愛玉凍凝膠機構之研究

A Study on the Mechanism of Gelatinization of Awkeo-Jelly

臺灣夏天有一種獨特且頗具鄉土風味之冷飲食品，被稱為愛玉凍，係以蓋灣特殊植物－－愛玉（Ficus Awkeotsang Makino）之陽乾瘦果（俗稱愛玉子）放入布袋，於6O～100倍水中揉搓約10分鐘所得之粘性液，放置約20分鐘後自行凝膠者。陽乾愛玉瘦果含水分約13～14%，總果膠約6～7%，而其可溶性果膠中之甲氧基含量約為10%，本係一種高甲氧性果膠。愛王瘦果與一般高等植物，如番茄比較時，其果膠酯酶之活性pH範圍偏向酸性。當吾人將愛玉子在水中搓揉時，高甲氧性果膠溶出，同特受愛玉瘦果本身所含之此種特殊果膠酯酶之作用一直行股甲基，則可漸次變為低甲氧性果膠，且與水中之雙價陽離子如Ca+2相交聯，成為更巨大分子之低甲氧性果膠之鈣塩，於是不需加糖或酸即可凝膠。愛玉凍之pH值在4.0左右，果膠含量為0.06～0.09%。以種子重量之60倍水製造愛玉凍時，水中鈣離子濃度宜為20～60ppm，以40ppm為最佳。

There is a kind of special food named 'Awkeo-jelly', served with added in cold light syrup and sold locally at summer time in Taiwan. This jelly is prepared with sun dried achenes (usually miscalled as seeds) of Awkeotsang (jelly fig, Ficus Awkeotsang Makino). When we put 1 part of so called Awkeo seeds in cloth bag and rub in 60~100 parts of water for 10 minutes, we can obtain a viscous solution and it may gelatinize in 20 minutes or more. The sun dried achenes contained about 13~14% of moisture and 6~7% of total pectin (as calcium-polygalacturonate). The methoxyl content of the soluble pectin is about 10%. It is a high methoxyl pectin (HMP). The active pH range of Awkeo pectinesterase (PE) tends to be more acidic when compared with that of usual higher plants, such as tomatoes. This special PE can successively demethylate the water soluble HMP, and finally convert it to low methoxyl pectin (LMP) which may easily cross linked by divalent cations, such as calcium, to become a much larger molecule of calcium salt of LMP, and form gel, without any addition of sugar or acid. The pH value of Awkeo-jelly was determined to be about 4.0 and pectin content was 0.06~0.09%. When we rub 1 part of sun dried achenes with 60 parts of water, Ca+2 concentration in water might range 20~60 ppm, and about 40 ppm is most preferable in Awkeo-jelly making.