3.2. Degradation of the main components in peanut cell wall
Viscozyme® L, as a complex plant hydrolase, decomposes the cell wall structure. During the process of aqueous enzymatic extraction, the main components in the wall, cellulose, hemicellulose and pectin, are progressively degraded, meanwhile protein and oil bodies are gradually released. To elucidate the degradation of the cell wall in the aqueous enzymatic extraction process in more detail, we analyzed the changes in the main cell wall components (Table 1).
The maximum degradation rate of CDTA-soluble pectin (67.4%), Na2CO3-soluble pectin (87.0%), hemicellulose (39.1%), and cellulose (57.1%) was reached at solid-liquid ratios of 1:3, 1:4, 1:5, and 1:3, respectively (Table 1). A high protein yield (86.64%) and the maximum yield of oil bodies (42.18%) were recorded at solid-liquid ratios of 1:3 and 1:4, at which the degradation rates of CDTA-soluble pectin, Na2CO3-soluble pectin, and cellulose were the highest (Fig. 1, Table 1). The highest degradation rate of CDTA-soluble pectin (81.1%), Na2CO3-soluble pectin (76.0%), hemicellulose (62.7%), and cellulose (55.1%) were obtained at enzyme concentrations of 1.00, 1.25, 0.75, and 1.00%, respectively. The highest protein yield (77.86%) and the maximum yield of oil bodies (35.76%) was attained at enzyme concentration of 1.25%, at which Na2CO3-soluble pectin had the best degradation rate (Fig. 1, Table 1). Enzyme hydrolysis parameters had a significant effect on the content of the main cell wall components (Table 1). The maximum degradation rate of CDTA-soluble pectin (75.5%), Na2CO3-soluble pectin (70.0%), hemicellulose (43.0%), and cellulose (44.8%) were reached at enzyme hydrolysis temperatures of 50, 45, 40, and 45 °C, respectively. The highest protein yield (78.54%) and the maximum yield of oil bodies (37.88%) was obtained at 55 °C and 50 °C, respectively, at which CDTA-soluble pectin had the best degradation rate. The degradation rates of CDTA-soluble pectin, Na2CO3-soluble pectin, hemicellulose, and cellulose were 62.2% at 80 min enzyme hydrolysis time, 51.3% at 60 min, 55.3% at 60 min, and 62.6% at 100 min, respectively. The maximum protein yield (80%) and the maximum yield of oil bodies (37.92%) was recorded when CDTA-soluble pectin had the most optimal degradation rate and the enzyme hydrolysis time of 80 min (Fig. 1).