Characterization of curd made with lao-chao culture filtrate and probiotics

The purpose of the study is to combine the physiological functionality of probiotics (Lactobacillus acidophilus and Bifidobacterium longum) and the milk-clotting activity of culture filtrate from lao-chao to develop a new dairy product which was different from the commercial yogurt. Rhizopus javanicus and Saccharomyces cerevisiae were chosen as a mold and yeast starter for production of culture filtrate. The probiotics of this dairy product grows well. The increase of β-galactosidase activity, lactic acid and acetic acid content accompany long incubation time. The more incubation time prolonged, the more curd firmness and syneresis increased. It is especially prominent when incubating time more than 2 hours. Storage results showed both L. acidophilus and B. longum exhibited excellent stability for 14 days at 4℃ in curd made with lao-chao culture filtrate. The suggested percentage of culture filtrate is 8-10% which has better effectiveness on the flavor and texture of this product.
Microencapsulation of probiotics and culture filtrates from lao-chao by spray-drying was also examined. The effect of moisture, water activity, particle density, encapsulated product size distribution, microencapsulation efficiency, milk-clotting activity, structure of the powders and viability of microencapsulated probiotics were studied. Among the various outlet air temperatures, probiotics showed the higher survival after drying in the lower outlet air temperatures. The survival of probiotics in simulated gastric juice and 0.3% oxgall was good since microencapsulation preventing probiotics from acid and oxgall damage. The milk-clotting activity has no significant differences during 5-week storage period. The survival percentage of 4℃ microcapsules is higher than 25℃ group.
Among varied antioxidant activity examined, yogurt has the highest inhibition of ascorbate autoxidation. The reducing activities among different treatments were 29.19-80.31%. The chelating effects of various treatments on ferrous ion showed that lao-chao culture filtrate, curd made with lao-chao culture filtrate, and yogurt were 88.88, 92.18, and 80.58% respectively. The rehydration of microcapsules made with various outlet air temperatures exert higher scavenging effects on superoxide anion.
This study intents to develop a new oriental flavor dairy product and provide consumer multi-choices. This product is full of nutrition and meets the increasing health needs across the globe.