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.

Improving dry sausage quality by controlling temperature and humidity

By Joseph Sebranek Ph.D on 2/1/2009
MeatingPlace.com

In this article:
Temperature considerations
Humidity considerations


The manufacture of dry sausage is probably the oldest form of meat preservation. Dry sausage was undoubtedly discovered by accident and gradually evolved into a popular means of preserving meat in a highly palatable form.

In fact, the development of dry sausage varieties can be traced to geographical areas where natural climatic conditions offered an environment in which temperature, humidity and other factors resulted in a product with distinguishing characteristics. Northern Italy, Hungary and Switzerland are some of the areas in Europe, for example, where dry sausage products have evolved over time to the point of becoming distinct products that are recognized all over the world. Pepperoni, Genoa salami and cervelat are some typical products from this region that are widely recognized. Other parts of the world have produced dry sausage varieties that resulted from environmental and cultural conditions characteristic of those localities.

Production of dry sausage clearly was a poorly understood but well-perfected art form for centuries. It has only been in the past 50 years or so that the physical and chemical changes that occur during dry sausage production have been studied and explained to permit improved control of the process.

While many factors including raw meat quality, salt, cure and pH are critical considerations for dry sausage quality, the very nature of "dry" sausage means that temperature and humidity will be critical during key steps of the process.


Temperature considerations
Temperature considerations for dry sausage are usually focused on temperatures used for the drying process, but it's important to realize that temperature effects on product quality actually begin with the raw meat used for product formulation. Meat must be kept very cold during grinding, mixing and/or chopping to avoid fat smearing, which can form a film of fat over the lean tissue and reduce the movement of water out of the product. Meat should be maintained at -2 degrees C to -4 degrees C (24 degrees F to 28 degrees F) to facilitate good fat/lean distinction and allow effective moisture migration.

Frozen meat is often used as part of the formulation to achieve temperature control. Use good quality frozen meat, because another temperature/quality issue can arise. Frozen meat stored at higher than ideal temperatures (above -20 degrees C/0 degrees F) is likely to develop rancid flavors that will subsequently be magnified by the drying process.

Avoiding fat smearing during stuffing is also important, particularly because a film of fat just under the casing can dramatically slow the migration of water out of the product. So, again, temperature becomes an important consideration and should not exceed -1 degrees C to 0 degrees C (30 degrees F to 32 degrees F) during stuffing. Using large-diameter, short-length stuffing horns can also minimize fat smearing in dry sausage.

Following stuffing, most dry sausage will be fermented, either in a "green room" or a fermentation chamber. Because most traditional dry sausage types are fermented with cultures that do best at relatively low fermentation temperature, a temperature of 22 degrees C to 24 degrees C (72 degrees F to 75 degrees F) is typical. Determining the best fermentation temperature for the culture used is important to producing the desired pH within the targeted time for achieving optimal product quality and safety. Relative humidity becomes important at this point, with 95 percent recommended to facilitate growth of the culture and active production of lactic acid.

Following the fermentation step is drying, which is the most critical step in the production of dry sausage and where temperature (and humidity) will have a major impact on final product quality. To be successful, the drying process must achieve surface evaporation at very nearly the same rate as moisture moves through the product to the surface.

It should be no surprise that the rate of migration within a product will vary with product diameter, pH and texture of the mixture. If drying is too fast, a crust forms on the outside of the product (case-hardening), and additional water removal becomes difficult and slow. This can also contribute to the problem of pepperoni slices "cupping" on pizzas when cooked. If drying is too slow, surface growth of mold and other microorganisms is likely to occur.

Successful drying requires control of conditions within a relatively narrow set of limits for temperature, relative humidity and air-flow rates. Recommended temperature in drying rooms is generally in the range of 10 degrees C to 13 degrees C (50 degrees F to 55 degrees F).

However, the temperature becomes an interactive factor with relative humidity and air flow at this point, and conditions need to be fine-tuned in a given drying facility to achieve the best performance. Air flow must be relatively slow to maintain uniform temperature and humidity, yet uniformity is difficult to achieve with slow air speed, especially in large drying rooms. The air contact with product surfaces will pick up moisture, meaning that relative humidity of the air is changing as the air moves through drying rooms. In large rooms, this means that uniformity is increasingly difficult. Air speeds of 0.15 ft/sec to 0.3 ft/sec (0.05 m/sec to 0.1 m/sec), or about 15 to 25 air changes per hour, are good starting points.


Humidity considerations
Relative humidity first becomes a consideration for fermentation when at least 90 percent is recommended and 95 percent or more is often used. For drying, however, the relative humidity must be reduced to achieve evaporation of water from the product surface. A relative humidity of 72 percent to 75 percent is recommended by many dry sausage experts. This level is usually sufficient to prevent surface mold growth while avoiding case-hardening.

For those products in which surface mold is desired, a higher relative humidity at the beginning of the drying process is necessary. The relative humidity may also be slowly decreased from just below 90 percent to 65 percent or 70 percent as drying progresses, if drying room control is sufficient to achieve these conditions.

As a general rule, the drying rate should not exceed about 1 percent per day during the early phases of green room curing and fermentation, and should not be more than 0.7 percent per day during drying. However, keep in mind that when it comes to dry sausage, every drying process should be fine-tuned for each product and drying environment that is used in order to maximize product quality.

