Development And Quality Improvement Of Tartary Buckwheat Dried Noodles With Low Glycemic Index

In recent years,due to the soaring incidence of obesity and diabetes,people have paid more and more attention to the glycemic index(GI)of food.Tartary buckwheat is a medicinal and food homologous crop.It is rich in bioactive substances,which is beneficial to reduce the production of postprandial blood glucose.At present,the researches on Tartary buckwheat flour(TBF)mainly focus on treatment methods to improve its processability,while the research on the development and quality improvement of low-GI Tartary buckwheat dried noodle(TBDN)is still lacking.In this study,starting with the processing characteristics,edible quality and in vitro digestibility of TBDNs,the optimum addition amount of TBF was determined,and then the feasibility of producing low-GI noodles with low GI materials instead of TBF was verified.Finally,the effects of common modifiers on the quality of TBDNs were explored.The main results are as follows:(1)The influence of different amounts of TBF on the processing characteristics,edible quality and in vitro starch digestibility of TBDNs were studied.The results showed that with the TBF increased from 0 to 100%,the rupture stress and elongation of TBDNs decreased,the cooking loss increased,the hardness,resilience and tensile properties decreased,the sensory evaluation scores decreased significantly(p<0.05)from 89.23±0.68 to 59.30±1.92,and the estimated glycemic index(e GI)decreased significantly(p<0.05)from 76.35±to 50.13±0.05.(2)The impact of partial replacement of TBF with Tartary buckwheat bran flour(TBBF)on the in vitro starch digestibility,processing characteristics and edible quality of TBDNs was investigated.The results showed that with the substitution of TBBF increased from 0 to 35%,the e GI values of TBDNs decreased significantly(p<0.05)from 59.49±0.33 to 53.17±0.22,the initial gelatinization temperature of TBDNs starch increased from 63.37±0.29~oC to 67.70±0.09~oC,and the crystallinity increased from 20.15%to 24.55%.The results of Fourier transform infrared spectroscopy(FTIR)showed that the hydrogen bonding interaction and the short-range ordered structure of starch were enhanced.The results of fluorescence spectra showed that the enzyme activities ofα-amylase and amylglucosidase decreased.It showed that the changes of starch structure and digestive enzyme activity decrease the in vitro digestibility of TBDNs.However,with the increase of TBBF,the rupture stress and elongation of noodles decreased,the water absorption decreased,the cooking loss increased,the cohesion and tensile properties decreased,and the score of sensory evaluation decreased significantly(p<0.05)from75.76±1.25 to 64.00±1.05.(3)The impact of partial substitution of high amylose corn starch(HCS)for TBF on the in vitro digestibility of TBDNs and its internal mechanism were studied.With the replacement of HCS increased from 0 to 35%,the e GI values of TBDNs decreased significantly(p<0.05)from 59.49±0.33 to 55.17±0.06,the initial gelatinization temperature and enthalpy of starch increased,and the crystal form of starch also changed from A+V to B+V.The results of FTIR showed that the hydrogen bond structure and short-range ordered structure of starch in the system were also enhanced.It showed that HCS reduced the in vitro digestibility of TBDNs by affecting the structure and properties of starch.It was worth noting that with the increase of HCS,the rupture stress and elongation of noodles increased at first and then decreased,and the maximum was 3.51±0.09 k Pa and 0.34±0.01 at 5%,respectively.Moreover,the cohesion,tensile force,tensile distance and sensory evaluation scores of TBDNs were also the highest when the addition of HCS was 5%.The observation of cold field emission scanning electron microscope(SEM)showed that the starch was uniformly filled in the pores of the noodle matrix,and the compactness of the noodle was enhanced.Subsequently,TBBF and HCS were mixed.When the addition amount of TBBF was 25%and that of HCS was 10%,the e GI value of TBDNs was 52.16±0.48.Moreover,its processability and the score of sensory evaluation were best.(4)The effects of enzymes(xylanase,transglutaminase,glucose oxidase)and hydrocolloids(xanthan gum,carrageenan,konjac gum)on the edible quality and in vitro starch digestibility of TBDNs were investigated.The results showed that all of enzymes could reduce the water absorption and cooking loss of TBDNs,and the hardness,cohesion and resilience decreased with the increase of xylanase while increased with the addition of transglutaminase(TGase)and glucose oxidase(GODase).The results of SDS-PAGE and SDS extractable protein showed that TGase and GODase promoted protein cross-linking and strengthened the gluten network structure of noodles.In addition,the results of starch digestibility showed that the e GI values of TBDNs increased significantly(p<0.05)from 53.04±0.25 to 60.75±0.11 with the increase of xylanase,but decreased significantly(p<0.05)with the addition of TGase and GODase.When the amount of GODase was 0.2%,the e GI value of TBDN was the lowest,which was 46.30±0.10.In addition,the three hydrophilic colloids significantly(p<0.05)improved the edible quality of TBDNs,and when xanthan gum,carrageenan and konjac gum were added at 1%,0.5%and 1%,the sensory evaluation scores were 81.96±1.25,78.58±1.54and 82.42±0.62,respectively.The results of in vitro starch digestibility showed that the three colloids significantly(p<0.05)reduced the e GI values of TBDNs,and when the amount of xanthan gum was 1.5%,the e GI value of TBDN was the lowest,which was 45.43±0.08.