It is time to draw the line!
Which line? The distinguishing line between carcass and meat quality traits. The two terms are frequently used interchangeably, however, this can lead to confusion or misunderstanding as they do not refer to exactly the same traits. This article aims to build a foundational distinguishing line between the two trait categories and provide insight into the differences between them.
To start, the comparative sides of the distinguishing line must be established. Carcass traits fall on one side and include (but are not limited to) rump fat (in mm), rib fat (in mm), eye muscle area (in cm2), and average intramuscular fat percentage. Meat quality traits fall on the alternate side and include (but are not limited to) tenderness, flavour, juiciness, and colour.
The difference between the two trait categories is made more concrete by the fact that muscle is not meat. Post slaughter, muscle fibres are converted into meat through an array of biochemical pathways which plays an integral role in influencing the meat quality traits. Since the conversion of muscle to meat most often occurs beyond what is visible to the naked eye, it can be challenging to observe a physical difference in states.
Let’s take a closer look at the traits in each of the groups.
Carcass traits are indicators of growth, yield and fat deposition. Carcass traits can be measured indirectly on the live animal by means of Real-time Ultrasound (RTU) scanning or directly by means of physically measuring on the carcass. Rib fat thickness is a subcutaneous fat depth measurement taken at the quartering site between the 5th and 13th rib. It is measured on a cold, quartered carcase. Rump fat depth, or P8 fat depth, is a measurement of fat depth at the P8 rump site. Even fat covering across the carcase is integral to protect the carcase from cold shortening and the potential associated toughening of the meat.
Eye muscle area (EMA) is a measurement of the loin eye muscle area at the quartering site at the 12th/13th rib site. Intramuscular fat percentage (IMF) is a measurement of the intramuscular fat or marbling between the 12th/13th rib. Intramuscular fat percentage has a positive correlation on juiciness, tenderness and taste of beef.
Meat quality traits are indicators of consumer eating experience. Meat colour can turn consumers away from a purchase if it is undesirable. Tenderness, juiciness and flavour of meat all affect the eating experience and consumers are less likely to repurchase based on toughness, dryness, or flavour.
Consumers may easily be put off purchasing a cut of beef if the meat has an undesirable colour such as it has started browning, appears pale, or reflects iridescently. Often the browning of meat results from oxidative reactions of myoglobin (protein in muscles) due to oxygen in muscles and not a result of spoiled meat. Pale meat on the other hand could be resultant of muscle pH that dropped too quickly whilst temperature was too high. Iridescence in beef can seem off-putting however, it may not be associated with spoiled meat. Iridescence can result when pigments within meat are exposed to heat or processing, or when light reflects off meat at specific angles.
The tenderness of meat is influenced by many factors, some of which include connective tissue and cross-links, myofibrillar integrity and sarcomere length. The juiciness of meat can be influenced by water-holding capacity, moisture content, and residual fluid that remains within the final product. Lastly, flavour results from reactions between amino acids and reducing sugars as well as the presence of various volatile molecular compounds. Flavour can also be influenced by fat through oxidation reactions of fatty acids.
Thus, a simpler characterisation may be to view carcass traits as being relevant on the live animal and on the carcass itself, and meat quality traits as being relevant in-store and on the plate. Whilst both carcass traits and meat quality traits should be kept in mind throughout the entire chain, carcass traits may be considered toward the producer and processer and meat quality traits may be considered toward the consumer, as they influence the consumer experience.
References
Meat & Livestock Australia, Fat – Rib fat thickness and distribution. Fat – rib fat thickness and distribution | Solutions to feedback (mla.com.au)
Angus Australia, Rib Fat, 2024. Rib Fat – Angus Australia
Angus Australia, Eye Muscle Area, 2024. Eye Muscle Area – Angus Australia
Angus Australia, Intramuscular Fat, 2024. Intramuscular Fat – Angus Australia
Warner, R.D., et al., 2022. Meat tenderness: Advances in biology, biochemistry, molecular mechanisms and new technologies. Meat science, 185, p.108657. Meat tenderness: advances in biology, biochemistry, molecular mechanisms and new technologies – ScienceDirect Smith, G. C. and Carpenter, Z. L., 1976. National Research Council. Eating Quality of Meat Animal Products and Their Fat Content. In Fat Content and Composition of Animal Products: Proceedings of a Symposium Washington,DC December 12-13, 1974. National Academies Press (US). Eating Quality of Meat Animal Products and Their Fat Content – Fat Content and Composition of Animal Products – NCBI Bookshelf (nih.gov)