Processing, Packaging and Nutritive Values of Different Milks | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Pasteurized Milk

• The process of pasteurization, named after Louis Pasteur, involves heating milk to specific temperatures to eliminate harmful organisms and enhance its shelf life.
• Dr. Soxhlet of Germany applied Pasteur's principles to milk in 1886, marking the beginning of pasteurization in the dairy industry.
• Today, pasteurization of market milk mandates heating every milk particle to at least 63°C for 30 minutes or 72°C for 15 seconds, followed by rapid cooling to 5°C or below.
• Purposes of Pasteurization:
  • Ensures milk safety by destroying pathogenic organisms, making it suitable for human consumption.
  • Improves milk's keeping quality by eliminating a significant percentage (85 to 99%) of organisms.
• Initial Objections to Pasteurization:
  • Encourages complacency in ensuring clean milk production.
  • Feared to mask low-quality milk.
  • Believed to diminish the nutritional value of milk.
  • Thought to reduce the cream line or volume in milk.
  • Suspected that pasteurized milk would not clot.
  • Concerns over the potential false sense of security due to careless pasteurization practices.
  • False belief that pasteurization fails to eliminate bacterial toxins.
  • Misconception that pasteurization is unnecessary in India due to consumer boiling of milk before consumption.
• It is important to note that these initial objections against pasteurization have been debunked over time.

Standards for Pasteurization

• Bacterial destruction:
  • Cent per cent for pathogens, Mycobacterium tuberculosis is chosen as the index organism for efficient pasteurization.
  • A specific temperature-time combination that kills TB organisms ensures the destruction of all other pathogens in milk.
• Cream line reduction:
  • The reduction of the cream line or cream volume occurs progressively during heating.
  • Consumers evaluate milk quality based on the cream line.
• Phosphatase inactivation:
  • Complete destruction of phosphatase through pasteurization is crucial (phosphatase test detects inadequate pasteurization).

Table: Time and Temperature Requirements for Pasteurization

• 30 minutes
  • 138°F/59.9°C
  • 142°F/61.1°C
• 15 seconds
  • 158°F/70°C
  • 160°F/71.1°C
  • 161°F/71.7°C
  • 162°F/72.2°C

As tuberculosis organisms require a slightly higher heat treatment than phosphatase, pasteurization is conducted at a temperature above that for phosphatase but below that for cream line reduction.

Standards for pasteurization aim to ensure the complete destruction of pathogens, negative phosphatase test results, and minimal damage to the cream line.

Pasteurization Process Summary

• Introduction to Pasteurization Process

  Before delving into the methods of pasteurization, it's crucial to understand the processes before and after pasteurization in the journey from receiving milk to its final marketing stage. These steps are illustrated in the Flow Chart for Pasteurization.

• Steps Involved in Pasteurization:

  • Receiving and Preparing Milk

    Includes grading, sampling, weighing, testing, pre-cooling, and storage at or below 5°C in storage tanks.

  • Standardization of Milk

    Refers to adjusting the fat and solids-not-fat content to meet legal or other requirements. It involves adding milk or cream with different fat percentages to achieve the desired composition.

    Example: Using the Pearson's square method to calculate the right proportions of materials for standardization.

  • Pasteurization Process

    Commonly done using the High Temperature-Short Time (HTST) method, involving heating milk to specific temperatures for set durations.

    Example: Heating milk at 72°C for 15 seconds or 63°C for 30 minutes.

  • Homogenization and Packaging

    Involves processes to ensure uniform distribution of fat globules in milk and packaging for distribution.

• HTST Method Details

  The High Temperature-Short Time (HTST) method involves key steps like pre-heating and filtration to ensure milk safety and quality.

  • Pre-heating Process

    Raw milk enters the balancing tank, then moves to the regenerator for initial heating through hot milk counterflow.

    Example: Pre-heating milk at 35-40°C for efficient filtration and clarification.

  • Filtration and Clarification

    Ensures removal of impurities and particles from milk for quality improvement.

