| With the increasing improvement of quality of life and the rapid development of food industry,the dietary consumption demand gradually tends to green,healthy,health care and nutrition functional food,the fermented walnut milk rich in functional conjugated fatty acids exactly meets what people need.At present,the research of walnut milk beverage is limited to the improvement of product formulation and optimization of processing technology,and the exploration of biological activity and the development of specific nutritional functions are few,which does not give full play to the resource advantages and nutritional health effects of walnut.Moreover,the flavor,stability and nutritional function of fermented walnut milk also bring some challenges to product development.This study aimed to develop a functional fermented walnut milk rich in conjugated fatty acids with good stability and flavor.Firstly,we discussed the growth characteristics of different strains at different water ratio of walnut milk,seven strains of probiotics with high conversion ability of conjugated fatty acids on MRS were inoculated into walnut milk with different ratio of material to water,depending on the p H and the number of viable bacteria,four strains of Lactobacillus plantarum ZS2058,Lactobacillus casei FZSSZ3-L1,Lactobacillus rhamnosus JSWX-3L-2 and Bifidobacterium breve CCFM683 were preliminary screened for walnut milk fermentation and the ratio of material to water were determined for 1: 5.By exploring the effects of different enzymatic hydrolysis conditions,fermentation time and free fatty acid content on the content of conjugated fatty acids in fermented walnut milk,it was found that conjugated fatty acids were only produced in fermented walnut milk by B.breve CCFM683.In addition,when the lipase content was 60 U/ m L,hydrolyzed at 37℃ for 3 h,inoculated with CCFM683 after pasteurization,and fermented for about 20 h,the maximum content of conjugated fatty acids reached 2.30 mg/ m L,of which CLA was about 1.29 mg/m L and CLNA was about 1.01 mg/ m L.Considering emulsification stability coefficient and centrifugal precipitation rate as indexes,it was found that pectin,gellan gum and CMC had certain stabilizing effect on walnut milk system by single factor experiment.The orthogonal experiment showed that under the optimal conditions of 0.6% CMC,0.04% pectin and 0.02% gellan gum,the emulsification stability coefficient and centrifugal precipitation rate were 1.13 times and 0.91 times,respectively,and the stability of fermented walnut milk was excellent.By the determination of volatile flavor substances and fatty acid composition,the changes of flavor quality of fermented walnut milk with different mass fraction and different kinds of antioxidants during storage were analyzed.Adding 0.016% vitamin E as an antioxidant could inhibit the oxidation of oleic acid,and the content of volatile phoenix flavor substances produced by the oxidation of linoleic acid and linolenic acid was also significantly reduced compared with other antioxidants,and the condition of fat oxidation in fermented walnut milk drink was improved.Combined with apparent preference,preference,taste preferences and texture preferences degrees this sensory evaluation on the four sensory properties,adding 10% 0.075% of walnut essence and sugar fermentation walnut milk has the highest overall preference,got point of 5.8,and the products were pale,with uniform texture,sweet and delicious taste,combined with walnut aroma and fermented flavors.The sensory properties,viscosity,particle size and centrifugal precipitation rate of fermented walnut milk at different storage temperatures were determined by accelerated experiments.The correlation coefficient between centrifugal precipitation rate and sensory score was relatively high,so the shelf life prediction model of fermented walnut milk was established based on centrifugal precipitation rate,and it was calculated that the shelf life of the product was 186 d under normal storage temperature. |
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