Coupling relationship between content of unsaturated fatty acid and drying system of corn grain after variable temperature and humidity drying

The content of unsaturated fatty acid (UFA) is an important index to evaluate the quality of corn. It is not only the main fatty acid of corn, but also a very important dietary fatty acid and essential nutrient in human body. In order to study the relationship between UFA content and the drying system coupling factor of corn, an orthogonal experiment was designed. This experiment was based on the actual drying parameters of the corn dryer in Harbin grain dryer. First, the drying process was divided into three stages, each stage had different hot air temperature and relative humidity, so as to establish a six factors and three levels of sectional temperature and humidity orthogonal drying experiment. There were a total of 30 groups of experiments. Then, the content of UFA in dry corn was determined by microwave extraction and gas chromatography. Finally, the relationship between drying system coupling factor and UFA content in corn was calculated. On the premise of meeting the drying standard of edible corn, the highest content of UFA was 6.553% under the drying conditions of hot air temperature of 35 °C-50 °C-50 °C and relative humidity of 30%-45%-30%.After repeated verification, the actual optimal value was 6.547%. It is proved that the actual optimal value was consistent with the predicted value through the verification of the predicted optimal combination. Then the coupling relationship between UFA and coupling factors of the drying system ( including accumulated temperature, the absolute water potential sum of the air, the absolute water potential sum of the grain, the difference between the absolute water potential sum of the air and the absolute water potential sum of the grain, the accumulated of the absolute water potential of the air, the accumulated of the absolute water potential of the grain, the difference between the accumulated of the absolute water potential of the air and the accumulated of the absolute water potential of the grain) were calculated, and the results showed that the order of coupling relationship between UFA content and drying system was as follows: STMMG (0.674 3)> DSTMMGA (0.660 2)> STMMA (0.608 9)> SGT (0.589 3)> DATMMGA (0.477 2)> ATMMA (0.315 7)> ATMMG (0.257 6)> EAT (0.203 8). The coupling relationship between UFA content and absolute water potential of grain was the best. The formula for calculating the absolute water potential of grain can explain the coupling degree between them, and also prove that the theory of water potential can analyze and predict the content of unsaturated fatty acids in corn grains.