Study On Volatile Components Of Wheat Flour During Storage

At present, few studies of volatile components in wheat flours during storage wereinvestigated at domestic and foreign. The effects of storage environment (such astemperature, humidity, etc.) and storage time on volatiles and the changes of volatilecomponents in wheat flours during storage are not clear. The different storage conditionswere analyzed in this study. The factors which affect the quality change of wheat flourswere explored. Changes of volatiles and correlation of the physical and chemical indexes inwheat flours were analyzed. Several volatile substances which reflect the quality changesof wheat flours were found during storage, which improves to control the deterioration ofwheat flour quality during storage and satisfy people’s demands for food quality and safety,and which contributes to the establishment of finished grain reserve system and assuranceof the nutritional quality and eating quality.Wheat flours were stored with three relative moisture content (13%,14%, and15%) andfour storage temperature (20°C,25°C,30°C, and35°C). Volatile compounds and chemicalindex of wheat flours were determined under different storage conditions every month.Extraction condition of volatile components, main changes of volatile compounds, fattyacid value, malondialdehyde (MDA), gluten, retrogradation, peak viscosity and finalviscosity in wheat flours were analysised during storage.And the correlation analysis wasinvestigated further between volatile compounds and fatty acid value, MDA, retrogradation.The results were listed as follows:1. Optimization of extraction conditions for volatile components in wheat flours.The volatile compounds of wheat flours were analyzed by using headspace solid-phasemicroextraction-gas chromatography and mass spectrometry.The optimized conditionsinclude: extraction fiber were DVB/CAR/PDMS, extraction temperature were80℃,extraction time were60min, and desorption time were3min, respectively.2. The changes of the content of volatile compounds in wheat flours.Retention times of various volatile components in wheat flours are same and the peakshape is similar under different storage conditions, but the content of each peak is different.Volatile compounds in wheat flours are aldehydes, alcohols, ketones, hydrocarbons andsome acid ester compounds, meanwhile, the content of hydrocarbons are the highest,followed by aldehydes and alcohols, and ketones are least.45kinds of volatile material canbe detected, but the content of relative percentage area of each volatile component is verylow. The kinds of aldehydes are the most in volatile components, followed by alkanes andalcohols, and the kinds of ketones are the least. The carbonyl compounds of aldehydes,alcohols and ketones are mainly some small molecules, while the molecular weights of thealkanes are higher, which are mainly C10-C24hydrocarbon substances. The peak retentiontimes of various volatile components are the same and peak shape is similar under different storage conditions, but the peak abundances of various volatile components are different.3. The changes of various physical and chemical indexes in wheat flours.With the increasing of storage time, the fatty acid value, MDA, retrogradation, peakviscosity and final viscosity in wheat flour were increased, but wet gluten was increasedfirst and then decreased. The higher the moisture contents were in wheat flours, the higherfatty acid values were in wheat flours under the same storage temperature and timeconditions. The higher the storage temperatures were, the greater the fatty acid values wereat the same humidity conditions. MDA contents in wheat flours were slowly increased withthe increasing storage time. When the storage temperature and time are the same, finalviscosity can be increased quickly with increasing the moisture content of wheat flour.4. The principle components in wheat flours were analyzed, and also the correlationbetween the principle volatile components and chemical index of wheat flours wereinvestigated.Using statistical software SPSS17,45kinds of volatile components obtained underdifferent moisture content and different storage temperature for6-month storage wereanalyzed by principal component method. When the moisture content of wheat flour was13%, the results show that main volatile components under different storage temperatureswere as follows: Hexanal,2-heptenal, Nonanal,2-Nonenal,2,4-Nonadienal,1-hexanol,dodecane, tetradecane. When the moisture content of wheat flour was14%, main volatilecomponents under different storage temperatures were as follows: Benzaldehyde, Octanal,1-Hexanol,2-ethyl-, Benzyl Alcohol,1-Octanol, Acetophenone, tetradecane. When themoisture content of wheat flour was15%, main volatile components under different storagetemperatures were as follows: Octanal,2-Octenal,2,4-Decadienal,1-Hexanol,2-ethyl-,1-Octanol, Acetophenone. There were seventeen volatile compounds in wheat flours beselected with principal component analysis: Hexanal,2-Heptenal, Benzaldehyde, Octanal,2-Octenal, Nonanal,2-Nonenal,2,4-Nonadienal,2,4-Decadienal,1-Hexanol,1-Hexanol,2-ethyl-, Benzyl Alcohol,1-Octanol, Acetophenone, Dodecane, Tetradecane.Under different moisture content and storage temperature, correlations between mainvolatile components and fatty acid value, malondialdehyde and retrogradation wereanalyzed by statistical software SPSS17. The results showed that volatile components ofwheat flour with different moisture content under different storage temperatures weredifferent. There are ten volatile compounds in wheat flousr are selected with correlationanalysis: Hexanal,2-Octenal,2-Nonenal,2,4-Decadienal,1-Hexanol,2-ethyl-, Benzyl,Alcohol, Acetophenone, Dodecane, Tetradecane. There were high positive correlationsbetween the10volatile components described above and fatty acid value, MDA andretrogradation.