The Research Of Japonica And Indica Quality Changes And The Main Volatile Substances Among The Rice During Storage

This paper mainly studied the variation of rice cultivars quality under the same storage conditions.The freshly harvested indica rice(14 species)and japonica rice(9 species)in 2015 were screened,removed,collected the water(13.5%±0.5%and 14.5%±0.5%respectively),and bagged bag,then stored at 25 ? for 360 days.The fatty acid value,texture characteristics,gelatinization characteristics,amylose,color difference and volatile substances were measured every 30 days.Through the PCA analysis,we aim to find out the unique substances of rice in order to achieve the purpose of distinguishing rice varieties.After the experimental analysis,the following conclusions:1.Storage time had significant effect on rice quality index.The quality indexes of different varieties of rice were different with the storage time,and the quality indexes of different varieties were different in the same storage period.Under the same storage conditions,the fatty acid value of different rice varieties increased gradually with the storage time.The hardness of the five kinds of japonica increased with the storage time and then decreased.The hardness of the five kinds of indica rice decreased with the shortening of the storage time.Precious rice.The adhesion of japonica and indica rice decreased with the storage time as a whole.The adhesion of indica rice is less than that of japonica rice.The elasticity of the five kinds of japonica has a certain fluctuation with the prolongation of the storage time,but the overall decrease is gradually.Compared with the rice,the elasticity of the five kinds of indica rice increases first and then decreases.The chewiness of japonica rice and indica rice increased first and then decreased with the storage time,and the recovery of japonica rice and indica rice increased with the prolongation of storage time.L value gradually decreased with the prolongation of storage time,and the value of a and b increased with the prolongation of storage time.2.All data were analyzed by SPSS and principal component analysis(PCA).Significant differences were found among amylose contents and RVA eigenvalues among the ten varieties of indica rice.Pasting properties parameter values have some relevance,with a wider range of variation coefficient(0.83%?32.30%).The change range of amylose content was 16.12%?24.80%in different rice cultivars,rice types were divided according to amylose content,including high type,medium type and low type,without extreme low and waxy type.The seven gelatinization characteristics were attributed to two main componentsby PCA,which were peak viscosity and peak time factor spectively.The samples collected from different regions can be distinguished,the rice types divided according to amylose content also can be distinguished.3.The fingerprint on volatile constituents of indica rice was investigated using HS-SPME/GC-MS.Results showed that the volatile constituents of indica rice can be well seperated using HS-SPME/GC-MS.Based on the analysis of GC chromatogram of 10 paddy samples collected from Hunan province,it was confirmed that 12 peaks in chromatogram can be selected as the fingerprint of peaks of volatile constituents,and it was established as the fingerprint chromatogram for indica rice.Moreover,the GC fingerprint was analyzed by similarity analysis.There is a high similarity among 10 kinds of indica rice.The established fingerprints could be used in quality assessment of paddy and provided helpful information for the comprehensive study of volatile consitituents of indica rice.4.The head space-solid phase microextraction method was used to extract the volatile components of indica rice and the extracted volatile substances were analyzed by gas chromatography-mass spectrometry method.A total of 265 volatile components were detected,of which 125 were the major volaties,including 56 kinds of hydrocarbons,alcohols 12 species,13 kinds of aldehydes,ketones 14 species,19 kinds of eaters,heterocylic 11 species.All species were detected high levels of 6,10,14-trimethyl-2-pentadecanone.Some varieties have unique substances,Kauri-15?ene only existed in Zhuliangyou 819 and Zaoyou,Tezao has a special bisabolene;iso-phytol,tetrahydrofurfuryl lavender alcohol and citronellol are Zhuliangyou819,Tezao and Zaoyou respectively;only Zaoxian 87 contained high levels of dihydroxyacetoph-enone;Benzoicacid ester of silicon occurred only in Zaoyou,chloroformate n-nonyl ester were only detected in Zhongzao 39,Only Zhuliangyou 819 and Zaoxain 51-4 have chloroformate n-octyl phthalate.The results of principal component analysis shows that olefin,alkanes,aldehydes and heterocylic were the main influencing factors.The contribution rate was 35.878%,19.267%,18.727%and 13.596%spectively,and the cumulative contribution rate was 87.467%.Samples were distinguished except Zhuliangyou 402,Tanliangyou 83 and Zaoxian 24 according to olefin;Zaoxian 87,Zaoxian 89 and Zaoxian 51-4 can be identified by alkanes;Zhuliangyou 819 and Zaoixan 51-4 were disciminated through aldehydes;Zaoxian 51-4 and Zaoxian 24 were identified in accordance with heterocyclic.