Study On The Comparison Of Nutritional Components Of Chinese Wild Rice And Effect Of Cooking Methods On The Quality

Chinese wild rice is a natural whole grain food rich in nutritional composition,which is abundant in resources all over the country.However,due to the lack of unified planting and harvesting,the rich wild rice resources in China have been idle.Starch is the most momentous nutritional component in wild rice,and its starch structure and volatile flavor substances will change after different cooking methods.This study intends to explore the comparison of nutritional components of wild rice in different regions of China and the effects of different cooking methods on the physicochemical properties of wild rice starch and volatile flavor substances of wild rice,a series of studies were carried out.The main results were as follows:Firstly,the differences of basic nutritional components,bioactive components and antioxidant capacity in Erhai in the southwest of China,Lixiahe in the east of China and Wudalianchi in the northeast of China were studied.There were obvious differences in environment and climate in the three kinds of wild rice were grown in different geographical locations,which led to different nutritional components,among which the contents of fat,ash and total starch were significantly different(P<0.05).The protein content of wild rice in Lixiahe is the lowest,and the total starch content and amylose content are the highest.Wild rice in Erhai has the highest protein content and the lowest fat content.The ash content,VB1 and VB2 content of wild rice in Wudalianchi are the highest.All the three kinds of Chinese wild rice contain 18 kinds of amino acids,including 8 essential amino acids.The first limiting amino acid was methionine and cysteine.Three kinds of wild rice are rich in mineral elements,including magnesium,potassium,sodium,iron,zinc and selenium.The selenium content of wild rice in lixiahe is the highest,reaching the standard of selenium-rich rice.Among the three kinds of Chinese wild rice,wild rice in Erhai has the highest content of total phenols and total flavonoids.DPPH free radical scavenging ability,ABTS free radical scavenging ability and ferric reducing antioxidant power(FRAP)of three kinds of Chinese wild rice were significantly different(P<0.05),and wild rice in Erhai had the best antioxidant ability.Secondly,wild rice in Lixiahe was selected to further study the effects of different cooking methods on the physicochemical properties of its starch.The results showed that compared with raw wild rice starch,the apparent amylose content of wild rice starch decreased after different cooking methods,and the apparent amylose content of starch after air expansion treatment was the lowest.After different cooking methods,the starch granules were depressions,cracks,holes and other phenomena,and the particle size of starch particles will increase,but the crystal type still a typical A-type crystal structure.Steaming and boiling treatment will increase the relative crystallinity of wild rice starch,while air expansion treatment will decrease.After different cooking methods,the layered structure of wild rice starch was destroyed,but the functional groups were not changed,and all of them had typical absorption peaks in FTIR spectra.Among them,steaming and boiling make the double helix structure more orderly,which also makes To,Tp and Tc larger;However,the air expansion treatment increases the disorder of double helix structure,so To,Tp and Tc become smaller,and starch is more likely to be gelatinized.The solubility and swelling power of all starches gradually increased with the increase of temperature,and the solubility and swelling power of starch after air expansion treatment was the largest.The digestion characteristics of starch show that RDS content will increase after different cooking methods,SDS and RS content will decrease after steaming and boiling,and SDS content will increase but RS content will decrease after air expansion treatment.Finally,different cooking methods will change the flavor and taste in wild rice.The results of electronic nose detection combined with PCA analysis showed that the aroma components of different cooking methods were obviously distinguished,which shows that the volatile smell of wild rice after different cooking methods is quite different.A total of 69 kinds of volatile flavor compounds were detected by HS-SPME-GC-MS,among which the number of volatile flavor compounds in steaming and boiling treatments decreased,and the most kinds of volatile flavor compounds were detected in the air expansion treatment group,and pyrazines also appeared,which were not found in the raw wild rice,steaming and boiling treatment groups.By calculating the OAV value,30 key volatile flavor compounds of wild rice by different cooking methods were obtained,and methyl palmitate,dihydroactinidiolide and decanal were the common key volatile compounds.The electronic tongue can well distinguish the overall taste of raw wild rice from that of wild rice processed by different cooking methods.The overall flavor of raw wild rice is astringent and the bitter taste of steamed wild rice is obvious.The overall flavor of boiled wild rice is salty,and the response value of fresh taste of air expansion wild rice is higher than that of other treatment groups.In summary,there are differences in nutrient contents of wild rice in different regions of China,each with its own distinct characteristics.In addition,different cooking methods have significant effects on the flavor and taste of wild rice starch and wild rice.This paper provides theoretical basis for the development and utilization of wild rice resources in China.