Efficacy of Alginate-Taro (Colocasia esculenta L. Schott) Starch for Yoghurt Starter Culture Encapsulation

Abstract

Yoghurt is a probiotic product due to the presence of beneficial microorganisms so-called lactic acid bacteria (LAB). However, the viability of LAB in the product must reach the optimum microflora balance of 106 to 108 cfu.ml^-1 to be considered as probiotic and for consumers to enjoy its health benefits. One of the alternatives in maintaining the viability of LAB in yoghurt is to encapsulate the LAB cells which would protect the cells from the environment. In this study, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, the yoghurt starter cultures, were encapsulated in different levels of alginate-taro starch matrix. Physico-chemical properties of the reconstituted skim milk medium and the sensory qualities of resulting yoghurt were determined. The developed alginate-taro starch encapsulated, non-encapsulated and pure alginate encapsulated starter cultures were compared in terms of their effectivity in yoghurt production. The highest percentage of taro starch (1.5%) was found to retain a high viable cell count of 3.4 x10¹⁰ cfu.ml^-1 after 12-day storage at 4oC. No significant effect of encapsulated starter cultures was observed on the physico-chemical properties (i.e. pH, TSS, and % lactic acid) of reconstituted skim milk. Incubation and storage periods significantly affected the physico-chemical properties of the reconstituted skim milk (p <0.05). No significant differences among the treatments were found for sensory qualities. However, the yoghurt produced from 4% alginate-1.5% taro starch-encapsulated LAB, which was stored for 2 weeks, was found to be acceptable due to its right degree of sweetness and acidity and similarity with the control treatment. It can be concluded that taro starch is, indeed, a potential wall material that can be used with alginate to encapsulate yoghurt starter cultures and can retain or increase the lactic acid bacteria cell viability without affecting the activity of the cultures.