Optimization Of Brewing Process Of Fermentation Frozen Mulberry Beverage Based On Thermosonic Sterilization And Its Physicochemical Properties

Mulberry is rich in phenols,polysaccharides and other bioactive substances,is a fruit with high nutritional value,and has more medicinal value.Fermentation can maintain or enhance the nutritional value of fruits and vegetables,and is a simple and economical biotechnology that can enhance the ideal taste of products.In this experiment,frozen mulberries from Hongluoxian Town,Huludao City were used as raw materials,and yeast and Lactobacillus plantarum were used as strains for fermentation to prepare fermented mulberry drinks.Firstly,the process conditions of thermal sonication mulberries were optimized by single-factor test and response surface to prevent bacterial contamination and undesirable flavor during fermentation.The optimal fermentation conditions for fermentation of mulberry beverages with compound cultures were determined by orthogonal optimization,and the changes of total sugars,total acids,total phenols,total flavonoids,total anthocyanins and other components during the fermentation process were determined.At the same time,the finished properties of fermented mulberry beverages with unfermented mulberry juice,yeast,lactobacillus plantarum and compound cultures were compared.Headspace solid phase microextraction-gas chromatography mass spectrometry(HS-SPME-GC-MS)was used to analyze the changes of aroma components of fermented mulberry beverages of different cultures.The results are as follows:1.By optimizing the thermal ultrasonic conditions through single-factor test and response surface,it was concluded that the optimal process was 11.5 min ultrasonic time,ultrasonic temperature 50.5 °C,ultrasonic power 153 W,and the total number of bacterial colonies and mold yeast colonies in mulberry pulp after thermal sonication were 0.33±0.57,0.67±0.57,respectively.The physical and chemical indexes of mulberry before and after ultrasound were compared,and the results showed that there was no significant change in the basic components of mulberry before and after ultrasound.2.Through single-factor test and orthogonal optimization,the optimal fermentation process conditions were 2:1 strain ratio,1% strain addition,fermentation time 60 h,fermentation temperature 30°C,and the optimal fermentation conditions were 7.5±0.20 °Brix,p H 4.12±0.12,and sensory evaluation was 89±1.34.During the fermentation process,the total sugar and Brix values of mulberry beverages fermented by compound cultures gradually decreased,p H first decreased and then increased,and the total acid content first increased and then decreased.The content of total phenols and total flavonoids gradually decreased;The total anthocyanin content first increased and then decreased,and in general,the total anthocyanin content in fermented beverages was greater than that of unfermented mulberry juice.3.Compared with the differences in material composition and properties of unfermented mulberry juice,yeast fermentation,lactobacillus plantarum fermentation and compound strain fermented mulberry drink,the results are as follows: the total sugar and sugar content values of mulberry drink fermented by Lactobacillus plantarum are the highest,while the total sugar and sugar content values of mulberry drinks fermented by yeast fermentation and compound culture are lower and the values are not much different.The mulberry drink fermented by Lactobacillus plantarum had the lowest p H value and the largest total acid content,and the mulberry drink fermented by compound cultures had a moderate p H value,and the total acid content was higher than that of unfermented mulberry juice and yeast fermented mulberry drink.The crude protein content of mulberry drink after fermentation was reduced,but the crude protein content in fermented mulberry drink with compound culture was higher than that in single-species fermented beverage.The SOD enzyme activity of fermented mulberry drink of complex culture was significantly higher than that of single-strain fermented and unfermented SOD enzyme,and it had the strongest DPPH free radical and ABTS free radical scavenging ability,indicating that the fermented mulberry drink of compound strain had strong antioxidant resistance.The total sugar content of fermented mulberry drink was 1.53±0.01 g/L,the Brix value was 7.50±0.20 °Brix,the total acid content was 9.74±0.08 g/L,the p H value was4.12±0.03,the crude protein content was 0.60±0.02%,the total phenolic content was5.57±0.04 g/L,the total flavonoid content was 0.67±0.01 g/L,the total anthocyanin content was 4.27±0.06,and the SOD enzyme activity was 5.95±0.29 The radical scavenging rate of unit and DPPH was 74.3±0.20%,the scavenging rate of hydroxyl radical was 53.09±0.24%,the scavenging rate of ABTS radical was 88.98±0.42%,and the total reducing capacity was 0.88±0.01.4.Through headspace solid phase microextraction combined with gas chromatography-mass spectrometry technology,the aroma components of yeast,lactobacillus plantarum and compound cultures fermented mulberry beverages were detected,and a total of 38 aroma substances were detected in the fermented mulberry drinks of compound strains,including 6 alcohols,23 esters,6 acids,2 ketones and 1phenol.Compared with unfermented mulberry juice,the types of alcohols,esters and acids in fermented mulberry drinks with compound cultures increased significantly,and the types of aldehydes and phenolic substances decreased slightly compared with fruit juice.Compound culture fermentation can significantly increase the volatile substances in mulberry beverages,and the aroma components are richer than that of single species fermentation.