Effects of heat treatments on the microbial reduction and germination rates of red radish sprout seeds (Raphanus sativus)

Abstract

This study was conducted to investigate the effects of various heat treatments on the microbial reduction and germination of red radish seeds for the development of effective and economical sterilization methods of improving microbial safety without reducting the germination rate. Hydrothermal treatment was conducted at 60, 65, 70, 75, 80, and 90℃ for 30 and 60 seconds, and dry heat treatment was performed at 70, 80, 90, and 100℃ for 5 minutes. In the seeds that underwent the hydrothermal treatment, time had little effect on the microbial reduction. There was no significant microbial reduction over time. However, there was significant microbial reduction as temperatures increased (p<0.001). The total plate count (TPC) was reduced by more than 3 logs, and Listeria monocytogenes was not detected at temperatures above 70°C. In the seeds that were subjected to the dry heat treatment, the TPC and the population of the L. monocytogenes were significantly reduced as the temperatures increased (p<0.001). After treatment at 100°C for 5 minutes, the TPC and the L. monocytogenes were reduced by 3 logs. As with the microbial reduction, time had little effect on the germination. There were no significant changes in the germination after the hydrothermal treatment over time; but at the temperatures above 75°C, the germination rate significantly decreased as the temperature increased (p<0.001). When the seeds were soaked after the hydrothermal treatment, their germination was stimulated. The dry heat treatment at temperatures of 80°C and higher significantly decreased the germination rate as the temperature increased (p<0.001). Dry heat treatment before the germination of the seeds soaked in distilled water for three hours significantly decreased the germination at temperatures greater than 90°C (p<0.05). This study showed that appropriate heat treatments can increase the microbiological safety and germination of red radish seeds.

Quality Characteristics of Beef by Different Cooking Methods for Frozen Home Meal Replacements

“…These pretreatments would increase the shelf life of the products after processing ( Jun and Lee, 2014 ). An initial thermal blanching step is normally applied in industry to inactivate oxidative enzymes in food and to reduce the contamination by microorganisms ( Lee et al ., 2002 ; Lee et al ., 2011 ).…”