| Brown rice is a kind of nutrient-rich whole grain food,but its gel products have the disadvantages of rough taste and poor gel elasticity,which hinders the sales and application of brown rice.Brown rice noodles have some problems,such as poor taste,high breaking rate and serious cooking loss.In this study,Lfermentum-L6 was used for solid state fermentation of brown rice flour(BRF),and the fermentation process conditions were optimized.Also the physicochemical components and processing characteristics of BRF before and after fermentation were compared to analyze the effects of fermentation on BRF.Then fermented brown rice noodles(FBRN)was prepared and lysine(1,3,5%(w/w))was added to improve the excessive acidic flavor produced by fermentation.Finally,the storage quality of FBRN was studied.The main research contents and conclusions are as follows:(1)The optimum conditions for solid state fermentation of BRF by L.fermentumL6 were obtained by single factor and orthogonal experiment:the inoculum was 10%(bacterial suspension,in which the concentration of L.fermentum-L6 was about 2.5/108 CFU/mL),fermentation temperature was 30℃,and fermentation time was 72 hours.After fermentation,the starch,amylose and fat contents of BRF decreased significantly,the polyphenol content increased significantly,the brightness increased,and the red and yellow degree decreased.The gelatinization temperature and gelatinization enthalpy of BRF decreased after fermentation.The fermentation did not change the crystal form of brown rice starch,but the relative crystallinity decreased by 12%.After fermentation,the peak viscosity,hold viscosity and final viscosity of BRF decreased significantly from 1978cP,1707cP and 3553cP to 1586cP,1334cP and 1968cP,respectively.The setback value also decreased significantly from 1828cP to 634cP.The rheological characteristics showed that the fluidity of fermented brown rice flour system was reduced,and it was less prone to shear thinning.The fermented brown rice flour could form a more stable gel network structure.When BRF was made into semi-dry rice noodles,the fermentation significantly improved the breakage rate of semi-dry brown rice noodles(from 19.37%to 1.60%,p<0.05),reduced cooking loss rate(from 6.66%to 5.56%,p<0.05),and improved appearance quality and texture structure score,but at the same time brought bad odor and over-acid taste problems to the rice noodles.(2)Then the sensory quality of semi-dry FBRN was improved by adding 1%,3%and 5%(w/w)lysine,and the effects of different contents of lysine on pH,color,cooking quality,texture characteristics,water distribution,crystallinity,apparent morphology and digestion characteristics of semi-dry FBRN were studied.With the addition of lysine,the pH value of FBRN was significantly increased,and the acidity was decreased.The addition of appropriate amount of lysine(0-3%)improved the sensory quality of FBRN,but when 5%(w/w)lysine was added,the excessive alkaline components made the rice noodles show a special alkali taste and made the rice flour lose its original flavor.With the increase of lysine addition,the value of L*gradually decreased,the values of a*and b*increased,and the color gradually became darker,when 5%Lysine was added,the rice noodles were reddish-brown.The addition of lysine did not significantly increase the breakage rate of FBRN,but the cooking loss rate of FBRN with 5%Lys was significantly increased by 59.9%(p<0.05).The results of texture characteristics showed that fermentation made brown rice flour soft and elastic.With the increase of lysine addition,the hardness first increased and then decreased,which was less than that of nature brown rice noodles(NBRN).At the same time,the addition of Lys reduced the springiness and chewability of FBRN.LF-NMR showed that fermentation decreased the content of bound water,increased the content of weak bound water and free water in rice noodles.With the increase of lysine addition,the content of bound water gradually increased,and the content of weak bound water and free water gradually decreased.The DSC results showed that the three gelatinization temperatures and gelatinization enthalpy of FBRN increased gradually with the addition of lysine,which inhibited the gelatinization and accelerated the aging of rice flour.The XRD results showed that the addition of lysine did not change the crystal shape of rice noodles,but decreased the crystallinity of fermented brown rice noodles samples from 41.27%(0%)to 39.18%(1%),30.17%(3%)and 29.68%(5%),respectively.The SEM results showed that the NBRN sample had many pores and loose structure,while the section structure of FBRN was dense and smooth.The addition of 1%and 3%lysine had little effect on the structure of FBRN,but the addition of 5%rice noodles had rough section and brittle structure.The results of digestion characteristics showed that fermentation significantly increased the content of RDS and SDS,significantly decreased the content of RS,and promoted the digestion of brown rice noodles,while lysine significantly decreased the content of RDS and SDS,significantly increased the content of RS,and inhibited the digestion of fermented brown rice noodles.In conclusion,we believe that the quality of FBRN is better when 3%(w/w)lysine is added to it.(3)The quality changes of 3%lysine added fermented semi-dry brown rice noodles(FBRN-3L)under vacuum packaging at 4℃,25℃,37℃ storage conditions were further studied.The results of pH,total number of colonies and sensory evaluation showed that NBRN was not suitable for storage at higher temperatures(25℃,37℃).while L.fermentum-L6 solid-state fermentation combined with lysine addition could significantly prolong the shelf life of brown rice noodles,and it did not spoilage when stored at three temperatures for 90 days.However,the color value showed that the brightness of FBRN-3L decreased and the reddish-yellow degree increased when stored at 37℃,making the rice noodles reddish-brown.Cooking quality showed that,compared with 0 days of storage,the breakage rate of NBRN significantly deteriorated and increased by 137%when stored at 4℃ for 10 days,and increased by 41%at 90 days.The cooking loss rate increased with time,from 6.66%to 13.2%at 90 days,an increase of 98%,indicating that low temperature storage was not good for the cooking quality of NBRN.When storing FBRN-3L at 4℃ and 25℃ for different times,the change of breaking breakage rate was not significant,and the breakage rate decreased slightly at 37℃,and the cooking loss rate of rice noodles stored at all temperatures increased slowly.The texture properties showed that the hardness of NBRN-4℃decreased significantly and the cohesiveness and chewability became worse with time during the storage period.The hardness and chewiness of FBRN-3L at three storage temperatures increased significantly with time,and the hardness of FBRN-3L-37℃>FBRN-3L-4℃>FBRN-3L-25℃.LF-NMR showed that the strong bound water decreased,the weak bound water increased and the free water did not change significantly when NBRN was stored at 4℃.When FBRN-3L was stored at 4℃and 25℃,the strong bound water decreased,the weak bound water increased,and the free water did not change significantly.When FBRN-3L was stored at 37℃,there was a significant decrease in strongly bound water(0%detected at day 90)and an increase in weakly bound water and free water content. |
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