Filtration and Clarification in Milk Processing

• Objective of Filtration/Clarification:
  • Filtration and clarification processes are crucial in improving the appearance of milk by removing visible foreign matter that may lead to consumer complaints.
  • Filtration eliminates suspended foreign particles through straining, while clarification removes them through centrifugal sedimentation.
  • Both processes reduce the depth of the cream layer in milk, especially noticeable with higher processing temperatures.
• Effect on Milk Quality:
  • Neither filtration nor clarification enhances the shelf life or keeping quality of milk.
  • It is advised not to filter or clarify milk after pasteurization to avoid contamination.
• Process of Pasteurization:
  • After filtration, milk enters the pasteurizer's heating section where it is heated to the required temperature using a plate heat exchanger.
  • The milk then moves to the holding section where it remains for a specific time as per regulations.
  • Subsequently, the milk reaches the flow diversion valve, which redirects the milk to the balancing tank if not heated adequately.
  • Properly heated milk re-enters the plate heat exchanger for further processing, including partial cooling by regenerating sections and final chilling by chilled water.
  • Chilled milk is directed to bottling or pasteurized milk storage areas.
• Key Components in Pasteurization:
  • Float Controlled Balanced Tank (FCBT): This maintains a constant head of milk for the raw milk pump and receives any sub-temperature milk diverted by the flow diversion valve.

Temperature Reading Points

• Chilled water (A) and cold water (A') are used for cooling.
• Regeneration (C) helps in the process.
• Various components include Filter (D), Heating (E), To bottling plant (F), From storage tanks (G), Temperature and holding time check points (H), Bulb (I), Flow diversion valve (J), Balance tank (K), Flow control valve (L), Milk pump (M), Hot milk recorder (N), Gold milk recorder (O), Temperature controller (P), Holder (Q), Air compressor (R), Steam boiler (S), Steam reducing valve (T), Diaphragm valve (U), Tank (V), Hot water set (W), Pump (X), and Steam Injector controller (Y).
• Controlled temperature flow is maintained between various components.

Pump and Plates in HTST System

Pump

• A rotary positive pump or a centrifugal pump ensures constant output.

Plates

• The plate heat exchanger is commonly used in HTST systems for heating milk.
• It consists of stainless steel plates with a rubber gasket for heat transfer.
• The design includes raised sections on plates for efficient heat transfer.
• Additional plates can be added for increased capacity.

Pasteurization Process Overview

• Regeneration Heating

  The incoming cold milk is heated indirectly by the hot outgoing milk, known as milk-to-milk regeneration. This enhances the efficiency of the process by reducing the amount of hot water needed to raise the incoming milk's temperature.

• Filter Units

  Filter units of various shapes are connected directly to the HTST system after the pre-heater or regeneration section. These units, typically cylindrical and equipped with 40-90 mesh cloth, allow for continuous operation by using two filters interchangeably.

• Holder

  The holding tube or plate ensures that the milk remains at the pasteurization temperature (72°C or 161°F) for a minimum of 15 seconds, crucial for the effectiveness of the process.

• Flow Diversion Valve (FDV)

  The FDV directs the milk post heat treatment. Properly pasteurized milk flows forward through the system, while inadequately pasteurized milk is redirected back for reprocessing at the FCBT, controlled by air pressure.

• Regeneration Cooling

  The pasteurized hot milk is partially cooled by the incoming cold milk, contributing to the efficiency of the process.

• Control Panel

  The control panel houses instruments, controls, SDV mechanisms, and holding systems, along with an air-insulated chamber containing the holding tube.

• Hot Water Set

  The hot water set circulates hot water through the heating system, an essential component of the pasteurization process.

• Automatic Control Devices

  Various automatic control devices such as steam pressure controllers, water temperature controllers, and milk temperature controllers manage the respective actions within the pasteurization system.

