Texture determines sensory quality

GLOBALLY, the popularity of convenience products is still increasing and both producers and consumers set ever-increasing requirements to end products. Local customs, flavors and shapes are important and in more and more markets, there is a focus on products that approximate a traditional home-made product.

What makes for a good end product is not easy to determine, can vary per producer and of course also depends on the flavour and local product requirements and expectations. However, some characteristics always play a part. For instance, the origin of the meat and the composition of the meat dough are important. Moreover, the portioning process itself is also essential; central to this is texture. Texture determines to a large extent the sensory qualities of a product, such as bite, cohesiveness and tenderness.

Maintaining the structure of the meat is the key to success in maintaining the texture. The influence of temperature and viscosity is enormous and, as such, it is vital that these parameters are controlled during the portioning process.

The portioning process transforms meat dough into end product. Some technological aspects – temperature, texture, shape and weight – are key in this transformation process with respect to the end product and the portioning technology.

Temperature and portioning

Every meat dough has specific characteristics that are influenced by the raw material, individual ingredients and composition. A meat dough recipe has its specific optimum processing temperature. Determining the optimum viscoelastic properties for a meat mass determines the optimum processing temperature.

Marel Townsend Further Processing (www.marel.com/further-processing) researched the functional properties of meat masses in relation to temperature, which has brought new insights and options in meat processing technology.

High-pressure portioning equipment – plates or drums with knock-out cups – only supports a product at the sides. Therefore a stiffer, thus colder mass is needed to prevent undesired premature ejection. Prematurely ejected products have a damaged appearance, which results in downgrading products, rejects, rework and loss of raw materials.

With the technological understanding and knowledge of the raw material aspects in mind, Marel’s low-pressure RevoPortioner provides processors with the flexibility to meet the optimum processing conditions for the preservation of the initial meat structure. It gives more room to realize the production of a larger variety of end products, such as tenderloins, chicken Kiev, whole muscle products (e.g. schnitzel), products with inclusions and 3D-products (e.g. meat balls or minced meat kebabs).

Furthermore, portioning at a higher temperature also has financial advantages. The change in enthalpy is big; moving from a liquid to a solid state requires a lot of energy. Processors can save a substantial quantity of coolants in the meat preparation process (compared to high-pressure portioning). When products move to the cooking process, they also contain less frozen water; melting ice-crystals is energy consuming.

Texture: A decisive quality aspect

The processing temperature has substantial influence on the texture. Colder meat dough contains more ice crystals and is more rigid than warmer dough, and more force (higher pressure) is required to pump the meat and fill the molds. Thus, in order to flow through the pump and into the molds, the frozen structure is disrupted. This has a destructive effect on the muscle structure and cells and influences the perceived and measured texture of a cooked product. Portioning experiments at various temperatures show (for the measured texture after cooking) increased loss of hardness (initial bite) and increased loss of cohesiveness with a colder meat dough.

Texture analysis can be carried out with a texture profile analysis (TPA). For the development of portioning equipment and processes, TPA assists in making the right choices for the process capabilities, functions and settings of the equipment. However, this type of analysis does not indicate whether the product is as palatable as desired; sensory evaluation does.

One way to connect sensory results to TPA is to check compression force of the product. For this, a sample is measured with a probe recording the forces when a product is compressed. The probe compresses the product twice or more, the forces measured are then translated into predictive numbers for the perceived texture by the sensory panels. Some sensory parameters of the end product that can be measured are cohesiveness, springiness, gumminess, chewiness and resilience (see Figure 1).

Reducing shape defects

A producer strives for consistent end products that all have the same shape as much as possible and show no faults. Shape consistency is desired even for home-made style products.

Some common defects in portioned fresh products are: Lips, knock-out cup markings and rough edges (product contour sharpness). All these defects are created by interactions between the meat dough, equipment and process.

That is why understanding meat properties and behavior was a key goal in the development of the RevoPortioner. Common end product defects were eliminated or at least reduced to a minimum. An important new technology that plays a significant role is the rotating drum made of breathable, sintered material.

Preventing lips and rough edges Lips occur because of the relaxation properties of meat, under influence of portioning pressure and filling accuracy. The technology incorporated in the RevoPortioner controls the relaxation of the meat. Lip creation is therefore prevented. High-pressure formers produce lips. Lips have to be scraped off the product, valuable rework is required and more meat dough is lost.

High-pressure formed products have a characteristic appearance with rough edges. This is caused by leakage between the forming plate and the upper and bottom plate. The pressure squeezes the meat between the plates and by tightening the plates together this can be limited somewhat, although this does increase wear. The sintered material drum and its sealing plate are well-matched and less pressure is needed. This gives the portioned product an unmatched product contour sharpness.

Smooth air ejection: no cup markings The rotating drum of the RevoPortioner supports products at the bottom and the sides of the mould. This allows for a slightly higher processing temperature. High-pressure formers with plates or drums cannot do this as the products would fall out prematurely and in an uncontrolled manner, which requires rework and causes waste. The sintered material of the drum makes gentle and accurate ejection possible using only air. This improves the quality of the products as knock-out cup markings do not occur. Water spraying or heating the cups to disguise ejection problems is not necessary.

Dimensional shrinking There are also shape aspects for cooked products that are of importance. It is important to know that meat always shrinks during cooking. However, producers want to avoid shrinkage as much as possible. Product shrinking is caused by shrinkage of the proteins in longitudinal and transversal direction. Some proteins shrink more than others. In general, chicken meat shrinks less than beef because of the difference in protein type.

Shearing of the mass Delicate treatment of the meat mass is of great importance for shrinkage control of the end product.

Energy input by friction (shear) in the meat mass must be prevented. For example, horizontal feeding augers transportation is based on shear and friction and must therefore be avoided. Positive displacement pumps perform much better, as this principle is not based on shear and friction. Shear forces also cause a smearing effect where the white-colored fat particles are sheared over the red-colored proteins, thus causing a pink blur. The initial red/white particle definition is lost.

Weight accuracy

Weight accuracy and giveaway play an important role in reducing costs and improving the efficiency of automated weighing systems, especially when products are sold as piece count.

Several researches under production conditions showed that the standard deviation in the weight of products made with low-pressure portioning is substantially lower (0.12 gram) as shown on Figure 2b, when compared to high-pressure portioned products (1.0 gram) as in Figure 2a

Technological knowledge translated

Years of intensive research at Marel Townsend Further Processing lead to the technological knowledge of the functional properties of meat masses, their behavior during portioning and the consequences of that portioning for various aspects of fresh and cooked end products. This knowledge was successfully translated into a new low-pressure portioning technology as applied in the RevoPortioner.

It enables effective portioning at higher temperatures with a lower pressure and therefore with minimum damage to the original meat structure and texture. It offers processors a wider operational window and allows the production of a wider variety of end products that have a consistent shape and weight, show little defects and are produced at a lower price per kilo product.