Evaporated Milk | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Evaporated Milk vs. Sweetened Condensed Milk

Evaporated Milk

• Evaporated milk, also known as unsweetened condensed milk, is derived from cow or buffalo milk, or a combination of both.
• It is produced by partially removing water from standardized milk and may include additives like calcium chloride, citric acid, sodium citrate, sodium salts of orthophosphoric acid, and polyphosphoric acid (up to 0.3% by weight).
• The product must contain a minimum of 8.0% milk fat and 26.0% milk solids.
• Evaporated milk undergoes preservation through final sterilization after canning.

Evaporated Skimmed Milk

• Evaporated skimmed milk is made from skimmed cow or buffalo milk, or a mix of both, through the partial removal of water.
• Additives such as calcium chloride, citric acid, sodium citrate, sodium salts of orthophosphoric acid, and polyphosphoric acid (up to 0.3% by weight) may be present.
• This type should have a minimum of 20.0% total milk solids and a fat content not exceeding 0.5% by weight.

Sweetened Condensed Milk

• Sweetened condensed milk differs from evaporated milk in its preservation method.
• During manufacture, sucrose is added to sweetened condensed milk, increasing osmotic pressure and inhibiting bacterial growth.
• Evaporated milk, on the other hand, is preserved through final sterilization post-canning.

Composition of Evaporated Milk (Percentage)

• Fat: 9.0%
• Milk Solids-not-fat: 22.0%
• Protein: 8.3%
• Lactose: 12.2%
• Ash: 1.5%
• Total Milk Solids: 31.0%
• Sucrose: Nil

These distinctions in processing and composition between evaporated milk and sweetened condensed milk are crucial in understanding their respective uses and qualities.

Composition of Unsweetened Condensed Skim Milk

• Details about the composition of unsweetened condensed skim milk are not provided as this product is rarely produced.

Food and Nutritive Value of Evaporated Milk

• Information regarding the food and nutritive value of evaporated milk has been discussed in relation to condensed milk.

Method of Manufacture, Packaging, and Storage of Evaporated Milk

• Evaporated milk is produced by heating milk until about 60% of its water content evaporates, after which it is homogenized, canned, and sterilized.
• The evaporated milk is then packaged in cans to ensure preservation and maintain its shelf life.
• Storage of evaporated milk should be in a cool, dry place away from direct sunlight to prevent spoilage.

Manufacture of Evaporated Milk

Receiving Milk:

• Raw milk needs to meet high heat stability requirements and undergo an alcohol test before concentration.
• A pilot sterilization test is conducted post-homogenization to determine the necessary chemical stabilizer amount.

Filtration/Clarification:

• This step involves filtration and clarification processes to ensure purity.

Standardization:

• The milk is standardized to achieve desired fat content and quality.

Forewarming/Preheating:

• Forewarming in evaporated milk is not for microbe destruction but to enhance heat stability and viscosity.

Evaporation:

• Evaporation is carried out in a vacuum pan without the addition of sugar.

Homogenization:

• After evaporation, homogenization ensures a uniform fat emulsion and minimizes fat separation during storage.
• A two-stage homogenization process reduces fat globules to less than 2 microns in diameter.

Cooling:

• The evaporated milk is cooled to either 7°C for same-day sterilization in small scale handling or 5°C for large scale handling.

Pilot Sterilization Test:

• Conducted to determine the appropriate chemical stabilizer amount for optimal heat stability.

Heat Stability:

• Heat stability of evaporated milk relates to its ability to resist coagulation during sterilization.
• Optimal heat stability depends on the balance of calcium, magnesium, phosphate, and citrate ions.

Summary and Explanation of Information

Calcium and Magnesium Balance in Food Processing

• Calcium Magnesium Citrate and Phosphate ratios are crucial in maintaining salt balance for heat-stability.
• If there is an imbalance in calcium and magnesium levels, it can affect the coagulation process in food production.
• To prevent coagulation issues, the right amount of soluble calcium or magnesium salts should be added.

Packaging Considerations

• Cans should be filled using volumetric fillers capable of withstanding pressure changes during sterilization.
• The seal on the cans must be airtight and robust to maintain product integrity.
• Temperature control during filling is essential to prevent foaming or flipping of cans.
• Flipping refers to the sudden deformation of cans from concave to convex, often accompanied by a sound.

