| 摘要: | 近年來台灣民眾對於食品添加劑的疑慮與不安日益加深。冰淇淋製造需添加安定劑以增加口感與延緩溶化時間，而以添加化學安定劑居多，目前尚未有屬於純天然安定劑的產品。枯草桿菌在納豆內發酵時所產生的黏液成分為天然多醣體，適合作為安定劑。本研究之目的在探討使用納豆菌發酵於牛乳製成冰淇淋對於物理性與機能性之影響。在曝氣發酵期間每2 hr測定一次菌數生長量，並將發酵不同時間之牛乳添加於混料中（牛乳、鮮奶油、砂糖和奶粉）進行陳化，將陳化後混料取部分進行黏度、顏色、pH值測定及抗氧化性（DPPH自由基清除率、螯合亞鐵能力與總還原力）。剩於混料進行攪凍與硬化製成冰淇淋，並測定冰淇淋膨脹率、第一滴水滴落時間、融化速率、質量保持率、抗氧化性及官能品評。
結果顯示：菌數生長在12 hr達平穩期（108~109 CFU / mL），發酵時間在14 hr後製成冰淇淋抗氧化效果包括DPPH：82.41％、螯合亞鐵53.12％、總還原力0.70皆較控制組顯著上升（p>0.05），混料在0 hr的DPPH自由基清除率與螯合亞鐵能力皆出現攪凍破壞（61.91 %下降至50.37 %、47.7 %下降至30.5 %）的現象，但經過納豆菌發酵14~35 hr皆未出現顯著（p>0.05）的攪凍破壞。膨脹率與抗溶化結果相似，膨脹率越高融化速率越快，在14~35 hr處理組時膨脹率顯著高於控制組（p>0.05），而膨脹率與溶化速率成正相關。官能品評結果顯示在整體喜好度在牛乳與0 hr到21 hr組別之間無顯著差異（p>0.05）。上述結果顯示，納豆菌發酵於牛乳14hr在抗氧化效果為較佳，且膨脹率也較好，整體喜好度接受與牛乳製成冰淇淋無顯著差異（p>0.05）。
因此本研究建議以納豆菌曝氣發酵牛乳14 hr製成冰淇淋為最佳選擇，在抗氧化效果與膨脹率最佳，官能品評結果與牛乳製成冰淇淋無顯著差異（p>0.05）。
Recently, food safety has become a major concernin Taiwan. Ice cream processing needs stabilizers to add taste and slow melting time.The main stabilizers used for ice cream processing are chemical products rather than pure or natural stabilizers. Natto mucus produced by Bacillus subtilis fermentationconsists of natural polysaccharides and is suitable to be used as an ice cream stabilizer. The purpose of this study was to investigate theeffect of the use of B. subtilisfermented milk on the properties of ice cream.Milk were fermented with B. subtilis for 0, 7, 14, 21, 28, 35 hr, and composition and growth of B. subtiliswere determinedat 2 hr interval.The mixture （milk, cream, sugar and milk powders）werefrozen-churning into ice cream, then overrun, pH value, color, viscosity, first drip time, melting rate, mass retention, stable free radical （DPPH）, chelating effects on ferrous ions and reducing power for estimating antioxidant activityand sensory evaluation were analyzed.Theviable cells of B. subtilisreached 108~109 CFU/mL after 12 hr of fermentation.At14 hr of fermentation,higher antioxidant effects including DPPH of 82.41 %, chelated ferrous iron of 53.12 %and reducing powerof 0.70 in ice cream were found.The stable free radical and chelating effects on ferrous ions at 0 hr had churning destructionbut after 14 ~ 35 hr of B. subtilis fermentation didn’t have churning destruction. No significant difference（p>0.05） on overrun was found at 14~35 hr fermentation time. The shortest first dripping time of623 sec was determined at the treatmentof21 hr.There was no difference in sensory evaluation among fermentation time from 0, 7, 14, to 21 hr. Natto fermentation time of 14 hr was suggested for ice cream processing to obtain better overall likeness, antioxidant properties, and overrun. |
