Friday, February 10, 2012: 04:08:54 PM


Sealed Tight

Geeta Bector elucidates on the importance of food preservation in the packaged food industry and talks about recent techniques in this field

The rising demand for packaged foods is largely influenced by urbanisation and the busy lifestyles of the modern consumer. Economic growth is buoying the purchasing power of Asia’s middle-class which is fuelling demand for bakery products in retail store, food joints, coffee shops across India.

Various demographic factors are responsible for the way people are consuming bakery products such as cakes, sandwiches, pastries, puffs, pizzas and croissants. Processed and preserved foods have been instrumental in bringing about a change in the food habits of a large urban population who have rediscovered value-added foods.

Factors such as the booming Indian economy, an increase in disposable income and the booming retail sector have lured a number of domestic and international bakery chains to expand their operations. Be it a vast majority of the working class that has no time to cook or a strong influence of the west, the Indian consumer is increasingly opting for fried, baked or toasted foods straight from the freezer. Given the changing consumption patterns, product innovations and unique retail formats are the need of the hour for adequate product visibility.

Preserving For Perfection
The basic aim of food preservation is to minimise the growth of micro-organisms during the storage period, ensuring a longer shelf life and reducing other food hazards. Food preservation can be defined as a process that treats food so that it stops or slows down food spoilage without its quality, edibility and nutritional value being compromised. The process of food preservation comprises prevention of the growth of bacteria, yeasts, fungi and other micro-organisms.

There has been an increase in consumption of processed foods across various sections of the population with the rising trend of eating at restaurants has grown manifold in the country. The market for processed food is, thus, expanding significantly. Thus, food preservation for extended shelf-life and safe guarding its quality is paramount to the food industry.

Lately, there has been a steady rise in various minimal preservation techniques. Various methods of food preservation such as sun-drying, pickling and fermentation have been practised in India since many decades. These methods can be supplemented with other techniques such as slow-freezing, quickfreezing, high osmotic pressure, osmosis, mechanical drying, spray drying, freeze-drying, sun-drying, dehydro-freezing, pasteurisation, canning, dehydration, foam mat-drying, smoking and radiation.

The Process
There are two types of preservation techniques that are popular in India— thermal and non-thermal food processing. The speciality of these two types of preservation is that they contain a range of heating and dispensation techniques suitable for various types of processed foods.

Radiation is a technique that makes food safer to eat by destroying bacteria; this process is similar to pasteurisation. On the flipside, radiation disrupts the biological process that leads to decay and the ability for a food to sprout. Since it is a cold process, radiation can be used to pasteurise and sterilise foods without causing changes in freshness and texture of food, unlike when heated.

Further, unlike chemical fumigants, radiation does not leave any harmful toxic residues in food, is more effective, and can be used to treat packaged commodities too. Radiation technology is used in preservation of food items such as potato, onion, rice samolina (sooji or rawa) wheat flour or maida, mango, raisins, dried dates, ginger, garlic, shallots (small onions) and meat products. Mentioned below are a few types of preservation techniques that are commonly followed in the industry:

Preservation by Sugar: Sugar syrup that contains 68 percent sugar is used for the preservation of fruits and vegetables. Sugar is used to preserve fruits—either in syrup with apples, pears, peaches, apricots, plums—or in crystallised form where the product is cooked in sugar to the point of crystallisation and the result is then stored dry. This high concentration of sugar reduces moisture content and prevents the growth of microbes. Jams, jellies and squashes go through this process.

Preservation by Salt: Preservation of food by adding salt to it is known as salting. Meat products and fish are covered with salt to drain out water by osmosis. Raw mango, lemon, amla, tamarind, and other fruits and vegetables are preserved by salting, thus inhibiting the growth of bacteria. Salting or curing draws moisture from the meat through a process of osmosis. Meat is cured with salt or sugar or a combination of the two; nitrates and nitrites are also often used to cure meat.

Deep Freezing: Souring food at sub-zero temperature in deep freeze or in cold storage at a temperature about –18 degree celsius is also a method of food preservation. This method is used for preserving fish, meat, fruits and vegetables.

Pickling: Under this method of preservation, food is placed or cooked in a substance that inhibits or kills bacteria and other micro-organisms. Oil and vinegar are used to make pickle because bacteria cannot survive in high acid contents of these materials. Vegetables and fruits such as raw mango or lemon chillies are preserved as pickles. Salt and sugar is added to the pickle to enhance its taste.

Canning and Bottling: Canning involves the cooking of fruits or vegetables, sealing them in sterile cans or jars, and then boiling the containers to kill or weaken any remaining bacteria; this is a form of pasteurisation. Various foods have varying degrees of natural protection against getting spoilt and this may require that the final step takes place in a pressure cooker.

High-acid fruits such as strawberries require no preservatives and only a short boiling cycle. However, marginal fruits such as tomatoes require longer boiling and addition of other acidic elements. Many vegetables require pressure canning. On the downside, food preserved by canning or bottling is at an immediate risk of spoilage once the can or bottle has been opened.

Jellying and Irradiation: Food may be preserved by cooking in a material that solidifies to form a gel. Such materials include gelatine, agar, maize flour and arrowroot flour. Irradiation of food is the processing of food with ionising radiation; either high-energy electrons or X-rays from accelerators, or by gamma rays (emitted from radioactive sources as Cobalt-60 or Caesium-137). The treatment has a range of effects such as the of killing bacteria, moulds and insect pests, reducing the ripening and spoiling of fruits, and at higher doses, inducing sterility.

Preservation by Chemicals: Citric Acid is added to pickles and some squashes, while sodium benzoate and sodium meta bisulphite are used as preservatives to preserve jelly, jams and squashes.

Preservation by Pasteurisation: It is the process of heat and cold treatment to which milk is subjected to make it bacteriafree. The milk is heated to 70 degree celsius for about 30 minutes and subsequently chilled.

Food processing involves the preparation and conversion of raw materials into finished goods through actual processing after which it is sold to the final consumers over-thecounter at restaurants, grocers, institutional food services, and wholesalers. The actual processing involved various procedures such as blanching, crushing, chopping, mixing or cooking.

These processes, along with those mentioned above, ensure that food can stay longer in pantries and refrigerators. 

The author is VP of Research Development at Mrs Bector’s food specialities

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