Process Optimization And Flavor Change Of Low-sugar Yeast Fermented Purple Potato Powder

Purple potato has extremely high nutritional value,and its rich anthocyanins and cellulose are very beneficial to human health.At present,due to the nutrition and health characteristics,purple potatoes have become a hot spot for consumption.There are a variety of processed products of purple potatoes,but there are also problems with poor color and quality of products and low levels of repetition.In recent years,the use of microbial fermentation to produce highly nutritious and flavorful products has become a research hotspot.At the same time,the proportion of fermented products in the market has grown rapidly and has shown good market prospects.In this paper,the fresh purple sweet potato is used as a raw material,the low sugar yeast is used to ferment the purple sweet potato powder,and the antioxidant capacity is used as the inspection index to determine the best preparation process of the fermented purple sweet potato powder,and analysis of its flavor characteristics.Provide a new way for the high value transformation and utilization of purple sweet potato,expand the industrial chain.Through the single factor test,the best process conditions of fermenting purple potato flour were obtained.Based on the single factor,the response surface analysis was carried out to establish a regression model.According to the actual situation,The optimal preparation process was adjusted as follows:yeast addition amount 0.95%,material-liquid ratio10:22(g/m L),fermentation time 16 h,fermentation temperature 23?.At this time,the antioxidant capacity of the fermented purple sweet potato powder was 404.94 mg V_C/100 g,the difference between the verified value and the predicted value was 0.56%,and the obtained model was reliable.By comparing analysis the antioxidant capacity,and the contents of total phenol and total flavonoids of purple sweet potato powder before and after fermentation,the results showed that the total phenol content of fermented purple sweet potato powder was 123.85 mg GAE/100 g,and the total flavonoid content was 610.64 mg rutin/100 g is higher than unfermented purple sweet potato powder,and the antioxidant capacity of fermented purple sweet potato powder is higher than unfermented purple sweet potato powder.Determination of anthocyanin content and stability of two purple potato powder,and it was found that the stability of anthocyanin in fermented purple potato powder was better than that of unfermented purple potato powder.Analysis and determination of free amino acids in five fermented purple sweet potato powders with different fermentation times,the results showed that 21 free amino acids were detected in 5 samples,of which glutamic acid and aspartic acid were the most abundant.The range of total free amino acid contents(TFAAs)for five samples was 1.03 mg/g-3.98mg/g;the range of essential amino acid contents(EAAs)was 0.07 mg/g-1.25 mg/g,the percentage of EAAs in TFAAs was 6.94%-31.27%,and the purple potato flour with fermentation time was 16 h has the best performed.At the same time,the content of free amino acids with the same taste characteristics has a similar change trend during fermentation.According to taste characteristics,the composition pattern of the tasted amino acids in the fermented purple potato powder at each time was consistent,and both showed a high content of umami and sweet taste amino acids.The taste intensity value(TAV)of glutamate is greater than 1,which contributes to the taste of fermented purple potato powder.The principal component analysis(PCA)results showed that the TFAAs of 5 samples extracted 4main components,and the cumulative contribution rate reached 96.962%,which can better reflect the basic information of the free amino acid contents(FAAs)of fermented purple potato powder.The fermented purple potato powder with 16 h had the highest score,followed by 8 h and 24 h,the32 h and 40 h had low scores.According to comprehensive analysis,the fermented purple sweet potato powder with 16 h is superior to other fermented purple sweet potato powders in terms of nutritional function and taste.To analyse the main flavor of fermented purple sweet potato powder by gas chromatography-mass spectrometry(GC-MS),and a total of 24 volatile components were found,which were esters,alcohols,ketones,aldehydes,and others.The relative content of esters was as high as 97.94%.The ester material provides the main flavor characteristics for the fermented purple sweet potato powder,gives the fermented purple sweet potato powder a sensory sweetness,and makes the aroma more mellow.The main component analysis of the volatile components in fermented purple sweet potato powder,and comprehensiv evaluation,the comprehensive score of fermented purple sweet potato powder is 24 h>16 h>8 h>32 h>40 h.The flavor characteristics of 16 h and 24 h are similar,and this result is also reflected in the artificial sensory evaluation.Artificial sensory evaluation results show that rose and sweet aromas are characteristic aromas of fermented purple potato powder.Fermented purple potato powders with fermentation times of 16 h and 24 h have a more intense rose aroma than other fermented purple potato powders.