The combined effects of grain supplementation and tenderstretching on alpaca (Vicugna pacos) meat quality

Techniques for postmortem tenderisation in meat processing: effectiveness, application and possible mechanisms

Abstract

Developing efficient and promising tenderising techniques for postmortem meat is a heavily researched topic among meat scientists as consumers are willing to pay more for guaranteed tender meat. However, emerging tenderising techniques are not broadly used in the meat industry and, to some degree, are controversial due to lack of theoretical support. Thus, understanding the mechanisms involved in postmortem tenderisation is essential. This article first provides an overview of the relationship of ageing tenderisation and calpain system, as well as proteomics applied to identify protein biomarkers characterizing tenderness. In general, the ageing tenderisation is mediated by multiple biochemical activities, and it can exhibit better palatability and commercial benefit by combining other interventions. The calpain system plays a key role in ageing tenderisation functions by rupturing myofibrils and regulating proteolysis, glycolysis, apoptosis and metabolic modification. Additionally, tenderising techniques from different aspects including exogenous enzymes, chemistry, physics and the combined methods are discussed in depth. Particularly, innovation of home cooking could be recommended to prepare relatively tender meat due to its convenience and ease of operation by consumers. Furthermore, the combined interventions provide better performance in controlled tenderness. Finally, future trends in developing new tenderising techniques, and applied consideration in the meat processing industry are proposed in order to improve meat quality with higher economical value.

Graphical abstract

Meat of South American camelids - Sensory quality and nutritional composition

Meat contains a range of nutrients in a highly bioavailable form and when meat is excluded from the diet, without being replaced with suitable alternatives, nutrient deficiencies may occur. For this reason, it is very important to extend our knowledge of nutrients in alternative red meats, such as that provided from the South American camelids- llama and alpaca. This review summarises the current information on the nutritional and sensory parameters of llama and alpaca meat and factors affecting quality. South American camelids produce lean carcases, with an uneven fat distribution across the carcase. Llama and alpaca meat quality traits are mostly influenced by animal nutrition, animal age and processing methods. A feeding strategy based on pasture and hay supplement of barley and alfalfa, and processing younger animals (18 months) has improved the fatty acid composition respectively in llama and alpaca meat, whereas meat colour and tenderness are influenced by processing treatments including electrical stimulation, tenderstretching and enzymatic infusion.

The effect of whole carcase medium voltage electrical stimulation, tenderstretching and longissimus infusion with actinidin on alpaca meat quality

The effect on alpaca meat quality from applying medium voltage electrical stimulation (ES) in combination with tenderstretching (TS; pubic symphysis suspended) to whole carcases was investigated, along with the effect of actinidin infusion on alpaca longissimus (LTL) quality. Carcases (n = 36) were allocated to either no ES + achilles hung; or ES + TS. The left- and right-hand side LTL of each carcase was allocated to one of three infusion treatments; no infusion (control), infusion with water or infusion with enzyme. Processing treatments reduced LTL and semimembranosus shear force without negatively impacting colour or oxidation traits. Infusion with enzyme reduced LTL shear force relative to control and water treatments but resulted in reduced consumer acceptance. The use of TS with ES in commercial alpaca processing is supported. There was no advantage to infusing alpaca LTL with actinidin as results indicate a net negative effect on consumer acceptance of this novel meat.

The effects of season and post-transport rest on alpaca (Vicunga pacos) meat quality

The effects of season (summer, autumn, winter and spring) and post-transportation rest on alpaca meat quality were investigated in 160 castrated male alpacas (23 ± 1 month of age) over a 12 month period. Twice per season, animals were randomly allocated to consignment groups of 20, transported 4 h to slaughter and allocated to either of two treatment groups: (1) overnight lairage pre slaughter (Direct) and (2) seven day rest period with access to feed pre slaughter (Rested). At slaughter, blood was collected for the analysis of plasma cortisol and a longissimus core sample obtain pre rigor for glycogen content determination. Alpaca muscle moisture loss increased through summer and spring in the longissimus thoracics. Seasonal differences did not reflect pasture seasonality or muscle glycogen content. Resting alpacas for 7 days pre-slaughter reduced muscle glycogen content and tenderness. Drip loss and purge was greater for rested animals indicating that resting alpacas post transport is not advantageous to alpaca meat quality.

The effect of electrical stimulation and tenderstretching on colour and oxidation traits of alpaca (Vicunga pacos) meat

The effects of tenderstretching (TS; carcase suspension by the pelvic bone) combined with medium voltage electrical stimulation (ES) on alpaca colour and oxidative traits was investigated. Castrated huacya alpacas were processed and treatments applied to the 36 split carcases, in a 2 × 2 factorial arrangement (Achilles hung; AH/TS and ES/non-ES). After 24 h chilling, colour stability analysis and thiobarbituric acid reactive substances evaluation (TBARS) was conducted on samples of longissimus and adductor femoris. An additional 30 cm of longissimus was prepared for TBARS evaluation and sensory assessment using an untrained consumer panel. Electrical stimulation increased lipid oxidation within the longissimus. However, overall oxidation levels were extremely low and as a result ES effects on oxidation were not detected at the consumer level. Therefore, the combined processing treatments did not dramatically impact alpaca meat eating quality or colour stability. Results also indicate that alpaca displays advantageous colour and oxidation traits when compared to other red meats.

Applied and Emerging Methods for Meat Tenderization: A Comparative Perspective

The tenderization process, which can be influenced by both pre- and post-slaughter interventions, begins immediately after an animal's death and is followed with the disruption of the muscle structure by endogenous proteolytic systems. The post-slaughter technological interventions like electrical stimulation, suspension methods, blade tenderization, tumbling, use of exogenous enzymes, and traditional aging are some of the methods currently employed by the meat industry for improving tenderness. Over the time, technological advancement resulted in development of several novel methods, for maximizing the tenderness, which are being projected as quick, economical, nonthermal, green, and energy-efficient technologies. Comparison of these advanced technological methods with the current applied industrial methods is necessary to understand the feasibility and benefits of the novel technology. This review discusses the benefits and advantages of different emerging tenderization techniques such as hydrodynamic-pressure processing, high-pressure processing, pulsed electric field, ultrasound, SmartStretch^™ , Pi-Vac Elasto-Pack® system, and some of the current applied methods used in the meat industry.

Muscle structure, sarcomere length and influences on meat quality: A review

The basic contractile unit of muscle, the sarcomere, will contract as the muscle goes into rigor post-mortem. Depending on the conditions, such as the rate of pH decline, the cooling rate and the mechanical restraints on the muscles, this longitudinal shortening will result in various post-mortem sarcomere lengths as well as lateral differences in the distances between the myosin and actin filaments. This shortening is underlying the phenomena described as rigor contraction, thaw rigor, cold shortening and heat shortening. The shortening in combination with the molecular architecture of the sarcomere as defined by the myosin filaments and their S-1 and S-2 units, the interaction with the actin filaments, and the boundaries formed by the Z-disks will subsequently influence basic meat quality traits including tenderness and water-holding capacity. Biochemical reactions from proteolysis and glycogen metabolism interrelate with the sarcomere length in a complex manner. The sarcomere length is also influencing the eating quality of cooked meat and the water-holding in meat products.