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Methods Of Food Preservation and Sterilisation (Part III) By Mumtaz Khalid Ismail
More Links Food Preservation - Part 1 Food Preservation - Part 2 Food Preservation - Part 4 This is most used and abused method of food preservation. Chemical preservatives serve as either anti-microbial, antioxidant or both. It also minimises the damage to some essential amino acids and the loss of some vitamins. Anti-microbial prevent the growth of molds, yeast, and bacteria where as antioxidants, they keep foods from becoming rancid, browning, or developing black spots. If one take rancid foods one may not fall sick, but they smell and taste bad.
Common chemicals used are sulphites, nitrites, calcium propionate, disodium EDTA, BHA, BHT, citric acid, antibiotics such as nisin Z etc. These chemical if used in approved quantity and for approved use it may not be that harm full based on our present knowledge. The other method is use of ozone. The use of passive air ozonation has reduced bacteria counts up to 300%.
Sulphites are used primarily as antioxidants to prevent or reduce discoloration of light-coloured fruits and vegetables, such as dried apples and dehydrated potatoes. This chemical is used to preserve food items such as baked goods, beer, wine, tea, condiments, vinegar, dairy product, processed seafood products, grain products, gravies, sauces, jam, jellies, nut products, plant protein isolates, dried fruit, fruit juices, fruits, vegetables, filled crackers, soup mixes, sugar, sweet sauces etc. In some countries the use of sulphites is banned on fruits and vegetables intended to be eaten raw, such as in salad bars and also in thiamine rich food such as enriched flour. Sulphite sensitive people are prone to develop breathing difficulty, stomach ache, and occasionally anaphylactic shock.
Nitrites are a favourite preservative of meat processors even though its excess use is restricted in many countries. This chemical stabilises the red colour of the meat and gives an appearance of fresh meat. Nitrites are used as a preservative for meat and meat products. Nitrite salts can react with certain amines in food to produce nitrosamines, which are known to cause cancer. Addition of Sodium ascorbate or sodium erythorbate inhibits nitrosamine formation and reduces the problem of nitrosamines. The use of nitrite and nitrate has decreased greatly because of refrigeration and restrictions on the amounts used. Even though nitrite and nitrate cause only a small risk, it is always better to have fresh meat and meat product.
Butylated Hydroxyanisole (BHA), a phenol chemical compound antioxidant, used as a preservative in Cereals, chewing gum, butter; meats, baked goods, beer, snack foods, potato chips, vegetable oil. It slows the development of off-flavours, odours, and colour changes caused by oxidation. Even though it is considered as safe some studies showed that it produce cancer in experimental animals.
Butylated Hydroxytoluene (BHT) is a related phenol compounds to BHA and has similar action. BHT retards rancidity in oils and used in cereals, chewing gum, potato chips, and oils. It has shown similar risk of developing cancer in experimental animals like BHA. It is better to avoid this or substitute it with less harmful methods.
Sodium Propionate is a preservative used in bread, rolls, pies, and cakes. It prevents growth of micro-organisms.
Citric Acid is one of the popular cheap and safe antioxidant used. It is used in preservation of fruit juices, cheese, margarine, and salad dressings.
EDTA is an agent, which help to separate metallic ions. It remove metal impurities in food thus prevent rancidity. This safe chemical is used in preventing rancidity in salad dressing, margarine, sandwich spreads, mayonnaise, processed fruits and vegetables, canned shellfish, and soft drinks.
Heptyl Paraben is used in beer and non-carbonated soft drinks as a preservative. This preservative is safe but rarely used.
Lecithin a natural substance present in animal and plant tissues used mainly as emulsifier but it is also used to retard rancidity in baked goods, margarine, chocolate, and ice creams.
Phosphoric Acid is the substance formed on exposure of phosphorus to oxygen. It is used in baked goods, cheese, powdered foods, cured meat, breakfast cereals, and potatoes. Excessive consumption of phosphates could lead to osteoporosis.
Propyl Gallate is an antioxidant. It is used for preservation of vegetable oil, meat products, potato sticks, chicken soup base, and chewing gum. It is shown that it causes cancer in experimental animals. It is preferably to be avoided.
Sodium Benzoate is a granular salt used as preservative in fruit juice, carbonated drinks, jellies, margarine, fast-food burgers, and pickles. It is a time tested preservative used for centuries.
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