| What
is Food? Food is any substance normally
eaten or drunk by living things. The term food also includes liquid drinks.
Food is the main source of energy and of nutrition for animals, and is usually
of animal or plant origin. There are 4 (four) basic food energy sources: fats,
proteins, carbohydrates and alchol. Historical developmentHumans are
omnivorous animals that can consume both plant and animal products. We changed
from gatherers to hunter gatherers. After the experience of
the Ice Age it is probable that humans wanted to create some feeling of security
by controlling what plants were growing and which animals were available. This
led to agriculture, which has continually improved and altered the way in which
food is obtained. Types of Food?
Fats In
biochemistry, fat is a generic term for a class of lipids. Fats are produced by
organic processes in animals and plants. All fats are insoluble in water and have
a density significantly below that of water (i.e. they float on water.) Fats that
are liquid at room temperature are often referred to as oil. Most fats are composed
primarily of triglycerides; some monoglycerides and diglycerides are mixed in,
produced by incomplete esterification. These are extracted and used as an ingredient.Products
with a lot of saturated fats tend to be solid at room temperature, while products
containing unsaturated fats, which include monounsaturated fats and polyunsaturated
fats, tend to be liquid at room temperature. Predominantly saturated fats (solid
at room temperature) include all animal fats (e.g. milk fat, lard, tallow), as
well as palm oil, coconut oil, cocoa fat and hydrogenated vegetable oil (shortening).
All other vegetable fats, such as those coming from olive, peanut, maize (corn
oil), cottonseed, sunflower, safflower, and soybean, are predominantly unsaturated
and remain liquid at room temperature. However, both vegetable and animal fats
contain saturated and unsaturated fats. Some oils (such as olive oil) contain
in majority monounsaturated fats, while others present quite a high percentage
of polyunsaturated fats (sunflower, rape).
Proteins
A protein is a complex, high molecular
weight organic compound that consists of amino acids joined by peptide bonds.
Protein is essential to the structure and function of all living cells and viruses.
Many proteins are enzymes or subunits of enzymes. Other proteins play structural
or mechanical roles, such as those that form the struts and joints of the "cytoskeleton."
Proteins are also nutrient sources for organisms that do not produce their own
energy from sunlight. Proteins differ from carbohydrates chiefly in that they
contain much nitrogen and a little bit of sulfur, besides carbon, oxygen and hydrogen.
Proteins are a primary constituent of living things. In
carnivores protein is one of the largest component of the diet. The metabolism
of proteins by the body releases ammonia, an extremely toxic substance. It is
then converted in the liver into urea, a much less toxic chemical, which is excreted
in urine. Some animals convert it into uric acid instead. Protein
nutrition in humans
In terms of human nutritional needs, proteins come in
two forms: complete proteins contain all eight of the amino acids that humans
cannot produce themselves, while incomplete proteins lack or contain only a very
small proportion of one or more. Humans' bodies can make use of all the amino
acids they extract from food for synthesizing new proteins, but the inessential
ones themselves need not be supplied by the diet, because our cells can make them
ourselves. When protein is listed on a nutrition label it only refers to the amount
of complete proteins in the food, though the food may be very strong in a subset
of the essential amino acids. Animal-derived foods contain all of those amino
acids, while plants are typically stronger in some acids than others. Complete
proteins can be made in an all vegan diet by eating a sufficient variety of foods
and by getting enough calories. It was once thought that in order to get the complete
proteins vegans needed to do protein combining by getting all amino acids in the
same meal (the most common example is eating beans with rice) but nutritionists
now know that the benefits of protein combining can be achieved over the longer
period of the day. Ovo-lacto vegetarians usually do not have this problem, since
egg's white and cow's milk contain all essential amino acids. Peanuts, soy milk,
nuts, seeds, green peas, Legumes, the alga spirulina and some grains are some
of the richest sources of plant protein. All eight essential
amino acids must be part of one diet in order to survive and are needed in a fixed
ratio. A shortage on any one of these amino acids will constrain the body's ability
to make the proteins it needs to function. Different
foods contain different ratios of the essential amino acids. By mixing foods that
are rich in some amino acids with foods that are rich in others, one can acquire
all the needed amino acids in sufficient quantities. Omnivores typically eat a
sufficient variety of foods that this is not an issue, however, vegetarians and
especially vegans should be careful to eat appropriate combinations of foods (e.g.
nuts and green vegetables) so as to get all the essential amino acids in sufficient
quantities that the body may produce all the proteins that it needs. Protein
deficiency can lead to symptoms such as fatigue, insulin resistance, hair loss,
loss of hair pigment (hair that should be black becomes reddish), loss of muscle
mass (proteins repair muscle tissue), low body temperature, and hormonal irregularities.
Severe protein deficiency is fatal. Excess protein can
cause problems as well, such as causing the immune system to overreact, liver
dysfunction from increased toxic residues, possibly bone loss due to increased
acidity in the blood, and foundering (foot problems) in horses. Proteins
can often figure in allergies and allergic reactions to certain foods. This is
because the structure of each form of protein is slightly different, and some
may trigger a response from the immune system while others are perfectly safe.
Many people are allergic to casein, the protein in milk; gluten, the protein in
wheat and other grains; the particular proteins found in peanuts; or those in
shellfish or other seafoods. It is extremely unusual for the same person to adversely
react to more than two different types of proteins. Amino
Acids Carbohydrates
Carbohydrates (literally hydrates of carbon) are chemical
compounds which act as the primary biological means of storing or consuming energy;
other forms being via fat and protein. Relatively complex carboyhydrates are known
as polysaccharides.The simplest carbohydrates are monosaccharides, which are small
straight-chain aldehydes and ketones with many hydroxyl groups added, usually
one on each carbon except the functional group. Other carbohydrates are composed
of monosaccharide units, and break down under hydrolysis. These may be classified
as disaccharides, oligosaccharides, or polysaccharides, depending on whether they
have two, several, or many monosaccharide units. Food Phenolics Phenolic
food compounds (also known as aromatic food compounds) occur naturally in all
foods: they give the food colour and flavour and help to prevent premature decomposition.
Aroma and Taste Molecules
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