Effect of Gamma Irradiation on the Microbiological and Physicochemical Quality Changes of Steamed Waxy Corns during Storage

Effect of gamma irradiation on the microbiological and physicochemical characteristics of steamed waxy corns was determined in order to develop preservation techniques to enhance shelf-life during storage at room or low temperature. The initial total microbial count, and yeast & molds steamed waxy corns before irradiation were $2.1{\times}10^3CFU/g,\;1.9{\times}10^3CFU/g$, respectively. However, the total microbial count were completely inactivated and the count of yeast and molds were only 34 CFU/g at 3 kGy treatment When non-irradiated steamed waxy corns were stored at $25^{\circ}C$ for 7 months, the growth of total microbial counts and yeasts & molds were rapidly increased up to $7.1{\times}10^6CFU/g\;and\;1.9{\times}10^7CFU/g$, respectively. However, the total microbial counts at 3 kGy treatment and yeast & molds at 5 kGy treatment for 7 month storage were completely inactivated Similar result was observed at $15^{\circ}C$ and $4^{\circ}C$ storage. The Hardness of the irradiated steamed waxy corns and irradiation dose were not significantly different from those of the non-irradiated steamed waxy corns before storage, but the hardness of non-irradiated steamed waxy corns was significantly increased during the storage, compared to those of irradiated corns. The water content of both irradiated and non-irradiated steamed waxy corns after 7 month storage were significantly decreased from $65{\sim}60%$ to 30% but the changes of water content among treatments or irradiation doses were not significantly different during storage. Sugar contents in the irradiated steamed waxy corns were less free than those of non-irradiated samples and the amount of free sugar slowly increased as storage temperature increased. Sensory evaluation result showed that total sensory scores in irradiated steamed waxy corns were better than those of non-irradiated samples and total sensory scores were increased as irradiation doses increased.

감마선 조사에 의한 증자 찰옥수수의 저장 중 미생물 및 이화학적 특성변화

찰옥수수를 중 저온에서 장기간 저장할 수 있는 방법을 개발하기 위하여 찰옥수수를 증자하여 진공포장한 후 감마선 조사하여 여러 온도에서 저장하면서 미생물의 생육변화 및 이화학적 성질을 조사하였다. 증자 찰옥수수를 감마선 조사한 후 저장전에 총균수는 3 kGy 조사에서 모두 사멸하였고 곰팡이 및 효모는 34 CFU/g을 나타내었으며, $25^{\circ}C$에서 7개월간 저장 후에 총균수 및 효모, 곰팡이는 대조구에서 $7.1{\times}10^6CFU/g,\;1.9{\times}10^7CFU/g$를 나타내었으나 3 kGy 조사구에서는 총균수가 검출되지 않았으며 효모 및 곰팡이는 5 kGy에서 완전히 사멸되었으며 이러한 결과는 $15^{\circ}C$와$4^{\circ}C$에 저장하였을 경우에도 비슷한 경향을 나타내었다. 감마선 조사직후 각 처리구는 무처리구에 비하여 경도의 차이가 없었으며 조사선량간에도 유의적인 차이가 없었다. $4^{\circ}C-25^{\circ}C$에서 7개월간 저장 후 초기 수분함량$65{\sim}70%$에서 약 30%로 현저하게 감소하였으나 저장 기간 동안 무처리구와 감마선 처리구에서의 수분 함량과 조사선량에 따른 차이는 거의 없었다. 환원당 함량은 각 처리구 모두 비조사구가 감마선 조사구에 비하여 많이 용출되는 경향을 나타내었으며 온도가 높을수록 환원당 용출이 약간 증가하는 것으로 나타났으며 저장기간이 지남에 따라 감마선 처리구가 무처리구에 비하여 종합적 기호도가 좋았으며 조사선량이 증가할수록 기호도가 향상되는 것으로 나타났다.