On-Farm Factors

When describing the quality of meat, certain attributes clearly stand out above others. These attributes or properties are tenderness, colour, colour stability and flavour. However, at the point of sale, the colour of fresh meat is the only criterion by which the consumer can judge meat quality. Typically consumers equate an attractive bright red colour with long shelf life and good eating quality, while discriminating against meat which has turned brown. Unfortunately this is not always the case. In an effort to maximise the overall quality attributes of meat, producers consider so-called production factors – i.e. factors or conditions in which the animals are reared prior to slaughter. In this regard the diet fed to an animal is one of the most important production factors.

Diet has a significant effect on meat quality as it affects meat composition (fatty acid profile, lipid content and antioxidant or vitamin E levels), meat colour, carcass fat colour, and meat shelf life with regard to colour stability and production of off-flavours such as rancid taints. Teagasc research has shown that, for example, diets rich in grass pasture such as those typical in Ireland increase the proportion of good fatty acids in meat and fat tissues (conjugated linoleic acid (CLA), linoleic, linolenic acids and polyunsaturated fatty acids) and that the benefits increase as the grazing season continues; such diets also produce carcass fat which is more yellow but this also depends on the duration of grazing. The colour of meat from cattle raised on pasture is often slightly darker but can have more stable colour with shelf storage in retail display and there is less off-flavour production (due to higher levels of vitamin E).

Ongoing research aims to further our understanding of the relationship between diet and retail colour stability. Carcass fat colour and lipid profiles also offer some promise in the study of meat authentication, an area of increasing importance. High energy diets (those based on grains such as barley or maize) give better animal weights (heavier) but also are fatter, with less yellow fat and with lipid profiles that tend to increase the saturated fatty acid content. Other factors, such as the treatment of animals prior to slaughter are also important. Animals which experience stress are prone to use up their muscle glycogen levels, which in turn, produces lactic acid, which then results in a rapid pH decline in their muscles. This has been shown in many studies to be undesirable as meat colour and tenderness are often adversely affected. aidan.moloney@teagasc.ie or peter.dunne@teagasc.ie