High Temperature - Short Time (HTST) Pasteurization

• Normal pressures in the HTST system:
  • Pasteurized milk: 15 psi
  • Heating/cooling medium: 12 to 13 psi
  • Raw milk
• Holding the test:
  • Correct holding time is crucial for proper pasteurization.
  • Measured using an electrical conducting device or dye injection method.
• Advantages of HTST Pasteurization:
  • Continuous process, minimizing time wastage.
  • Requires less floor space compared to the Holder Method.
  • Lower initial equipment costs for large-scale operations.
  • Efficient use of regenerative heating and cooling, reducing heating and refrigeration expenses.
  • Easily cleaned and sanitized equipment.
  • Eliminates external contamination due to closed system operation.
  • Prevents bacterial growth issues.
  • Precision controls ensure effective pasteurization.
• Disadvantages:
  • Not suitable for handling small milk quantities.
  • Gaskets require regular maintenance and sanitation.
  • Narrow temperature margin for effective bacterial destruction.
  • Less efficient pasteurization of high thermoduric raw milk counts compared to the Holder system.
  • Increased milk stone accumulation in the heating section.

Other Methods of Pasteurization

• Batch/Holding Pasteurization:
  • Also known as Low Temperature - Long Time Method.
  • Milk heated to 63°C/145°F for 30 minutes then rapidly cooled.
  • Heating occurs indirectly through a metal wall.
• Types of Pasteurizers:
  • Water-jacketed vat.
  • Water spray type.
  • Coil-vat type.
• Advantages of Water-jacketed Vat:
  • Offers flexibility for handling various fluid milk products.
  • Known for multipurpose use.
• Disadvantages of Coil-vat Type:
  • Coils are challenging to clean, leading to decreased usage.

Milk Pasteurization and Packaging

• Heating Methods:
  • Plate or tubular heat exchangers are used for pasteurizing milk.
  • In-the-vat pasteurization involves heating milk in vats, allowing continuous milk flow but potentially leading to the growth of thermophilic organisms.
  • In-the-bottle pasteurization entails filling and sealing bottles with raw milk, then subjecting them to specific temperatures for optimal pasteurization.
• Advantages and Disadvantages of In-the-bottle Pasteurization:
  • Advantage: Prevents post-pasteurization contamination.
  • Disadvantages:
    • Transfers heat slowly.
    • Increased risk of bottle breakage.
    • Requires oversized bottles to accommodate milk expansion during heating.
    • Utilizes special water-tight caps.
• Bottling and Packaging:
  • Pasteurized and cooled milk is promptly bottled to protect against contamination and degradation.
  • Glass bottles are commonly used for packaging due to their transparency.
  • Various bottle treatments like titanising and hard-coat treatments help minimize breakage.
  • Different processes exist for filling bottles, ranging from manual hand fillers in small plants to automatic mechanical fillers in larger facilities.

Caps and Capping

• The capping machine in milk packaging serves to retain milk, protect from contamination, and seal against tampering.
• Types of caps include cardboard discs with moisture-proof layers, aluminum foil caps, and crown corks.
• In modern dairies, aluminum foil caps are predominantly used for efficient capping processes.

Packaging

• Glass milk bottles have been traditional, but single-service paper/plastic containers and sachets are becoming more popular.
• Sachets, made of flexible waterproof materials, are filled using a form/fill/seal system for convenient packaging.
• Advantages of paper/film packaging over bottling include being lightweight, cost-effective, and tamper-proof.

Storage

• Milk plants require refrigerated rooms to store milk at temperatures below 5°C to prevent bacterial growth.

Distribution

• Efficient distribution involves physical equipment, personnel, sales promotion, and advertising.
• Successful distribution requires high-quality products, attractive packaging, courteous sales personnel, and effective advertising.

Route Organization

• Route organization varies based on the business size, with separate handling of wholesale and retail distributions.
• Trucks should be utilized efficiently to maximize milk distribution.

Sales Outlets

• Sales outlets for milk include home delivery, milk booths, stores, vending machines, and institutions like hospitals and restaurants.

Anticipating Daily Demand

• Forecasting daily demand is crucial, considering past trends, holidays, and special events.

Frequency of Distribution

• In regions with variable temperatures like India, milk is distributed twice daily to maintain freshness.

Utilization of Returned Milk

• Unsold milk should be managed carefully to prevent quality deterioration, with options like processing into other products.

Bulk-vending Machines

• Bulk-vending machines offer loose milk distribution, with a system where consumers bring their containers for milk.
• This system aims to provide milk at a lower cost and reduce the overheads of traditional packaging.

