ABSTRACT
Worldwide, numerous varieties of vegetables and fruits for consumed by human but only a very portion is preserved through lactic acid fermentation to avoid perishability, improving palatability and enhancing nutritional quality. Fermented vegetables and fruits are part of the human diet throughout the world. In some places they constitute a minor 5 per cent of the dietary intake (Swain et al. 2014), and are often used during times of hardship, such as famine and drought. This ancient preparation and preservation technique has several advantages like increased digestibility, immunity, lowering of serum cholesterol, inhibiting carcinogenic compounds in the gastro-intestinal tract by reducing the fecal bacterial enzyme activity, etc. (Montet et al. 2014). During the process of lactic acid fermentation, carbohydrates are broken down by single or mixed forms of lactic acid bacteria (LAB) into lactic acid. The fermented products can be produced by using native knowledge, skill and traditional cultures, or by modern techniques employing defined starter culture (Bevilacqua et al., 2010). Fermented fruits and vegetables are vital foods of choice due to their excellent functional and nutritional properties aided by fermenting microorganisms, and novel bioactive compounds from these foods are an emerging area of research showing great promise. Bioactive compounds may be described as ‘food-derived components that in addition to their nutritional value exert a physiological effect on the body (Vermeirssen et al. 2014). Most lactic acid fermenting microorganisms produce organic acids, such as lactate, acetate, propionate and butyrate,
exerting anti-microbial compounds. Moreover, LAB are the predominant microbes in the fermented food products that produce various lowmolecular-carbon mass compounds, such as hydrogen dioxide, carbon dioxide, diacetyl (2, 3-butanedione), acetaldehyde, etc. and high-molecularmass compounds such as anti-microbial peptides and bacteriocins (Ray and Joshi 2014). Yeasts and moulds are associated with biosynthesis of enzymes, antioxidants and melatonin (Mas et al. 2014). An overview of bioactive compounds synthesized by microorganisms in fermented vegetables and fruits is depicted in Fig. 1.
