Volatiles Of Rice During Storage Variation And Its Correlation With The Physical And Chemical Indicators

Adjust the moisture content of2011new japonica were13.5%,14.5%,15.5%and16.5%, respectively, and adjust the oxygen concentration of2%,5%,8%and21%in the5L jar, placed the samples in artificial climate chambers at15°C,20°C,25°C,30°C and stored180d. Tested once volatile substances and physical and chemicalindicators of the paddy every30days, analysis the differences of volatile substancesunder different storage conditions and the changes of storage quality,and then obtainthe correlation of them. The following are the main results:（1）The best extract condition of volatiles:the solid phase microextraction spire was50μmDVB/CAR/PDMS, the equilibration time was60min, the extraction time was45min, the parsing time was5min, respectively. At this extract conditions, theoriginal sample and the sample after storaged180d, each of the volatile substances inthe sample had achieved the best separating effect. At the same time, the variety ofingredients in the paddy volatiles were aldehydes, ketones, alcohols, hydrocarbons,esters and heterocyclic. The greatest change of ketones was6,10,14-trimethyl-2-Pentadecanone, reduced to only0.8%from its peak of25.74%.（2） Changes in paddy volatile substances: The results show that under differentstorage conditions, the peak of the retention time and the spike in paddy GC-MSchromatogram were similar, but the height of each peak was different. Paddy weredetected in82kinds of volatile components,, but the matching degree above80%were only62kinds although there were many different types of volatile components.Before storaged120d, ketones were the most in the volatile substances while thehydrocarbons was the heightest in the120d to180d. Most types of volatilecomponents are hydrocarbons, followed ketones and aldehydes, alcohols, at least. Acarbonyl compound such as aldehydes, alcohols and ketones is some small molecules,while the larger molecular weight alkanes, primarily C₁₀-C₂₂alkanes.（3） The changes of the physical and chemical indicators in paddy: With the extensionof storage time, the higher of the temperature, the faster of the rate of increase of thefatty acid value, the lower of the oxygen concentration can delay the fatty acid valuedecreased. The conductivity increases with the storage time, showing that thesignificant increase in the trend, the lower moisture content can delay the rise in theconductivity.（4） The correlation of physical and chemical quality with volatile substances: The results show that, under the different storage conditions, there was the negativecorrelation of hexanal,6,10,14-trimethyl-2-Pentadecanone, with fatty acids andconductivity, and P<0.01showed that a very significant to them; while the1H-Naphtho[2,1-b]pyran,3-ethenyldodecahydro-3,4a,7,7,10a-pentamethyl-,[3R-（3.alpha.,4a.beta.,6a.alpha.,10a.beta.,10b.alpha.）] had a significant negative correlation withfatty acid value and conductivity.6,10-dimethyl-5,9-Undecadien-2-one had the samecorrelation with fatty acid value and conductivity, but with the change of storageconditions, they showed significant differences. Under the conditions of30°C,nonanal and2-ethyl-1-hexanol had a negative correlation with the fatty acid valuefollowing the content changes of water, showing different significant differences.