Shreds of evidence show the process of fermentation to be used by man as early as 7000 BC to extend the shelf life of food that was available during the time of plenty to be consumed during the times of food shortage. Both plant and animal materials such as raw fruits, seeds, vegetables, tubers, legumes, cereals, meat, milk, fish, etc. have been preserved by exploiting this technique. However, the distribution and popularity of the type of fermented food vary from one region to other. In Southern India and much of southeast Asia, fermented legumes such as soyabean; vegetables, fish, and meat form an essential component of the diet. Similarly in Europe, North America, and the Northern regions of India fermentation of cereals is carried out for bread making. While fermented seeds make an important dietary component in Africa and South America.
Fermentation is predominantly an anaerobic process in which microorganisms obtain energy from available food items, and act on them to convert them into alcohols, carbon dioxide, and/or organic acids. Ethanol and Lactic acid are two such products resulting from the primary fermentation of sugars. In addition fermentation, depending on the type of food material or substrate used for the process also results in the production of propionic acid, acetic acid, citric acid, and malolactic acid. During fermentation, microorganisms also carry out the reaction in which many healthy metabolites such as conjugated linoleic acid (produced by conversion of fats), amino acids, bioactive peptides, short chain fatty acids ( SCFA), vitamins, etc. are produced adding value to the fermented food product.
Fermentation of foods is mainly carried out through microbial populations naturally inhabiting the raw food. However, in certain cases, microbial culture may be taken from previously fermented products. Bacterial populations abundantly found in different fermented foods are Lactococcus lactis, Lactobacillus acidophilus, Pediococcus, Leuconostoc, Acetobacter, Arthrobacter, Bacillus, Bifidobacterium, Brachybacterium, Brevibacterium, Enterobacter, Klebsiella, Micrococcus, Pseudomonas, and Staphylococcus. Similarly, the yeast genera identified in various fermented foods include - Saccharomyces, Saccharomycodes, Saccharomycopsis, Schizosaccharomyces, Torulopsis, etc and filamentous molds include- Aspergillus, Mucor, Neurospora, Penicillium, Rhizopus, etc.
Fermented foods have been linked with several health benefits such as – easy and quick digestion, high nutrient value due to the presence of certain bioactive compounds released during fermentation ( as mentioned above), growth-promoting effect on gut microbiota, and inhibition of disease-causing microbes in the gut. Consumption of yogurt has health benefits such as the reduced risk of cardiovascular diseases, type II diabetes, and mortality. Similarly, fermented dairy products have been reported to be associated with weight management. Another fermented food popular in Korea called ‘Kimchi, is reported to show anti-diabetic and anti-obesity effects. Further, studies also show fermented foods to be associated with mood, brain function, and the gut microbiome.
Sonam Mhavale, Medical Biotechnology student.
Fermented foods are easily digestible as complex carbohydrates and proteins undergo breakdown during the process of fermentation. The transformation of certain components present in raw foods during fermentation process makes them safe to be consumed by people having intolerance towards them. For example, lactose intolerant people can consume fermented products like cheese in which the level of lactose is significantly reduced. Further fermentation also decreases certain anti-nutritional substances present in raw food.
Bioactive peptides produced by different bacteria during fermentation have several health benefits. Isoleucine–proline–proline (IPP), valine–proline–proline (VPP) and angiotensin-1-converting enzyme (ACE)-inhibitory peptides are a few of these that confer anti-hypertensive benefits. Additionally, the exopolysaccharides ( EPS), produced by fermenting bacteria have been reported to have the ability to lower cholesterol levels and immunomodulatory effects. Many studies have shown the modulation of the gut microbiome by fermented foods. This could either be due to the microorganisms present in fermented foods or due to the nutrients available in them.
All these applications of fermented foods make them a very valuable healthy food, especially now when several emerging pieces of evidence highlight the role of gut microflora in the total well-being of the body and mind as well as in the management of many metabolic disorders