The effect of processing temperature on microbial safety and antioxidant activity of minimally processed "raw food"

Abstract

The assessment of the effect of dehydration temperatures (40 °C, 50 °C, and 60 °C) on the microbiological quality, antioxidant activity and oxidative stability of lipids of buckwheat-based minimally processed "raw food" (MPRF) was performed. Buckwheat flakes with various ingredients were soaked in sterile distilled water for 20 h, then MPRF samples were formed and dehydrated at constant temperature. Total viable counts, coliform, fungi, yeasts and aerobic spore-forming bacteria counts were evaluated in dehydrated products. While fungi were effectively reduced at all drying temperatures, higher total viable and coliform counts were found in MPRF samples after drying at 40 °C and 50 °C. Generally, antioxidant activity of MPRF samples did not significantly differ, and superoxide dismutase activity remained constant with the increase of drying temperature. The inhibition of lipid peroxidation was significantly higher in MPRF samples dehydrated at 40 °C than in those dehydrated at higher temperatures. Lipid oxidation stability measured by peroxide value, conjugated dienes content and thiobarbituric acid-reactive substances assay was not substantially affected during the dehydration process. Preparing MPRF by dehydration at 40 °C and 50 °C was considered as representing a microbial hazard whereas overall antioxidant activity was found to be minimally influenced by the dehydration temperatures. © 2016 National Agricultural and Food Centre (Slovakia).