Sterilization Process

• Each can undergoes leak testing before sterilization to ensure product integrity.
• Sterilization aims to eliminate all microbial life and enzymes, preserving the product.
• The process also enhances viscosity and texture, providing a creamy consistency to the final product.

By maintaining the right balance of calcium and magnesium and following proper packaging and sterilization procedures, the quality and stability of the food product can be ensured throughout the production process.

Sterilization Process of Evaporated Milk

• During sterilization, the temperature of evaporated milk is rapidly raised to 116 to 118°C (240 to 245°F) and maintained at this temperature for 15 minutes.
• There are two types of sterilizers: batch and continuous. Batch sterilizers involve a large horizontal autoclave with a rotation frame inside.
• The sterilization process in batch sterilizers includes coming up, holding, and cooling, all within the autoclave.
• To ensure even heating and cooling, the frame rotates around a longitudinal axis, and steam is introduced over the length of the autoclave via a tube with holes.

Key Components of a Successful Sterilizing Routine

• Coming up time
• Holding temperature
• Holding time
• Cooling time

Cooling Process

• Immediately after the holding time, the evaporated milk is cooled within 15 minutes to 27-32°C (81-90°F) to prevent bulging.

Additional Steps in the Process

• Shaking: Done to achieve a smooth consistency after sterilization, typically for one-fourth to two minutes.
• Storage: Commercial evaporated milk is usually stored at 5 to 16°C (40 to 60°F) for up to 2 years, with humidity levels below 50% to prevent spoilage.

Judging and Grading of Evaporated Milk

• A scorecard prepared by the American Dairy Science Association is used for evaluating evaporated milk based on flavor, texture, color, fat content, total solids, and the absence of adulterants and preservatives.
• The examination process is similar to that of condensed milk, with a focus on flavor defects, body issues, and other quality aspects.

Common Defects in Evaporated Milk

• Flavor: "Cooked Flavor" due to high heat treatment, body defects like coagulation, age-thickening, and fat separation.
• Viscosity: Gradual increase leading to stiff consistency, potential causes being inadequate homogenization or high storage temperatures.
• Gassiness: Results from improper sterilization heating, causing bloats or gas formation in the product.

Understanding Colour Defects in Evaporated Milk

• Causes of Browning and Discoloration: Browning and discoloration in evaporated milk occur due to excessive heat treatment during sterilization or storage at high temperatures. This defect affects the quality of the milk.

Requirements of High Grade Evaporated Milk

• Quality Characteristics: High-quality evaporated milk should possess a mild and pleasant flavor, a relatively viscous body, a uniform smooth texture, and consistent color similar to condensed milk.

Uses of Evaporated Milk

• Homogenized Product: Evaporated milk, being homogenized, forms a soft curd in the stomach, making it easily digestible.
• Sterility: During manufacturing, evaporated milk is rendered sterile, which makes it suitable for reconstitution into milk for infants and individuals with sensitive stomachs.
• Applications: Evaporated milk finds uses in various food and beverage preparations, such as ice cream, tea, coffee, and more, due to its versatility and nutritional benefits.

Unsweetened Condensed Milk and Evaporated Milk

• Definition: Evaporated milk, known as unsweetened condensed milk, is derived from cow or buffalo milk, or a blend of both, through the partial removal of water.
• Composition: It must contain at least 8.0% milk fat and 26.0% milk solids. Additional components like calcium chloride, citric acid, sodium citrate, sodium salts of orthophosphoric acid, and polyphosphoric acid are allowed up to 0.3% by weight.
• Evaporated Skimmed Milk: This variation is made from skimmed milk, containing at least 20.0% total milk solids and a maximum of 0.5% fat by weight.
• Preservation Difference: Sweetened condensed milk uses sucrose for preservation, increasing osmotic pressure to inhibit bacterial growth. In contrast, evaporated milk is sterilized after canning for preservation.

Composition of Evaporated Milk (Percentage)

• Water: 69%
• Protein: 8.3%
• Fat: 9.0%
• Milk Solids-not-fat: 22.0%
• Lactose: 12.2%
• Ash: 1.5%

Condensed Skim Milk

• Information on the composition of unawcotoned condansod skim milk is not provided as this product is rarely produced.

Evaporated Milk

• Details regarding the food and nutritive value of evaporated milk were discussed in the context of condensed milk.
• Explanation of the method of manufacturing, packaging, and storage of evaporated milk:
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  • Evaporated milk is made by heating milk until about 60% of the water content evaporates, resulting in a slightly caramelized flavor.
  • Once evaporated, the milk is homogenized, canned, and sterilized to ensure preservation.
  • It is important to store evaporated milk in a cool, dry place to maintain its quality and shelf life.

