Preparation of Cultured Milks | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Fermented Milk Beverages

• Historical Significance

  • Mankind has a long history of utilizing milk and its products as food sources.
  • Early records indicate that fermented milk beverages were crucial components of simple diets.
  • Milk from various animals like cows, sheep, goats, and mares was likely contaminated with diverse microorganisms due to the challenges in cleaning the leather bags used to transport the milk.

• Geographical Origins

  • Most fermented milk beverages originated in southern and eastern Europe, particularly in regions like Russia, the Balkan States, and along the Mediterranean.
  • Some varieties were also known in Scandinavian provinces, Asia, Africa, and South America.

• Fermentation Process

  • Milk fermentation involves a change in milk due to the activity of microorganisms.
  • Normal fermentation results in lactic acid production under typical conditions.
  • Abnormal fermentations can lead to various changes like sweet-curdling, ropiness, gas formation, color alteration, and changes in flavor and odor.

• Cultured Milks and Starters

  • Cultured milks are produced by using selected microorganisms to develop specific flavors and textures.
  • Advantages include increased palatability, enhanced nutritive value, easier assimilation, potential presence of beneficial antibiotics, therapeutic properties, and even claims of increasing human longevity.
  • A 'starter' refers to an active bacterial culture used in making fermented milks.

• Manufacturing Process

  • An active starter culture plays key roles in acid production, flavor development, and prevention of undesirable microorganism growth.
  • Specific starter cultures are required for each fermented milk product, prepared by commercial laboratories from carefully selected bacterial species.
  • Proper selection of milk, heat treatments, and container considerations are essential for producing quality fermented milk beverages.

Manufacturing Processes of Dairy Products

Buttermilk Production

• Inoculation Process: Inoculation involves adding a small amount (1%) of culture to milk under sterile conditions. This culture is mixed thoroughly by rotating the container.
• Incubation: The inoculated milk is placed in a controlled incubator at 22°C and left undisturbed for 14 to 16 hours until it reaches a specific acidity level.
• Cooling: After reaching the desired acidity, the milk is rapidly cooled to 5°C to maintain culture activity. Rapid cooling is crucial to prevent loss of activity.

Bulk Starter Preparation

• Heating and Inoculation: Bulk starter milk is heated, inoculated with a 1% culture, and then rapidly cooled to the desired temperature for incubation.
• Ripening: The inoculated bulk milk is allowed to ripen for 14 to 16 hours until it reaches the desired acidity level.

Characteristics of Starter

• Flavor and Aroma: Starters should have a mild, pleasant flavor, nutty smell, and a clean acid taste.
• Texture and Body: The curd should be soft, firm, smooth, and free from gas holes or whey pockets.
• Titratable Acidity: The acidity level should ideally be between 0.75% to 0.85%.

Buttermilk Varieties

• Natural Buttermilk: Produced as a by-product of churning cream, it undergoes a clean lactic fermentation process.
• Cultured Buttermilk: Made by inoculating and incubating pasteurized skim milk with lactic culture.

Vitamin D Milk Production

• Methods of Fortification: Vitamin D milk production involves metabolized, irradiated, or fortified methods to increase vitamin D content in regions with limited sunlight exposure.

Soft Curd Milk

• Definition: Soft curd milk forms a gentle curd when coagulated with rennet or pepsin under standardized conditions.
• Characteristics: Soft curd milk is characterized by low casein and calcium content, resulting in a curd tension of less than 25g.

Milk Composition and Preparation Methods

Casein and Calcium Content of Different Milks

• Indian Cow
  • Casein: 2.5%
  • Calcium: 0.13%
• Indian Buffalo
  • Casein: 3.0%
  • Calcium: Q.19%
• Human
  • Casein: 0.4%
  • Calcium: 0.03%

Mother's Milk Benefits

Mother's milk is considered the best choice for feeding human infants. It forms a soft curd in the stomach, which is easier for infants to digest compared to cow or buffalo milk.

