Managing broiler meat tenderness in poultry processing

Boneless, skinless broiler breast meat is one of the most consumed meat products in the U.S. It has many positive attributes that make it popular with consumers. It is relatively low in fat, has a bland flavor profile making it versatile in food dishes, and is reasonably priced. It is also available in a variety of forms. Broilers are typically raised to various market ages to produce birds of various weights depending on the intended markets.

As production has increased over the years due to market demands, these markets have evolved from a whole bird-dominated market to the further processed-dominated market of today. To maximize the amount of meat that is available for use in further processing, birds have been selected for high breast yields and they have also been grown to older ages, or heavier weights, in order to obtain even more meat.

Factors impacting breast meat tenderness

Tenderness of broiler breast meat is one of the most important attributes to consumers. Broilers have traditionally been considered an inherently tender product; however, there are factors that can negatively impact the tenderness of broiler breast meat, including deboning time, age of the broiler and moisture of the product.

In the past couple of decades, some changes have occurred in production and processing of broilers that have made these factors more or less important. For example, postmortem aging times have shortened by harvesting breast meat earlier and bird size/age has increased in recent years.

In fact, over 50 percent of commercial broilers are now greater than 6 lbs. (6 to 10 lbs. liveweight). This particular market segment has more than doubled in proportion in the past 15 years. Most of these broilers processed today go through some sort of further processing that can be as simple as portioning and marination, or as complex as producing deli meats or chopped and formed products.

The whole-muscle products are particularly susceptible to tenderness issues. Overall, there has been a trend for a decrease in tenderness of broiler breast fillets in the U.S. poultry industry. This can lead to decreased consumer acceptance of products in the marketplace.

Aging gives way to processing throughput

As the poultry industry developed, one of the simpler forms of adding value was to debone breast meat. Initially, this deboning process was commonly done anywhere from 8 to 24 hours postmortem to allow for meat to age on the bone for a period of time. This aging period allowed for rigor mortis completion (a metabolic process) and the results were a tender product.

However, aging carcasses prior to deboning was (and is) expensive due to costs associated with refrigeration, labor and lost yield. Therefore, in the past couple of decades, aging periods have shortened considerably to allow increased throughput of the product in order to meet consumer demands for breast meat, as well as to obtain increased yields associated with early deboned meat.

While there are economic benefits associated with reduced aging, these shortened aging periods do not always allow rigor mortis completion prior to deboning. When deboning in a pre-rigor mortis state (less than 4-6 hours postmortem), muscle can contract because of the sufficient energy supplies that remain in the muscle when the stimulus (cutting action) is applied. The sarcomeres, or basic contractile units of muscle, shorten during contraction (Figure 1). This results in a denser muscle (more myofibrillar overlap) and, therefore, tougher meat when cooked.

Aging time prior to deboning

Because of this toughening effect, it has been recommended that broiler carcasses be aged at least 4 to 6 hours prior to deboning to allow for energy to be depleted sufficiently. It is well documented that tenderness (as measured by shearing) improves as the aging time prior to deboning increases (Figure 2). Furthermore, the variation of tenderness among fillets is much greater when fillets are deboned early postmortem so that some fillets may be much tougher than others. This variation decreases as aging time increases.

Figure 3 illustrates the consumer perception of broiler meat tenderness deboned at different times postmortem. Broilers deboned at 2 hours postmortem have a high percentage of consumers considering that meat as “too tough." In contrast, fillets deboned at 24 hours postmortem have a considerably lower percentage of consumers considering fillets as “too tough.”

However, in today’s environment, this traditional aging period of 4 to 6 hours is even too long for most processors if they want to streamline their process as much as possible. Many processors are deboning breast meat right out of the chiller, which is as early as 2 hours postmortem. While this can improve yields (muscle comes off frame more easily, and reduced drip loss) and reduce costs associated with labor and storage, deboning early can significantly impact meat tenderness in a negative way.

In addition to debone time, or sarcomere shortening, age of the bird can also influence meat tenderness. Older birds tend to be slightly tougher than younger birds which may be due to changes in collagen solubility and/or muscle fiber properties such as fiber diameter. Though there is a tradeoff for processors in terms of economics and quality, there are some other means to provide a tender product even when deboning early, including electrical stimulation and marination.

Electrical stimulation allows earlier deboning

Postmortem electrical stimulation (ES) is a processing technique that can be used to alleviate toughness of early harvested breast meat. Currently, ES is being commercially implemented more widely than ever before in the poultry industry, specifically with broilers. Systems used in the industry today are generally the low voltage systems (e.g., 50 to 250 volts, 30 to 90 seconds) and may be used at either the pre-scald or post-pick stage.

Electrical stimulation speeds rigor development and allows for earlier deboning without producing objectionably tough meat, but it does not necessarily eliminate aging altogether, especially when maximum tenderness (equivalent to 24 hours postmortem deboning) is desired.

Though ES can substantially reduce the aging period, achieving a product similar to 4 to 6 hours aging is more realistic. Furthermore, broilers used for deboning are now typically large birds (more than 6 lbs.) which require additional dwell time in the chiller, so this can extend the aging period without affecting product flow. When using ES combined with these longer chill times (deboning after chill), the result can be an acceptably tender product similar to product aged to 4 to 6-plus hours.

Reducing the aging period and streamlining the process can reduce costs associated with aging, such as labor, cooler space, refrigeration, sanitation and lost yield, thereby saving the processor thousands of dollars. For processors deboning early without any further tenderizing methods, electrical stimulation is a useful process to help maintain product quality.

Marination can help alleviate toughness

Another method of tenderizing tough broiler meat is marination. In recent years, the use of marination of fresh boneless breast fillets has dramatically increased in the poultry industry. It can alleviate the toughness associated with early harvesting of broiler breast fillets. Marination can also improve water holding capacity (i.e., moisture/juiciness) and improve quality uniformity.

Marinades typically consist of water, salt, phosphate and other possible ingredients. Marinades can be added at various levels depending on the product; however, a 12 percent to 15 percent addition is common for enhanced broiler breast fillets commonly found in retail and foodservice. The enhanced fillets generally have low levels of salt, approximately 0.5 percent to 0.75 percent, and may contain phosphate up to 0.5 percent (USDA regulated) in the form of sodium tripolyphophate (STP) or a blend of STP and other phosphate forms. Marinade ingredients help in improving meat tenderness and water holding capacity by aiding in protein solubilization and water binding through dispersion of ions into the muscle.

The benefits of marination, specifically tenderization, depend on various factors, such as deboning times, duration of time between deboning and marination, meat characteristics (e.g., thickness, pH), type and concentration of ingredients, level of marinade used, and method of marination (e.g., tumble, inject, etc.).

Quality control and brand loyalty

There is a need for a quality control program for eating quality characteristics, specifically regarding the tenderness of broiler breast meat. There are many factors that can play a role in the variation of product quality that consumers can encounter. These include various bird ages, shortened aging times, use of tenderizing methods, such as electrical stimulation, and marination along with the factors that influence its effectiveness in improving product quality.

Once consumers have a bad experience with a certain product, they are less likely to purchase the product and/or brand again for some time. This can definitely affect product loyalty.

Tenderness issues will continue to be an issue for the broiler industry, but there are ways to alleviate toughness to some degree to provide high quality products to consumers.