The Changes Of Lipids And Rheological Properties Of Long-grain Glutinous Husked Rice In The Process Of Storage

With the accelerating rhythm of life,the some quick-frozen food such as dumplings,rice dumplings,rice cakes and so on,which made by glutinous rice,are more and more loved by consumers.So the storage of glutinous rice becoming extremely important.Due to the glutinous rice losts the protection of shell and cortex,the dust and broken rice would easily cause the harm of insect,mildew,etc.It is difficult to store and keep its quality.But when storing in the form of husked rice,it not only takes up less storage space,but can reduce the workload and the cost of transportation.At the same time, husked rice still gets peel and seeds and has germination ability.Therefore,the research of long-grain glutinous husked rice storage characteristics has a far-reaching significance to husked rice storage and glutinous rice flour processed products.In this experiment,the long-grain glutinous husked rice were stored in different temperature(15℃,25℃ and 35℃) and controlled atmosphere storage(air sealed,N2 sealed,CO2 sealed,vacuum sealed).We stored the husked rice for 180 d,and measured its lipid indexes(fat,acidity,fatty acid values,malondialdehyde,lipase activity,catalase activity and carbonyl value),gelatinization characteristics,volatile components,structure characteristics of dumplings and the sensory quality every 30 d.The experimental results showed that:1.In the process of long-grain glutinous husked rice storage,as the extension of storage time,moisture content and fat content showed a trend of decline.In low storage temperature the decomposition rate of nutrients was significantly lower than high temperature, and the controlled atmosphere storage could also effectively restrain decomposition of nutrients of long-grain glutinous husked rice.The acidity and fatty acid values were in decline after rising first,and the higher temperature had a lager variation,it arrived the peak until 120 d.Low temperature can effectively reduce the increase of acidity and fatty acid value in the process of storage,the controlled atmosphere storage can effectively inhibit the increases of fatty acid value,but had no significant effect on the acidity.The content of malondialdehyde increased stably in the process of storage,the low temperature could effectively reduce the increase of malondialdehyde,however,the effect of controlled atmosphere storage was obvious only at the early stage of the storage.Lipase and catalase activitis decreased when the time extended and as storage temperature rose,it showed decline after rising first,and in the higher temperature the lipase activity and catalase activity decline faster.With the rise of storage temperature,the carbonyl value increased obviously.2.Through the analysis of RVA pasting characteristics of long-grain glutinous husked rice,we found that as the extension of storage time,all of the attenuation value,peak viscosity,low viscosity,final viscosity and retrogradation value of long-grain glutinous husked rice had rising trends,and with the increase of the temperature they changed obviously.But the peak viscosity and the attenuation value declined in 35℃.In controlled atmosphere storage,the husked rice had a similar changed trends under 15℃,25℃ and 35℃.And no obvious difference in the group of controlled atmosphere storage.This showed that the temperature was the main influence factor of husked rice gelatinization characteristics, but the controlled atmosphere storage had a little effects on it.3.Using SPME and GC-MS detected volatile substances of long-grain glutinous husked rice.At different storage conditions, the ion peaks of volatile components in husked rice had same retention time,and the peak shapes were similar.In general we chected out 60 species of volatile substances,their matching degrees were higher than 80%.In which there were as many as 18 kinds of aldehyde material sort,ketone were the least,and the most of them were acids matter contents.The rise of temperature,volatile component content of husked rice will also be increased accordingly.Generally speeking, the volatile components increased with the extension of storage time.4.The determinations of quick-frozen dumplings made by storaged husked rice using Texture Analyzer showed that the indicators were extremely influenced by temperature,the controlled atmosphere storage had no obvious influences.Through the sensory evaluations of dumplings,we found that temperature and controlled atmosphere storage had little effects on the edible quality of the dumplings in the early storage time;At 35℃ the edible quality of dumplings declined in 60 d,but the dumplings in controlled atmosphere storage had no changes;The edible quality of dumplings began to decline after 90 d under other temperature conditions,no obvious effect on controlled atmosphere storage.5.Through the experiment research indicates that the main affecting quality of husked rice storage temperature, at low temperature can better reduce the deterioration of quality, for the deterioration of quality of brown rice slow down the controlled atmosphere storage function advantage, the more obvious with the increase of temperature, vacuum storage effect optimal. Therefore, brown rice during storage, as far as possible choose low temperature storage, and under the condition of low temperature coordinate using gas storage can better maintain the edible quality of brown rice.