Study On Evaluation Index Of Storage Character Of Wheat Flour

Wheat flour is one of the main grain in China, and it can not be stored for long time. But in order to regulate supply and demand or deal with emergencies, a constant amount of wheat flour must be stored, to ensure that there is ample supply of wheat flour whenever routine or emergency situations. Therefore, it is an urgently problem need to solved to ensure the stable quality and safety of wheat flour and reduce storage costs.At present wheat breeding, processing quality was studied by many scholar. Researches on components, dough properties and edible quality of wheat flour indicated that there are some more consistent conclusions , but little systematic research on storage quality has been conducted. Compare with wheat, due to loss of seed capsule protection and small particles, quality of wheat flour was easily affected by environment during storage. Quality deterioration such as: agglomeration, heat, mildew and invasion of insect pest. Therefore, it's important to find out reasons for quality change and indexes for quality evaluation when stored.This paper studied on the change of exterior quality, nutritional quality, edible quality and deterioration products of wheat flour by controlling storage environment (temperature, relative humidity). All these study is to explore its variation, select the representative indexes and set up guidelines for evaluation of storage characteristics. The study showed that:1. The analysis of moisture content indicated that: during the first 20-30 days, the moisture content of wheat flour could get balanced, which showed different value when wheat flour stored under different conditions. At the same temperature, as relative humidity increased, the moisture content increased, on the contrary, it decreased. At the same relative humidity, as temperature increased, the moisture content decreased, on the contrary, it increased.Analysis of variance (ANOVA) of storage temperature and relative humidity on moisture content were discussed, which presented a significant binary linear dependence with moisture. (Y =8.3150+11.0674X₁-0.08102X₂ R²=0.9073, X₁: relative humidity; X₂: temperature). The change of the moisture content, whiteness and other qualities were compared and analyzed, the result showed that wheat flour was significant affected by moisture content, therefore, we consider moisture content should be controlled under 14% during storage. Although the moisture content can not be an index to evaluation the storage quality, it must be a good guide for storage conditions selecting.2. The analysis of cooking quality indexes indicated that, color and odor can reflect the change of wheat flour ahead of other indexes in time. The physical chemistry indexes compared with edible quality was analyzed, the result showed that deterioration of wheat flour reflected by fatty acid, SRC and water absorption of gluten.3. Fatty acid changed markedly when wheat flour stored under the mid and low relative humidity. The correlation of fatty acid and cooking quality showed that: fatty acid and odor, surface color were negatively correlated (r=-0.83311,-0.77772). It can be as an index for evaluation of storage character, and critical value of sample used in this experiment was about 97.49mgKOH/100g.4. 5% sodium carbonate SRC, 5% lactic acid SRC and 50% sucrose SRC represent the different quality of wheat flour, and they changed markedly during storage. At the mid and low relative humidity, they all showed positively correlation with odor, surface color of steamed bread, which may consider to be good indexes for evaluation. Wheat flour used in this experiment would go moldy, musty, and heat when 5% sodium carbonate SRC<83.7%, 5% lactic acid SRC<97.1% and 50% sucrose SRC<115.0% during storage.5. As an index of guidelines for evaluation of storage character, water absorption of gluten changed markedly when wheat flour stored under the mid and low relative humidity. It showed negatively correlation with odor, surface color of steamed bread, and can be considered to evaluate wheat flour storage character. In order to keep the quality, the critical value of water absorption of gluten of sample used for experiment was not less than 182.6%.6. The change of wheat flour become quick and the quality decrease rapidly when it's stored under high relative humidity. Because stored in ventilate packing, wheat flour was changeably, and become agglomerate, moldy, taste abnormal. Therefore, it's better to select gas-proof packing for storage of wheat flour, and control the moisture content strictly to slower the change.7,The result of storage experiment was analyzed, and it showed that evaluating storage quality of wheat flour was considered by overall consideration of physical chemistry index, instrumental index and sensory evaluation, and not depend on only one index.