Di d2 9tj

where V is the velocity of the sphere, r the radius of the sphere, t) the viscosity of the continuous phase, dx the density of the continuous phase and d2, the density of the disperse phase, and g the force of gravity. In an oil-in-water emulsion, the oil globules of lower density will tend to rise through the more dense aqueous phase. They will rise more rapidly if they coalesce into larger globules, and their separation will be slowed by increased viscosity.

When an oil is finely divided in a aqueous phase, a tension is created due to the increased surface energy created by division. The oil tends to coalesce to reduce this tension by returning to the lowest free energy state. An emulsifier (surface active agent) will reduce this tension by adsorption at the interface between the two antagonistic phases, thus reducing the free energy (amphiphilic).

Some surfactants further stabilize food emulsions by inhibiting coalescence due to contributing an electrical charge (usually negative) at the fat globule surface. The likely charged globules repel one another, further reducing the opportunity for coalescence.

Most food emulsions produced today contain added surface active agents (emulsifiers). Modern food processing procedures are designed to produce food with long-term shelf life and to withstand the rigors of transportation, including temperature extremes and mechanical abuse. Added surfactants contribute significantly to long-term emulsion stability. As an example, salad dressings that would normally separate in a matter of hours are stable and acceptable to the consumer after months of storage.

Most surfactants used in food processing are esters of fatty acids, and although found in nature, they are in most cases not present in the food after processing in sufficient quantity to provide the desired emulsion stability. Emulsifiers are characterized by the fact that they are amphoteric; that is, they posses both an oil-loving and a water-loving moiety within the same molecule. Since they are neither completely lipophilic (oil loving) nor hydrophilic (water loving) they proceed to the interface between both components and orient themselves in a structure making the fat and water more compatible.

Table 1. Estimation of the Globule Size

Globule size (urn)

Appearance

>1

Milky white

Homemade Pet Food Secrets

Homemade Pet Food Secrets

It is a well known fact that homemade food is always a healthier option for pets when compared to the market packed food. The increasing hazards to the health of the pets have made pet owners stick to containment of commercial pet food. The basic fundamentals of health for human beings are applicable for pets also.

Get My Free Ebook


Post a comment