酪梨後熟期間果實密度及性狀特徴之研究

Abstract

酪梨（Persea americana）是一種全球貿易的水果，果實收穫時的狀態會影響後熟與否和達到最佳食用狀態所需的時間。 儘管關於酪梨採收的判斷已有許多採收指標，但用於預測後熟期的非破壞性技術仍然不足。本研究旨在建立一種非破壞性的密度測量方法，以三維重建法作為預測酪梨後熟的指標，並了解‘Red Fairy’、‘Choquette’和‘Hass’三個品種酪梨在後熟期間的物性變化。自果實採收後開始，在果實後熟期間每 2 天進行重量、體積、硬度和果皮顏色的測量。此外，每 2 天拍攝果實的三維模型，並在成熟時評估種子特性。當質構儀測得的水果硬度達到 10N 以下時，即視為完全後熟。根據果實第一次密度測量的結果將其分為高、中、低共3 組密度。當有果實開始達到後熟時，‘Red Fairy’和‘Hass’的最高密度組顯示出較高的硬度和較綠的顏色，表明成熟較慢；‘Choquette’的最高密度組顯示出顯著較低的硬度和較大的顏色變化，表明成熟較快。由於整個水果密度與不同天數的硬度或顏色指標之間存在顯著相關性，因此建立了回歸模型。然而，模型的 R 平方值小於 0.50，說明在建構的模型尚無法很好的預測，所使用的參數可能需要更多考量，雖然進一步考慮種子大小或種子空間，但並未改善相關係數和 R 平方值。最後，以‘Red Fairy’為材料，確定應用三維重建法是否可以取代傳統用於測量水果體積的排水法。使用兩種不同方法進行的體積測量具有顯著的相關性（R2 = 0.988，p<0.01），說明使用三維重建法可以替代傳統排水法，而三維拍攝重建法量測體積具有好的效率。基於重建法的密度分類也表明最高密度組傾向於成熟緩慢，這與排水法獲得的結果相符。總和以上結果，對採收後、剛開始後熟的果實，以簡單的果實物理特性測量結果可以提供酪梨後熟行為的初步預估。

Avocado (Persea americana) is a globally traded fruit, and its condition during harvest can affect the successful ripening and time required to reach the optimal edible state. Although numerous harvesting guidelines exist, non-destructive techniques for predicting the ripening period are insufficient. This study aimed to establish a nondestructive density measurement by the 3D reconstruction method as an indicator for avocado ripening prediction. Fruits of ‘Red Fairy’, ‘Choquette’, and ‘Hass’ were measured for weight, volume, firmness, and skin color every 2 days during ripening. Besides, 3D models of fruits were acquired every 2 days, too, and seed characteristics were evaluated at ripening. When the firmness of a fruit measured by a texture analyzer reached below 10N, it was regarded as ripe. The fruits were divided into 3 groups based on the first density measurement. When the earliest fruits reached ripening, the highest density groups of ‘Red Fairy’ and ‘Hass’ showed significantly higher firmness and greener color, indicating slower ripening; that of ‘Choquette’ exhibited significantly lower firmness and bigger color change, indicating faster ripening. Although the opposite trend was observed, it roughly succeeded to classify slow- or fast-ripening fruit by density. Then, regression models were developed since significant correlations were observed between whole fruit density and firmness or color indicators from different days. However, their R-squared values were less than 0.50, implying that those models may not be suitable for predicting those parameters practically. Further consideration of seed size or seed space did not improve correlation coefficients and R-squared values. Finally, an investigation was conducted with ‘Red Fairy’ to determine whether the 3D reconstruction method could replace the displacement method, which has been conventionally used in measuring the fruit volume. Volume measurements using two different methods showed a significant similarity (R2 = 0.988, p < 0.01), highlighting the efficiency of the 3D reconstruction method. Density classifications based on the reconstruction method also demonstrated that the highest-density group tended to ripen slowly, matching the results obtained by the displacement method. Those results demonstrate that simple fruit characteristic measurements can provide a preliminary estimation of avocado ripening behavior.