短時溫湯處理對採後紅龍果果實保鮮的影響

Short-term hot water dipping influences preservation of red-fleshed pitaya (Hylocereus polyrhizus sp.) fruits

冷害、腐爛和失水是影響紅肉種紅龍果採收後果實品質的主要因子並進一步降低果實經濟價值。溫湯處理是控制上述採後問題的可靠方法之一。本研究的目的是評估短時溫湯浸泡(HWD)對紅龍果果實採後的品質和保存的影響。在篩選溫度的預試驗中已發現低於60°C的熱水處理不會造成熱傷害。紅肉種紅龍果利用58°C的溫湯分別浸泡15秒和30秒，再分別於5°C儲藏3週和5°C兩週後移至25°C儲藏1週這2種儲藏條件下，結果顯示58°C溫湯處理15秒不僅可降低5°C貯藏期間的果實罹病等級、延緩櫥架期間呼吸率上升的幅度，也不影響貯藏期間果實的品質，且在25°C貯藏下與對照組相比可延長2.6日的櫥架壽命。總體而言，建議紅龍果果實在採後利用58°C溫水浸置15秒不會造成熱傷害，也不會影響採後果實品質，同時能延長紅肉紅龍果果實的貯藏天數。

The chilling injury, decay, and water loss are the main postharvest problems which affect fruit quality of the red-fleshed pitaya (Hylocereus polyrhizus sp.) and further reduce fruit economical values. Hot water treatment is one of the reliable methods to control those postharvest problems. It has been found that hot water treatment below 60°C did not cause thermal damage for red-fleshed pitaya fruit after screening temperature in a pre-test. The objective of this study was to evaluate the effect of short-term hot water dips (HWD) on the quality and preservation of pitaya fruit. Postharvest short-term hot water dips at 58°C for 15 sec and 58°C for 30 sec influenced the physiological responses and quality of red-fleshed pitaya fruit during three-week storage at 5°C or two-week storage at 5°C, and subsequently one week of shelf-life at 25°C, respectively. In both storage conditions, HWD reduced weight loss, fruit bract withering, the chilling injury index and postharvest decay occurrence, which resulted in lower carbon dioxide (CO2) respiration production and extended 2.6 days of shelf-life for marketing. Moreover, the short-term postharvest HWD did not affect total soluble solids (TSS), titratic acid (TA), or TSS/TA. Overall, it is suggested that postharvest HWD at 58°C for 15 sec may extend red-fleshed pitaya fruit preservation without causing heat damage and affecting postharvest quality.