Effects of optimizing fermentation time and stabilizers using response surface methodology on physicochemical properties of camel milk yoghurt

Abstract

The objective of this study was to produce camel milk yoghurt with desired qualities using optimized processing conditions (fermentation time) and ingredients (stabilizer and calcium chloride). The conditions were obtained through Response Surface Methodology (RSM) by lactic acid fermentation by inoculating the milk with Lactobacillus delbrueckii subsp. Bulgaricus (YF-L903, CHR Hansen, Denmark. The study also determined the effects of fermentation time and ingredients on the quality of yoghurt. Fermentation time ranged from 2 to 22 h while stabilizer (corn starch) and calcium chloride (salt) ranges were 1.65–3.34 and 0.061–1.23 % respectively. The quality was monitored hourly for a fermentation period of 2–22 h by determining pH, total titritable acidity (TTA) and viscosity. Results indicated that viscosity was influenced by fermentation time, stabilizer and calcium chloride. The viscosity was increased from 0.01 to 0.4 and 0.01 to 0.3 by fermentation time, 0.01 to 0.2 and 0.01 to 0.3 by stabilizer and 0.01 to 0.5 and 0.01 to 0.6 Pa s by calcium chloride. Whereas the combined effects of calcium chloride and stabilizer increased the viscosity of yoghurt to 0.94 Pa s. Prolonged fermentation time, led to an increase in TTA and a decrease in pH. The finding from this study indicated that the optimal conditions required to produce camel milk yoghurt with desired qualities are a fermentation time of 10 h using 2.33 and 0.60 % corn starch and calcium chloride respectively. Under these conditions the produced camel milk yoghurt quality properties were a pH of 4.07, 0.32 % TTA and a viscosity of 0.35 Pa s.

Keywords

• Optimization
• Viscosity
• Fermentation time
• Camel milk
• Yoghurt