Dairy Products, Yoghurt, Butter, Cheese production

Notes on Dairy Products

1. Why are they made?

· Milk is converted into products like cheese, butter, cream, kefir, and yoghurt for preservation.

· This process changes the water content and acidity, which improves the texture, taste, and flavour.

2. How are they made? (General Process)

· Pasteurization: Milk is first heated to destroy unwanted microbes.

· Fermentation: Helpful bacteria called Lactobacilli are added.

· The Science:

  · Bacteria eat the lactose (milk sugar) and convert it into lactic acid.

  · The lactic acid coagulates (clumps together) the milk proteins, making it thick.

  · This process also creates new flavours (e.g., Diacetyl, which tastes like butter).

3. Microbes Used:

· Most products (Yoghurt, Butter): Use bacteria.

· Cheese: Uses bacteria and fungi.

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Yoghurt

· Microbes Used: Streptococcus thermophilus and Lactobacillus delbrueckii (added in a 1:1 ratio).

· Process:

  1. Milk is boiled and cooled.

  2. Condensed milk powder is added to maintain protein content.

  3. Bacterial strains are added.

· The Science:

  · Streptococcus produces lactic acid, which makes the proteins gel and gives yoghurt its thick consistency.

  · Lactobacilli produce compounds like acetaldehyde that give yoghurt its characteristic taste.

· Varieties: Fruit juices (e.g., strawberry, banana) are added for flavour.

· Shelf Life: Pasteurization can make it last longer and improve its probiotic properties.

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Butter

· Two Types: Sweet cream and Cultured.

· Only the cultured variety is produced using microbes.

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Cheese

· Microbes Used: Lactobacillus lactis, Lactobacillus cremoris, and Streptococcus thermophilus (they add sourness).

· Key Ingredient:

  · An enzyme called protease (obtained from fungi) is used to coagulate the milk and make it dense. This makes the cheese vegetarian.

  · (Traditionally, an enzyme from cattle stomachs was used).

· Main Steps:

  1. Separate the solid part from the liquid whey.

  2. Process the solids by cutting, washing, rubbing, salting, and adding microbes/flavours.

  3. Press the cheese into a shape.

  4. Store it for ripening (aging).

· Types of Cheese:

  · Soft Cheese (e.g., Cottage, Cream, Mozzarella): Freshly made, not aged.

  · Semi-Hard Cheese (e.g., Cheddar): Aged for 3-12 months.

  · Hard Cheese (e.g., Parmesan): Aged for 12-18 months.

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Important for Industry

· Factories must be very clean and use sterilized equipment because viruses can attack the bacteria used.

· To solve this, scientists develop virus-resistant and mutant varieties of bacteria.