Food technology

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When food is broken down by the body, glucose is formed. It occurs in the blood of all animals because blood carries glucose around the body to cells where it is needed. The level of glucose in the blood is regulated by the hormone insulin which is secreted by the pancreas.

2. Fructose has a similar composition to that of glucose but it is sweeter. Fructose occurs in honey and in the juices of fruits and plants. Fructose is absorbed very rapidly into the body and is used more quickly than glucose. It is harmless to people with diabetes. Fructose may be produced from sugar and is known as ‘commercial sugar’.

3. Galaxtose is present in milk combined with glucose.

The molecules of glucose, fructose and galactose all contain 6 carbon atoms, and therefore are called hexoses. They are all monosaccharides, that is to say, all composed of one sugar unit.

Disaccharides

Sucrose, maltose and lactose: all have the same chemical components but different arrangement of atoms within their molecules. Disaccharides are all white crystalline solids which dissolve in water.

Sucrose is the most common sugar in our diet. Both cane and beet sugar consist of purified sucrose and nothing else. Invert sugar is the name given to the mixture of glucose and fructose formed by the hydrolysis of sucrose.

When sucrose is digested, the enzymes split the link between the glucose and the fructose.

Polysaccharides

There are five main polysaccharides:

- Starch

- Dextrin happens when you heat or fry an item and the item changes colour and dextrin is formed

- Glycogen is the only animal source of carbohydrate, this comes from liver

- Pectin is used for its property in baking to set jam

- N.S.P (fibre)

Starch is the only polysaccharide that we eat for nutritional value. We eat these foods to give us energy.

Fats

Fats are also known as lipids.

Fat is solid at room temperature, i.e. butter, lard, dripping and suet.

Oil is liquid at room temperature; sunflower oil, vegetable oil.

The structure of a fat is one molecule of glycerol and three fatty acids. This is a triglyceride. A diglyceride only has two fatty acids. A fatty acid is a chain of carbons with hydrogen and acid.

Stearic acid is a fatty acid, it is the most common and is found commonly in beef.

Butyric acid is found in butter while oleic acids are found in oils.

Fatty Acids

They can be classified as saturated or unsaturated. All fatty acids are chains of carbons. The carbons in saturated fatty acids have four chemical bonds, and so are joined onto four hydrogens with single bonds and no more bonds can be made. Stearic and butyric acids are saturated fatty acids. It just depends on the number of carbons in the chain.

There are four unsaturated fatty acids. An unsaturated fatty acid has to have more than one double bond in its structure.

Oleic acid has one double bond.

Linoleic has two double bonds.

Linolenic has three double bonds and arachodonic has four double bonds. These three fatty acids are all polyunsaturated.

Oleic acid comes from olive oil and arachodonic acid comes from fish oil. Fats are ‘energy dense’ and have twice as many calories in 1g as in 1g of carbohydrate or protein. A cis fatty acid has carbons all in a straight line whereas a transfatty acid branches out in different directions.

Protein

Protein is the most important nutrient. It consists of carbon, hydrogen, oxygen, nitrogen and sometimes phosphorous and sulphur. The nitrogen makes protein different from fats and carbohydrates. We eat hundreds of nutrients for growth and repair.

There are five high protein foods which are: meat, fish, eggs, cheese and milk. They are all animal products and the only vegetable products that have as much protein are quorn and soya. Nuts and pulses etc. all contain protein but aren’t as high as soya and quorn.

Proteins are made from amino acids which join together in different ways. There are 22 occurring amino acids and 8 of those are essential acids. The essential amino acids are called: isolevicine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. The primary structure of a protein is the order/pattern of amino acids in the chain, this can never be altered.

Protein deficiency diseases are widespread in poor countries. Proteins are large polymers built of amino acids, although there are over 80 amino acids, only 20 are found in food protein, they are all common but 8 are essential. Glycine and cystine are two amino acids. Amino acids can be further sub divided into essential amino acids which are indispensable in the diet and non-essential amino acids. There are 8 essential amino acids:

Valine, leucine, threonine, methionine, isoleucine, phenylalanine, tryptophan and lysine. Proteins in food can be classed on their amino acid content. Proteins that contain all of the essential amino acids, e.g. meat proteins, in proportions capable of promoting growth are described as complete proteins or proteins of high biological value. These proteins used to be called first class proteins and proteins deficient in one or two amino acids were second class proteins.

When two amino acids condense together, a dipeptide is formed and where many combine, a polypeptide is formed and finally, a protein. Each amino acid is linked to the next by peptide bonds o build up a chain of hundreds or even thousands of amino acids.

The structure of proteins is different from that of other food components in that several orders of complexity have been recognised. Firstly, there is a primary structure which is the sequence of amino acids in the protein chain. The secondary structure is where the amino acids are further linked by other bonds to give the protein a definite shape which is often in the form of a spiral. The most important