Meat quality testing
Meat testing involves assessing quality, safety, performance and compliance with prescribed standards and legislation. When a quality assurance programme is developed, all factors that affect quality must be identified and controlled.
Most routine testing measures physical, chemical and microbiological parameters and sensory attributes. Physical parameters include temperature, acidity (pH), water activity (Aw), water binding capacity, light intensity and texture. An important temperature measurement is the cooling rate of the carcass post-slaughter; if the muscle is cooled too quickly early in the post-mortem conversion of glycogen to lactic acid, this may lead to ‘cold shortening’ and tough eating meat. Carcass hygiene, meat colour, bone-taint and in-pack drip may also be affected.
Electronic temperature measurement with digital probes is most commonly used, although non-contact measurement such as infra-red, which measures the surface temperature, is useful for screening and the measurement of oven temperatures.
The pH of meat is a measurement of acidity and is key in the conversion of muscle to meat. During early post- mortem changes, the pH of muscle falls from around 7.0-7.2 to a value known as the ‘ultimate pH’, which can depend on the species, muscle type and stress during the pre-slaughter period. Variation in ultimate pH influences factors such as colour and the ability of the meat to retain water; drip loss testing may be used as a quality indicator. A low ultimate pH results in meat proteins having decreased water-holding capacity and a lighter colour; this can have consequences for uptake and retention of added water during further processing.
Measurement of the amount of free water available for the growth of microorganisms is a useful predictor of growth of bacteria, yeasts and moulds. Aw testing is important in products like biltong, which are made safe by lowering Aw to a value that will not allow dangerous pathogens to grow or where it is part of a series of hurdles for product safety.
Tenderness, toughness, springiness and firmness are all used to describe meat quality and these can be measured objectively, for example using shear force for firmness or toughness of meat, and compression for properties such as hardness, springiness and stickiness. Advice should be sought from experts, so that the correct test is chosen to give the most meaningful results.
Consumers associate meat colour with sensory properties and freshness, so it is important that meat colour matches their expectations. However, meat colour is influenced by many factors, including pigment content, ante- and post- mortem conditions and the form and type of storage. We use a digital imaging system which accurately and reliably captures the colour of the meat.