Homogenization and Pasteurization

Dairy Products. Sodium citrate is an important stabilizer used in whipping cream and vegetable-based dairy substitutes. Addition of sodium citrates to ice cream, ice milk, and frozen desserts before pasteurization and homogenization reduces the viscosity of the mix, making it easier to whip. 

Ice cream serves as a wonderful (and tasty) example of a complex, dynamically heterogeneous food system. A typical ice cream mix contains milk or cream (water, lactose, casein and whey proteins, lipids, vitamins, and minerals), sucrose, stabilizers and emulsifiers, and some type of flavor (e.g., vanilla). After the ingredients are combined, the mix is pasteurized and homogenized. Homogenization creates an oil-in-water emulsion, consisting of millions of tiny droplets of milk fat dispersed in the water phase, each surrounded by a layer of proteins and emulsifiers. The sucrose is dissolved in... 

It is well established that pasteurization and homogenization of milk reduce its XO activity (Cerbulis and Farrell 1980 Zikakis and Wooters 1980). In a study in which the activity of XO was assayed in 195 commercially processed dairy foods, it was found that commercial processing (homogenization, pasteurization) destroyed about 82% of the XO activity in raw milk (Zikakis and Wooters 1980). 

Pasteurization and homogenization completed ice cream was collected in a service tank from which it was fed by gravity into the ice cream making machines. 

The mix is next pasteurized to reduce the number of viable microorganisms to a level that is safe for human consumption, and homogenized to break the fat particles down into many small droplets. Figure 4.3 shows a flow diagram of a factory pasteurization and homogenization process. Much energy is needed to heat the mix up to the pasteurization temperature. To maximize the energy efficiency. 

UF of pasteurized and homogenized milk with 3.2% protein and 1.5% fat antifouling properties flux recovery, irreversible flux loss, total flux loss, and fouling resistance of modified membranes were enhanced due to an increase in membrane hydrophilicity (Rahimpour et al. 2009)... 

The milk flows from the silo through the processing line, where the milk is separated, standardized, pasteurized and homogenized. At the end of the processing line the milk is packed in different sizes of cartons varying from I/2,1,1 A, and 2 litre sizes. For simplicity we assume that all the raw milk will be processed to consumption milk and ignore the fact that a part of the cream is used... 

Low sodium milk—Ninety-five percent or more of the sodium that occurs naturally in milk can be removed by ion-exchange. Thus, the sodium content of whole milk generally can be reduced from a normal amount of about 49 mg to about 2.5 mg per 100 g of milk. Fresh whole milk is peissed through an ion-exchange resin to replace the sodium in milk with potassium, following which the milk is pasteurized and homogenized. 

All samples were commercially pasteurized and homogenized reduced-fat milk (2% milkfat) free of off-flavors at time of manufacture. Samples were packaged in either pint or half-pint high-density polyethylene (HOPE) contoured bottles with screw caps. Thirty samples of milk were sampled consecutively from the production line at a dairy plant the day of processing. This sampling scheme was conducted on six occasions over a 7-month period. 

Nicol et al. (2005) performed one of the few case studies for determination of the influence of the regeneration step in pasteurization and partial or total homogenization processes on the total energy and specific energy of the whole pasteurization process in an operating fluid milk pasteurization plant. The plant handled 24,000 L/h of milk with a plant... 

In a preliminary study, Tomasula et al. (2009) simulated the fluid milk process to identify energy usage and GHGs associated with HTST pasteurization and the related unit operations, such as homogenization. Physical property data for milk and cream were provided to the simulator. Packaging was not included as part of the simulation. GHGs were... 

A quantitative objective measurement of citrus juice turbidity was used by Loeffler (15, 16) to show that pectic enzyme changes occurred so rapidly after the juice was reamed from the fruit that at least a partial coagulation of the cloud occurred before the juice could be screened, deaerated and heated to a pasteurization temperature. He showed that juice turbidity was increased by flash-pasteurization and also by homogenization of the juice before pasteurization. Loeffler (15, 16) presented data on turbidity of flash-pasteurized citrus juices (heat exposure for 16 to 18 sec) after storage at several temperatures. He found that "samples pasteurized at 918C (196°F) lost their cloud when stored at 35°F (95°F) but others pasteurized at 93-95°C (199-2038F) retained their cloud almost indefinitely". 

The physicochemical models consistent with foam formation and stabilization are derived from the work on pasteurized and UHT processed miUc-creams advanced by Besner (1997). Foam formation and stabilization can basically be explained as a multistage process, with some significant differences between non-homogenized (pasteurized cream) and homogenized (UHT cream) systems. These differences... 

Preparation of the ice cream mix, including homogenization, pasteurization and ripening at about 4°C to allow full hydration of proteins and hydrocolloids present in the mix. 

Sainz et al. (2009) examined the combined effect of pressure (300-600MPa), temperature (40°C-60°C), and homogenization on the protease activity in milk. Inactivation of protease could extend the shelf life of milk. Protease was found to be very resistant to high pressures pressure stability was higher in raw milk than in pasteurized milk and... 

Production generally involves pretreatment of milk (standardization, pasteurization, and/or homogenization), slow quiescent acidification, gelation. 

Meaures of Control Proper Phase I and Phase II management, especially full term pasteurization reduction of ammonia and water in finished compost and homogenous consistency of compost structure (avoidance of densely compacted zones). 

Today, most milk is homogenized, pasteurized, and fortified (at leeist with vitamin D), the details of which follow ... 

Fluid milk is retailed as pasteurized milk, homogenized milk, fortified milk (usually vitamin D), skim milk, and flavored milk. Of the milk used for manufacturing in 1990, 31.9% was used for making cheese (exclusive of creamed... 

The processing operations for fluid or manufactured milk products include cooling, centrifugal sediment removal and cream (a mixture of fat and milk semm) separation, standardization, homogenization, pasteurization or sterilization, and packaging, handling, and storing. 

The homogenize must be placed appropriately ia the system to assure the proper temperature of the incoming product, provide for clarification, and avoid air iacorporation that would cause excessive foaming. The homogenize also maybe used as a pump ia the pasteurization circuit. 

The equipment needed includes a balance tank, regenerative heating unit, positive pump, plates for heating to pasteurization temperature, tube or plates for hoi ding the product for the specified time, a flow-diversion valve (FDV), and a cooling unit (Fig. 4). Often the homogenizer and booster pump also are incorporated into the HTST circuit. 

A homogenizer or rotary positive pump may be used as a timing or metering pump to provide a positive, fixed flow through the pasteurization system (Fig. 6). The pump is placed ahead of the heater and the holding section. Various control drives assure that the pasteurized side of the heat exchanger is at a higher (7 kPa (1 psi)) pressure than the opposite side. 

Fig. 6. Homogenizer used as a timing pump for HTST pasteurization. Details of bypass, relief lines, equalizer, and check valves are not included (10).

The basic mix is made up in liquid form, pasteurized, homogenized and cooled, using chilled water in plate heat exchangers. It is then aged for a few hours and, for this, it will be stored at 2-3°C in jacketed tanks, with chilled water in the jacket. 

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