Effects of various heat treatments on the induction of cold tolerance and on the postharvest qualities of `Star Ruby' grapefruit
Ron Porat, David Pavoncello, Jacob Peretz, Shimshon Ben-Yehoshua and Susan Lurie
Postharvest Biology and Technology Vol: 18 Issue: 2 Pages: 159-165.
2000
บทคัดย่อ
We examined the effects of various heat treatments on the induction of cold tolerance in red grapefruit (Citrus paradisi cv. Star Ruby) and evaluated their effects on various other postharvest quality parameters such as decay development, weight loss, peel color, and juice total soluble solids (TSS) and acid content. Various heat treatments, including prestorage conditioning regimes of 3 days at 21°C and 7 days at 16°C, a hot water dip (HWD) at 53°C for 2 min, a hot water brushing (HWB) treatment at 60°C for 30 s, and curing (3 days at 36°C) achieved 70¯90% reduction in the chilling injury (CI) index, as compared with control untreated fruit, following 6 weeks of cold storage at 2°C and an additional week at 20°C. Of the various treatments that induced cold tolerance, only HWB significantly reduced postharvest decay development. Conditioning and curing, which required longer exposure periods of 3¯7 days at relatively high temperatures, significantly increased fruit weight loss, enhanced peel color alteration, and increased the juice TSS/acid ratios. On the other hand, the short postharvest heat treatments, including the HWD at 53°C for 2 min and the HWB at 60°C for 30 s, did not affect fruit weight loss, color, or TSS and acidity levels. Overall, it is concluded that short postharvest heat treatments, including either HWD or HWB are preferable, since they effectively induce tolerance to cold temperatures in `Star Ruby' grapefruit without impairing any other postharvest qualities. Of these treatments, the new HWB is faster and could be used to clean and disinfect the fruit, and simultaneously to enhance its CI tolerance.