Three tips for creating more stable meat emulsions

By Ana Elia Rocha McGuire on 4/1/2009
http://www.meatingplace.com/MembersOnly/technology/details.aspx?item=10030

In this article:
Use high-quality meat and some additional ingredients
Chop just enoughBe aware of fat type and quality
Comments and insights

An emulsion is a colloidal suspension of two immiscible liquids, such as oil and water. Usually, a non-polar liquid is dispersed within a polar liquid. One-third of an emulsion can be an emulsifying agent, which is required for emulsion stability. In meat processing, a meat emulsion is made of a continuous phase (protein) and the discontinuous phase (fat).

In a meat emulsion, meat proteins act as emulsifying agents. Meat proteins must surround the small fat particles to make the emulsion stable before the cooking process.

In the meat, the major structural protein is myosin, and it is the most important of the proteins to ensure fat emulsification and water binding in emulsified meat products.

There are a number of factors that affect emulsion stability, but these three suggestions should be most helpful for achieving a stable emulsion for different meat products.


Use high-quality meat and some additional ingredients
Several factors can interfere with the functionality of myosin and its ability to emulsify fat. Before rigor mortis, myosin is readily available in the muscle of animals, but after rigor mortis myosin and actin — another meat protein — combine, forming actomyosin. In this form, myosin loses some of its water-binding and fat-stabilizing capacities.

The pH of the meat is another factor that must be monitored, since the water-holding capacity of the meat is at its minimum at what is called the iso-electric point (pI) of proteins. The pI is the pH at which the proteins have equal positive and negative charges and therefore cannot attract more positive and/or negative charges, making them unable to bind water. The pI for fresh post-mortem beef and pork generally occurs at a pH of about 5.3.

However, meat pH can be manipulated with the addition of ingredients, and increasing or decreasing pH away from the pI will create more positive and/or negative charges, allowing the proteins to bind water and fat. Salt is an excellent aid to solubilize proteins, but it can also increase the pH of the meat. Phosphates, mainly alkaline ones, will increase the pH of meat to the greatest extent.


Chop just enough
For fat to enter the discontinuous phase, it must be transformed in very small-size particles so extracted meat proteins can coat, entrap and hold the fat droplets, creating a matrix. When chopping time is not sufficient, fat particles will be too large, resulting in an unstable emulsion. On the other hand, if excessive mechanical action is applied — too much chopping — the surface area will be too large, requiring perhaps more protein to coat the fat particles. If there is not enough protein, the result will be an unstable emulsion.

Another effect of over-chopping is an increase in temperature, and depending on the type of fat, a higher or lower temperature can be dangerous (see below). Generally, high temperatures at the end of the chopping process may result in a protein coating of the fat particles that is too thick and inflexible, which will tend to fracture during fat expansion upon cooking. Thinner protein coatings will form a series of pores that could act as "escape valves" to hot expanding fat.

To reduce excessive chopping, the fat portion of the emulsion initially should be ground separately from the lean tissue and added to the chopper or emulsifier later. In general, lean meat ingredients should be well ground and chopped before higher-fat ingredients are added. Final chopping temperatures for fats of beef, pork and poultry origin should be below 63 degrees F, 53 degrees F and 43 degrees F, respectively.


Be aware of fat type and quality
The characteristics of fats can influence emulsion stability. Some evidence suggests that it is easier to emulsify short-chain saturated fatty acids than their longer-chain counterparts. The degree of saturation is also important; in fatty acids with similar chain length, it is easier to emulsify those that are less saturated. Similarly, there seems to be a relationship between the melting point of the fat and its degree of dispersion and absorption by the continuous protein film.

As temperature of the meat emulsion during chopping gets closer to that of the fat melting point, the meat batter viscosity decreases, and since fat particles are less dense than the aqueous phase, they tend to float to the surface. These floating particles are less likely to be coated by the protein film and will be prone to coalesce during the thermal process, resulting in product defects. (See Tips to prevent common product defects in sausage on Meatingplace.)

According to various research in which types of fat have been studied, regardless of the final chopping temperature, at lower levels of fat addition, all kinds of fat yield stable emulsions. However, at higher levels of fat addition, those with higher melting points are more stable.