Study On The Processing Technic Of Fermented Walnut Milk With Probiotics And Product Optimization

Seven suspected lactic acid bacteria strains were isolated from the special fermented foods white sour soup and pickled Chinese cabbage in Guizhou province of China.After the analysis of physiology and biochemistry and 16S r DNA gene sequence,the results showed that the percentage of ties of consanguinity between ST-2?ST-5 and lactobacillus plantarum,SC-3 and lactobacillus plantarum CE28.17,ST-4 and lactobacillus plantarum CE7.11,SC-2 and lactobacillus plantarum KCC-1,SC-1?SC-4 and lactobacillus plantarum C42 was higher than 99%.Based on the result of growth characteristic experiment,the isolated strains had excellent growth performance and acid-production efficiency.The walnut slag was selected as raw material to screen the dominant strains in the fermented walnut milk.The growth performance,acid-production efficiency,sensory properties and ability of decomposing protease of seven strains in walnut slag were investigated.The results demonstrated that after 12h fermentation in 37?,the viable count,pH value and amino acid nitrogen of SC-2 and ST-2 bacteria in seven strains were 9.87×10~8 cfu/mL and 1.06×10~9 cfu/mL,3,87 and 3.71,57.4mg/kg and 56mg/kg,separately.The SC-2 and ST-2 bacteria had a higher acid-production efficiency,stronger growth performance,better sensory properties and texture.In addition,the protein production ability of these two strains were 0.801U/mL and 2.045U/mL,and the protein production ability of other five strains were not detected.As the result,the two strains SC-2 and ST-2 were selected as the dominant bacteria in the fermented walnut milk.The SC-2 and ST-2 were screened as the dominant bacteria and the response surface method was used to optimize the fermentation process of walnut milk.The pH value,acidity,viable count and sensory test score after 12h ripening were regarded as reference indexes,the response surface optimization combined experiment with four-factors(inoculum size,ratio of strain,fermentation time and temperature)and three-levels was built to explore the optimal processing conditions.The results showed that the optimal processing conditions were 2:1 of ratio of strain,7%of inoculum size,41?fermentation temperature and 12h of fermentation time.Under these conditions,the pH value,acidity,viable count and sensory test score after 12h ripening were 3.89,22.5g/kg,7.65×10~8cfu/mL and 80,respectively.Compared with the walnut milk without fermentation,the amount of amino acids in fermented walnut milk was increased by 0.1627%.And furthermore,compared with the lactic acid content in walnut milk fermented with the single lactobacillus,the lactic acid content in walnut milk fermented with the SC-2 and ST-2 bacteria was significantly higher.It showed that the combination of SC-2 and ST-2 bacteria was beneficial for the fermentation of walnut milk.A sour milk beverage was developed using the fermented walnut milk.The sensory test score using fuzzy mathematics method was regarded as the reference index,the response surface method with three-factors and three-levels was used to investigate the optimal processing method of the novel sour milk beverage.The results showed that the additive amount of fermented walnut milk,sugar and compound stabilizer were 55.21%,6.24%and 0.37%,separately.Under these conditions,the sour milk beverage had uniform texture,suitable acidity,strong flavor,and the sensory test score was 85.8.In addition,the physicochemical indexes of this sour milk beverage matched the requirements of GB7101-2015.