Effect Of Controlled Atmosphere Storage With N₂on Quality Of Soybean

The influences of controlled atmosphere storage with N2on soybean physical andchemical qualities were studied in the paper. The soybean samples with12.2%,13.6%and14.9%moisture content were stored in rich nitrogen atmosphere (N2content98%,90%and78%) at20±1℃,25±1℃and30±1℃respectively. Some physical andchemical characters such as fatty acid value, fatty peroxide value, crude proteincontent, soluble protein content, physiological and biochemical indexes of aging andcompression character were analyzed every30days, the main results were as follows:(1) The fatty acid value and fatty peroxide value of stored soybean increased duringstorage under different storage conditions. The more moisture content and higherstorage temperature were, the faster acid value and peroxide value increased. Highnitrogen concentration can delay the decline of soybean qualities. The influence ofstorage factors on acid value of stored soybeans was moisture content﹥storagetemperature﹥nitrogen concentration, while the influence of storage factors onperoxide value of stored soybean was moisture content﹥storage temperature﹥nitrogen concentration. Moisture content was the most important factors affecting oilquality of stored soybeans.(2) There was no obvious change about crude protein of stored soybeans, and thecrude protein content was maintained in the range of39.12%to41.74%duringsoybeans stored. The nitrogen soluble index (NSI) of stored soybean wascontinuously reduced during soybeans stored. The NSI would be rapidly decreasedwhen soybeans were stored in higher moisture content, higher temperature and lowernitrogen condition. The influence of storage factors on NSI of stored soybeans wasstorage temperature﹥moisture content﹥nitrogen concentration.(3) The germination percentage of stored soybean decreased during storage underdifferent storage conditions, while conductivity of soybeans extract andmalondialdehyde (MDA) content was increased constantly. Activity of some enzymeswere changed, the catalase (CAT) activity was gradually decreased, while theperoxidase (POD) activity firstly was increased and then decreased. There wassignificant correlation between germination percentage and conductivity, thecorrelation coefficient was-0.986. Aging and deterioration of soybeans could bedelayed by rich N2condition, and the soybean quality could be kept well under lower moisture content and temperature.(4) The compression features of stored soybeans changed under different storageconditions. The compressive deformations were increased at break point and thehardness of stored soybeans was decreased during soybeans stored. The highermoisture content and temperature led to soybean hardness dropping, and it was notconducive to be processed.The results showed that controlling moisture content of soybean was an importantcondition to ensure the stability of stored soybeans. The storage period of soybeanscan be extended under lower storage temperature, while controlled atmospherestorage with N2would prolong the storage time of soybeans under lower moisturecontent and lower temperature.