Methods of Preparing Soft Curd Milk

• Dilution with Water:

  This method lowers the casein and calcium contents of milk.

• Heat Treatment:

  Boiling milk is a common practice in India. Soluble calcium is precipitated, resulting in soft curd formation.

• Homogenization:

  High pressure homogenization reduces curd tension by affecting fat globules.

• Enzyme Treatment:

  Proteolytic enzymes like trypsin can reduce curd tension in milk.

• Addition of Salts:

  Sodium citrate, sodium pyrophosphate, and sodium hexametaphosphate can lower curd tension.

• Base-Exchange Treatment:

  Passing acidified milk through a zeolite filter-bed can exchange calcium ions for sodium, affecting curd tension.

Special Milk Types

Acidophilus Milk

Acidophilus milk, produced using Lactobacillus acidophilus, is believed to have therapeutic properties. It can alter intestinal pH, potentially inhibiting the growth of harmful bacteria.

Manufacturing Details of Dairy Products

• Sterilized Milk Production
  • Skimmed or partially defatted milk is utilized.
  • Milk with over 1% fat content should undergo homogenization.
  • Fresh milk is heated to 115°C (240°F) for 15 minutes for sterilization.
  • Inoculation of milk with 3-5% inoculum after cooling to 40°C (104°F).
  • Incubation at 38-40°C (100-104°F) until milk coagulates.
  • Coagulum is broken up and cooled to 10°C (50°F).
  • Addition of 5-10% lactose if desired.
  • Stirring until smooth, packaging, and storing at 5°C (40°F).
• Challenges with Lactobacillus acidophilus
  • Strains of Lactobacillus acidophilus are challenging to maintain due to bacterial contamination issues.
• Bulgarian Buttermilk Production
  • Utilization of a single strain starter of Lactobacillus bulgaricus.
  • Incubation temperature ranges from 38 to 43°C (100-110°F).
  • The final product is characterized by higher acidity (1.2-1.5%).
• Yoghurt Manufacturing
  • Originally made from boiled concentrated whole milk.
  • Modern methods use whole or partly defatted milk with small amounts of skim milk powder.
  • Fat content in yoghurt ranges from 0 to 5% and solids content from 9 to 20%.
  • Utilization of Lactobacillus bulgaricus and Streptococcus thermophilus for lactic fermentation.
  • Importance of culture control in yoghurt production for maintaining quality.
  • Extreme sensitivity of microorganisms to penicillin necessitates the use of antibiotic-free milk.
• Bulk Starter Production
  • Addition of skim milk powder/concentrate to whole or partly defatted milk to increase solids content.
  • Heating milk to 60°C (140°F) and homogenizing.
  • Heating in a vat to 85°C (185°F) for 30 minutes, then cooling and inoculating with bulk starter.
  • Packaging after proper mixing, ensuring temperature does not fall below 41°C (106°F).

Yoghurt Production Process

• The time gap between filling and sealing the inoculation should not exceed 15 minutes.
• Yoghurt is left undisturbed in its packaging at a temperature of 41-42°C (106-108°F) for approximately 3 hours until it reaches a titratable acidity of 0.75%.
• After incubation, it is cooled in refrigeration at 5-7°C (40-45°F) for about 8 hours before it is ready for distribution.
• The final product should have an acidity of 0.9%.

Flavoured Yoghurt

• Flavours can be synthetic, natural with synthetics, or natural fruits.
• Ingredients like flavoring agents, sugar, and color are added before fermentation.
• Advantages of flavored yoghurt include reduced acidity, fewer off-flavors, and less need for concentrated milk.

DAHI - Indian Curd

• DAHI, commonly known as Indian curd, is a popular fermented milk product in the country.
• Around 40% of India's milk production is used to make DAHI, an essential step in producing indigenous butter and ghee.
• It is consumed daily or as a refreshing beverage when diluted.

