Food fermentation One of the oldest methods to preserve food The most common ferment foods Dairy products 優酪乳、養樂多 優生菌 probiotic bacteria 乳酸菌 Lactic acid bacteria (LAB) Lactobacillus, Lactococcus, Streptococcus 雙叉桿菌 Bifiodobacterium

objective Principles Inoculate lactic acid bacteria to ferment milk Lactic acid bacteria is the main probiotic bacteria After fermentation, physical and chemical properties such as texture, flavor, aroma, and pH are changed. Bacterial must be alive to offer the beneficial effects.

Materials and Methods Reconstituted Milk LAB culture Commercial yogurt Milk powder + water LAB culture Commercial yogurt A菌:嗜酸乳桿菌 (Lactobacillus acidophilus） B菌:雙叉乳桿菌(L. bifidus; Bifidobacterium lactis) Each group choose their own culture Each group has three tubes

養樂多 Yakult代田菌(Lactobacillus casei Shirota) 比菲多 Bifidobacterium bifidum 味全優酪乳 ABLS A菌-Lactobacillus acidophilus B菌-Bifidobacterium Iongum L菌-Lactobacillus bulgaricus S菌-Streptococcus thermophilus 養樂多 Yakult代田菌(Lactobacillus casei Shirota) 比菲多 Bifidobacterium bifidum Each group must record the bacterial culture and ingredient in the product

Methods Milk powder add water Boiling for 1-2 min Separate the sanitized milk to the other sterile tubes Each tube has 10 mL milk Each group has 6 tubes Add about 0.1 mL of the bacterial culture or the commercial product into one tube Incubate at 37℃

After 24 incubation (11/17), take one and place the tubes in a refrigerator (4℃). Keep fermenting. After 48 (11/18) incubation, place the other tube into a refrigerator.

Streak the fermented milk onto MRS plate On next Monday (11/23), observe the physiochemical characteristics of the products pH, texture, aroma, color, taste Streak the fermented milk onto MRS plate

Lactobacilli MRS Agar and Broth Approximate Formula* Per Liter Proteose Peptone No. 3 ........................................... 10.0 g Beef Extract ..............................................................10.0 g Yeast Extract .............................................................. 5.0 g Dextrose ...................................................................20.0 g Polysorbate 80 ........................................................... 1.0 g Ammonium Citrate .................................................... 2.0 g Sodium Acetate ......................................................... 5.0 g Magnesium Sulfate .................................................... 0.1 g Manganese Sulfate .................................................... 0.05 g Dipotassium Phosphate .............................................. 2.0 g Agar .........................................................................15.0 g pH 6.5 ± 0.2

pH values in last year (24 hour fermentation) Milk: 6.641 Yakult : 4.572 Unipresident- AB 3.945 48 hour fermentation Yakult: 3.875 Unipresident- AB: 3.836 pKa value of lactic acid: 3.08

Streptococcus and Lactobacillus casei Shirota(養樂多)

Bifidobacterium Lactobacillus

發酵的型式 乳酸發酵 酒精發酵 醋酸發酵

乳酸發酵 係指乳酸菌(lactic acid bateria；LAB)在厭氧環境下，將碳水化合物代謝產生ATP供其生長所需，而乳酸則為主要副產物。發酵食品中常用的乳酸菌多屬於革蘭氏陽性菌，依菌體對葡萄糖代謝副產物的差異，分為同質乳酸發酵菌(homofermentative LAB)與異質乳酸發酵菌(heterofermentative LAB)。

同質乳酸發酵菌：其主要代謝副產物為乳酸，而其他化合物的產量甚少。 異質乳酸發酵菌：其代謝過程除了乳酸外還會連帶產生醋酸、 酒精、二氧化碳等副產物。

homofermentation Glycolysis pathway Lactococcus, Streptococcus, Pediococcus, Some of Lactobacillus

heterofermentation Phosphoketolase pathway Leuconostoc Lactobacillus

Pyruvate (3) ethanol (2) + CO2 Acetate Lactate (3) propionyl(3) -CoA Propionate (3) propionate (3) Acetate + CO2 Acetobacter Priopionibacterium Glycolysis pathway

Saccharomyces cerevisiae 酒精發酵 酒精發酵(alcoholic fermentation)係指酵母菌代謝葡萄糖後產生乙醇（酒精）之作用，其反應式如下： 葡萄糖 → 2丙酮酸 → 2乙醛＋2二氧化碳 → 2乙醇 Saccharomyces cerevisiae

醋酸發酵 醋酸發酵(acetic fermentation)係指醋酸菌將乙醇（酒精）氧化成為醋酸之。 2乙醇＋氧 → 2乙醛＋水 2乙醇＋氧 → 2乙醛＋水 2乙醛＋氧 → 2醋酸＋水

發酵乳製品 乾酪 發酵乳 酸凝酪 發酵酪乳 保加利亞酪乳 克弗酒

發酵乳之製程 發酵乳的微生物學 原料乳→ 均質→ 殺菌→ 冷卻→ 接種→發酵→ 均質→ 調味→ 成品。 Mesophilic starter Thermophilic stater Bifidobacterium bifidum

Bacteriocin inhibit the growth of similar or closely related bacterial strain(s) Nisin Lactococcus lactis Inhibit Gram + or - ?

乳酸菌對人體具有正面的效益，自1961年至1998年間，國際上已完成研究並發表在知名學術期刊的乳酸菌人體臨床試驗共計143件，受測人數達7,526人，均未有負面的結果報導，其中主要曾被報導的正面功效包括：(1) 增進食品之營養品質，(2) 促進維生素合成及酵素產生，(3) 穩定腸道菌相，並去除腸內病菌，(4) 產生抗菌物質，增強宿主免疫力，(5) 降低膽固醇含量，(6) 降低大腸癌之風險，(7) 抑制腫瘤等。但並非每一株乳酸菌皆具有前述功效，需每一樣品及每一菌株分別進行獨立測試，而由相近之菌株所推估的資訊是不能被採信的。 於前述143件人體臨床試驗中，最常被科學家用來測試的乳酸菌為嗜酸乳桿菌(Lactobacillus acidophilus，即俗稱的A菌)，其次為凱氏乳桿菌(Lactobacillus casei，即俗稱的C菌)，其他較常被測試的菌尚有雙歧桿菌(Bifidobacterium sp.，即俗稱的B菌，又稱雙叉桿菌或比菲德氏菌)、保加利亞乳桿菌(Lactobacillus delbrueckii subsp. bulgaricus)、嗜高溫鏈球菌(Streptococcus thermophilus)，後兩者即是由鮮乳製造優酪乳過程中所必需添加的兩株乳酸菌。

市售最常見的發酵乳產品分為三種：凝態發酵乳（凝態優格）、濃稠發酵乳（飲用優酪乳）及稀釋發酵乳。非乳脂肪固形物(Solid notfat，SNF)是指牛奶在除去水分及脂肪後所得的成分，依據國家標準CNS3058發酵乳規定，「濃稠發酵乳的SNF應該在8％以上；，8％以下者，為稀釋發酵乳，SNF在2％以上」， 衛生標準，「大腸桿菌群」MPN在10以下，「大腸桿菌」最確數為陰性