Advantages of Dairy Packaging

• Elimination of costs related to bottles, bottle-washers, detergents, and other packaging materials.
• Prevention of temperature rise during distribution, ensuring customers receive milk at 5°C or lower.
• Low-temperature distribution helps maintain milk quality by reducing exposure to outside atmosphere.

Judging and Grading of Milk

• Consumer acceptability is based on organoleptic quality (palatability) - taste, smell, texture, etc.
• Quality of dairy products is strongly influenced by the quality of raw materials used.

Scoring System for Milk Quality

• Flavour (Smell and Taste): 45 points
• Bacteria content: 35 points
• Sediment presence: 10 points
• Temperature, Container, and Closure quality: 5 points each
• Total Perfect Score: 100 points

Explanation:

• Organoleptic quality plays a crucial role in determining consumer satisfaction. For example, the taste and texture of milk influence its market acceptance.
• The raw materials used in dairy production, such as milk quality, directly impact the final product. High-quality raw materials lead to superior dairy products.
• The scoring system by the American Dairy Science Association provides a structured way to evaluate and grade packaged market milk based on specific criteria, ensuring quality standards are met.

Marketing Defects in Milk

• Closure (cap) inspection is crucial post-sampling.
• Check glass container for fullness, cleanliness, and leakage.
• Inspect for correct Gillage and presence of fly pupae indicating bottle washing issues.
• Examine flavor after opening the bottle.
• Ideal milk temperature is 16-21°C (60-70°F).
• Check for sediment using standard discs for comparison.
• Flavor defects in milk are critical; understand causes and prevention.
• Assess milk for 'Bacteria' using Standard Plate Count.

Flavour Defects

• Barny
• Bitter
• Cooked
• Feed
• Foreign
• Highly acid/sour

Flavour Defects in Milk: Causes and Prevention

• Improper ventilation of milking byre/barn.
• Milk left in the byre for too long post-production.
• Intake of bitter weeds by milch animals.
• Overheating of milk and feeding milk-tainting feeds.
• Absorption of foreign odors in milk.
• Excessive lactic acid development due to microbial growth.

Prevention Strategies

• Ensure proper ventilation in milking areas.
• Prompt milk removal after production.
• Eradicate harmful weeds and use normal lactation milk.
• Avoid overheating, milk-tainting feeds, and storing near odorous materials.
• Store milk at 5°C (40°F) or below to inhibit bacterial growth.

More Flavour Defects

• Malty
• Rancid
• Oxidized, oily
• Metallic
• Tallowy
• Sultry
• Weedy

Causes and Prevention

• Growth of specific micro-organisms in milk.
• Fat oxidation from contact with copper or iron.
• Exposure to light and fat hydrolysis due to lipase action.
• Intake of milk-tainting weeds and mastitis in animals.

Prevention Measures

• De-aerate/vacuumize-pasteurized milk.
• Avoid mastitis or late lactation milk.
• Properly tin milk vessels or use suitable materials.
• Eradicate milk-tainting weeds and store milk appropriately.

Nutritive Properties of Pasteurized Milk

The nutritional content of pasteurized milk closely resembles that of raw milk, with minimal vitamin loss. Despite slight reductions in Vitamin C (20% in Holder Process) and Thiamine (10%), pasteurized milk is considered safe for consumption due to the absence of harmful bacteria.

Standardization of Milk

• Definition: Vacuum pasteurized milk refers to milk with adjusted fat and solids-not-fat content to specific levels.
• Process: Standardization is typically achieved by mixing with freshly reconstituted skim milk in appropriate ratios.
• PFA Rules: According to the PFA rules (1976), standardized milk for liquid consumption must contain a minimum of 4.5% fat and 5.5% solids-not-fat nationwide.
• Composition: Standardized milk can be cow milk, buffalo milk, or a blend, standardized to specific fat and SNF percentages.

Advantages of Standardization

• Ensures consistent composition and nutritional value for consumers.
• Surplus fat can be used to produce butter and ghee.
• Enables the provision of more affordable milk.
• Enhanced digestibility due to reduced fat content.

Standardization and Preparation Method

• Vacuum pasteurized milk is prepared following specific standards and procedures.