Using pre-rigor meat to improve sausage yield and texture

By Joseph Sebranek Ph.D on 2/1/2009
MeatingPlace.com

In this article:
What is pre-rigor meat?
Handling and preparation
Advantages of pre-rigor meat in sausage

One of the most fragile and variable properties of meat as a raw material for sausage products is the ability of meat to bind and retain water during and after processing and packaging. Drip losses, low product yields and package purge are all common problems that result from poor water-binding.

Because the retention of water is critical to texture, mouthfeel and juiciness, water-binding problems during processing carry over to consumer-perceived product quality. Further, because water-binding is a meat property that is sensitive to changes in processing procedures, it often serves as a warning indicator for other product changes. For example, in emulsified products such as frankfurters, water-binding ability is one of the first changes to occur when the emulsion is becoming less stable. This means that a decrease in yields may be a warning that the emulsion is close to breaking down with release of fat as well as water if corrective action is not taken.

Lean meat has an inherent water content of about 70 percent, and water is often added during formulation. Consequently, retaining both inherent and added water in sausage is a significant challenge. One of the most effective ways to meet this challenge is with the use of pre-rigor meat. Pre-rigor meat offers some tremendous advantages over post-rigor meat for sausage and processed products, but must be handled correctly to realize those advantages.


What is pre-rigor meat?
Simply stated, pre-rigor meat is meat that has been "hot-boned," or removed from the carcass prior to chilling and before development of rigor mortis. Pre-rigor meat is characterized by a pH well over 6.0 — usually in the range of 6.4 to 7.0 — and a high degree of protein solubility.

The muscles of live animals have a normal pH of just over 7.0, but biochemical changes in muscles that begin immediately postmortem will generate lactic acid, which in turn will change the meat pH to about 5.2 to 5.6 over a period of several hours. The reduced pH is typical of post-rigor meat and means that the proteins in the meat now have a weaker molecular attraction for water molecules.

At the same time, the reduced pH stimulates irreversible muscle contraction. Contraction or rigor mortis results in less structural space between muscle protein filaments as the muscle attempts to shorten. This physical effect reduces the space within the muscle that is available for water.

The combined effect of a weaker molecular attraction for water as well as less space for water means that post-rigor meat has considerably less ability to hold water than does pre-rigor meat. The key to retaining the advantages of pre-rigor meat is to minimize the pH change and the muscle shortening that normally occur as postmortem muscle develops rigor mortis.


Handling and preparation
To fully realize the advantages of pre-rigor meat, it is critical to remove the meat from the carcass as soon as possible following slaughter. However, this process introduces three potential problems.

First, intact muscles removed from the carcass will contract and shorten excessively if allowed to go into rigor, greatly reducing the space available within the muscle structure for water binding. This problem is easily overcome by coarse-grinding the meat immediately to break up the muscle contractile structure.

Grinding introduces a second potential problem in that the biochemical changes in muscle that produce lactic acid are accelerated by grinding. It is critical at this point to blend the meat mixture with salt, because salt disrupts the acid-producing enzymes and virtually stops the production of acid to prevent further decline in meat pH. It is important to add salt as soon as possible in order to retain the meat pH at the highest possible value.

Salting pre-rigor meat has additional advantages of solubilizing salt-soluble proteins to a greater extent than in post-rigor meat. This results in a firmer texture in cooked products and more effective stabilization of fat in emulsified products.

The salt concentration used may be in the range of 1.5 percent to 4 percent, depending on the salt concentration desired in the product in which the pre-rigor meat is to be used. The salting step is also the appropriate time to add nitrite if the pre-rigor meat is intended for use in a cured product, making the mixture similar to a pre-blend but with the advantages of pre-rigor meat. Typically, one-half of the final product nitrite concentration is used in pre-blends.

The third potential problem that can arise in handling pre-rigor meat is rapid bacterial growth in the warm, coarsely ground mixture. Rapid chilling such as with carbon dioxide snow in a mixer/blender becomes an important step. Rapid chilling also helps to slow the production of lactic acid, and when combined with salting will virtually stop the change in pH. If the pre-rigor meat is to be used for an uncured product such as pork sausage, it may be of value to chill prior to or with the addition of salt to minimize the effects of salt on fresh meat color.

Thus, to maximize the advantages of pre-rigor meat, deboning must be done as quickly as possible, followed immediately by coarse-grinding, blending with salt (and nitrite if appropriate) and chilling as rapidly as possible to 28 degrees F to 30 degrees F.


Advantages of pre-rigor meat in sausage
With proper preparation, use of pre-rigor meat brings several advantages to sausage products. Cooked product yields can be dramatically improved, with increases of 4 percent to 10 percent reported in research literature. Both fat and moisture retention are improved, resulting in improved palatability. Product texture also is modified due to greater protein extraction, with firmer texture resulting from pre-rigor meat.

In the case of cured products, the pre-cured, pre-blended mixture provides superior binding for emulsions and improved cured color. In the case of fresh uncured sausage, pre-rigor meat provides a brighter fresh meat color and longer color life in a product that is typically very color-sensitive.

Finally, the rapid chilling and early addition of salt keeps bacterial numbers low and results in longer product shelf life in terms of bacterial spoilage. Consequently, there is little not to like about using pre-rigor meat for sausage products.