| Mung beans(Vigna radiata L.)rich in nutritional value,with low fat,high protein and other characteristics,has more than two thousand years of cultivation history in China.According to GB/T 10462-2008,mung beans can be divided into ming mung beans,hairy mung beans,yellow mung beans and mixed mung beans.Among them,ming mung beans have bright skin color,regular shape,uniform seed size,and relatively high nutrient content.Ming mung bean is rich in dietary fiber and a variety of nutrients,including protein,vitamins and minerals,which is an important source of plant-based protein,with a variety of effects such as clearing heat and detoxifying,diuretic and anti-swelling,widely welcomed by consumers.Ming mung beans are widely cultivated,with the quality of ming mung beans produced in different regions varies due to geographical and climatic factors.Zhangjiakou City,located in Hebei Province,is one of the major and dominant producing areas of mung beans in China,whose mung beans are well know in the market for a long time.In order to analyze the quality of mung beans from different producing areas,screen for high quality producing areas and establish a traceability model,this study collected ming mung beans from Zhangjiakou areas(Xuanhua,Wanquan,Yuxian,Yang Yuan and Huai’an counties)and non-Zhangjiakou areas(Guangdong,Fujian and Gansu)for systematic analysis and comparison.Firstly,the basic nutritional composition of ming mung beans from different origins were analyzed,comparing the effectiveness of NIR spectroscopy and Raman spectroscopy in origin tracing and the quantifying of nutritional indicators.Secondly,UPLC-QTOF-MS and GC-MS techniques were used to qualitatively analyze and origin-trace the bioactive substances in ming mung beans,so as to comprehensively evaluate the non-volatile and volatile substances in ming mung beans of different origins.Finally,a multi-flavored high protein mung bean crackers was developed based on the protein content of mung beans selected from Zhangjiakou.The main research contents and conclusions are as follows:(1)Comparative analysis of the basic nutritional composition of ming mung beans from different origins.The basic nutritional parameters(total starch,protein,moisture,ash,lipids,amino acids)of ming mung beans from different origins were determined;the methanol extracts of ming mung beans were prepared,and the contents of total phenols,total flavonoids,phenolic substances(p-coumaric acid,catechins,rutin,vitexin,gallic acid and isovitexin)as well as the total antioxidant capacity were determined.The results showed that the total starch content of Zhangjiakou ming mung bean was 38.27-50.30%,protein content was 20.12-26.74%,moisture content was 6.88-12.54%,ash content was 2.35-3.47%,and lipid content was 0.43-1.77%;the total starch content of non-Zhangjiakou ming mung bean was34.77-48.22%,protein content was 21.63～25.51%,moisture content was8.82～10.36%,ash content was 2.22～3.73%,and lipid content was 0.46～0.88%.The highest glutamic acid content(4.09-4.48 g/100g)and the lowest cysteine content(0.02-0.03 g/100g)were found in ming mung beans.The differences in total phenolic and total flavonoid contents between Zhangjiakou and non-Zhangjiakou areas were slight;there were significant differences in the contents of phenolic substances(p-coumaric acid,rutin,vitexin,gallic acid and isovitexin),which may be mainly due to the differences in cultivation locations and storage time.In conclusion,it can be seen that the nutritional characteristics of ming mung beans from different origins differ,but all have high starch,high protein and low lipid characteristics.(2)Establishing a traceability model for ming mung beans of different origins based on spectroscopic techniques and chemometric methods.Near-infrared and Raman spectra of ming mung bean samples were collected and combined with chemometrics to establish a traceability model for the origin of ming mung beans in Zhangjiakou.The NIR and Raman spectra of ming mung bean samples were collected,together with chemometrics,to establish a traceability model for the origin of Zhangjiakou ming mung bean;combined with different spectral pre-processing methods to establish a partial least squares quantitative regression model for the nutrient composition(total starch,protein and moisture)of ming mung bean.The results showed that in the supervised mode chemometric analysis,both NIR and Raman could accurately identify ming mung beans from Zhangjiakou and non-Zhangjiakou regions(both Q~2 were greater than 92%,and the discriminatory accuracy of SVM was greater than 96%);in the quantitative model of nutrient composition,NIR showed better performance than Raman,the models for predicting moisture(Rc=99.9%,Rp=85.3%)and protein(Rc=91.4%,Rp=91.5%)contents based on NIR spectra achieved excellent external prediction performance,but the external prediction model for predicting total starchneeds further improvement.In conclusion,it can be concluded that the origin traceability of mung beans as well as the quantitative model of nutritional composition can be established based on nondestructive testing technology combined with chemometrics,which can provide reference for future research on origin traceability of mung beans.(3)Exploring the differences of small molecule compounds in ming mung beans of different origins and their discriminatory modeling based on mass spectrometry and chemometrics.Non-volatile and volatile substances in ming mung beans were identified by UPLC-QTOF-MS and GC-MS techniques;the traceability models for the origins of ming mung beans in Zhangjiakou were established by combining chemometrics.The preliminary identification of 55 non-volatile compounds(flavonoids,isoflavonoids and their derivatives,saponins,amino acids and organic acids,etc.)and 50 volatile compounds(alkanes,aldehydes,alcohols,etc.);the Q~2 of the OPLS-DA model based on UPLC-QTOF-MS and GC-MS techniques were 76.3%and 94.6%,respectively,indicating that there was good differentiation between Zhangjiakou and non-Zhangjiakou ming mung beans samples were well distinguished from each other.In summary,UPLC-QTOF-MS and GC-MS techniques can also be used to establish a traceability model for ming mung beans,and at the same time,provide a more comprehensively and systematically qualitative analysis of the bioactive substances in ming mung beans.(4)Development of high-protein mung bean crackers.Zhangjiakou ming mung beans were used as the main raw material to make high-protein mung bean crackers,investigating the differences in sensory characteristics,color difference and textural characteristics of mung bean crackers with different additions of mung bean powder.The results showed that the sensory characteristics of mung bean crispies were best at40%addition of mung bean powder,and its protein content reached 16.98%,which was in accordance with the regulations of high protein food in GB 28050-2011.The mung bean crackers seasoning was further adjusted to produce a variety of flavored mung bean crackers products,and the nutrient composition and flavor substances were analyzed,and it was concluded that there was little difference in their nutritional composition,but there were large differences in flavor substances such as maltol(sweet caramel flavor,marshmallow flavor,jam flavor,and toast flavor)and 2-tridecanone(fat flavor,dairy flavor,coconut flavor,and nut flavor).In summary,the multi-flavored high-protein mung bean crackers developed in this chapter could help provide consumers with nutrient-rich,healthy foods. |
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