Study On The Change Of Flavor Compounds In Malt And Rice Under Various Storage Conditions

The beer flavor is related to product quality and market competitiveness,is one of the most important characteristics and quality indices of beer.The quality of malt and rice have great effect on flavor and flavor stability of beer. Methods for analysis of volatile flavor compounds of malt and rice of beer raw materials.based on solid-phase micro-extraction (SPME) and gas chromatography. and analysis of free fatty acids of rice using high performance liquid chromatography (HPLC) were established.which have priorities over tradition methods in peration complexity.quantitativeness. time consuming, etc. The dynamic changes of flavor compounds during storage were studied, the main results were concluded as follows.(1)A method based on SPME coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed for the determination of volatile flavor compounds in malt. The sample pretreatment ways of malt include malt crushing, saccharification. adding 20?L alcohol,0.5g salt,1mL wort sample in 20mL headspace bottle. The results showed that a DVB/CAR/PDMS fiber extracting for 60 min at 45? was the optimum extraction condition.Compared to the traditional way. this method has advantages of high accuracy, simple operation process and suitability for routine and efficient analysis of volatile flavor compounds in malt.The content of volatile flavor compounds in malt has species differences, and associated with the processing technology of malt. During three month storage of 4 malts.the contents of flavor compounds basically increased.meanwhile high temperature storage of malt has a bigger effect on the increase of flavor compounds than low temperature storage.therefor the storage of malt should be under low temperature and humidity conditions as far as possible.(2)A method based on SPME coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed for the determination of volatile flavor compounds in rice. The sample pretreatment ways of rice include rice grinding, sieving to get fine powder, adding 0.4g rice sample.10?L alcohol in 20mL headspace bottle. The results showed that a DVB/CAR/PDMS fiber extracting for 60 min at 40? was the optimum extraction condition. Compared to the traditional way. this method has advantages of high accuracy.simple operation process and suitability for routine and efficient analysis of volatile flavor compounds in rice. The content of volatile flavor compounds in malt has species differences, and associated with the finess degree of rice. During one month storage of 3 rice varieties, the contents of flavor compounds basically increased, meanwhile high temperature storage of malt has a bigger effect on the increase of flavor compounds than low temperature storage, therefor the storage of rice should be under low temperature and humidity conditions as far as possible. Combined with the analysis of sensory evaluation, the sensory score is high positive correlation with the lipid oxidation aldehyde (aldehyde.hexanal, trans-2-Nonenal) and amyl alcohol, heptanal. capraldehyde. The content of trans-2-Nonenal should be less than 8?g/Kg in order to control the quality of rice.(3)A method based on using HPLC to determine free fatty acids in rice by 2-bromoacetophenone derivation was developed as following.After rice crushing,isopropanol extraction, centrifugal, dried under nitrogen.blowing was performed to get the free fatty acids in rice.The derivative procedure was fulfilled by adding 2-bromoacetophenone/acetone and trimethylamine/acetone. heating in water bath for 15min at 100?, then adding acetic acid solution after cooling to terminate the reaction. Compared to the traditional way. this method has advantages of high accuracy and can quantitate unsaturated fatty acid, such as oleic acid, linoleic acid of rice accurately. The content of free fatty acids of rice is connected with rice processing finess degree, and the total acid value and free fatty acid is not completely correspondent. The free fatty acids in rice are mainly linoleic acid, oleic acid, stearic acid.which occupy the most part of free fatty acids of rice. During one month storage of 3 rice, the contents of free fatty acids basically increased, meanwhile high temperature storage of malt has a bigger effect on the increase of free fatty acids than low temperature storage, therefor after buying large quantities of rice, the storage of rice should be under low temperature and humidity conditions as far as possible, meanwhile using rice as soon as possible. Combined with the analysis of sensory evaluation, the sensory score is high positive correlation with the content of free fatty acids and fatty acid value. The content of free fatty acids should be no more than 800 mg/Kg in order to control the quality of rice.