Antioxidant and Antibacterial Activity, and the Amino Acid Profile of Pistachio (Pistacia vera L.) Waste Peptides Produced by Enzymatic Hydrolysis and Solid-State Fermentation

The pistachio nut (Pistacia vera L.) is a rich and high-quality source of protein, as is its waste. This study investigated the potentials of pistachio nut waste proteins to obtain bioactive peptides exhibiting antioxidative and antibacterial activities, and their amino acid profile. Enzymatic hydrolysis with pepsin, trypsin, chymotrypsin, and savinase was applied to the pistachio protein isolate (PPI) obtained from pistachio waste. In addition, solid-state fermentation (SSF) was applied to defatted pistachio with Bacillus subtilis, and peptides were produced. The highest degree of hydrolysis was obtained at 28.2% by using pepsin (p < 0.05). The highest ABTS radical scavenging activity was found as 232 µmol TE/g defatted pistachio (d.b.) for trypsin hydrolysate (p < 0.05). The maximum DPPH radical scavenging activity was found as 70.2 µmol TE/g defatted pistachio (d.b.) by hydrolysis with savinase. After gel filtration, the highest ABTS radical scavenging activity was found to be 0.1166 mg TE/mL in the T7 sample (p < 0.05), while the highest DPPH scavenging activity was found to be 0.0573 mg TE/mL in the S8 sample (p < 0.05). The sample showing the highest antibacterial activity was chymotrypsin hydrolysate with MIC = 0.378 mg/mL against Staphylococcus aureus. The total amino acid contents (TAA) of PPI, hydrolysate samples, and the SSF sample ranged from 63.136 to 76.665 g/100 g protein. It was also seen that proteins and peptides obtained from pistachio waste have a rich amino acid profile, especially Asp and Tyr, and good antioxidant activity.