The dual effectiveness of Opuntia ficus indica extracts for browning inhibition and microbial inactivation on fresh-cut apples was investigated. Prepared apple slices were treated with 25, 50, 100, 200 mg/mL Opuntia ficus indica extracts, packaged in polyethylene bags, and stored for 10 days at 4, 21oC. Results indicate that Opuntia ficus indica extracts significantly (P < 0.05) inhibited the browning reaction of fresh-cut apples. This treatment also reduced peroxidase activities. The populations of Staphylococcus aureus significantly decreased with increasing extract concentration (p < 0.05). In particular, S. aureus was reduced to non-detectable levels after 2 days in 100 mg/mL treatment at 4oC and 21oC. Opuntia ficus indica extracts therefore have antibacterial and antibrowning effects. The results suggest that Opuntia ficus indica extracts could be useful as a natural food preservative.

갈변과 미생물 증식으로 인해 저하되는 양상추의 품질을 향상시키기 위해 양상추를 최소처리하여 이들 품질저하요인을 제어하고자 하였다. 갈변억제방법으로는 다양한 침지수에 따른 화학적인 방법을 사용하였고, 미생물 증식억제방법으로는 염소처리법과 전기분해수 그리고 유기산 처리에 의한 방법을 사용하였다. 그 결과 양상추의 갈변은 색도에 있어서 ascorbic acid 1와 citric acid 1 혼합침지수로 처리하였을 때 초기 L 값이 5 수준에서 유의적으

This study was performed to evaluate the inactivation and microbial regrowth of heterotrophic and nitrifying bacteria using chloramine as a secondary disinfectant for drinking water distribution system. Three sets of the three reactors filled with the Cl2/NH3-N ratio of 3:1, 4:1 and 5:1 were used in these experiments. Chloramine concentration were applied to each set of the reactors with 1㎎/ℓ, 2㎎/ℓ and 3㎎/ℓ, respectively. For the set with 1㎎/ℓ was applied, all the reactors showed that the residual chloramine concentration gradually decreased with elapsed time and reached to zero level after 7 days. Heterotrophic bacteria remarkably increased and nitrification occurred after 11 days. For the sets with 2㎎/ℓ and 3㎎/ℓ, however, the residual chloramine was maintained through the experimenatal period (21 day). Furthermore the regrowth of heterotrophic bacteria and nitrification were not found. More than 2㎎/ℓ of chloramine with Cl2/NH3-N ratio of 3:1, the nitrification could be inhibited by 2 days of contact time.