Milk Processing and Preservation: Techniques and Methods
Milk Processing and Preservation
Homogenization
Homogenized milk ensures uniform fat distribution by passing it through a fine filter, breaking down and spraying fat droplets for better consistency.
Pasteurization and Sterilization
Pasteurization eliminates non-sporulated microorganisms at lower temperatures, while sterilization targets spores at higher temperatures.
Thermization
Thermization, a brief heating process (15 seconds at 67-78°C) before cream separation, prevents organism proliferation.
Lactose and Whey Management
Lactose, the primary component of whey, can be hydrolyzed into galactose using lactase at a pH of 2. Common whey applications include bioethanol and cottage cheese production, whey concentrate, cheese spreads, energy drinks, and fruit products.
Milk Concentration and Evaporation
Cream, with higher fat content, promotes faster organism growth. Concentrated milk contains more water than evaporated milk. Sterilization is applied to evaporated milk due to its higher fat content, while concentrated milk undergoes pasteurization.
Evaporated milk is also used in the initial stage of milk powder production.
Lactose hydrolysis enables its conversion into bioethanol through fermentation, shifting it from a residue to a valuable byproduct.
Cheese Production
Lactic acid bacteria are used in cheese making, creating porous casein and a significant amount of whey. This method is employed for soft cheeses like de Burgos.
Hard cheeses utilize enzymatic coagulation, resulting in compact casein and easier whey removal. The enzymatic method yields a denser cheese structure.
Thermophilic Bacteria
Thermophilic bacteria, being more resistant, require longer exposure to high temperatures for destruction.
Cream and Butter
Cream is an oil-in-water emulsion with high milk fat content. Butter is produced by churning cream, causing fat particles to coalesce.
Milk Powder Production
Milk powder is created by spraying fine droplets of milk into a stream of hot, dry air. The air removes the watery component, leaving behind the solid milk powder.
Evaporation and Drying Efficiency
Reducing water content to 50-55% enhances drying tower efficiency. Concentrated milk facilitates easier breakdown of fat droplets compared to using an evaporator, which would result in an emulsion.
Multiple Effect Evaporators
Multiple effect evaporators offer cost savings on auxiliary materials and energy, increasing process efficiency.
Condensed Milk Production
Condensed milk production involves visual inspection, clarification, and three stages of sucrose addition during warming and evaporation. A 30% water reduction is achieved through evaporation. Normalization adjusts components, followed by cooling, lactose addition, storage, and distribution. The staged sucrose addition ensures better dissolution and even distribution.
Microbial Control
Microbial control can be achieved through direct destruction (lethality) or growth inhibition. Lethality is faster but can impact sensory qualities, while inhibition is slower but preserves sensory components.
Factors Affecting Milk Quality
Key factors influencing milk quality include acidity, temperature, and fat content.
Effects of Heat Treatment
Heat treatment denatures proteins, affecting enzyme activity and microbial viability.
Q10 Value
The Q10 value quantifies temperature’s impact on biochemical reactions. Higher temperatures accelerate reactions and microbial destruction.
HTST and UHT Processing
High-Temperature Short-Time (HTST) and Ultra-High Temperature (UHT) processing utilize short durations and high temperatures, with HTST requiring less time than UHT.
Sterilization Methods
Sterilization can be performed in bulk or after packaging. Bulk sterilization requires an inert atmosphere and sterile equipment, while packaged sterilization necessitates clean containers and proper sealing.
Bulk vs. Packaged Sterilization
Bulk sterilization offers advantages in terms of faster cold point temperature achievement, uniform temperature distribution, and reduced equipment and space requirements compared to packaged sterilization.