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April 08, 2021 Thursday 12:15:15 PM IST

Enrich and Preserve Food

Guest Column

In our country, the preparation of fermented foods is a widespread tradition. The fermented products supply protein, minerals and other nutrients that add variety and nutritional fortification to otherwise starchy, bland diets. The fermentation process changes the physical and chemical properties of the original food and has been shown to improve the digestibility of carbohydrates and proteins, as well as increasing the levels of some vitamins and the availability of certain minerals. The whole process increases the shelf life and decreases the need for refrigeration or another form of food preservation technology. It also adds value to the product by improving nutrition quality and by adding variety to the original food. It is, therefore, can be a highly appropriate technique as a method of food processing.

What is Fermented Food?

Natural fermentation occurs when microorganisms are allowed to react with susceptible organic substrates. Fermentation, initiated by the action of micro-organisms occurs naturally and is often part of the process of decay, especially in fruits and vegetables. However, fermentation can be controlled to give beneficial results. Fermentation makes changes in food materials that were quickly recognized to be desirable.

Fermented foods are those foods, which are prepared involving micro-organisms (or enzymes) to alter the properties of the food, for example, yoghurt, cheese, wine or bread. The purpose of fermenting food is often to get a better taste or texture and enhance the shelf life of food.

Ancient and Indigenous

Fermentation is one of the most ancient and most important food processing technologies in the world. Indigenous fermented foods such as bread, cheese and wine, have been prepared and consumed for thousands of years and are strongly linked to culture and tradition, especially in rural households and village communities.

Fermentation is a relatively efficient, low energy preservation process that increases the shelf life and offers unique opportunities and challenges to food processing industries. It is, therefore, a highly appropriate technique for use in developing countries and remote areas where access to sophisticated equipment is limited.

The main advantages of fermentation as a method of food processing are:

The production of food with special flavors or textures, which cannot be produced by other methods.

The use of mild conditions of pH and temperature, helps in maintaining the nutritional properties and sensory characteristics of the food.

Generally simple technology, relatively low capital and operating costs, and low energy consumption due to mild operating conditions.

In addition to the roles of fermentation in the preservation and providing variety to the diet, there are further important consequences of fermentation. Several of the end products of food fermentation, particularly acids and alcohols are inhibitory to the common pathogenic micro-organisms that may find their way into food.

Fermented foods often are actually more nutritious than their unfermented counterparts. Micro-organisms not only are catabolic, breaking down more complex compounds but they also are anabolic and synthesize several complex vitamins and other growth factors. Thus the industrial production of such material as riboflavin, vitamins B12 and the precursor of vitamin C is largely by special fermentation processes.

Improved Nutrition

The second important way in which fermented foods can be improved nutritionally has to do with the liberation of nutrients locked into plant structures and cell by indigestible materials,(in case of certain grains and seeds). Milling processes do much to release nutrients from such items by physically rupturing cellulosic and hemicellulosic structure surrounding the endosperm, which is rich in digestible carbohydrates and proteins. Fermentation especially molds breaks down indigestible coatings and cell walls both chemically and physically. Molds are rich in cellulose- splitting enzymes, in addition mold growth penetrates food structures by way of its mycelia. This alters texture and makes the structures more permeable to the cooking water as well as to man’s digestive juices. Similar phenomena result from the enzymatic actions of yeasts and bacteria.

A third mechanism by which fermentation can enhance nutritional value, especially of plant materials, involves enzymatic splitting of celluose, hemicellulose and related polymers not digestible by man into simple sugars and sugar derivatives. Cellulosic materials in fermented foods similarly can be nutritionally improved for human consumption by the action of microbial enzymes.

Changes to Food

The mild conditions used in food fermentations produce few of the deleterious changes to nutritional and sensory quality that are found with many other unit operations. Complex changes to proteins and carbohydrates soften the texture of fermented products.

Food becomes more nutritious (curd, paneer, cheese). Microorganism secrete vitamins into the food and improve nutritious value. Fermented products are a great source of amino acids, vitamins, and minerals. The process of fermentation increases the amounts of some vitamins. Fermented milk is a great source of energetic B vitamins while fermented vegetables are a great source of Vitamin C.

Fermentation foods are safe for consumption. (complex changes to protein & carbohydrates softens the texture of products.

Improved digestibility (for example, in case of Arhar)

Taste / Flavour changes

Reduction in sweetness and increase in acidity due to fermentation of sugars to organic acids.

An increase in saltiness in some foods (pickles, soysauce, fish and meat products due to salt addition)

Reductions in bitterness of some foods due to the action of debittering enzymes.

The aroma of fermented foods is due to a large no. of volatile chemical components (is amines, fatty acids, aldehydes esters and ketones) and products from interactions of theses compounds during fermentation and maturation.

Colour Changes

Added chemicals (i.e. nitric and nitrate salts in fermented meat products).

Enzymes changes to pigments (i.e. degradation of chlorophyll and enzymic browning)

Fermentation of brown pigments by proteolytic activity.

Production of pigments by micro-organisms (i.e. the red colouration of fermented rice by Monascus purpureus.

Microbial Activities

Some of the most common and significant types of microbial activity in foods are indicated below.

Sugar fermented by yeast, such as saccharomyces cerevisiae and s.ellipsoideus yields ethyl alcohol and carbon dioxide. This is the basis of wine and beer production and the leavening of bread. Alcohol from yeast fermented cider, in the presence of oxygen will be further fermented by bacteria such as Acetobacter acetic to acetic acid. This is the milk, fermented by streptococcus lactic bacteria gives lactic acid which curdles the milk to yield cottage cheese or curd from which other cheeses can be made.

Acids produced from fermentation in the presence of oxygen can be further broken down by proteolytic bacteria such as Proteus vulgaris and other organisms yield a wide range of nitrogen containing compounds that give putrid and decayed odours to food.

Lipids broken down by lipolytic bacteria such as Alcaligenes lipolyticus other organisms yield fatty acids. These and their subsequent breakdown products contribute to rancid and fishy odours.

Low acid foods supporting growth of Clostriduim botulerium may contain toxins produced by this bacterium. This food – poisoning organism will not grow in fermented foods high in acid.

Fortification

Fermented foods offer great opportunities in food fortification as it offers many desirable changes in food. Food fermentations can be used for the production of varied fortified products from milk, fruits, vegetables, cereals, legumes and meat  etc. There is tremendous scope and potential for the use of micro-organisms towards meeting the growing world demand for food, through efficient utilization of available natural food and feed stocks and the transformation of waste materials. Optimal conditions for fermentation process i.e an appropriate substrate and microorganism, suitable environmental conditions for the growth of selected microorganism in order to get desired fermented product need to be studied which could be used for food fortification.




Dr Anupama Singh

Professor & Head Department of Food Engineering National Institute of Food Technology and Entrepreneurship Management (MOFPI), Haryana.

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