Toned Milk

• Toned milk is a type of milk produced by mixing water and skim milk powder with whole milk, typically whole buffalo milk in practice.
• According to the Prevention of Food Adulteration (PFA) rules from 1976, toned milk must contain at least 3.0% fat and 8.5% solids-not-fat nationwide.

Introduction and History

• Toned milk was pioneered by D.N. Khurody in India in 1916 and first produced at the Central Dairy of the Aarey Milk Colony in Mumbai.
• Khurody's innovation involved adding skim milk powder to reduce fat content while maintaining solids-not-fat levels, leading to the creation of toned milk.

Advantages of Toned Milk

• Increases milk supply by 100-150% using buffalo milk.
• Reduces milk prices, making it more affordable for lower-income groups.

Manufacturing Process

• The process involves steps like preheating, addition of skim milk powder and whole buffalo milk, filtration, pasteurization, cooling, packaging, and storage.
• A flow chart illustrates the manufacturing process of toned milk.

Problem and Solution

• Given initial milk composition and desired toned milk composition, calculations are made to determine the amount of water and skim milk powder required.
• Equations are formed based on fat and solids-not-fat (SNF) content to find the quantities of water and skim milk powder needed.
• Solution: Approximately 1382.1 kg of water and 141.5 kg of skim milk powder are required to produce toned milk as per specifications.

Manufacturing Details

• The manufacturing process involves heating water, adding skim milk powder, incorporating whole buffalo milk, and ensuring thorough mixing throughout the process.

Sterilized Milk and its Variants

• Homogenized Milk

  • Homogenized milk is produced by pumping milk through a filter and pasteurizing it at a specific temperature.
  • After pasteurization, the milk is rapidly cooled, packaged, and stored under refrigeration until distribution.

• Double Toned Milk

  • Double toned milk is similar to toned milk but must contain a minimum of 1.5% fat and 0.0% solid-not-fat as per PFA rules.
  • The manufacturing process is akin to toned milk, following specific standards set for double toned milk.

• Sterilized Milk

  • Sterilized milk undergoes continuous heating at specific temperatures to ensure preservation for an extended period.
  • It offers advantages such as remarkable shelf life, no cream plug formation, and a distinctive flavor due to homogenization.
  • However, disadvantages include increased production costs and some loss in nutritional value compared to pasteurization.
  • Manufacture involves stringent quality control measures, including preheating, homogenization, and sterilization in sealed containers.

Manufacturing Process of Sterilized Milk

The production of sterilized milk involves several key steps to ensure quality and safety:

1. Receiving and cooling the raw milk for storage.
2. Preheating the milk for filtration and clarification.
3. Standardizing the milk to meet legal requirements for fat and solids content.
4. Homogenizing the milk to prevent cream separation.
5. Clarifying the homogenized milk to remove any sediment.
6. Filling and capping the milk in sanitized bottles for sterilization.
7. Sterilizing the bottles at specific temperatures for a set duration.
8. Cooling the sterilized milk bottles to room temperature for distribution.

Advantages of Sterilized Milk

• Extended shelf life without the need for refrigeration.
• No cream plug formation, making it suitable for infants and invalids.
• Distinctive rich flavor due to homogenization.

Disadvantages of Sterilized Milk

• Higher production costs compared to other methods.
• Loss of some nutritional value during processing.
• Challenges in accurate testing for quality control.

Ultra High Temperature (UHT) Process

• Ultra High Temperature-Short Time Process (UITST) involves heating milk to 135-150°C for a few seconds using a plate or tabular heat exchanger.
• Milk is sterilized in a continuous flow sterilizer, allowing large volumes to be processed efficiently.
• Sterilized milk is aseptically filled into containers for distribution, sometimes using superheated steam to sterilize cans and lids.
• Common packaging methods include tetra pack single-service containers.
• Despite acquiring a cooked flavor, the milk's color remains unaltered or may even appear whiter.

Distribution and Testing

• Sterilized milk is distributed weekly, making it popular in warm regions without widespread household refrigeration.
• Tests conducted include turbidity tests and bacterial counts, with the phosphatase test being inapplicable to sterilized milk.

