Effects Of Different Processing Methods On Nutritional Properties And Antioxidant Activity Of Kidney Beans

Our country has rich resources of kidney beans varieties,widely planting area,highly yield.Kidney beans have a high nutritional value and functional properties,recent years,studies have shown that darkly bean biologically active substances could better prevention and treatment some chronic diseases associated with certain free radical damage,which attracted more and more people’s attention by its nutritional and functional properties,but the different processing methods on kidney beans nutrition,phenolic content and antioxidant capacity research component were rarely reported.Therefore,the system study on variation of different processing methods on three dark kidney beans’nutrients,phenolics and antioxidant capacity,which helps people better to understand the nutritional and functional properties of the processed beans,and provide a theoretical basis on improved the added value and deep processing industry of kidney beans,and promote the comprehensive development and utilization of beans resources.In this research,we selected the main produced areas and high yield of dark kidney beans(black beans,purple speckled kidney beans and kidney beans)for study,respectively studied on the changes of atmospheric boiled 40min,pressure steamed 70min,high pressure boiled 30 min,autoclaved 60 min,germination 0,2,4,6d and baked 0,10,30,60,120 min conditions of conventional nutrients(crude protein and amino acids,minerals and crude ash,crude fat,starch),phytic acid,phenolics,flavonoid content of 70%acetone acidic extracts and antioxidant capacity(DPPH,ABTS,FRAP,ORAC),And deeply analysised the composition and content of phenolics of different processing beans by UPLC-MS.The main results were as follows:1.Three beans had high nutritional value,low fat,rich protein and carbohydrates,a wealth amino acid composition and the body must contain eight kinds of amino acids,and also rich in K,P,Mg,Ca,Fe,Zn and other mineral elements,a typical high-K(1348.95～1968.25 mg/100g),high-Mg(178.28～190.53 mg/100g),high-Ca(203～55.4 mg/100g),low Na beans;After processing,the composition of routine nutrients of three kidney beans has a little change as whole,only small part of the processing methods has effect on nutrients,such as when baked 60 min,the crude protein percentage content respectively decreased by 13.26%,9.34%,12.45%;Cooking and germination has less effect on phytic acid content of three beans,but the phytic acid content of baking process(0～120 min)beans were greatly reduced.2.phenolics content and antioxidant capacity purple black beans and purple kidney beans were higher than Speckled kidney beans;After processed,the phenolics,flavonoids content and four antioxidant value(DPPH,ABTS,FRAP,ORAC)of three beans were significantly reduced or slightly increased(p<0.05);Overall,the phenolic content and antioxidant capacity of processed beans in descending order:baking and unprocessed,germination,steamed,boiled,baking lost minimal phenolics,when baked 30～60 min,the phenolics content and antioxidant capacity evev increased;the phenolics content and antioxidant capacity of different cooking(atmospheric boiling,steaming pressure,high pressure boiling,high pressure steam,soup)kidney beans in descending order:pressure steam,high pressure steam,pressure cook for a long,high-pressure cooking,the phenolics content and antioxidant capacity of beans soup were close or significantly higher than(p<0.05)cooked kidney beans;the content of phenolic compounds and antioxidant capacity of beans has a significantly lower trend as whole when germinated 0-6d;the phenolics,flavonoid content and four antioxidant value of processed beans were significant correlation(p<0.01),however,the phenolics content only has a higher correlation with ABTS value,ORAC values(r>0.685)after baking.3.UPLC-MS analysis revealed that there were some differences in the composition and content of phenolic of three beans,for example,the highest phenolic content was purple beans,the species of phenolics was richer than others,the major phenolic compounds of kidney bean extract are:(+)-catechin,trans-ferulic acid,p-hydroxy benzoic acid,2,3,4-three hydroxy acid,while the content of(+)-catechin was the highest(26.76～281.50μ/g);the content of part phenolic compounds were reduced or not detected,but at the same time produced new phenolic substances,For example,(+)-catechin levels were lower by thermal processing,may produce more heat-stable phenolics like(-)-catechin and(-)-gallocatechin,but the the types of phenolic compounds of germinate beans were decreased,UPLC measured total phenolic content of processed beans in descending order:baking,raw,steamed,boiled,germination,and the total phenolic content of baked beans was higher than unbaked.4.It found that benzoic acid derivatives was more heat-stable than cinnamic acid derivative during baking;in addition,We also found that there may be four phenolics in three beans:(+)-catechin glucoside,a proanthocyanidin dimers,isoquercitrin,kaempferol glucoside.