1. 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

2. objective – Inoculate lactic acid bacteria to ferment milk Principles – 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.

3. Materials and Methods Reconstituted Milk – 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

4. – 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

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

6. After 24 incubation (11/18), take some of the ferment milk into 15-mL tubes. One product into one tube. Place the tubes in a refrigerator (4 ℃ ). Keep fermenting. After 48 incubation, place the ferment product into a refrigerator. On 11/19, take he ferment milk out of the refrigerator.

7. On next Monday (11/24), observe the physiochemical characteristics of the products – pH, texture, aroma, color, taste

8. 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

9. Streptococcus and Lactobacillus casei Shirota( 養樂多 )

10. Bifidobacterium Lactobacillus