|關鍵字： 番石榴；採前套袋；採前噴鈣；預冷；比重分級；果實品質；Guava；Preharvest bagging；Preharvest calcium application；Precooling；Specific Gravity Grading；Fruit quality
|摘要： 臺灣番石榴外銷量逐年攀升，為了改善夏季果實不耐低溫貯運及品質較差等問題。本試驗目的在探討從田間栽培改善做起，利用採收前套袋及噴鈣處理，調查果實採收品質及低溫貯運能力，並於採收後進行預冷處理和比重分級，期望能建立有效的夏季果實採收後處理流程，供臺灣番石榴外銷作業參考。 ‘珍珠’番石榴以白色紙袋內襯白色舒果網進行套袋處理，有效改善單獨以白色紙袋套袋延緩果實生長速率及大小的問題，夏季果實採收期與塑膠袋內襯白色舒果網處理差距在7天以內，且貯藏期間果實硬度、可溶性固形物及抗壞血酸含量均高於塑膠袋內襯白色舒果網處理，低溫貯藏的寒害症狀也受到改善，顯示白色紙袋內襯白色舒果網處理能保有單獨使用白色紙袋提升果實品質、降低貯藏期間品質劣變及寒害發生的優點，也能使果實鮮重、大小與塑膠袋內襯白色舒果網處理相近，維持‘珍珠’番石榴夏季果實品質。番石榴幼果期進行2-4次鈣源噴施，結果以0.1M奈米鈣和乳酸鈣處理能顯著增加番石榴植株葉片鈣含量，噴施4次後套袋果實的鈣含量也明顯提升，惟須注意乳酸鈣可能有果實變小的問題，而在葉片鈣元素轉移試驗中以0.05M硝酸鈣最具潛力，可能為另一種鈣源噴施的新選擇。 採收後立刻進行5℃的預冷處理，結果顯示以冰水預冷冷卻最快，其次為壓差預冷，最慢為一般室冷，貯藏品質以壓差預冷可有效延緩果實貯藏期間硬度下降，但是在可溶性固形物及抗壞血酸含量方面，不同預冷處理則無明顯差異效果，經回溫後冰水預冷的果實即出現明顯果皮褐化及腐爛現象，顯示冰水並不適合做為番石榴預冷方法，採收後以壓差預冷處理較佳。番石榴以果實比重作為分級的結果顯示，比重與硬度有較好的相關性，但受到果實個體差異、不同產地、栽培技術及季節等因素所影響。於5、6月份採收的果實以比重0.92-0.93進行分級可區分六分熟及八分熟果實，但至8月份採收的果實以比重0.95進行分級較為恰當。在貯藏品質調查顯示，兩者在官能品評上差異不大，低成熟度(SG ≥ 0.95)果實低溫冷藏後果皮褐化及維管束褐化等症狀較高成熟度輕微，但可能會有酒精傷害的疑慮。The amount of guava export t in Taiwan has increased year after year, but guava fruits are not resistant to cold storage and have poor quality during summer.The objectives of this research is to investigate the effect of preharvest bagging materials, calcium foliar application, postharvest precooling and specific gravity grading on fruit quality and cold storage capacity of ‘Jen Ju’ guava (Psidium guajava L.), and to establish an effective postharvest processing method for guava export. ‘Jen-Ju’ guava fruits bagged with white paper bag lined with expanded polystyrene net sleeve (WP+EPNS) showed reduced chilling injury, maintained higher firmness, total soluble solid, and ascorbic acid during cold storage, and demonstrated highter fruit growth rate.These results indicated that white paper bag lined with expanded polystyrene net sleeve (WP+EPNS) can effectively improve export quality of guava fruits and the bagged fruits showed decreased quality deterioration, less chilling injury and comparable yield to conventional cultivation. Furthermore, 2-4 times preharvest spray of 0.1M nano calcium or calcium lactate in young fruit stage of guava resulted in significant increase of the calcium content in leaf and fruit, but calcium lactate application may cause small fruit.Results from calcium nitrate application showed that it is the most potential source of calcium transferred in leaf and can be considered as a new source for calcium application. Results from different pre-cooling treatments immediately after harvest, showed that hydrocooling was most efficient in lowering fruit temperature, followed by forced-air cooling and then general room cooling.Forced-air cooling could reduce firmness loss during storage, however, no significant difference on total soluble solid and ascorbic acid values can be observed among different pre-cooling treatments. Hydrocooling is not suitable for guava, because the fruits displayed skin browing and decay after rewarming at 25℃. In summary, forced-air cooling is the most appropriate precooling method for guava harvested from field.In specific gravity graded ‘Jen-Ju’ guava fruits, a good correlation between fruit firmness and specific gravity was noticed. However, this correlation was influenced by fruit size, production site, cultivation method and season.Guava fruits harvested in May and June, can be graded into 60% and 80% maturity by their specific gravity between 0.92-0.93.In contrast, fruits harvested in August were better graded by 0.95.In trems of storage quality, no significant difference in organoleptic qualities was recored.After cold stograge, low maturity fruits (SG ≥ 0.95) showed less skin browning and vascular browning compared to higher maturity fruits (SG < 0.95).