Effects of stabilizers and exopolysaccharides on physiochemical properties of fermented skim milk by Streptococcus thermophilus ST1

Abstract

In this study, the effects of exopolysaccharide (EPS) produced by Streptococcus thermophilus ST1 and stabilizers on the textural and microstructural properties attributes of fermented skim milk were investigated. ST1 had a high capacity to produce acids and EPS. Within 4.5 h, the pH dropped to 4.5, the acidity reached 0.8%, and EPS reached 65.27 mg/L. ST1 was more effective at increasing viscosity as well as water holding capacity and reducing spontaneous whey separation compared with control sample (ST0). ST1 combined with carrageenan had the highest viscosity and the best water holding capacity as well as the lowest spontaneous whey separation. ST1 combined with whey protein concentrates showed better results with xanthan, but worse with carrageenan. The microstructure of the fermented milk was examined using scanning electron microscopy. ST1 combined with carrageenan resulted in compact and uniform structure, which is agreed with quality improvement of fermented skim milk that used ST1 combine carrageenan as fat substitute. Key words: Streptococcus thermophilus ST1, exopolysaccharide, fermented skim milk, texture.