Optimisation of aflatoxin B1reduction in pistachio nuts by kefir grains using statistical experimental methods

The presence of aflatoxin B1 (AFB1) in pistachio nuts has a serious impact on public health. Kefir grains (KGs) contain several probiotic microorganisms well known for their aflatoxin decontamination effects. In this study, the capacity of KG to remove AFB1 from pistachio nuts was investigated and the detoxification method was optimised using certain statistical approaches. Five variables (toxin concentration, KG level, contact time, incubation temperature and pre-treatment heat level) were considered in the study. Pistachio samples were spiked with 5, 10, 15, 20 and 25 ng/g AFB1 stock solutions and then treated with 5, 10, 15, 20 and 25% (w/w, based on the amount of pistachio paste) KG already heated at 70 and 110 °C. AFB1 concentrations in the samples were determined using high-performance liquid chromatography. Results of the study indicated that: (1) KG caused significant decrease in AFB1; (2) cell viability of KG was not necessary for its decontamination effect; (3) the amount of AFB1 reduction depended on toxin concentration and contact time; and (4) the interactions between toxin concentration and KG level, toxin concentration and contact time as well as incubation temperature and contact time had significant effects on AFB1 reduction. The optimum conditions for the highest AFB1 reduction (96%, compared to the control sample) included a 20 ng/g toxin concentration, 20% KG level, 6 h contact time and 30 °C incubation temperature. To verify the findings of this study, the efficiency of KG needs to be confirmed in vivo.