In natural milk, the diameter of the fat balls is uneven, ranging from 1 to 10 µm, generally 2 to 5 µm. These fat balls float on the milk surface due to buoyancy to form a layer of cream, causing the milk to layer. . The presence of these fat globules greatly affects the appearance and taste of milk and dairy products.
If the milk is homogenized, the diameter of the fat globules can be controlled at about 2μm. At this time, the surface area of the milk fat increases and the buoyancy decreases, so as to avoid stratification and achieve the effect of homogenization. The unique effect of homogenization improves the quality of the product in terms of appearance and taste.
Three types of high shear homogenization, high pressure homogenization and ultrasonic homogenization:
High shear homogenization
The mechanical action forces the liquid material to pass through a very narrow gap at a very high speed. Under the action of hydrodynamics, the material is dispersed and refined through strong shear, grinding, impact and cavitation.
High pressure homogenization
Under high pressure conditions, the suspension is allowed to pass through the gap of an adjustable flow-limiting homogenization valve, resulting in comprehensive effects such as loss-of-pressure expansion explosion, shearing and high-speed impact, and crushing particles and oil droplets in the liquid into small sizes;
Ultrasonic cavitation and other physical effects in the liquid to achieve a homogeneous effect.
Physical action refers to that ultrasonic waves can effectively agitate and flow in the liquid to destroy the structure of the medium and smash the particles in the liquid. It is mainly the collision between the liquids, microphase flow and shock waves that cause the surface morphology of the particles to change.
Cavitation means that under the action of ultrasound, the liquid produces cavitations, namely small bubbles, in places with weaker strength. The small bubbles pulsate with ultrasound, and the cavities will collapse within one sound cycle. Ultrasonic cavitation will also produce a strong mechanical effect, producing fast jets or acoustic impulses near the solid interface, and generating powerful shock waves in the liquid. Under the appropriate ultrasonic frequency, the minimum power density can reach the ideal within a certain period of time. Dispersion effect.
Milk homogenized by ultrasonic has better evaluation results than high-speed discrete homogenization and high-pressure shear homogenization.
Compared with other yogurts, the yogurt made by using ultrasonic homogenized milk has rich milk flavor, smooth taste, fine appearance, and the shape of the milk block is basically unchanged within 30 minutes, indicating that the curd is in good condition and can resist mass production. The problems of turbulence and turbulence in the medium and long distances are conducive to medium and long-distance transportation.
The acid production rate and acid production rate of the ultrasonically homogenized milk during the fermentation process are easy to control.
Ultrasonic homogenizers will produce a lot of unpleasant noise during the production process, which can be overcome by installing a soundproof box; large ultrasonic homogenizers have the problem of high prices that need to be resolved.
Contact Person: Ms. Hogo Lv