Manufacturing Process of Evaporated Milk

• Receiving Milk:
  • Raw milk must meet high heat stability requirements and undergo an alcohol test.
  • A pilot sterilization test is conducted after homogenization to determine the appropriate chemical stabilizer amount.
• Filtration/Clarification
• Standardization
• Forewarming/Preheating:
  • Forewarming in evaporated milk is not for microorganism destruction but to enhance heat stability and ensure medium viscosity.
• Evaporation:
  • No sugar is added during evaporation or condensing in the vacuum pan.
• Homogenization:
  • Evaporated milk is homogenized to achieve a uniform fat emulsion and prevent fat separation.
  • A two-stage homogenization process reduces fat globules to less than 2 microns in diameter.
• Cooling:
  • Evaporated milk is cooled to specific temperatures based on scale handling requirements.
• Pilot Sterilization Test:
  • This test determines the necessary chemical stabilizer amount for optimal heat stability.

Heat stability of evaporated milk refers to its resistance to coagulation in the sterilizer, influenced by the balance of calcium, magnesium, phosphate, and citrate ions.

Calcium and Magnesium in Food Processing

• Changes in the concentration of calcium and magnesium disrupt the salt balance, affecting heat-stability.
• Deficiency or excess of calcium and magnesium can lead to coagulation issues in food processing.
• Packaging:
  • Cans are filled with volumetric fillers, needing to endure pressure changes during sterilization.
  • Ideally, cans should be airtight and robust. The temperature during filling should be around 5°C to prevent issues like foaming or flipping.
  • Flipping refers to the sudden outward bulging of cans, often accompanied by a sound.
• Sterilization:
  • Each can is checked for leaks before sterilization by submerging them in hot water.
  • Sterilization aims to eliminate all germs and enzymes, preserving the product and enhancing viscosity for a creamy consistency.

Sterilization Process for Evaporated Milk

• Temperature and Duration: During sterilization, the temperature of evaporated milk is rapidly raised to 116 to 118°C (240 to 245°F) and maintained for 15 minutes.
• Types of Sterilizers: There are two types of sterilizers - batch and continuous. Batch sterilizers involve a large horizontal autoclave with a rotating frame inside.
• Batch Sterilizer Operation: Tins are placed in crates inside the autoclave. Rotation of the frame ensures even heating and cooling. Steam is introduced for heating, and water is sprayed for cooling.
• Sterilization Routine: A successful sterilizing routine includes coming up time, holding temperature, holding time, and cooling time within specific ranges.
• Cooling: After the holding time, the evaporated milk is cooled within 15 minutes to 27-32°C (81-90°F) to prevent bulging.

Post-Sterilization Processes

• Shaking: Shaking is done post-sterilization to achieve a smooth consistency. Excessive shaking should be avoided to maintain viscosity.
• Storage: Commercial evaporated milk is stored at temperatures between 5 to 16°C (40 to 60°F) for optimal quality. Storage below 16°C is recommended to prevent rapid deterioration.

Judging and Grading

• Score Card: The American Dairy Science Association provides a score card for judging evaporated milk based on flavor, texture, color, fat content, total solids, and the absence of adulterants and preservatives.
• Common Defects: Common defects in evaporated milk include cooked flavor, coagulation, age-thickening, fat separation, and gassiness, each caused by specific factors during processing and storage.

Colour Defects in Evaporated Milk

• Cause of Browning and Discoloration: Browning and discoloration in evaporated milk occur due to excessive heat treatment during sterilization or storage at high temperatures. This defect affects the visual quality of the milk.

Requirements of High Grade Evaporated Milk

• Flavor: High-quality evaporated milk should possess a mild and pleasant flavor that enhances its overall appeal.
• Texture: It should have a relatively viscous body with a smooth and uniform texture, similar to condensed milk.

Uses of Evaporated Milk

• Homogenized Nature: Evaporated milk is a homogenized product that forms a soft curd in the stomach, aiding in digestion.
• Sterility: During its manufacturing process, evaporated milk is rendered sterile, making it safe for consumption.
• Applications: Evaporated milk is commonly reconstituted into milk for infants and individuals with sensitive stomachs in developed countries. It is also utilized in various culinary applications such as in ice cream, tea, and coffee for its rich texture and flavor.