Processing Technology And Quality Analysis Of Sugarcane Yoghurt

For a long time,Chinese sugarcane industry has been dominated by white granulated sugar,with a single product variety and weak market competitiveness,which has led to a difficult situation in the development of the industry.The development of diversified products to increase the economic growth point of the sugarcane industry is an important way for the transformation and upgrading.Therefore,in this study,concentrated sugarcane juice was used instead of white sugar to prepare a new dairy product that combines the flavors of sugarcane and yogurt,providing a new idea for the diversification of sugarcane industry products.Coupling fuzzy mathematics and response surface method to optimize the processing technology of sugarcane yogurt,compound stabilizers suitable for sugarcane yogurt,and study the quality,nutrition and flavor of sugarcane yogurt.The experimental results are as follows:(1)Screening of starter for sugarcane yogurt.Eight kinds of commercial starters are used to make sugarcane yogurt.The physical and chemical indicators of yogurt samples(p H value,titratable acidity,viscosity,water holding capacity,color value),total phenol content and its antioxidant capacity(DPPH free radical scavenging rate,ABTS~+free radical scavenging rate.Based on the analysis,the results show that the p H of No.7(Chuanxiu 10 strain)starter fermented yogurt sample is the lowest,4.41±0.02;the titer acidity is the highest,80.33±0.58°T;the number of lactic acid bacteria colonies is the most,8.81±0.02 lg(CFU/m L);the highest total phenol content,13.76±0.10 mg GAE/100g;the strongest antioxidant activity,its DPPH free radical scavenging rate and ABTS~+free radical scavenging rate are 43.10±0.43%,40.83±0.73%(Yogurt sample concentration is 0.4 g/m L);at the same time,its viscosity,water holding capacity and color are all within the acceptable range,so Chuanxiu 10 strain is suitable as a fermentation strain for sugarcane yogurt.(2)Optimization of sugarcane yogurt fermentation process and determination of stabilizers.The fermentation process of sugarcane yogurt is optimized by single factor combined with response surface analysis.The optimal fermentation process conditions are sugarcane juice concentrate addition amount of 10%,total bacterial inoculation amount 3%,ferment for six hours.On the basis of optimal fermentation conditions,through a single factor test,using yogurt viscosity and water holding capacity as evaluation indicators,it is determined that the composition of the sugarcane yogurt compound stabilizer is pectin,carrageenan,and propylene glycol alginate.Their ratio is 1:5:7,the addition amount is 0.15%;the obtained sugarcane yogurt has the highest viscosity and water holding capacity,which are 8.21±0.06 Pa·s and82.91±0.17%,respectively.(3)Quality and flavor substance analysis of sugarcane yogurt.The p H value of sugarcane yogurt is 3.41±0.01,and the titratable acidity is 78±0.11°T;the protein content is 3.37±0.02 g/100g,which is 0.07 g/100g higher than the control yogurt(p>0.05);the total number of lactic acid bacteria colonies is8.80±0.20 lg(CFU/m L),which is 0.05 lg(CFU/m L)higher than that of the control yogurt(p>0.05).The total phenol content of sugarcane yogurt is 13.75±0.18 mg GAE/100g,which is significantly higher than that of the control yogurt(p<0.01).The scavenging rates of DPPH and ABTS~+free radical are 43.15±0.12%and 40.53±0.21%respectively(the concentration of yogurt sample is 0.4g/m L),significantly higher than the control yogurt(p<0.01).Compared with the control yogurt,the differences in the content of four elements,aluminum,iron,potassium and magnesium,are extremely significant(p<0.01),while the content of calcium,zinc and sodium is significantly difference(p<0.05),.Sugarcane yogurt is rich in amino acids,such as threonine,glutamic acid,serine and other15 amino acids with a total of 66.56 mg/100g,while the control yogurt contained 14 amino acids with a total of 5.74±0.02 mg/100g,and the difference is extremely significant(p<0.01).sugarcane yogurt contained 5 essential amino acids(threonine,valine,phenylalanine,The sugarcane yogurt contained five essential amino acids(threonine,valine,phenylalanine,leucine,isoleucine),of which threonine has the highest content(0.99±0.00 mg/100g),which is significantly higher than the control yogurt(p<0.05).Sugarcane yogurt contained 39 volatile components,14 more than the control yogurt,and their contents and types are significantly different,their contents of aldehydes,esters,acids,olefins and alkanes were higher than those of the control yogurt.The above indicates that sugarcane yogurt has better quality and flavor.(4)Study on the quality stability of sugarcane yogurt.The changes of physicochemical indexes(p H,viscosity,water holding capacity),microbiological indexes(total number of Lactobacillus colonies,Escherichia coli colonies,yeast colonies,mold colonies,Staphylococcus aureus colonies),total phenolic content and antioxidant activity(DPPH radical scavenging rate and ABTS+radical scavenging rate)were studied in sugarcane yogurt store at4?and 25?for 20 days.The results showed that the physicochemical indexes,total number of Lactobacillus colonies and total phenol and antioxidant capacity of sugarcane yogurt showed a decreasing trend with the increase of storage time,and the higher the temperature,the more obvious the decrease.During the whole storage period,E.coli and S.aureus are not detected in the yogurt,while yeast and mold are slightly increased,and the content always met the national standard.The quality of yogurt at storage temperature of 4?decreased significantly after the 15th day,and the quality of yogurt at 25?decreased significantly after the 7th day.It is recommended that the storage period of sugarcane yogurt should be 15 days at 4?and 7 days at 25?.