During production, processing, distribution and storage, food undergoes deterioration from chemical and microbial processes.
Typically, oxidative deterioration of meat and meat products result from degradative reactions of fats in raw meat.
The mechanism involves the peroxidation of unsaturated fatty acids, most often from the phospholipids.
Furthermore, oxymyoglobin oxidises with storage to form metmyoglobin, which gives meat an unattractive brown colour.
In fact, both deteriorative processes seem to be closely related; according to Chan, Faustman, and Decker, the process of myoglobin oxidation is a catalyst of lipid oxidation.
Comminution of meat and subsequent exposure to air can result in oxidised flavour within 1 h
Ground meat tends to become brown and rancid more rapidly than whole muscle retail cuts.
Grinding not only exposes more surface to air and microbial contamination, but also accelerates the loss of intracellular reductants, which are known to minimise metmyoglobin formation (Ledward & Macfarlane, 1971).
When the colour of ground meat changes from bright red (oxymyoglobin, the oxygenated form of the muscle pigment myoglobin) to brown (metmyoglobin), consumers discriminate against the product, since they associate these changes with a loss of quality.
The colour of fresh meat is the most important quality attribute influencing the consumers decision to purchase.
Therefore, pigment and lipid stability in ground meat are very important for meat packers and consumers.
A common approach to extending the colour shelf-life of fresh red meats is the use of modified atmosphere packaging (MAP), preferably in the dark or under lighting free of UV radiation.
MAP is widely used to extend the shelf life and quality of chill stored beef, pork and poultry.
It is well known that relatively high levels of carbon dioxide inhibit microbial growth.
The atmospheres used combine oxygen (O2), carbon dioxide (CO2) and nitrogen (N2) to maintain the quality of fresh red meat, both from a microbiological and an organoleptic point of view.
Principal components analysis confirmed these results.
In addition to MAP, the rate and extent of oxidative deterioration can be reduced by various means, including the use of antioxidants.
The incorporation of antioxidants protects lipids from oxidation and also stabilises oxymyoglobin.
Concern about safety and renewed interest in natural products resulted in increased research on natural antioxidants.
The protective effect of natural antioxidants may be reached by adding them directly to meat or meat products during processing.
Ascorbic acid possesses antioxidant properties, although it can act as an antioxidant or as a prooxidant depending on the concentration, the presence of metal ions and the tocopherol content.
A large number of authors found rosemary to have a very favourable effect on slowing down the process of oxidation of fat in various meats, such as sausages.
Rosemary contains a large number of compounds, including carnosic acid, carnosol and rosmarinic acid, and provides a major source of natural antioxidants used commercially in foods
Carnosine is a β-alanyl-histidine dipeptide found in skeletal muscle. Pork, beef, and chicken muscle contain approximately 4.0, 8.0, and 15.0 mM carnosine, respectively.
Carnosine has been shown to inhibit lipid oxidation catalysed by most oxidants.
The antioxidant mechanism of carnosine has been suggested to be due to a combination of metal chelation and free radical scavenging.
However, Zhou, Dickinson, Yang, and Decker (1998) reported that the antioxidant effect of carnosine was due to the contamination with hydrazine of its commercial preparations.