Cultured Dairy Foods

1. Cultured Dairy Foods

2. Cultured Dairy Products • Bovine milk suitable for microbial fermentation • contains 5% lactose, 3.3% protein, pH6.6-6.7, aw~1.0

3. Cultured Dairy Products • Evolved on every continent • Easy to produce, good shelf-lives, free of harmful substances, pleasant sensory appeal • Yogurt like products • Dahi (india), Jaban (Egypt, Lebanon), Jugar (turkey) • Kefir and koumiss-made with lactose-fermenting yeasts in addition to lactic acid bacteria • Contain alcohol

4. Consumption of Cultured Dairy Products • Most popular cultured dairy products in the US • Yogurt: >50% of all cultured dairy products (mostly non-fat or low fat) • Sour cream (and sour cream-based dips): increasing • Cultured buttermilk: decreasing • US consumption much less than EU • Catch on new trends

5. Probiotics and Prebiotics • Probiotics • Live microbes which when administered in adequate amounts confer a health benefit on the host (WHO) • Live and sufficient amount • Health benefit beyond GI tract • Suggested health benefits • Reduce blood cholesterol • Maintain intestinal health • Alleviate intestinal bowel diseases • Modulate immune system • Reduce incidence of GI infections • Reduce incidence of urinary and vaginal infections • Alleviate lactose intolerance • Anti-cancinogenic and anti-tumorogenic • Reduce incidence and severity of diarrheal diseases

6. Probiotics and Prebiotics • Prebiotics • Non-digestible food ingredients that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and then improves host health (Gilbson and Roberfroid, 1995) • Polysaccharides or oligosaccharides (Fig 1) • FOS (fructooligosaccharides) • GOS (galactooligosaccharides) • Resemble the oligosaccharides found in human milk • May promote the growth of bifidobacteria in nursed infants

7. Common probiotics • As culture adjunct intend to promote health, instead of fermentation • Lactobacillus acidophilus-~80% yogurt in the US • Bifidobacterium • Both in yogurt and other cultured and non-cultured dairy products • Some strains also involved in fermentation • Yakult-Japanese product made using a human GI isolate of Lb. casei (strain Shirota) • Cultura-a European “bioyogurt” made with a human isolate of Lb. casei F19 • Unfermented products as carriers of probiotics • Sweet Acidophilus Milk • Table 4.2

8. Fermentation Principles • Milk and LAB culture (Table 4.3) • Cultured versus “directly set” • Functions • Lactose • Precipitate casein (pH4.6) • Flavor compounds • Syneresis • Separation of water from the coagulated milk • Considered unfavorable; to reduce, • Increase milk solids • heat well above pateurization temp to denature whey proteins • Incorporate stabilizers • Using strains produce exopolysaccharide • “Ropy” strain-EPS released or dis-attached • EPS remains attached to the cells surface

9. Yogurt Cultures • S. thermophilus and Lb. delbrueckii subsp. bulgaricus • 1:1 ratio • Synergistic growth • S. thermophilus growth first, use free aa and small peptides in milk, lower pH etc, preferred environment for Lb. delbrueckii subsp. bulgaricus • Lb. delbrueckii subsp. bulgaricus proteolysis helps S. thermophilus to grow • Lb. delbrueckii subsp. bulgaricus produce more acid, S. thermophilus will decrease • So the cultures are grown separately, harvested and mixed

10. Frozen Yogurt and Other Yogurt Products • Frozen yogurt • No federal standard of identify • Some states have their own definitions • Marketing purpose • Minnesota definition • “Frozen dairy products made from a mix containing safe and suitable ingredients including, but not limited to, milk products. All or a part of the milk products must be cultured with a characterizing live bacterial culture that contains the lactic acid producing bacteria Lactobacillus bulgaricus and Streptococcus thermophilus and may contain other lactic acid producing bacteria.” • Some stated require minimum acidity, ranging from 0.3% to 0.5%

11. Cultured Buttermilk • Buttermilk is the fluid remaining after cream is churned into butter • Thin, watery liquid • Rich in phospholipids • Rarely consumed as a fluid drink, but good source of natural emulsifiers • Typically spray dried and used as an ingredient in processed food products • Cultured buttermilk • Skim or low-fat milk fermented by suitable LAB • Butter granules or flakes are occasionally added to provide butter flavor and mouth feel

12. Cultured Buttermilk Manufacture • Fig. 4-5 • Milk • Heat • Cool and inoculate mesophilic starter culture • Cultures • Acid producing: flavor producing ~5:1 • Acid producer: homolactic L. lactis subsp. lactis or cremoris • Flovor producer: L. lactis diacetylactis, Leuconostoc mesenteroides subsp. cremoris, or Leuc. lactis (hetero) • Citrate fermentation

13. Sour Cream • Same culture used for cultured buttermilk • Use cream instead of milk • Cream pasteurized but not extend as for buttermilk or yogurt • Cream homogenized • Starting material in the US 18-20% cream, or low fat version (10%) • Fig 4-7

14. Kefir • One of the most popular cultured dairy products in Middle East, Eastern Europe and Central Asia • Kefir grain added as insoluble particles • Retrieved after fermentation by filtration • LAB and yeast • Contain as much as 2% ethanol • US has to be lower or non-ethanol producers • Fig 4-8, Table 1