Shelf Life Profile Of Soymilk Beverage Using Starter Culture (lactobacillus Bulgaricus And Streptococcus Thermophilus).

1.0 INTRODUCTION

Soymilk is a rich creamy liquid extract of soybean (Glycine max) (Tunde-Akintunde and Souley, 2009) and is the most available soy product. Soymilk is a popular nutritive beverage alternative to cow’s milk and is even cheaper(Soya-Agrodok, 2005). Soymilk has become a very interesting food due to its extraordinary nutritive value and health characteristics. It is a very rich source of highly valuable proteins, unsaturated fatty acids, soluble and insoluble dietary fibres, and isoflavones whose presence in everyday diet is very important (Boani, 2006). In some countries, soymilk is intended for the population who cannot digest milk due to lactose intolerance, allergy to milk proteins, or vegetarian way of diet. Soymilk has limited consumer acceptability due to its undesirable beany flavour. to improve its acceptability due to reduction in objectionable flavour and oligosaccharides such as starchyose and raffinose that cause flatulence (Wang et al., 2002). (Akabanda et al. 2010) reported that fermentation of soymilk provides a possibility for modifying or improving its flavour and texture so that it becomes more acceptable. 

In western countries, soymilk is intended forpopulation who cannot digest milk for reasons like lactose intolerance, allergy to milk proteins, or vegetarian way of diet. Fermenting soymilk with lactic acid bacteria considerably increases its health value. Because of greater antioxidative actions (Wang etal. 2006), they are considered healthier than pure soymilk. The purpose of fermentation is to remove the undesirable beany taste which is mostly due to the presence of n-hexanal and pentanal , and to improve on the nutritional characteristics of soymilk. Several studies (Hong et al., 2004; Song et al., 2008) have reported numerous benefits of fermented soymilk including degradation of soybean allergens during fermentation by proteolytic enzymes. Due to the characteristics of milk that is highly perishable, the purpose of milk fermentation using lactic acid bacteria is to prolong its shelf life as well as to preserve the nutritious component of milk.

1.1 PROBLEM STATEMENT  Development of a beany flavour during processing of soy milk has limited its use amongst populations. Thus much effort has been directed toward elimination of beany flavour in processing of soy milk. Heating of the soybeans either before or during initial processing to inactivate lipoxygenase and the use of fermentation has been used to stop undesirable flavours in soymilk. 

The heating process during conventional soy milk making considerably destroys most of the anti-nutritional factors in soy milk and improves the digestibility of soy protein, as well. However, compounds, like phytic acid, which interferes with the availability of calcium, is not reduced effectively (Onourah et al., 2007). At the same time, over-heating to eliminate trypsin inhibitor activity to a great extent can cause damage to amino acids, as well as loss in the overall nutritional value of soy milk. Incorporating the fermentation process into soy milk production has become a popular method to improve the acceptability and health properties of soy milk.

1.2 AIM

• The aim of this study is to examine the effect of starter culture (lactobacillus bulgaricus and streptococcus thermophilus) in the fermentation of soymilk.

1.3 OBJECTIVES

• To examine the effect of Lactobacillus bulgaricus and Streptococcus thermophilus in the soymilk mixed with milk respectively.

• To know the effect of Lactobacillus bulgaricus and Streptococcus thermophilus in the soymilk mixed with sugar respectively.

• To know the effect of both organisms (lactobacillus bulgaricus and streptococcus thermophilus)in the soymilk mixed with sugar and milk respectively.

• To examine the proximate analysis of both fermented and non-fermented soymilk

• To examine the sensory evaluation of the fermented soymilk product. 

• Determination of shelf life of the final product.