In the USA, boneless broiler breast fillets are much in demand for several market segments including retail, food-service and further processing. Broilers are reared to a variety of weight ranges to meet specific customer needs, and the processing of large birds weighing 2.7-4.1kg is becoming increasingly popular. These larger birds are used for de-boning markets that feed into food-service and further processing markets due to increased meat yields and product weight per man hour, thereby improving the efficiency of both labour and the overall process.

The use of sizing and portioning of breast fillets from large birds provides uniform products that meet strict customer specifications, e.g., weight and/or size, especially for the food-service market.

Types of portioning

Portioning generally involves either cutting fillets horizontally (slitter), vertically or a combination of both. The part with the intact membrane (epimysium) is considered to be the premium piece because it most resembles the natural fillet and can be used for a large variety of products, both breaded and non-breaded. The remaining piece is commonly used for battering, breading or other further processing operations.

The portioning process is now usually automated but may be done manually. There are a variety of techniques for cutting including band-saw blades and water jet technology. In automated systems, a mould or template is employed for horizontal/vertical cut combinations using vacuum or pressure.

Flattening-type pressure can also be used for horizontal cuts, while water jet technology is often used for vertical cuts. Breast fillets are often subjected to horizontal cutting followed by vertical cutting unless these steps are combined using specialised equipment.

Portioning can take place immediately follow the de-boning process or after a further period of aging.

Each of these factors influences quality issues such as tenderness, water-holding capacity and appearance, as well as yield and size.

Tenderness factors

Many factors affect the tenderness of portioned breast fillets, and some of these such as age of bird and time of de-boning are related to the initial quality of the whole breast fillet.

The time at which breast fillets are de-boned can significantly impact meat tenderness. De-boning breast fillets pre-rigor, or early post mortem (within 4 hours) can result in tougher meat because energy is still present in the muscle. When the de-boning process occurs, the cutting action can stimulate muscle contraction, resulting in a denser muscle and subsequently tougher meat when cooked. The variation of tenderness among fillets is much greater when fillets are de-boned early post mortem - some fillets may be much tougher than others.

In the past, it was recommended to age carcasses for 4 to 6 hours prior to de-boning to achieve acceptable tenderness because it allowed the completion of rigor mortis. While that aging time is still recommended, more processors are now de-boning immediately out of the chiller as early as 1.5 hours post mortem to improve process efficiency.

In addition to de-bone time, age of the bird can also influence meat tenderness. Older birds tend to be slightly tougher than younger birds. These birds may be more stress-susceptible and, therefore, can have more quality issues such as decreased water-holding capacity and yield.

Time of portioning can also impact fillet tenderness, especially of the premium piece, much like a whole breast fillet can be affected by time of de-boning. If processors immediately portion fillets using vertical cuts after de-boning early, the meat can become even tougher compared to the whole fillet because the cut is across muscle fibres, much like cutting wood against the grain. This is similar to the de-boning process and can stimulate the muscle to contract if energy is still present (early post mortem).

While vertical cutting can cause toughness, horizontal cutting has less impact on tenderness regardless of the time of portioning because the cutting action is with the muscle fibres rather than across them. Nevertheless, tenderness of slittered fillets may be negatively affected by some types of machines. Equipment that results in any cuts that are made across the muscle fibre, i.e. vertically, has the potential to impact tenderness when cut early post mortem.

To reduce the chance of increased toughening due to portioning, the process should be performed after the product has aged for 4 to 6 hours post mortem to allow for rigor mortis completion, especially if the product is to remain as a single ingredient item, i.e. not marinated. By allowing for this aging period, energy is depleted in the muscle and is not available for reaction.

Marination issues

In recent years, the use of marination of fresh boneless breast fillets portioned or not has dramatically increased in the poultry industry: it is one of the methods used by the industry for tenderisation of early harvested broiler breast fillets as it reduces the aging time required for meat tenderisation. Marination improves water-holding capacity and quality uniformity. These benefits, specifically tenderisation, however, depend on various factors like de-boning times, time between de-boning and marination, type of product, type and concentration of ingredients, level of marinade used and method of marination, e.g. tumble, injection.

Marinades are generally included at 12-15% for breast fillets. Primary ingredients of a typical marinade include salt, phosphate and water, while other ingredients may also be added. Salt and phosphate help to improve water-holding capacity and tenderness of pre- and post-rigor de-boned meat. Salt concentrations often vary in products, ranging from approximately 0.5 to 1.25%, depending on the product. Phosphate concentrations are limited to 0.5%. The lower salt concentrations are commonly used to enhance' boneless breast fillets, including portioned fillets, in order to improve water-holding capacity, tenderness, yield and overall quality and uniformity of products. The size or thickness and topography of the fillet impact the amount of time required for appropriate, or targeted, marinade pick-up.

Portioned meat can have other issues such as yields associated with drip loss, marination pick-up, marination retention and cook yields. Portioned fillets can potentially pick up more marinade in the tumbler due to the increased surface area of the exposed muscle fibres, especially with the vertically cut fillets. Additionally, because slittered fillets are substantially thinner than normal non-portioned fillets, the marinade is more quickly and evenly distributed throughout the meat. The thickness of the fillet has a significant impact: for the same reasons for increased pick-up, the retention and/or cooked yield has the potential for being worse than for a non-portioned fillet.

There is also an effect from the type of ingredients used to aid water retention. The salts and phosphates offer eating quality advantages such as tenderness and juiciness. With the even distribution in the meat, the effects of salts and phosphates on these attributes can be realised.

Equipment effects

Equipment used for portioning and the resulting cut can also impact fillet quality because the edge cut affects the time required for marinade pick-up. If the cut surface of the fillet is smooth, there is a smaller area for marinade pick-up than with a jagged cut.

Since the edges of the fillet are cut during portioning, there is also more potential for the fillet to lose integrity, especially if going through further processes such as flattening and/or marinating. Loss of integrity decreases product yield. The bottom portion of the fillet (non-premium piece) is more susceptible to loss of integrity through tears or holes, which is why this piece is often used for breaded products.

Equipment also impacts consistency of the fillet shape, especially the premium piece. If the consistency is poor, it may be necessary to adjust the fillet size after portioning to meet customer specifications or to achieve a specific cook time. This applies particularly if the fillets are of variable thickness.

Many factors are involved in the quality of portioned breast fillets. Understanding these factors will help to maximise quality for the food-service industry and other markets.