包裝氣體調整技術應用於’珍珠拔’番石榴採後處理暨貯運之研究

Abstract

番石榴( Psidium guajava L.)屬寒害敏感型熱帶水果，利用長程低溫貯運或低溫檢疫易發生寒害，嚴重阻礙行銷國際市場。本試驗探討改變大氣成份減輕‘珍珠拔’番石榴低溫檢疫處理後寒害的適當條件。‘珍珠拔’於0˚C環境有氧呼吸消失點為O2 3%，果實維持最低生理活性，若O2 再降低則會誘發明顯無氧呼吸，造成果肉組織乙醇、乙醛累積及CO2釋放率提高：高CO2傷害使果皮黃化；低溫檢疫處理（0℃處理14天）後回溫3天期間維持低O2可抑制果皮PPO活性，因而減緩褐變寒害徵狀發展。以塑膠袋進行降低O2提高CO2之主動氣變包裝及真空包裝處理，經低溫檢疫處理回溫3日後，‘珍珠拔’寒害指數為1.2級（褐化面積15%）、Hue angle值105.5˚，且皆能維持果實硬度4.5 N、可滴定酸0.4~0.5%、可溶性固形物8.7~8.8%，較對照組寒害指數4級（褐化面積>50%）、Hue angle值103.1˚能有效減輕寒害褐變與維持果實品質，雖然兩者都會引起果肉乙醇、乙醛明顯累積，但並不影響品評風味。真空包裝雖較主動氣變包裝操作簡單，但真空處理在模擬5˚C船運7天後回溫3日易發生品質迅速劣變；而主動氣變包裝回溫後則仍能維持果實品質，為減輕‘珍珠拔’低溫檢疫寒害的最佳氣變包裝條件。

Guava (Psidium guajava L.) is a chilling sensitive tropical fruit. The fact that long-term cold transportation and cold quarantine treatment usually render severe chilling injury impedes exporting for international markets. The purpose of this research is to investigate the effect of atmosphere modification technology on cold quarantine treatment of guava fruit. The aerobic respiration extinction point of ‘Jen-Ju Bar’ guava at 0˚C was 3% O2, which reduced physiological activity of the fruit onto its minimum. However, a storage condition with O2 lower than 3% stimulated aerobic respiration of the fruit companied with accumulation of ethanol and acetaldehyde in pulp tissues. On the other hand, a symptom of orange-yellowish color on the peel was obviously found when the surrounding CO2 concentration was high. During a 3-day at 20℃ stage following the cold quarantine process (0℃ for 14 days), low O2 was effectively suppressed enzymatic activity of polyphenol oxidase and, therefore, alleviated peel discoloration of chill injury symptoms. The effects of different active and passive modified atmosphere packaging (MAP) conditions by using plastic bag on chilling injury of ’Jan-Ju Bar’ guava after cold quarantine were evaluated. Among the trials, reducing O2 and enhancing CO2 of active MAP and vacuum packaging were considered the best two treatments based on maintenance of fruit quality, including firmness 4.5 N, titratable acidity 0.4~0.5%, and soluble solids 8.7~8.8%. Moreover, the chilling index and peel Hue angle of fruit from both treatments were similar and were grade 1.2 (15% browning area) and 105.5˚, respectively, which implied a significant reduction of chilling injury symptom when compared with grade 4 (> 50% browning area) and 103.1˚ from fruit of the control. Although marked accumulations of ethanol and acetaldehyde in the pulp tissues were found in the fruit with these two treatments, there was no adverse effect on the taste and flavor of the pulp assessed by sensory evaluation. Vacuum packaging has an advantage of easier operation than active MAP; however, fruit packed by vacuum packaging exhibited accelerating deterioration during a 7-day simulating transportation at 5˚C followed by 3 days at 20˚C. Under the same process fruit treated with active MAP, in contrast, could maintain sensory quality as well as alleviate browning symptom caused by chilling injury after cold quarantine. Therefore, the later was considered the best MAP condition for reducing chilling injury of cold quarantine-treated ‘Jan-Ju Bar’ guava.