Physicochemical, rheological, and micro-structural properties of yogurts produced from mixtures of camel and bovine milks

Abstract

This study evaluated the influence of supplementing bovine milk with increasing levels of camel milk (0–60%) on different properties of yogurt. Fresh raw camel and bovine milks were heated separately at 85 °C for 5 min and mixed before fermentation with lactic acid bacteria. The decrease in gel strength after camel milk addition caused a decrease in viscosity and related parameters including G', G", stringiness, and syneresis. The Bostwick consistency values increased with increasing proportions of camel milk providing further evidence that the produced yogurts are less viscous and have higher water holding capacity and lower gel contraction during storage. Scanning electron micrographs showed that the addition of camel milk to bovine milk led to larger and less differentiated casein micelles. After fermentation, the pH of all yogurts was 4.5–4.6 and it decreased to 4.3 after 2 weeks of storage suggesting that the soft gels caused by the addition of camel milk is due to the structure and concentration of its proteins rather than limitations related to bacterial growth. The results obtained in this work are of particular interest especially in the understanding of how variation in milk protein composition may affect its gelation properties.