Study On Color And Volatile Components Of Rapeseed During Storage

In recent years, the fast target detection technologies which can characterize quality ofproducts mainly through determining the physical properties such as color, smell, textureand shape, have received widespread attention of domestic and foreign scholars. In thisstudy, changes rule of main quality index, color parameters and volatile compounds ofrapeseed during storage time were systematically analyzed. One or several key colorparameters and characteristic volatile compounds which can characterize the changes ofrapeseed quality were explored during storage, which further improves and perfects theevaluation system of the qualities of rapeseed, and also provides a scientific basis for thesafe storage of rapeseed. The main works are as follows:1. Storage conditions on changes of main quality index of rapeseed.With the increasing of storage time,conductivity, free fatty acid(FFA)content,peroxide value (POV) of rapeseed increased under different storage conditions, in contrast,the germination rate decreased.The influence size of storage conditions to the main qualityindex of rapeseed is as follow: conductivity, germination rate, peroxide value (POV):moisture content>storage temperature>storage time> oxygen concentration; FFA content:moisture content>storage time>storage temperature>oxygen concentration; Taken together:moisture content was what affected quality of rapeseed the most; followed by storagetemperature and storage time, and oxygen concentration was the least.2. Analyze the principle color parameters in rapeseed and the correlation between theprinciple color parameters and main quality index of rapeseed.Using statistical software SPSS19.0, color parameters obtained under differentstorage conditions for60-day storage were analyzed by principal component method. Theresult showed that main components of color parameters under different storage conditionswere as follows: a~*(△a~*)、C(△C)、△E; The correlation-analyzed results indicatedthat:a~*(△a~*)、C(△C)、△E displayed significant positive correlation with conductivity,free fatty acid(FFA)content and peroxide value (POV)；and they displayed significantinverse correlation with germination rate. In the sense of the high correlation between colorparameters and quality index, and whether or not it can correctly reflect the color changesof rapeseed, we eventually chose a~*(△a~*)、C(△C)、△E as the best color parameters forcharacterizing the quality of rapeseed.3. Optimization of operation conditions of electronic nose and SPME-GC-MS forvolatile components in rapeseed.The volatile compounds of rapeseed were analyzed by using electronic nose andheadspace solid-phase micro-extraction-gas chromatography and mass spectrometry(SPME-GC-MS). The optimized conditions include: Electronic nose: quantity of sample:5.00g,injection volume:2.50mL, the equilibrium temperature:60℃, the equilibrium time:10min; SPME-GC-M: extraction fiber were DVB/CAR/PDMS, extraction temperature was60℃,extraction time was60min, and desorption time was3min, respectively. Under the optimalexperimental conditions, the original sample and the deteriorated sample can bedistinguished by Electronic nose, the degree of differentiation was94%; both the two kindsof samples were also detected by SPME-GC-MS, the result showed that: Volatilecompounds in rapeseed are aldehydes, alcohols, ketones, hydrocarbons, some acid estercompounds, and heterocycle group, in which alkane was the most group.4. Changes of volatile compounds in rapeseed with both high temperature and highmoisture content during storage were analyzed by Electronic nose and SPME-GC-MS.The original sample and sample with high temperature(35℃)、high moisture (13.5%)for different storage time can be distinguished by Electronic nose, the degree ofdifferentiation is91%; Volatile compounds in rapeseed were analyzed by usingSPME-GC-MS, the results showed that main volatile components were as follows: Withthe increasing of storage time, the content of Nonanal, Benzaldehyde,2-hydroxy-4-methyl-,Tetradecane, Tetradecane,4-methyl-, Butylated Hydroxytoluene decreased significantly;the content of Pentadecane,2-methyl-, Hexadecane,2-methyl-, Heptadecane, Octadecaneincreased significantly;1-Octanol was only detected in the sample of the original andstored at the early stage of storage; Benzaldehyde,2-hydroxy-6-methyl-, acetophenone,Styrene, Hexadecane,3-methyl-, Heneicosane were detected in the sample stored at themid-to-late stage of storage; Benzeneacetaldehyde, Phenylethyl alcohol,3-Octanone,1-Octen-3-ol were detected in the sample stored at whole storage.