Comparisons of Processing Stability and Antioxidant Activity of the Silkworm Pupae Protein Hydrolysates by Spray-dry and Freeze-dry

Silkworm pupae protein (SPP) was pretreated by different processing (heat/alkali/pepsin) and then hydrolyzed by five proteases (trypsin/flavorzyme/papain/protamex/alcalase), respectively. It was found that the combination of heat pretreatment and alkali pretreatment followed by enzymatic hydrolysis with trypsin and flavorzyme could remarkably improve the protein recovery. The hydrolysates obtained from silkworm pupae protein hydrolyzed with trypsin and flavorzyme were stable at the pH range of 4.0-8.0, remaining 95% of its original reducing power and 90% of its OH center dot scavenging activity. However, they were susceptible to alkaline treatments (pH > 10.0) and lost > 30% of their antioxidant activities. Pasteurization (65 degrees C x 30 min) or autoclaving sterilization (121 degrees C x 20 min) did not show notable effects on the antioxidant activities. It was concluded that silkworm pupae protein hydrolysates (SPPH) were better to be applied in either neutral or acidic food system rather than in alkaline conditions.