Okara yoghurt – a high value-added fermented product from soybean curd residue

Abstract

Okara is a by-product that consists of insoluble parts of soybean that remain after filtration of the pureed soybean during the manufacturing of soymilk or tofu, which is often underutilized or dumped into the landfills and caused environmental pollution. However, being rich in nutrients, it can, therefore, serve as a good growth medium for lactic acid bacteria (LAB) and developed as fermented products. The purpose of this study was to develop a yoghurt formulation using okara and determine the physicochemical properties and chemical composition of the okara based yoghurt. In this study, different formulations were assessed to develop the okara yoghurt. Higher numbers of colony forming units (CFU/mL) of the LAB starter cultures were observed in okara yoghurt (4.3×109CFU/mL) in comparison to plain milk yoghurt (1.43×109 CFU/mL). A lower pH was attained due to the higher amount of titratable acidity (1.421±0.53%) produced at a faster rate, especially for okara yoghurt (without skimmed) in comparison to milk yoghurt. The chemical composition of the okara yoghurt showed a substantially higher amount of protein (4.46±0.0424%), carbohydrate (16.15±0%), fibre (4.43±0%) and energy (101±0 kcal), in comparison to the commercial milk yoghurt. Furthermore, the addition of okara in the yoghurt formulation also showed an increase in microbial growth during the fermentation due to the presence of dietary fibre. In conclusion, the incorporation of okara with the fortification of skimmed milk not only can enhance probiotic growth but also assist in improving the texture and producing a better taste of okara yoghurt. Therefore, the development of new okara yoghurt from soy by-product is a valuable approach where the low value and low-cost by-products can be turned into a high value-added product with health benefits.