Application Of Lactic Acid Bacteria In Fermented Waxy Corn Niandoubao Production

Niandoubao is a kind of fermented cereal food from ethnic minority region in the northern China.Waxy corn Niandoubao has the advantages of rich nutrition,unique flavor and it has a long history and widespread popularity in our country.However,the traditional natural fermentation has some shortcomings such as long fermentation period,unstable quality and poor safety of product,which has seriously restricted its industrialization.Application of lactic acid bacteria fermentation in the production of waxy corn Niandoubao not only can shorten the fermentation period,standardize the production and improve the quality of waxy corn Niandoubao,but also the innovation of the natural fermentation.Therefore,this study seems to be of great necessity and significance for the standardized and industrialized production of waxy corn Niandoubao.The screening of lactic acid bacteria and the ratio of lactic acid bacteria were studied.And the medium and culture conditions were explored.Moreover,the effects of fermentation conditions on the quality of waxy corn Niandoubao were invetigated.The fermentation conditions of waxy corn Niandoubao was optimized by the response surface methodology(RSM).Compared with the natural fermentation,the qualities of waxy corn Niandoubao fermented by lactic acid bacteria were analyzed.The results are as follows:(1)The Lactobacillus plantarum A9 and Leuconostoc mesenteroides LN1 were selected as the starter culture according to the fermentability(pH value and titratable acidity)and growth characteristics of lactic acid bacteria.When the proportion of Lactobacillus plantarum A9 and Leuconostoc mesenteroides LN1 was 2:1,the pH value,titratable acidity and viable counts were3.65±0.03,(1.11±0.03)%,and(8.97±0.15)×10~8 CFU/mL,respectively after 24 h incubation.It indicated that there was a significant advantage of the acid production and viable counts compared with other ratio(P<0.05).Moreover,the optimal medium components were obtained by orthogonal test,which were 150 g/L skim milk,30 g/L glucose,10 g/L corn protein powder and 40g/L corn juice.Furthermore,the optimal culture conditions were 50 mL/250 mL loading volume at30?and initial pH 7.0.Under the optimal conditions,the viable counts of lactic acid bacteria were up to(2.36±0.05)×10~9 CFU/mL.(2)The screened lactic acid bacteria starters were used for the production of waxy corn Niandoubao.With the quantity of lactic acid bacteria,fermentation temperature and time as the variables of the single-factor test,the effect of process parameters on the texture quality and sensory evaluation of waxy corn Niandoubao,the titratable acidity of the fermentation broth were studied.Furthermore,the RSM was employed to optimize the fermentation parameters.When the fermentation time was 7 d,the titratable acidity of the fermentation broth was more appropriate,the adhesiveness of the Niandoubao was higher,its hardness and gumminess was lesser,and sensory quality of the Niandoubao was better.When the quantity of lactic acid bacteria was 3%and 4%,the hardness and chewiness were smaller,the adhesiveness was larger,and the sensory score was higher.Moreover,the titratable acidity of the fermentation broth was moderate,the adhesiveness and sensory score of the Niandoubao were higher when the fermentation temperature was from 25?to 30?.The fermentation parameters of the Niandoubao were optimized:the addition quantity of lactic acid bacteria was 4%and the waxy corn was fermented at 25?for 7 d.(3)The fermentaion process and quality of waxy corn Niandoubao produced by natural fermentation and lactic acid bacteria fermentation were analyzed.The pasting temperature,peak viscosity,hot paste viscosity and setback were significantly increased by natural and lactic acid bacteria fermentation,while the final viscosity were significantly decreased compared with that of unfermented samples(P<0.05).There was no significant difference in the pasting temperature of waxy corn flour between natural and lactic acid bacteria fermentation(P>0.05),but the peak viscosity and hot paste viscosity of waxy corn flour fermented by lactic acid bacteria were significantly higher than those of natural fermentation(P<0.05).The contents of crude protein,fat,fiber and ash in waxy maize flour obtained by the two treatments were significantly decreased compared with those in unfermented samples,while the content of starch in waxy maize flour fermented by lactic acid bacteria was significantly higher than that in unfermented samples(P<0.05).The total amount of amino acids in the fermented waxy corn flour all decreased compared with the unfermented group,and the content of most amino acids in naturally fermented waxy corn flour was lower than that of lactic acid bacteria fermentation.The adhesiveness and chewiness of waxy corn Niandoubao fermented by lactic acid bacteria were significantly higher than that of natural fermentation,and their sensory quality were significantly better than that of natural fermentation(P<0.05).The volatile flavors detected in Niandoubao by lactic acid bacteria and natural fermentation are the same,but the content of various ingredients are slightly different.Lactic acid bacteria fermentation can significantly reduce the fermentation period of waxy corn Niandoubao from 12 d to 7 d,thereby improving production efficiency and saving water resources.