LECTURE NOTES 04/08 “HOMOGENIZATION PROCESS” SAIFUL IRWAN ZUBAIRI PMIFT, Grad B.E.M. B. Eng. (Chemical-Bioprocess) (Hons.), UTM M. Eng. (Bioprocess), UTM ROOM NO.: 2166, CHEMISTRY BUILDING, TEL. (OFF.): 03-89215828, FOOD SCIENCE PROGRAMME, CENTRE OF CHEMICAL SCIENCES AND FOOD TECHNOLOGY, UKM BANGI, SELANGOR 28 MAY 2008
Emulsification: “ is the formation of a stable emulsion by the intimate mixing of two or more immiscible liquids”
Results: the dispersed phase is formed into very small droplets within the second (continuous phase)
Homogenization: “A mechanical treatment of the fat globules in the milk brought about by passing milk under high pressure through a tiny orifice” Results: 1) Decrease in the average diameter & increase in number & surface area of fat globules. 2) Reduced tendency for creaming of fat globules. The Homogenization process actually has a little @ no effect on nutritional value @ shelf life e.g: margarine & low-fat spreads, salad cream, mayonnaise, sausage meat, ice-cream & cakes
Use high-frequency sound waves (18-30kHz) to cause alternate cycles of compression & tension in low viscosity liquid & cavitations of air bubbles, to form emulsion with droplet sizes (1-2 µm).
Used for the production of salad creams, synthetic creams, baby foods & essential oil emulsions.
Also used for dispersing powders in liquids.
(4) Hydro shear homogenizers & microfluidisers
Is a double-cone shaped chamber which has a tangential feed pipe at the centre & outlet pipes at the end of each cone.
Feed liquid enters the chamber at high velocity, reaches the centre & discharged, differences in velocity causes high shearing forces together with cavitations, ultra-high frequency vibration, break droplets in the dispersed phase.
Assignment: 1. What is the process of homogenization? 2. Why is it used for milk? 1. Homogenization : One of the oldest applications of homogenization is in milk processing, aim to prevent @ delay the separation of cream from the rest of the emulsion. This is done by forcing the milk at high pressure through small orifices. 2. Milk contains little globs of fat which rise to the surface as what we call cream. Homogenization breaks these little globs of fat into very tiny globs which are so small that the force making them rise to the top doesn't overwhelm random bumps and swirls from the milk around them.
The process of reducing the particle size of fluid products such as milk, fruit juice & sauces, under conditions of extreme pressure, sheer, turbulence, acceleration & impact to make them more stable & better texture
The effect achieved by forcing product through a special homogenizing valve at high pressure.
Particles enter the homogenizer with sizes ranging typically from 0.2 - 20 microns.
Large particles are dispersed to produce a product with particles ranging typically from 0.4 to 1 micron depending on the application.
Providing time for fat crystallization, so the fat can partially unite.
Allowing time for full protein and stabilizer hydration and a resulting slight viscosity increase.
Allowing time for membrane rearrangement and protein/emulsifier interaction, as emulsifiers displace proteins from the fat globule surface, which allows for a reduction in stabilization of the fat globules and enhanced partial unite.
OTHER CONSIDERATION DURING THE PROCESS:
Aging is performed in insulated or refrigerated storage tanks, silos, etc.
Mix temperature should be maintained as low as possible without freezing, at or below 5 o C.
An aging time of overnight is likely to give best results under average plant conditions.
A "green" or unaged mix is usually quickly detected at the freezer.