Effects of coating pistachio kernels with mixtures of whey protein and selected herbal plant extracts on growth inhibition of Aspergillus flavus and prevention of aflatoxin during storage

Abstract

AbstractWhey protein concentrate (WPC) mixed with various concentrations of Shirazi thyme (ST), sage, and cumin seed (CS) extracts separately. Then pistachio kernels (PK) contaminated with Aspergillus flavus (Af) were coated with each extract and the Af mycelium and generated aflatoxins measured after 3, 5, and 7‐days at 20°C. The ST, sage, and CS had two major antioxidants of thymol (~27%) and carvacrol (~41%), α‐thujone (~28%) and camphor (~14%), and cumin‐aldehyde (~21%) and safranal (~20%), respectively. While the Af mycelium diameter on PK without extract became >90 mm within 3 days, it was shrunk after 7 days when the WPC‐coated PK had 4,000 ppm ST extract. When ST concentrations increased in WPC‐coated PK linearly, the Af growth and aflatoxins production decreased logarithmically. No aflatoxins (B1, B2, G1, and G2) detected in PK after 9 days when the extract concentrations of ST, sage, and CS in WPC reached, respectively to 5,000, 4,500, and 6,500 ppm. Sage extract had significantly (p < .01) the highest TPC (lowest IC50) and preventing power for aflatoxin generation in comparison with ST and CS extracts. The PK will be safe and healthy if the extract concentration of sage, ST, and CS exceed 950, 1,400, and 1,700 mg/kg, respectively.