Raw Vegan Meal: The Effect of Moderate Drying Temeprature on Antioxidant Properties and Microbial Contamination

Abstract

A raw food vegan (RFV) diet is one that consists of only uncooked plant-derived products. Since the fresh food products can deteriorate during storage, the moderate temperature treatment is allowed up to 46°C according to the popular literature. RFV adherents believ that plant-derived food prepared in such a way keep the nutrients almost untouched. The effect of moderate drying temperature (40°C–80°C) on the antioxidant properties of various fruits and vegetables was assessed using meta-analytical approach. While ascorbic acid content has decreased with the increase in drying temperature, total phenolic and flavonoid content did not reduce with the increase of drying temperature. In order to elucidate the effect of moderaty drying temperature on the quality of RVF diet, buckwheat-based cookies we prepared according to the popular recipe including soaking of ingredients in tap water, formation of cookies followed by their drying at various temperatures. Antioxidant properties measured in terms of DPPH and ABTS radical scavenging activity were significantly reduced when compared with raw matter (after soaking). However, drying at 40°C, 50°C or 60°C for 20 h gave similar values for all the parameters indicating that increasing drying temperature did not affect antioxidant properties. In addition, the same trends were obtained for inhibition of lipid peroxidation and superoxid dismutase activity in buckwheat-based samples. Drying buckwheats or other ingredients at 40°C may exhibit serious microbial hazard. In our experiments, significant reduction of coliforms has occured after drying at 50°C and total bacterial count decreased after drying at 60°C. Aerobic-spore forming bacteria count remained constant at each temperature level. Soaking process was identified as the critical point regarding the proliferation of coliform bacteria, particuarly when soaked at ambient temperature. Drying at 40°C resulted in sharp increase in Escherichia coli count. Although buckwheat-based products dried at 40°C have retained high antioxidant properties than those dried at higher temperatures, serious health implication may occure due to the high content of bacteria, particluarly E. coli.