ADVANCES IN PREBIOTICS AS FUNCTIONAL INGREDIENTS

Prebiotic components are non-digestible, carbohydrate-based food ingredients that selectively stimulate the growth and/or activity of one or a limited number of bacteria in the colon. Prebiotics consist mainly of oligosaccharides, which are sugar molecules of three to six monomers in chains. These include fructooligosaccharides (FOS), galactooligosaccharides (GOS), xylooligocsaccharides (XOS) etc. These prebiotic components are not digested by enzymes of the gastrointestinal tract, but are digested and metabolized by specific bacteria in the large intestine, potentiating the function of probiotics and promoting gut health. The biological properties of prebiotics such as immunomodulatory activity, anticancerous activity, growth regulatory activity, antimicrobial activity, and other biological activities are other added significant characteristics of the molecules mediated by the probiotic bacteria. Many are used as functional ingredients in food systems to modify texture and mouth feel or as fat replacers. The potential of these non-digestible oligosaccharides as prebiotics has drawn the attention of functional food researchers, molecular biologists, immunologists and clinicians. Attempts are being made to produce XOS from the xylan in agricultural biowastes, such as cereal bran and corn cob; FOS from fructans; FOS and GOS by enzymatic biosynthesis and fermentation technology using microbes.

Based on preliminary screening of forty-eight foods consumed in south India, Nendran banana (1.43 g/100g) and country garlic (15.5 g/100g) were found to contain significant amounts of fructan. Among the banana cultivars studied, Nendran contained FOS, particularly 1-kestose. Low temperatures during ripening accumulated fructan in the fruit. Nendran banana showed the highest Prebiotic Activity Score, even higher than commercial FOS and inulin. Garlic contained more inulin than FOS. Fructan composition was affected by processing, namely steaming, pureeing and drying in Nendran banana. The garlic fructan incorporated in dry mixes such as soup mix, rasam mix and atta was altered by the processing methods. Atta incorporated with garlic extracted fructan showed less than 7% degradation of fructan during processing.

The enzymatic conversion of xylan from rice bran and finger millet seed coat to XOS, followed by evaluation of their prebiotic efficacy and enrichment of bread was successfully carried out. XOS were incorporated in bread and cookies by partial replacement, up to 30% of the sugar.