Food Additives - Preservatives

Having read about the various Food Additives added to food, now it is time to understand each type of additive. The first type of food additives that we shall discuss about are the food preservatives. Food preservative is a substance which when added to food, is capable of inhibiting, retarding or arresting the process of fermentation, acidification or decomposition of food.

It is classified into Class 1 and class 2 preservatives. 

Following are the few factors which influence the choice of preservatives:

1. Properties of food: Determined by the pH, composition, nature of spoilage during handling, processing and storage, various physical and chemical properties as well as method of application. E.g. Protein and fiber in foods can affect the activity of a preservative.
2. Level and type of microorganisms: Nature of food production can influence the microbial flora and load as well as the method of food preservation. Choice of preservative depends on the microbial spectrum and load. A preservative cannot be used as replacement for sanitation and hygiene in a food processing operation.
3. Other treatments such as pasteurization, partial dehydration, refrigeration and packing too can affect. E.g. packing can prevent growth of moulds and aerobic bacteria.
4. Safety - It should not be toxic and should be safely ingested and absorbed.
5. Water activity - regulation of water in food is very important. Dehydration, freezing and addition of solutes such as salt and sugar can determine microbiological growth and biochemical reaction to be controlled.

Here are some examples of a few of the preservatives which are added to the several types of food products:

Sulphur dioxide, sulphites and bisuphites are used in fruit and beverage preservation and in dehydrated fruits and vegetables, soups and other mixes to control browning. Its salts are used to prevent fermentation and spoilage by yeasts and molds. E.g. Grape juice which may have Acetobacter cells is inhibited. Saccharomyces are found in juices, soft drinks and wine industry which are inhibited. These are used as temporary preservatives in fruit pulps and juices in raw and semi-finished products and may be removed during processing. Also used in sausages and other processed meats, cherries and berries, fruit juice concentrate, jams, jellies, squashes, preserves, marmalades, refined sugar, beer, gelatin, corn flour, pickles, dehydrated vegetables and fruits, cocoa powder, chocolates and its products etc.

Benzoic acid and its salt are used as preservative in jams, jellies, tomato puree, ketchup, sweets like halwa, jalebi, soft drinks, sauces, squashes, syrups and sherbets, coffee extracts etc. They are used to control yeasts and molds. Sodium benzoate is used in margarine, mayonnaise, margarine, fruits juices etc.

Sorbic acid is used widely in bakery industry and confectionary products like cakes, fillings for chocolates etc. It has been used to increase the shelf life of ready to eat chapathis etc. It is widely used in cheese and cheese spreads where its potassium salts may be used and also used in brine solution for ducting of cheese and also the sorbic acid treated wrappers are useful for packing of smoked fish products. It is used in fermented vegetable products and in cured meats with nitrites. Also used to preserve prunes and fruit pulps, jams and jellies to prevent mould growth and also to sterilize wines.

Nitrates and Nitrites are used for curing and pickling of meats. They prevent gas formation in cheese such as Gouda cheese and inhibit the toxins formed by Clostridium botulinum and Staphylococcus aureus. It is mainly used as a color fixative. They react with myoglobin forming nitrosomyoglobin which has a bright red colour and is not affected by atmospheric oxidation. They delay off colour development during storage of processed meat products.

Various fumigants such as ethylene oxide and ethyl formate are used to control microorganisms on spices, nuts and dried fruits.

Propionic acid and propionates are also used for preserving foods.

So turn those food packets and read what are the preservatives added to them. Happy reading!

 Post by Faiz Lahori