本研究擬以微生物發酵紅茶茶湯,首先由27種GRAS等級菌株中篩選出Lactobacillus delbrueckii ssp. bulgaricus做為發酵紅茶茶湯之菌株,後續深入探討以L. delbrueckii ssp. bulgaricus發酵紅茶茶湯與未發酵紅茶茶湯理化性質、化學成分、揮發性成分及感官品評差異。結果顯示經L. delbrueckii ssp. bulgaricus發酵之茶湯pH值及色澤會顯著改變,且其茶湯中除游離胺基酸含量有顯著性增加,多酚類、單寧、類黃酮及茶皂苷皆無顯著性改變。推測L. delbrueckii ssp. bulgaricus無法於紅茶茶湯中進行生物轉換。後續利用頂空固相微萃取-氣相層析質譜法分析發酵紅茶茶湯與未發酵茶湯間揮發性成分差異,並藉由感官品評之描述分析法進行感官特性差異比較,最後以紅茶茶湯中揮發性化合物及描述特性強度進行主成分分析 (principle component analysis, PCA)評估,其統計結果顯示利用12種揮發性化合物區分紅茶茶湯結果與15種描述特性強度區分紅茶茶湯結果不一致,故頂空固相微萃取-氣相層析質譜法及感官品評之描述分析法兩者方法無法相互取代。綜合以上結果可知,結合茶湯化學組成及感官特性差異較能全面了解以乳酸菌發酵紅茶茶湯之特性。
In this study, we aim to develope a new black tea beverage fermented with microorganism. First of all, we selected Lactobacillus delbrueckii ssp. bulgaricus to ferment black tea infusion from 27 GRAS level strains. Next, we investigated physicochemical properties, chemical components of this fermented black tea infusion. Our results showed that fermented black tea infusion had lower values of pH and Hunter L, a, b compared to the non-fermented black tea infusion. No changes of the contents of catechins, flavonoids and tea saponins were observed. Total free amino acid contents of fermented black tea infusion (49.84 mg/L) were significantly higher than those in non-fermented black tea infusion (34.11 mg/L). These results indicated that L. delbrueckii ssp. bulgaricus might not be able to bioconvert chemical components into smaller compounds. In addition, HS-SPME-GC-MS was used to qualify and quantify 12 volatile organic compounds in 7 different black tea infusions. Descriptive test was used to qualify and quantify 15 attributes in 7 different black tea infusions. Comparing the results of 12 volatile organic compounds and 15 attributes in 7 different black tea infusions by principal component analysis (PCA), the results showed the inconsistency between the two methodologies. However, combining the results of chemical components and sensory characteristics would be the best way to characterize the lactic acid bacteria-fermented black tea infusion.