Investigating The Diversity Of Mung Bean Starch In Chinese Cultivars And Application Of Various Processing Methods Affecting The Structure,Digestibility For Low GI Products

Mung beans are widely cultivated and consumed in Asian countries due to their strong nutraceutical and nutritional properties.There are many mung bean varieties in China,but there are few systematic studies on the physicochemical structure and digestive characteristics of mung bean starch among different varieties,which is not conducive to the raw material screening,processing and utilization of mung bean products from nutritional and health perspective.Therefore,in this thesis,starch from newly bred and established Chinese mung bean cultivars was extracted and investigated to check the differences in the physicochemical properties and its digestion rates.In this study out of total 27 studied cultivars,15 mung bean cultivars cultivated in different areas were screened and their effects on starch physicochemical properties and glycemic index were analyzed.Results indicated that amylose content ranged from 27.30 to 36.34(g/100g DM).Differential scanning colorimetry(DSC)analysis indicated the peak gelatinization temperature varied over a broad range significantly(p<0.05)from 61.75?C to 70.46?C.Resistant starch content and estimated glycemic index(eGI)in the cooked samples varied significantly(p<0.05)from 7.63 to 15.42(g/100g DM)and76.47 to 81.48 respectively.However,Pearson's correlation analysis and linear discriminate analysis(LDA)established the similarity index and relationships on the basis of performed analyses in different cultivars.Since,the genetic backgrounds of newly developed and established cultivars might be very close due to which large variations among the data were not observed.It was found that mung bean cultivar“JLV 8”was having the lowest glycemic index and was used in all subsequent experiments.It is well known that beans and cereals are cooked prior to consumption where it undergoes a series of changes in its structure and digestion properties.So,Mung bean starch was hydrothermally processed to different temperatures and the changes in its structure and functionality were observed.DSC endotherms indicated the transitional changes occurring during gelatinization which increased the onset temperature(T_o)from 66.33?C to 76.69?C whereas the enthalpy of gelatinization(?H_g)and retrogradation(?H_r)were reduced from 14.07 to 6.77(J/g)and 10.06 to 6.68(J/g)respectively.Molecular order(DMO)and degree of double helix(DDH)calculated from Fourier transform infrared spectroscopy(FTIR)were significantly(p<0.05)reduced from 1.35 to 1.01 and 1.38 to 0.98respectively.Rapid viscosity analysis(RVA)showed that peak and final viscosities were decreased significantly(p<0.05).The digestion kinetics and logarithm of slope(LOS)plot indicated that degree of gelatinization increased the access of enzymes which significantly(p<0.05)increased the digestion of mung bean starch.Different thermal processing methods were also used to determine the best thermal processing technique for mung beans powders and its implications on structure for maintaining lower digestibility.The X-ray diffraction analysis indicated the reduction of relative crystallinity from 18.56%(native)to3.65%(roasted)in various thermally treated samples.SEM micrographs displayed that more the damage of granular structure,higher was the digestibility of starch and proteins primarily due to extent of gelatinization and uncoiling of the double helical protein structures.The extent of gelatinization(C?)was varied significantly from 26.83%to 87.85%in native to roasted samples respectively.Pasting was found best thermal treatment followed by microwave,boiling,steaming and roasting respectively as they caused damage to the crystalline and ordered structure of starch which impacted the digestion properties significantly(p<0.05).Two different milling methods(dry and wet)were used for making flour of mung bean in which dry(cyclone)milling displayed increased starch damage,thermal and pasting properties.The cooking quality of wet milled 70:30(wheat:mung bean composite)noodles was found satisfactory for milling and morphological features were also validated by electron microscopy.Morphological characteristics indicated that cyclone milled noodles were deeply embedded in gluten matrix and gave smooth and uniform surfaces as compared to wet milling while cracks and fissures were observed in wet milled noodles.The cyclone milled noodles analysis indicated greater cooking loss and breakage ratio.Wet milling showed lower digestion of starch(86.18±0.35)in noodles as compared to cyclone(89.62±0.44)milling method.The estimated glycemic index(eGI)of cyclone milled noodles was 94.67±1.50as compared to 90.00±0.56 which will lead to greater post prandial glycemic responses in human body.It was concluded that wet milling method is more suitable for grinding and noodles making which can be further processed efficiently in the food industries.This study provides basis for lowering down the glycemic index in mung bean products during processing.