Faults and Innovations

• Common faults in sterilized milk include browning, leading to flavored and colored varieties being more favored.
• Double milk is a modified sterilized milk with increased fat and SNF percentages, packed in paper reinforced by aluminum foil.

Homogenized Milk

• Homogenized milk prevents cream separation by breaking down fat globules to less than 2 microns in diameter.
• The process involves forcing milk through a homogenizer to subdivide fat globules, resulting in a more stable emulsion.

Advantages of Homogenized Milk

• Stabilizes milk fat emulsion, preventing cream separation.
• Enhances palatability and digestibility, making it suitable for infant feeding.

Disadvantages of Homogenized Milk

• Increased production costs and difficulties in salvaging returned homogenized milk due to fat recovery challenges.
• Greater sedimentation and susceptibility to flavor defects are noted drawbacks.

Factors Influencing Homogenization

• Temperature and pressure are critical factors affecting the homogenization process.
• Temperatures above the fat melting point and specific pressures are required for effective homogenization.

Reconstituted Milk

• Reconstituted milk is made by mixing dried whole milk powder with water in specific proportions.
• Advantages:
  • Addresses the shortage of fresh milk in developing countries.
  • Utilized by Armed Forces in various nations.
• Manufacturing Process:
  • Water is heated in a vat, milk powder is added gradually with agitation, mixed thoroughly, filtered, pasteurized, and then cooled for distribution.

Recombined Milk

• Recombined milk is created by combining butter oil, skim milk powder, and water in correct proportions.
• Requirements:
  • Must contain a specific percentage of butter fat and milk solids other than fat.
  • The milk fat can be sourced from various sources like unsalted butter or plastic cream.
• Manufacturing Process:
  • Water is heated, skim milk is added, followed by butter oil, mixed thoroughly, pasteurized, homogenized, cooled, and then packaged for distribution.
• Significance:
  • Helps in meeting the demand for milk in developing countries.
  • Contributes to stabilizing milk prices in urban areas.
• Historical Context:
  • Recombined milk production was a part of the 'Operation Flood' initiative in major Indian cities during the 1970s, supported by donations from international organizations.

Filled Milk and Flavoured Milk

Filled Milk

• Resembles recombined milk but uses vegetable fats instead of butterfat.

Flavoured Milk

• Milks with added flavors like chocolate, coffee, or other edible flavors, colors, and cane sugar.
• Must be pasteurized or sterilized.
• If labeled as "milk," it should have a milk fat percentage meeting the legal requirement; otherwise, it's termed a "drink" for lower fat levels (1-2%).

Advantages of Flavoured Milk

• Makes milk more appealing to those who don't enjoy plain milk.
• Utilizes skim milk effectively.

Main Types of Flavoured Milk

• Chocolate milks/drinks
• Fruit-flavored milks/drinks
• Sterilized flavored milks/drinks

Details of Manufacture

Chocolate Milks/Drinks

• Ingredients: Cocoa powder, sugar, stabilizer (e.g., Sodium Alginate).
• Milk is standardized, preheated, homogenized, and then mixed with cocoa, sugar, and stabilizer.
• The mixture is pasteurized, cooled, bottled, and kept refrigerated until use.

Fruit-Flavored Milks/Drinks

• Uses permitted fruit flavors, colors, and sugar in preparation.
• No acidic substances should be added to prevent curdling.
• Ratio: 1 part fruit syrup (45-55% sugar) to 5 parts milk.

Sterilized Flavored Milks/Drinks

• Similar preparation method to chocolate milks/drinks but with permitted fruit flavors.

Manufacture of Sterilized Flavoured Milk/Drinks

• Receiving Milk for Clarification
• Mixing Flavor/Essence, Color, and Sugar
• Filling and Capping for Storage at Room Temperature

Details:

• When receiving milk for clarification, the process is identical to that of sterilized milk preparation.
• During the mixing stage, flavoring agents, colorants, and sugar are combined to enhance the taste and appearance of the product.
• The final step involves filling the flavored milk into containers and capping them for storage at room temperature.

Example:

• For instance, when producing strawberry-flavored milk, the manufacturer would add natural or artificial strawberry flavor, red coloring, and sugar to plain milk.of d