In the western world, people have access to a great variety of different types of food and even complete ready-prepared meals. The choice of what food is actually eaten is usually on the basis of personal preference.
List below some general (i.e. not necessarily nutritional) guidelines which you would use in planning one or more good meals (buying ingredients, preparing them, etc.) for yourself or your family.
> - enjoyable flavour or texture - different meat/ starch source ("ringing the changes")
> - cheap / good value / easy to prepare - fresh ingredients : 5 fruits/vegetables per day?
> - (bulk buys) food which keeps / stores well etc
However, a major factor should be the extent to which the food items contribute to a balanced diet: the combination should provide enough energy and also enough of each of the components of diet to keep the eater healthy. This may vary according to the lifestyle. The planned diet should cover several meals, so that deficiencies in one may be made up by another, or the converse. Snacks should also be included.
Over-eating of foods containing fats and sugars is likely to result in weight gain, putting strain on the heart and other body systems, as well as other problems like tooth decay and skin problems.
On the other hand, slimming is extremely difficult. This involves reducing the intake of energy-producing food (fats, carbohydrates) without going short of other components of diet, so that the body will use up
stored fat to release the energy that is required. Such a "diet" requires much self control and motivation, and if it becomes an obsession it may result in psychological problems like anorexia nervosa.
Most prepared foods nowadays have nutritional information on their packaging to help purchasers to make decisions about their use. In the list of ingredients, the most common component is placed first, and
the others follow in decreasing order. Usually the content is expressed in relation to 100g. of food product, but sometimes there is also information presented in terms of the usual portion of food eaten.
In the case of some diet components which are seen to be cause for public concern, some manufacturers and retailers also provide further information. This may, for example, include the further subdivision of
carbohydrates into starch and sugars, fat into saturates and unsaturates, and further into mono- and poly- unsaturates, as well as sodium.
Why subdivide carbohydrates like this?
> Starch is a necessary (?) ingredient in many meals providing "bulk" or at least a satisfying form of carbohydratee whereas sugar (sucrose?) is added as a sweetener (in excess?) or sometimes as a preservative. It may be said that starch takes longer to be broken down to glucose and is less likely to cause tooth decay. What are the advantages and disadvantages of these two carbohydrates?
> starch is gradually broken down (digested) to maltose and other sugars used in respiration and sucrose contributes to tooth decay
What is indicated by a high proportion of saturates in fat?
> animal origin - possible link with heart problems
Why are some people concerned about the level of sodium in their diet?
> sodium ions (e.g. from salt) may affect the heart - raising blood
pressure etc.
Exercise - record your own diet
Preferably taking your own diet for a whole day, use the columns below to list the nutritional contribution made by the various items of your diet. Total this up and compare it with the recommendations, and with examples of "healthy" and "unhealthy" diets.
Food type
Amount eaten
Energy content (kJ)
Carbohydrate
Fat/oil
Protein
Fibre
Vitamins/
minerals?
Totals
FOOD ADDITIVES
Various chemical substances may be added to prepared foods, mostly in order to preserve them, to enhance their colour, or to prevent oxidation or separation of fats from the mixture.
There is much debate about the reasons for including these additives in foods, especially in relation to safety. One point that is often advertised is that some additives are "natural", i.e. derived from living organisms, whilst others are synthetic, i.e. produced by chemical means, but there is no rational reason to believe that natural additives are any better than synthetic ones.
Some of these substances have been used for a long time, so they have achieved a form of acceptability
(and they are also quite cheap). Fill in the names of three such substances below.
Vinegar is used as a preservative, because it is a weak acid, and lowers the pH of the food to about 3 -
3.5, so that bacteria cannot grow, because their digestive enzymes work at a different pH.
We may become used to (and even enjoy) the different taste of the pickled food, and when we eat it we
dilute the acid so that we can digest it, using our own digestive juices.
Sugar is sometimes added (up to 60%) to foods like fruits in the process of making jams and conserves; this is not specifically to sweeten it but to prevent growth of bacteria and moulds, by using the principle of osmosis; any such micro-organisms which get into the food lose water and become effectively dehydrated, so they either cannot grow, or die.
Similarly, salt has a preservative effect on meat, fish and some vegetables, by exactly the same principle of dehydrating by osmosis.
Some modern food manufacturers have reduced both sugar and salt content in their foods (in response to consumers' health concern, or commercial pressure?).
What (problems) may happen to food as a result of these reductions?
> go off more quickly - mouldy etc.
What must consumers do to prevent these problems? Not adding more sugar or salt to foods!
> put the food in the refrigerator > eat the food more quickly!
More recent additives have been classified by a system of E numbers,
which signify that these substances are considered to be safe for most people. However, there is evidence that some groups of people (asthmatics, hyperactive children, etc) may be adversely affected by them, and so food labels must give details, to enable consumers to avoid them if they wish, but much public opinion is ill-informed.
What does it mean if an additive is the last in the list of ingredients on a food label?
> it is the least in quantity
The classification is fairly systematic, and there are broad bands for each category, although natural and synthetic additives are included in each. The information below is not exhaustive, but there are many books (including leaflets from supermarkets) which give more details.
By surveying food from your own kitchen at home, food labels in the lab or the textbook, try to find some examples of foods containing each category below.
Permitted colours (E100-180)
These substances are usually added to make food look better, perhaps because they lose natural colour due to processing.
This practice is controversial, and there is definite cause for concern in the case of some chemical additives in the azo group (derived from coal tar), e.g. E102 tartrazine, E104 quinoline yellow, 107 yellow 2G, E110 sunset yellow, E122 carmoisine, E123 amaranth, E 124 ponceau 4R, E 127 erythrosine, 128 red 2G, E131 patent blue V, E132 indigo carmine, 133 brilliant blue, E142 green S
"Natural" colours include extracts from plants or animals:
E100 turmeric root, E101 riboflavin - vitamin B2, E120 cochineal - from insects, E140 chlorophyll, E150 caramel, E160(a) carotene - from carrots and other vegetables, E160(b) from annatto seeds, E160(c) from paprika, E160 (d) from tomatoes. Examples of foods containing these additives (specify which):
>
Preservatives (E200-290)
Likely additives:
E200-203 sorbic acid and salts, E210-219 benzoic acid and salts, E220-227 sulphur dioxide and sulphites, E250-252 nitrites and nitrates, E260-263 acetic acid and salts, E270 lactic acid
Examples of foods containing these additives (specify which):
>
Anti-oxidants (E300-321)
Likely additives:
E300-304 ascorbic acid and salts
Examples of foods containing these additives (specify which):
>
Emulsifiers, stabilisers, etc. (E322-494)
E322 lecithin, E330 citric acid, E400-405 alginic acid and alginates
Examples of foods containing these additives (specify which):
>
There are other categories of miscellaneous additives, and some substances have no E prefix if there is a doubt about their acceptability, e.g. the "flavour enhancers" 620 glutamic acid - a natural amino acid found
in practically all protein, and its salt 621 - monosodium glutamate - widely used in chinese cooking.
>
Interestingly, flavourings are not covered by this system.
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