阿拉比卡咖啡品種間之圓豆比例與品質比較

摘要咖啡屬於茜草科（Rubiaceae）是重要的經濟作物之一。通常咖啡漿果含有兩個半橢圓形的種子（平豆），但有時只有兩個胚珠中的一個受精成功，因此單粒種子會發育成圓形或長橢圓形，是異常種子之一，稱為圓豆（peaberry）。圓豆形成的原因可能是:子房中的兩個胚珠之一受精和座果失敗，或胚乳發育失敗。而上述兩個條件給剩餘的一個種子有機會在咖啡漿果的腔體內有足夠的空間發展成圓形。本試驗在台南市東山區「大鋤花間」咖啡園於2021年11月12日到2022年3月25日的咖啡產季進行，此咖啡園位於北緯23°28'，東經120°51'（海拔650~710公尺），共種植維尼西亞（Venecia）、黃波旁（Yellow bourbon）、紫葉（Purpurascens）、鐵比卡（Typica）、藝伎（Geisha）等五個品種。果實採收調查後，經水洗處理後製，日曬搭配烘箱乾燥到9.8~11.6%含水率，0.56~0.61的水活性，並於台灣咖啡研究室進行杯測品評評鑑。本試驗結果如下: 圓豆率為8.22~15.64%，平均10.81%，明顯高於坊間咖啡教學單位或咖啡公司宣稱的5~10%圓豆率，在品種間有顯著差異，而以鐵比卡8.22%為最少，藝伎15.64%為最多。換豆率為從漿果到後製加工成為生豆的比率，五個品種間並沒有顯著差異；平豆換豆率為14.38~18.55%，平均16.36%，換算比例為6.11:1，與台灣咖啡農所稱的換豆率6:1相符。另，圓豆的換豆率為12.40~14.62%，平均13.37%，換算比例為7.48:1，以比例計算圓豆換豆率是比平豆少22.59%。各品種的圓豆著果位置，在果樹的任何位置都會發生，而在樹枝中段、稍段的數量較多，並非民間所稱因為輸送到枝條末梢的營養不足而形成圓豆，且均集中長在末梢。漿果比重上，圓豆和平豆的比重在品種間均有顯著差異，各品種在A級別（浮豆）的比例約為4.49~14.71%，平均浮豆比例為10.60%，其中以維尼西亞最低 4.49%、紫葉最高14.71%。各品種的比重大部分落在class C，為56.17~76.99%。而生豆單株產量在品種間有顯著差異，以鐵比卡（1464.48 g）最多，紫葉（223.94 g）最少。官能品評杯測的結果，圓豆和平豆之間的品評總分上並沒有顯著差異，沒有坊間所謂的圓豆風味更好更珍奇的情形。台灣咖啡種植面積10年來已經翻倍達1150公頃以上，然而台灣的人工及土地成本高，因而臺灣咖啡豆價格高於進口豆，因此提供高品質的咖啡將是臺灣咖啡農最好的選擇。然而在日益極端氣候、逐漸暖化的臺灣氣候也是咖啡農更大的挑戰。本試驗的結果指出，圓豆的比率為8.22~15.64%，著果在咖啡樹整株各個位置，而在風味上圓豆和平豆也沒有顯著差異，上述結果與坊間流傳的圓豆資訊相異。如上所述期待本試驗結果得以提供農民和研究單位在咖啡栽培上的參考，對臺灣咖啡未來的研究發展有所助益。關鍵字：咖啡、圓豆、風味、比重、產量、官能品評

關鍵字

咖啡；圓豆；風味；比重；產量；官能品評

並列摘要

Abstract Coffee belongs to the Rubiaceae family which is one of the important economic crops. Usually, coffee berries contain two semi-oval seeds (flat beans), but sometimes only one of the two seeds can be fertilized successfully. Thus, a single seed develops into a round or oblong shape, which is one of the abnormal seeds also called peaberry. The causes of forming peaberry are suspicious of two reasons as below: (1) two ovules in the ovary failed to fertilize and fruit set, (2) failure of endosperm development. However, the above two failure conditions provide a chance for the remaining one seed, which has enough space in the cavity of the coffee berry to develop into a round shape. This experiment was carried out in the coffee production season from November 12, 2021 to March 25, 2022 in Dachu Coffee Estate in Dongshan District, Tainan City. This coffee farm is located at 23°28'N latitude, 120°51' E longitude (650~710 meters above sea level). In addition, there are five varieties of Venecia, Yellow bourbon, Purpurascens, Typica and Geisha were planted. The fruit after harvesting and investigating will be under process of post water washing, drying in the sun and dryer to a moisture content of 9.8~11.6% and a water activity of 0.56~0.61. The green beans then were delivered to Taiwan Coffee Research Laboratory for cupping tasting evaluation. The experimental results are as follows: The proportion of peaberry is 8.22~15.64%, with an average of 10.81%, which is significantly higher than the 5~10% peaberry proportion claimed by the coffee educational institution or coffee companies in the market. The proportion of peaberry has significant among varieties. The lowest is 8.22% for Typica, and the highest is 15.64% for Geisha. The bean exchange rate is the ratio from berries to post-processing into green beans, there are no significant differences among the five varieties; the bean exchange rate for flat beans is 14.38~18.55%, with an average of 16.36%, and the conversion ratio of 6.11:1 is comparable with the bean exchange rate of 6:1 which is claimed by Taiwanese coffee farmers. In addition, the exchange rate of peaberry is 12.40~14.62%, with an average of 13.37%, and the conversion ratio is 7.48:1, the bean exchange rate of peaberry by proportional calculation is 22.59% less than the flat beans. The fruit-carrying positions of peaberry of various varieties can occur anywhere on the coffee tree, but there are more in the middle and a tip section of the branches. It is not as the folks say that peaberries are formed because of insufficient nutrients delivered to the tips of the branches, and they are all concentrated at the tips. In terms of the density of berries, the density of peaberries and flat beans are significantly different among varieties. As for the density of floating fruits on each variety in grade A is about 4.49~14.71%, and the average density of floating fruits are 10.60%. Among them, Venecia has the lowest 4.49%; Purpurascens is the highest with 14.71%. Most of the density of each variety falls in class C, which is 56.17~76.99%. The yield per plant of green beans was significantly different among the varieties, with the most Typica (1464.48 g) and the least Purpurascens (223.94 g). According to the results of the sensory tasting and cupping test, there is no significant difference in the total score between peaberries and flat beans, and there is no so-called peaberry tastes better and is rarer. The coffee planting area in Taiwan has doubled to more than 1,150 hectares in the past 10 years. However, due to the high labor and land costs in Taiwan, the price of Taiwanese coffee beans is higher than imported beans. Therefore, providing high-quality coffee will be the best choice for Taiwanese coffee farmers. In addition, the increasingly extreme and warming Taiwan climate is also a bigger challenge for coffee farmers. The results of this experiment pointed out that the proportion of peaberry was 8.22~15.64%; the fruit was grown on various sections of the coffee tree, and there was no significant difference in flavor between peaberries and flat beans. The above results are different from the common information about peaberries spreaded in the market. Even it can greatly improve the quality of coffee beans. As mentioned above, it is expected that the results of this experiment will provide farmers and research institutions with a reference for coffee cultivation, and will be helpful for the future research and development of coffee in Taiwan. Key words: Coffee, peaberry, flavor,density, production, sensory evaluation