| Camel milk is a kind of special dairy products with high nutritional value and medicinal value, and form many probiotic groups with good passage and unique flavor under natural fermentation. However, due to the significant differences between camel milk and the other special milk as well as the scarcity of resources, the current degree of development of camel milk is at a low level. This study started with the strains screening from naturally fermented camel milk with good fermentation characteristics, then optimally complex with the universal yogurt fermentation agent, for preparing high vigor camel milk fermentation agent. Continue to study the impact of different formulations and processing conditions on camel milk fermenting and sensory quality. Using sugar alcohols instead of sucrose, and study the additive amount and fermentation time for developing the long-shelf-life and low-calorie fermented camel milk products. The main conclusions are as follows:1. Isolating and identificating the lactic acid bacteria from Xinjiang naturally fermented camel milk, and ultimately get 60 lactic acid bacteria. 46 of them are Lactobacillus helveticus, 6 of them are Pediococcus pentosaceus, 6 of them are Lactobacillus plantarum, 3 of them are Pediococcus acidilactici, and 3 of them are Lactobacillus kefiri. The 16 S rRNA gene sequence analysis showed that the similarity ratio of 99% or 100%.2. Traditional yoghurt culture inoculated with different amounts into camel milk, which found the Lactobacillus bulgaricus and Streptococcus thermophilus in traditional yoghurt culture capable of growth and metabolic activity preferably in camel milk, so that the pH value of camel milk significantly reduced. When added Traditional yoghurt culture in an amount of 0.1%(mass fraction), the fermented camel milk has the best sensory qualities. The growth activity five different lactic acid bacteria was measured and found the viable cell count reached 109 cfu/mL after 14 hours’ cultivation in culture. By bile salt and acid resistance test that screened out five lactic acid bacteria can not tolerate acidic and bile salt environment of the gastrointestinal tract. By fermenting agent complex experiment shows that Lactobacillus helveticus compared to the other lactic acid bacteria has better acid production, and gives the product better sensory quality. Getting the best complex add ratio: Lactobacillus helveticus fermentation agent added 2%, traditional yoghurt culture 0.1%.3. Depending on the product stability combined time cost production industrialization, select 1: 9 ratio of water to flour camel milk powder recovery, and the refrigerating time after recovery is 10 h. After the termination of fermentation, the ripening time of the product is determined as 30 h. According fermentation acidity and sensory qualities in different additive amounts of sugar, the amount of sucrose determined to be 7.5%(mass fraction). Combining the impact of different sterilization conditions on the product stability, rheological properties, storage stability and sensory quality, select 90℃ 2 s sterilization conditions on fermented camel milk for secondary sterilization.4. In the low-calorie fermented camel milk experiment with sugar alcohol substituting sugar, finding that with the increase of the added amount of xylitol, after 6 h fermentation, the acidity of the milk system can reach 80 oT. When the amount of xylitol was 8%, fermented camel milk products had the highest sensory quality. The effect of erythritol on the fermentation process agent acid production was not significant at a small amount. But when the amount exceeds 10% and gradually increased, the acidity of fermented camel milk reduced and pH increased. Adding the amount of erythritol at 11%, the sensory quality of the product was the best. However, there are still significant differences compared to the optimal amount of xylitole. In the L9(33) orthogonal test, the optimum amount of complex programs is added xylitol and erythritol are both 4%(mass fraction), and fermentation time is 6 h. |
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