Development Of Quinoa Milk Fermented By Kefir And Its Freeze-Dried Food

In recent years,as the pace of life changes,most people are in the state of sub-health,and the development of a functional food that is beneficial to human digestion has become a hot topic.In the field of dairy products,compared with animal-based fermented milk,plant-based fermented milk has the characteristics of low fat and no cholesterol.As a plant food with comprehensive nutrition,quinoa has quickly entered people’s horizons and is widely popular with nutritionists.In this paper,quinoa malt thick pulp is used as raw material to obtain quinoa fermented milk after Lactobacillus kefir fermentation.The quinoa fermented milk is mixed with sea buckthorn puree,yellow peach thick pulp and carrot thick pulp,and then it is made into grain,fruit and vegetable crisp products by vacuum freeze-drying.Using an in vitro model of gastrointestinal digestion simulation,the digetive properties and antioxidant properties of the quinoa thick pulp unfermented group,quinoa milk fermented by kefir group,and fruit and vegetable juice mixed with quinoa milk fermented by kefir group were studied.It has laid a solid theoretical foundation for further research on the freeze-dried grain,fruit and vegetable crisp products.The research results are as follows:1.Quinoa from Jingle in Shanxi,Wutai in Shanxi and Gansu were selected.Protein,reducing sugar,starch,fat,flavonoids and polyphenols were used as evaluation indicators.The result shows that quinoa from Jingle in Shanxi is the best variety.Quinoa seeds were germinated in a constant temperature incubator at 22℃ for 34 hours,and stored at-20℃ for 24 hours;After drying and smashing,quinoa malt powder was obtained,the thick pulp was refined at a ratio of 1:5;the condiantions for gelatinization was identified as 80°C,30 min;after single factor experiment and orthogonal experiment,the experimental conditions of liquefaction and saccharification process are determined as follows: liquefaction temperature is 75℃,liquefaction time is55 min,and α-amylase addition amount is 18 U/g;saccharification temperatu-re is 55℃,saccharification time is 90 min and β-amylase addition amount is240 U/g.2.After germination,refining,gelatinization,liquefaction and saccharifi-cation,quinoa seeds were made into quinoa thick pulp,which is connected to Lactobacillus kefir bacteria to enter the fermentation stage.The acidity and the number of viable bacteria were used as the evaluation indicators of single factor experiment and response surface optimization experiment to study the influence of inoculum amount,fermentation time and fermentation tempe-rature on fermentation effect.The results are as follows: the best process parameters of kefir fermented quinoa are that inoculation amount is 5.2%,fermentation time is 12.4 h and fermentation temperature is 37.4℃.Under this process condition,the acidity of quinoa fermented milk is 85.62。T,and the number of viable bacteria is 9.33 log CFU/m L.3.Using quinoa milk fermented by kefir,sea buckthorn puree,yellow peach thick pulp and carrot thick pulp as raw materials,the effect of different raw material ratios on the overall score of the product was studied,which was mixture of fruit and vegetable juice and quinoa milk fermented by kefir.According to single factor experiment and orthogonal experiment,the best raw material ratios are as follows: the addtion of quinoa milk fermented by kefir is 50 g,the addtion of sea buckthorn puree is 13 g,the addtion of yellow peach thick pulp is 30 g and the addtion of carrot thick pulp is 10 g.Under these conditions,the solid content is 19.9%,the sensory score is 81.4 and the comprehensive score is 62.95.4.The freeze-dried products of the quinoa thick pulp unfermented group,quinoa milk fermented by kefir group,and fruit and vegetable juice mixed with quinoa milk fermented by kefir group were rehydrated and subjected to in vitro gastrointestinal digestion simulation and antioxidant analysis.The results show: through digesting,the content of flavonoids and polyphenols of quinoa thick pulp unfermented group,quinoa milk fermented by kefir group,and fruit and vegetable juice mixed with quinoa milk fermented by kefir group increase significantly;DPPH free radical scaveng-ing rate,hydroxyl free radical scavenging rate,superoxide anion free radical scavenging rate and iron reducing power of the fruit and vegetable juice mixed with quinoa milk fermented by kefir group are 10.9%,7.6%,11.8%,0.190 higher than those of the quinoa thick pulp unfermented group,respectively,and 4.8%,1.9%,4.1%,0.022 higher than those of the quinoa milk fermented by kefir group,respectively.