Microbiological and biochemical changes and sensory evaluation of camel milk fermented by selected bacterial starter cultures

Abstract

The microbiological and biochemical changes that occur during fermentation of camel milk inoculated with each of five selected starter cultures at 43oC for 6 h, were studied as well as the sensory evaluation of the products. The total viable counts of the starter cultures throughout fermentation period (6 h) showed that the combination of Lactobacillus bulgaricus CH2 plus Streptococcus thermophilus 37(1:1) had more counts and produce more acid (lower pH) compared to the single starter cultures. Also when comparing the different treatments, the amount of FAG released after 6 h was highest in the mixed starter cultures than in the corresponding single starter cultures. The final fermented milk products were free from pathogenic bacteria such as Salmonella spp, Staphylococcus aureus, Listeria monocytogenes, Escherichia coli O157:H7 and Bacillus cereus, while the total coliforms, yeasts and molds counts were less than 10 cfu per ml. The results of the sensory evaluation study indicated that the camel milk fermented by mixed yogurt culture was the most accepted while the one fermented by Lactococcus lactis was the least. However, the consistency of all fermented camel milk products was watery and showed a fragile, poor structure (poor scores). In general mixed yogurt culture showed superior growth, acid production and proteolytic activity than single starter cultures and acceptable fermented camel milk. Key words: Cultures, pathogenic bacteria, yeast, molds, camel milk.