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Ensuring long life with preservatives
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Tuesday, 01 January, 2013, 08 : 00 AM [IST]
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Sumit Pant, Tom Thomas
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fiogf49gjkf0d Humans have been eating cooked food from the time they discovered fire and since then people might also be preserving food to extend their keeping qualities, previously it was done just using salt and sugar as preservatives(we all do have fond memories of our mother making pickles at home and preserving it with sugar and salt), but today with advent of technology in food production operations, preservation also uses lot of technology.
In fact, now technology is so advanced that it is aiding not only in food preparation but preservation as well. And food preservation is now considered a very important part of the food and beverage industry and is given equal importance in the hospitality industry.
Food Preservation
Food preservation is the process of treating and handling food to stop or slow down food spoilage , loss of quality, edibility or nutritional value and thus allow for longer food storage. Preservation usually involves preventing the growth of bacteria, fungi (such as yeasts), and other micro-organisms, as well as retarding the oxidation of fats which cause rancidity. Food preservation can also include processes which inhibit visual deterioration, such as the enzymatic browning reaction in apples after they are cut, which can occur during food production.
Typically, preservatives attack the enzymes inside the microbes and this stops their cell reactions. Some can disrupt the microbe's cell wall so that substances cannot enter or leave the cell. These two processes kill or seriously slow the growth the food-spoiling microbes. Probably the most important use of preservatives from the food safety point of view is in processed meats such as ham, bacon, salami and sausages. Bacteria like clostridium botulinum can produce deadly poisons and the use of preservatives in such products is absolutely essential. Many processes designed to preserve food will involve a number of food preservation methods. Preserving fruit by turning it into jam, for example, involves boiling (to reduce the fruit’s moisture content and to kill bacteria, yeasts, etc.), sugaring (to prevent their re-growth) and sealing within an airtight jar (to prevent recontamination). Maintaining or creating nutritional value, texture and flavour is an important aspect of food preservation, although, historically, some methods drastically altered the character of the food being preserved. In many cases these changes have now come to be seen as desirable qualities – cheese, yoghurt and pickled onions being common examples.
The basic idea behind all forms of food preservation is either
- To slow down the activity of disease-causing bacteria
- To kill the bacteria altogether
In certain cases, a preservation technique may also destroy enzymes naturally found in a food that cause it to spoil or discolour quickly. An enzyme is a special protein that acts as a catalyst for a chemical reaction, and enzymes are fairly fragile. By increasing the temperature of food to about 150 degrees Fahrenheit (66 degrees Celsius), enzymes are destroyed.
Types of food preservation techniques Canning Food
In canning, the food is boiled in the can to kill all the bacteria and seal the can (either before or while the food is boiling) to prevent any new bacteria from getting in. Since the food in the can is completely sterile, it does not spoil. One problem with canning, and the reason why refrigeration or freezing is preferred to canning, is that the act of boiling food in the can generally changes its taste and texture (as well as its nutritional content).
Dehydrating Food
Many foods are dehydrated to preserve them example dehydrated milk, Since most bacteria die or become completely inactive when dried, dried foods kept in air-tight containers can last quite a long time. Soup and milk are easy to dry and last for years. Normally, drying completely alters the taste and texture of the food.
Freeze-Drying
Freeze-drying is a special form of drying that removes all moisture and tends to have less of an effect on a food's taste than normal dehydration does. In freeze-drying, food is frozen and placed in a strong vacuum. The water in the food then sublimates -- that is, it turns straight from ice into vapour. Freeze-drying is most commonly used to make instant coffee, but also works extremely well on fruits such as apples.
Salting and Pickling
Salting, especially of meat, is an ancient preservation technique. The salt draws out moisture and creates an environment inhospitable to bacteria. Pickling was widely used to preserve meats, fruits and vegetables in the past, but today is used almost exclusively to produce "pickles," or pickled cucumbers. Pickling uses the preservative qualities of salt (see above) combined with the preservative qualities of acid, such as acetic acid (vinegar).
Chemical Food Preservation
Chemical food preservation means, preserving food stuff using chemicals and additives. There are three classes of chemical preservatives commonly used in foods:
Benzoates (such as sodium benzoate, benzoic acid)
Nitrites (such as sodium nitrite)
Sulphites (such as sulphur
dioxide)
Another common preservative that you will commonly see on food labels is sorbic acid. All of these chemicals either inhibit the activity of bacteria or kill the bacteria.
Sorbic Acid / Sorbate
Sorbic acid (and its salts) are naturally occurring substances and they are among the most important food preservatives for industrialised countries.
Sorbic acid has two main advantages:
It is effective over a wide range of foods and beverages
It gives no taste or flavour to products
Sorbic acid is used in beverages, dairy products, fish and seafood, fat-based products, fruit and vegetable products, baked goods and confectionery product
Benzoate: Sodium Benzoate & Benzoic Acid
The two are related because sodium benzoate produces benzoic acid once dissolves in water, These have anti-microbial properties, best used for pickling. Naturally found in cranberries, prunes, plums, cinnamon, ripe olives, and apples
Sodium Benzoate is used in fruit products, relishes, beverages, dressings, salads, pies & pastries fillings, icing, olives.
