Effects of Microwave Pretreatment on the Pressing Characteristics of Peanuts

Abstract

In an effort to provide a theoretical basis and data reference for the efficient processing and utilization of peanuts, changes in the moisture content, browning degree, particle texture parameters, water state and distribution, and protein denaturation degree of peanuts before and after microwave pretreatment were investigated, as well as the effect of microwave pretreatment on the yield of screw-pressed peanut oil. The results were compared with those obtained using vacuum oven drying. Meanwhile, for each pretreatment, the Pearson correlation between oil yield and moisture content, browning index (BI), particle texture parameters, water state, and protein denaturation degree was determined. The results showed that after microwave treatment for 7 min at 900 W or vacuum oven treatment at 85 ℃ for 89 min, the moisture content of peanuts decreased from 5.25% to 2.27%, with the highest oil yields of 45.85% and 45.76% being obtained, respectively. Under these conditions, the shear stress formed between peanuts and the oil press was moderate, peanuts were fully squeezed and deformed, with a large amount of oil flowing out, and peanuts had the best plasticity, the most ideal moisture state and a moderate degree of protein denaturation, so that not only a large amount of oil flowed out, but also peanuts were not easily broken, thus not affecting the formation of peanut cake.

Keywords

• microwave; peanut; oil yield; particle texture parameters; protein denaturation degree; correlation analysis