Overview of Dahi Production and Composition

• Definition and Standards:

  According to the PFA Rules (1976), dahi is a product made from pasteurized or boiled milk through natural souring or with harmless bacterial cultures. It should match the fat and solids-not-fat content of the milk used. Different types of dahi like sweet, sour, whole milk, skim milk, and sweetened dahi are classified based on their composition and preparation method.

• Food and Nutritive Value:

  Dahi enhances the nutritional value of milk, making it more digestible and palatable. It is believed to offer therapeutic benefits for stomach and intestinal issues due to its antibiotic properties. People who dislike drinking milk often find dahi easier to consume.

• Composition:

  The average composition of whole milk dahi includes water, fat, protein, lactose, ash, and lactic acid. It contains a slightly higher concentration of milk solids compared to the initial milk, providing additional nutrients.

• Method of Preparation:

  There are traditional and commercial methods for preparing dahi. In traditional methods, milk is cultured with a starter, set overnight, and then cooled. Commercial production involves filtration, standardization of fat and solids, pasteurization, inoculation with starter culture, fermentation, and storage under specific conditions.

Production of Dahi

• Ingredients like sugar caramel and gur are added during production of dahi.
• Standard method involves preheating, clarification, standardization, homogenization, pasteurization, inoculation, incubation, cooling, and packaging.
• Packaging and Storage: Dahi traditionally stored in earthenware cups, but modern packaging includes glass bottles and plastic cups.
• Keeping Quality: Dahi has short shelf life at room temperature, but refrigeration extends its freshness.
• Carbonated Dahi: Developed for longer shelf life without refrigeration by bubbling carbon dioxide through milk.

Uses of Dahi

• Whole milk dahi is consumed directly or used in various preparations like chakka and makkhan.
• Skim milk dahi is consumed by heart patients and low-income groups due to its low fat content and affordability.

Lassi

• Also known as chhas or matha, lassi is a butter-milk produced during churning of curdled whole milk.
• Composition: Varies based on dahi composition, churning process, and fat removal efficiency.
• Food and Nutritive Value: Rich in milk proteins and phospholipids, lassi is a refreshing beverage.
• Uses: Consumed as a beverage with ice, sugar, or salt, and used as a starter culture for milk coagulation.

Srikhand

• A semi-soft sweetish-sour whole milk product made from lactic fermented curd.
• Preparation: Curd is partially strained to produce chakka, which is mixed with sugar to make Srikhand.
• Additional Sweet: Srikhand-wadi sweet is made by desiccating Srikhand over an open pan.
• Popular in Western India: Srikhand, chakka, and Srikhand-wadi are well-loved dairy products in the Western region.

Composition of Chakka, Srikhand, and Wadi

• Chakka, Srikhand, and Wadi composition is influenced by milk composition, fermentation level, whey removal, and sugar content.
• Chakka, Srikhand, and Wadi have varying moisture, fat, protein, lactose, ash, sugar, and lactic acid percentages.
• Example:
  • Chakka has 63.2% moisture, 14.7% fat, 10.3% protein, 15.9% lactose, 1.0% ash, and 1% sugar.
  • Srikhand has 59.6% moisture, 22.4% fat, 7.7% protein, and 0.8% lactic acid.
  • Wadi has 6.5% moisture, 7.4% fat, and 1.0% lactic acid.

Method of Preparation

• Start with sweet buffalo milk standardized to 6% fat.
• Pasteurize the milk at 71°C for 10 minutes and cool to 28-30°C.
• Inoculate with lactic culture and ferment at 28-30°C for 15-16 hours.
• Remove whey by hanging the curd in a muslin cloth for 8-10 hours to obtain chakka.
• Mix chakka with sugar, knead well, and add color and flavor to get Srikhand.
• Further desiccate Srikhand to get Srikhand-wadi by heating in an open pan over direct fire.

Uses

• Chakka is used to make Srikhand.
• Srikhand is consumed directly or used to make Srikhand-wadi sweet.
• Srikhand-wadi is consumed directly.