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

열처리 방법이 적무 새싹종자(Raphanus sativus)의 미생물 저감화 및 발아율에 미치는 영향

  • Jun, So-Yun (Department of Food Science and Nutrition, Kyungpook National University) ;
  • Lee, Yeon-Kyung (Department of Food Science and Nutrition, Kyungpook National University)
  • 전소윤 (경북대학교 식품영양학과) ;
  • 이연경 (경북대학교 식품영양학과)
  • Received : 2014.02.12
  • Accepted : 2014.06.02
  • Published : 2014.08.30

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 $90^{\circ}C$ for 30 and 60 seconds, and dry heat treatment was performed at 70, 80, 90, and $100^{\circ}C$ 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 $70^{\circ}C$. 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 $100^{\circ}C$ 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 $75^{\circ}C$, 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 $80^{\circ}C$ 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 $90^{\circ}C$ (p<0.05). This study showed that appropriate heat treatments can increase the microbiological safety and germination of red radish seeds.

Keywords

microbial reduction;germination rate;heat treatment;Listeria monocytogenes;red radish sprout seeds

Acknowledgement

Supported by : 농림기술관리센터(ARPC)

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