol damage to the liver, and improves the immune system's anti-inflammatory response and that the medium chain fatty acids and monoglycerides found primarily in coconut oil have tremendous healing power.
19.2.1.12 Fish oils
Fish oils, omega-3 containing eicosapentaenic acid, EPA and docosahexaenoic acid, DHA, are taken as supplements to lower total serum triglycerides and maintain healthy levels of cholesterol.
19.2.1.13 Ice-cream (icecream)
Ice-cream is a foam preserved by freezing. Under a microscope you can see solid globules of milk fat, air cells, ice crystals, solution of concentrated sugars, salts and suspended milk proteins. The ice crystals were formed by water freezing out of the solution to a point where the lowering of the freezing point caused by the concentration of the remaining solutes in the water corresponds to the freezer temperature. Manufacturers can expand the ice-cream with air to double its volume. Expanded ice-cream feels fluffier and has a warmer taste. Ice-cream containing Less milk fat has bigger ice crystals, coarser texture and colder taste but the addition of emulsifiers and stabilizers can mask these low fat properties but prepare the ice-cream sticky. If not stored at a low enough temperature partial thawing causes the smaller crystals to melt and later refreezing to larger crystals. Ice-cream on the tongue crystallizing out the lactose, milk sugar, which stays on the tongue after the ice has melted leaving a sweet taste.
Use a coffee tin with a plastic lid about 159 X 156 X 134 mm. Half fill the coffee tin with equal volumes of cream or double cream and whole milk. Add 1 teaspoon of vanilla extract. Firmly attach the plastic lid. Put the coffee tin in a plastic bucket with a tight lid. Add ice cubes and 200 g of rock salt around the coffee tin to the same level as its height. Almost fill the bucket with ice cubes and attach the bucket lid. Turn the bucket on its side and roughly roll it forwards and backwards for 10 minutes. Open the bucket and coffee tine and observe the layer of frozen ice-cream lining the inside of the coffee tin. Friction between ice cubes in the rolling bucket causes some ice to melt but not refreeze because the salt has lowered the freezing point. The super chilled water so formed cools the walls of the coffee tin. The ice-cream mixture starts to freeze but does not form big crystals because of the motion of the bucket.