Quality Evaluation of Soycorn Yoghurt Fermented with Starter Culture and Corn Steep Water

Abstract

This study aimed at producing yoghurt from corn and soybean milk using starter culture and corn steep water for fermentation and evaluating its qualities. Yoghurt was produced from three blends of corn milk and soymilk (70:30, 50:50, 30:70) and starter culture (Streptococcus thermophilus and Lactobacillus bulgaricus) and corn steep water were used for fermentation for 16 h at 36 oC respectively. After fermentation the yoghurt samples were refrigerated for 3 h to terminate the process of fermentation and the yoghurt samples were homogenized, sweetened and flavoured. The physico-chemical properties, physical properties, chemical composition and microbiological quality of the yoghurt samples were determined. Organoleptic properties of the yoghurt samples was evaluated using 10- membered panel and the yoghurt samples were compared with Hollandia yoghurt. All results were subjected to analysis of variance (ANOVA) at P< 0.05 and means were separated using Duncan multiple range tests. The pH (6.1- 6.3) of the samples was not significantly different before fermentation but became significantly different after fermentation (4.0- 4.4) at P< 0.05. The titratable acidity was 0.17% before fermentation but was 0.66 – 1.07% which was significantly different after fermentation. The specific gravity before fermentation ranged from 1.01- 1.02 and 1.01 and 1.03 after fermentation with no significant difference. There was significant difference in the syneresis (16.3 – 27.4 %) with samples fermented with starter culture having higher rate of syneresis. Chemical composition of the samples differ significantly though there was no marked difference between samples fermented with starter culture and corn steep water. The lactic acid bacteria count ranged between 1.0 × 104 - 5.0 × 104 Cfu/ml and the results of sensory evaluation showed that there was no significant difference in all the yoghurt samples except the control. Thus, there was no marked difference in the qualities of soycorn yoghurt fermented with starter culture and soycorn yoghurt fermented with corn steep water.