產胞外多醣體之乳酸菌對羊乳酸酪乳品質之影響

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题名:	產胞外多醣體之乳酸菌對羊乳酸酪乳品質之影響
其它题名:	The effects of exopolysaccharide-producing lactic acid bacteria on the qualities of caprine yogurt
作者:	盛兆盈 Sheng, Chao-Yin
贡献者:	洪連欉 Hung, Lien-Tsung 東海大學畜產與生物科技學系
关键词:	羊乳酸酪乳;胞外多醣體;黏質乳酸菌;黏絲性;黏度;乳清析出率 caprine yogur;exopolysaccharide;ropy lactic acid bacteria;thread forming property;viscosity;syneresis
日期:	2002
上传时间:	2011-05-19T05:48:23Z (UTC)
摘要:	實驗旨在利用可產胞外多醣體之黏質乳酸菌以改善羊乳酸酪乳之品質。實驗菌株為本實驗室篩選出之黏質乳酸菌Streptococcus thermophilus A1、A2、Lactobacillus bulgaricus B2、E、與一般商用菌?S. thermophilus CCRC 12257(S) 與L. bulgaricus CCRC 14009(L)。分別接種球菌A1、A2與桿菌B2、E等四株黏質乳酸菌於10% TS之還原羊乳中，並於32℃與42℃發酵72小時。結果顯示，四株黏質乳酸菌於發酵期間之pH值隨培養時間而下降，菌數、黏絲性、黏度則呈現出二次元程式之曲線，產酸能力以42℃大於32℃，而32℃時以球菌A1、A2之產酸能力較高。最高乳酸菌數與最大黏度皆為42℃高於32℃者，且以球菌A1、A2高於桿菌B2、E。黏絲性與胞外多醣體產量皆為32℃高於42℃，且球菌A1、A2高於桿菌B2與E。而胞外多醣體產量則隨著培養時間而呈降低之趨勢。分別以黏質乳酸菌與一般商用乳酸菌單獨使用、黏質乳酸菌之球菌與桿菌互相配對、黏質乳酸菌與一般商用乳酸菌之球菌與桿菌互相配對之方式，在27、32、37與42℃下發酵至pH值達4.5-4.6，製成羊乳酸酪乳。結果顯示，所有組別之酸酪乳其乳酸菌數皆能達8個對數值以上。在各培養溫度下之黏絲性與黏度，黏質酸酪乳皆比一般酸酪乳高(P<0.05)，且以培養溫度32℃與37℃培養者高於27℃與42℃者(P<0.05)，單株菌為球菌高於桿菌，混合菌則為黏質乳酸菌互相配對者高於黏質乳酸菌與一般商用乳酸菌配對者(P<0.05)。在各培養溫度下之乳清析出率，黏質酸酪乳皆比一般酸酪乳低(P<0.05)，且32℃與37℃培養者低於27℃或42℃(P<0.05)，單株菌之乳清析出率為球菌低於桿菌(P<0.05)，混合菌之乳清析出率則以黏質乳酸菌互相配對者低於黏質乳酸菌與一般商用乳酸菌配對者。胞外多醣體之產量單株菌於27℃培養者為最低，而混和菌低於單株菌(P<0.05)，胞外多醣體產量與酸酪乳黏度兩者間並無相關。物性方面，以培養溫度為主要影響因子，黏質酸酪乳之凝乳強度隨培養溫度之上昇而提高，在同樣培養溫度下比較，單株黏質乳酸菌之凝乳強度較單株商用菌者高，而混合菌在黏質酸酪乳與一般酸酪乳間並無明顯之差異。在貯存期間，黏質酸酪乳皆能保持較高之黏度與較低之乳清析出率(P<0.05)。官能品評之結果，黏質酸酪乳之外觀及口感較一般酸酪乳黏稠，且第零週之風味與總接受度亦較高，但經貯存兩週後則無明顯差異。 Ropy lactic acid bacteria were used to manufacture ropy caprine milk yogurt, in order to improve the qualities of caprine milk yogurt. Four ropy strains, Streptococcus thermophilus A1, A2, Lactobacillus bulgaricus B2, E and two commercial strains, Streptococcus thermophilus CCRC12257 (S) and Lactobacillus bulgaricus CCRC14009 (L) were used. Ropy strains were incubated in 10% TS caprine milk at 32 and 42℃ for 72 hours. The pH value of samples decreased during the incubation. The bacterial counts, thread forming properties and viscosity displayed a quadratic curve. The exopolysaccharide (EPS) concentration had a trend toward reduction. The lactic acid production, maximal bacterial counts and viscosity of samples fermented at 42℃ greater than those were fermented at 32℃, while A1 and A2 sets were predominant. The thread forming properties and EPS concentration of samples fermented at 32℃ greater than those were fermented at 42℃, while A1 and A2 sets were predominant. Caprine yogurt were made at 27, 32, 37 and 42℃ by single ropy strains or mixed strains .The bacterial counts of all samples reached 108 cfu/ml. The thread forming properties and viscosity of ropy yogurt were higher than those of commercial yogurt at all incubation temperature. The incubation temperature of 32 and 37℃ resulted in the higher viscosity while the A1 and A2 sets were better than B2 and E sets. The mixed strains sets of ropy and ropy strains were better than the mixed strains sets of ropy and commercial strains. The syneresis of ropy yogurt were lower than commercial yogurt at all incubation temperature and the incubation temperature of 32 and 37℃ resulted in the lower syneresis while the A1 and A2 sets were lower than B2 and E sets. The mixed strains sets of ropy and ropy strains were lower than the mixed strains sets of ropy and commercial strains. Ropy yogurt had the least amounts of EPS at 27℃.The mixed strains resulted in less amounts of EPS than single strains, but did not affect the other characteristics. There’s no relationship between the viscosity and EPS concentration. The rheology of caprine yogurt was mainly affected by the incubation temperature. The gel strength of ropy yogurt increased with the increased incubation temperature. There’s no difference between ropy yogurt and commercial yogurt at the same incubation temperature. The ropy yogurt had the higher viscosity and the lower syneresis than commercial yogurt during the storage. The appearance and mouth-feel of ropy yogurt were higher than those of commercial yogurt. The flavor and overall acceptability of ropy yogurt were higher than those of commercial yogurt at the beginning of storage, but there’s no difference after 2 weeks.
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