Food fermentation One of the oldest methods to

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 – 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 p. H are changed. – Bacterial must be alive to offer the beneficial effects.

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

– 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 m. L milk • Each group has 6 tubes • Add about 0. 1 m. L 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.

• On next Monday (11/23), observe the physiochemical characteristics of the products – p. H, 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 p. H 6. 5 ± 0. 2

• p. H 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 – p. Ka value of lactic acid: 3. 08

Streptococcus and Lactobacillus casei Shirota(養樂多)

Bifidobacterium Lactobacillus

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

heterofermentation Phosphoketolase pathway Leuconostoc Lactobacillus

Pyruvate (3) ethanol (2) + CO 2 Acetate Acetobacter Lactate (3) propionyl(3) -Co. A Propionate (3) Acetate + CO 2 propionate (3) Priopionibacterium Glycolysis pathway

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