The modeling and optimization effects of cleaning and moisture content on the physical and microbial characteristics of wheat by response surface methodology

Background and objectives: Wheat grain has an important value in the world nutrition. Physical and microbial properties of agricultural products (such as wheat, ...) play an important role during harvesting with machines, cleaning process and waste reduction. In this study, the first research in Iran, the optimized effects of cleaning and moisture content at 40 °C on the physical (Useful besatz, Unuseful besatz, hectoliter, weight thousand seed) and microbial (total count of microorganisms and mold counts) properties of wheat grain (n-80 variety) in Golestan province, were modeled.
Materials and methods: After determining the basic moisture content, samples with three levels of cleaning (0-100%), and different moisture content (10-14% wet basis) at 40 °C were studied and modeled by response surface methodology using central composite design (face center) includes 21 tests with five repeats at the central point.
Results: The results showed that by reducing moisture content and increasing cleaning levels, useful and unuseful besatz were decreased and hectoliter was increased. Also increasing the percent of cleaning was more effective than reduce the moisture content in reducing useful besatz and unuseful besatz. The lowest rate of hectoliter was 72.58 (0.01kg. lit-1) at 40 °C. The highest weight of thousand seed at moisture content 14% (wet basis) and cleaning level 100%, was 36.80 gr. Increase in weight of thousand seed in the higher moisture content was more effective than the higher level of cleaning. With increasing moisture content and reduction in cleaning, total count of microorganisms and mold counts were increased. Linear parameters of cleaning and moisture, in the linear model had a significant effect (p < 0.01) at a temperature of 40 °C on the total count of microorganisms. The population of total microorganisms and molds in moisture content 14% (wet basis) and cleaning level of 10%, compared to moisture content 10% (w.b), was increased 52.7 and 90%, respectively. High values of factor R2 for useful besatz, unuseful besatz, hectoliter, weight thousand seed, total count of microorganisms and mold counts, respectively were 0.9463, 0.9818, 0.9677, 0.8255, 0.8547 and 0.9674. The optimize results at a temperature of 40 °C showed that 100% cleaning level and 10% (wet basis) moisture content, would be cause the storage of grain wheat with the desirability of 94.1%.
Conclusion: For all studied properties, due to non- significant lack of fit and high values of R2 and R2 adjusted, our selected models could accurately predict the experimental values.