蘋果調理醋加工過程中生成那塔對醋液化學組成之影響

Abstract

醋是一種酸性的天然加工食品，食用消化吸收後可改變人體成為弱鹼性體質，由生理的角度來看可視為一種鹼性食品。本研究之目的在探討新鮮蘋果及濃縮果汁還原後之蘋果汁加工製成蘋果浸漬醋中之成分差異，並與生成那塔 (nata)之新鮮蘋果浸漬醋中醋液之成分與香氣做比較，此外，本研究亦進一步分析蘋果浸漬醋加工過程中生成那塔的菌種及醋液中菌相，並探討蔗糖濃度對還原蘋果汁浸漬醋中抑制菌種生長的影響。 實驗結果顯示蘋果浸漬醋與生成那塔之蘋果浸漬醋經過30天的浸泡，生成那塔的蘋果浸漬醋所含可溶性固形物平均下降0.5oBrix；氨態氮含量降低0.2 % (g/g)；甲醛態氮增加0.7 mg/100g；醋酸含量下降約2700 mg/kg、蘋果酸與葡萄糖酸則增加約320 mg/kg與2910 mg/kg；揮發性香氣成分中醋酸所佔相對百分比下降20.5%；而揮發性的氨類化合物所佔相對百分比則上升7%。還原蘋果汁浸漬醋所含成分與蘋果切片浸漬醋比較，差異在於氨態氮多與甲醛態氮分別高出0.16 % (g/g)與0.19 mg/100g；醋酸含量多867 mg/kg，蘋果酸與葡萄糖酸含量較蘋果切片浸漬醋分別少435 mg/kg與1180 mg /kg，主要的揮發性香氣成分則十分相似。還原蘋果汁浸漬醋添加蔗糖至可溶性固形物含量達到30oBrix以上，即可抑制木質醋酸菌代謝營養源生成那塔。商用糯米醋中並未發現活菌存在，新鮮蘋果經過表面清洗後之浸醋與濃縮還原蘋果汁浸漬醋依然有那塔生成的情況可能來自加工過程的污染。蘋果浸漬醋中生成那塔之細菌經証實為葡萄糖醋桿菌(Gluconacetobacter xylinus)。

Vinegar is a natural acidic food, however, it is generally considered as a physiological alkaline food because it will metabolize into a nalka -line environment in the human body after digestion. The objectives of this study are to investigate the characteristic differences of apple vinegar made from fresh apple slice maceration (ASV)and reconstituted apple juice blending (RAJV); to compare the chemical composition and flavor volatiles of the nata-forming apple slice vinegars (NASV) and ASV; to identify the microflora in NASV and ASV; and to investigate the effect of sucrose concentration on the inhibition of nata-forming bacteria in RAJV. The results of this study showed that the total soluble solids, ammo -nia nitrogen, and acetic acid contents in NASV decreased 0.5oBrix, 0.2 % (g/g), and 2700 mg/kg, respectively, as compared to ASV after 30 days of maceration, however, the formaldehyde nitrogen, malic acid, and gluconic acid content increase 0.7 mg/100g, 320 mg/kg, and 2910 mg/kg, respectively. In the results of flavor analyses showed that, acetic acid decrease 20.5 %, and ammonia compound increase 7 % in NASV, as compared to ASV. Compare the chemical compositions of RAJV and ASV indicate that, ammonia nitrogen, formaldehyde nitrogen, and acetic acid contents increased 0.16 % (g/g), 0.19 mg/100g, and 867 mg/kg, respectively in RAJV; and malic acid and gluconic acid contents decreased 435 mg/kg and 1180 mg/kg, respectively. The aroma volatiles contents of RAJV and ASV are relatively similar. Addition of sucrose to RAJV soluble solids content to above 30oBrix effectively inhibited the growth of nata-forming bacteria. No viable bacteria is found in commercial rice vinegar and washed apples, which indicated the nata-forming bacteria found in NASV and nata-forming reconstituted apple juice blending vinegars (NRAJV) may come from contamination. The nata-forming bacteria in NASV was identified as Gluconacetobacter xylinus.