Sulfur Dioxide
This preservative was known to the Romans, Ancient Greeks and Egyptians who used the gas to preserve wine. These preservatives are multifunctional food ingredients which act as preservatives, antioxidants and colour stabilisers. They have a much more pronounced antibacterial effect than other preservatives and are therefore used when control of bacterial growth is essential. Sulfur dioxide is used in a wide range of products including packet soup, dried bananas and apricots, tinned crabmeat, sausage meat, beer, wine, quick frozen chips and jams.
There are other types of preservatives which are widely used, these are:
Propionates
These are antimicrobial preservatives used in bakery products, cheese and fruits, The propionates are other examples of naturally occurring preservatives. They work better in the more alkaline conditions of bakery products and may be used, for example, to delay the green mould growth on bread.
Nitrites and Nitrates
These are antimicrobial used mainly in meat products example:
Potassium and sodium nitrate, these synthetic additives are capable of performing many functions in food preparation. They act as preservatives, stabilisers and flavours. There are health concerns about their use. However, without their contribution there would undoubtedly be many more deaths from botulism which is caused by the bacterium clostridium botulinum. Potassium and sodium nitrite are particularly important in the preservation of cured meat products.
Propyl Gallate: These are antioxidant used in baked foods and meats.
BHA and BHT: These are antioxidants used mainly in baked foods and snacks, meats, breakfast cereals, potato products
Tert- Butyl hydroquinone (TBHQ): These are antioxidant used in baked foods and snacks, meats.
Erythorbic Acid (iso-ascorbic acid) and Citric Acid: These are anti- enzymatic mainly used in soft drinks, juices, wine, and cured meats.
Food preservatives can also be classified as:
Class I preservatives or the natural preservatives such as salt, sugar, vinegar, syrup, spices, honey and edible oil; and
Class II preservatives or the chemical preservatives such as benzoates, sorbates, nitrites and nitrates of sodium or potassium, sulphites, glutamates, glycerides and the like.
Both, natural and chemical preservatives are categorised into 3 types:
Antimicrobials that destroy or delay the growth of bacteria, yeast and moulds. E.g. nitrites and nitrates prevent botulism in meat products. Sulphur dioxide prevents further degradation in fruits, wine and beer. Benzoates and sorbates are anti-fungal used in jams, salads, cheese and pickles.
Anti-oxidants that slow or stop the breakdown of fats and oils in food that happens in the presence of oxygen (Oxidation) leading to rancidity. Examples of anti-oxidants include BHT, BHA, TBHQ, and propyl gallate.
Anti-enzymatic preservatives : These block the enzymatic processes such as ripening occurring in foodstuffs even after harvest. E.g. Erythorbic acid and citric acid stop the action of enzyme phenolase that leads to a brown colour on the exposed surface of cut fruits or potato.
Food preservatives do have their merits and demerits:
Merits
Artificial food preservatives keep food from spoiling on the shelves, and they keep bacteria from growing in food after it is exposed to air, light, fungus or yeast. Some preservatives keep food from clumping or separating, and they help keep the texture consistent. Preservatives also can add nutrients lost in processing or include nutrients that the food does not normally contain. Flavours and colourings are added to foods to ensure that the food does not turn brown or to make food taste better to the consumer.
De-merits
Although these additives are essential for food storage, they can give rise to certain health problems. They can cause different allergies and conditions such as hyperactivity and Attention Deficit Disorder in some people who are sensitive to specific chemicals.
The foods containing additives can cause asthma, hay fever and certain reactions such as rashes, vomiting, headache, tight chest, hives and worsening of eczema. Some of the known dangers of food additives and preservatives are as follows:
Sodium Benzoate
Sodium benzoate, or benzoic acid, is a common preservative used in soft drinks, juices and pickles. It is used to prevent the growth of bacteria in foods that are highly acidic.
Nitrates
The problem with this preservative is that a cancer-causing agent called nitrosamines are created during the cooking process or in the stomach. The risk of getting cancer from hot dogs is small, but this preservative still has the potential. Even all natural products that contain no nitrites might still have high natural nitrites. The replacement is celery powder that sometimes contains 10 times the amount of nitrites as regular meats.
To minimise the risk of developing health problems, one should avoid the foods containing additives and preservatives. Before purchasing the canned food all the ingredients should be checked, one should buy organic foods, which are free from artificial additives. Freshly prepared foods should be consumed rather than processed or canned foods or to natural food preserves like rosemary extract, hops, salt, sugar, vinegar, alcohol, diatomaceous earth and castor oil are also used as traditional preservatives. Certain processes such as freezing, pickling, smoking and salting can also be used to preserve food. Another group of preservatives targets enzymes in fruits and vegetables that start to metabolise after they are cut. For instance, the naturally occurring citric and ascorbic acids in lemon or other citrus juice can inhibit the action of the enzyme phenolase which turns surfaces of cut apples and potatoes brown if a small amount of the juice is applied to the freshly cut produce. Vitamin C and Vitamin E can also be used as preservatives.
Even if we are bound to use ready to cook food because of our busy lifestyle and shortage of time , we must limit the intake of the food with preservatives.
(The writers are assistant professors, Banarsidas Chandiwala Institute of Hotel Management, New Delhi)
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