Introduction

The desired colour of meat products is one of key attributes of good quality. That is why it is extremely important to achieve proper colouring of the product. It is very difficult to define correct colouring due to high diversity of meat products. The colour of meat and meat products is a visual impression caused primarily by the presence of colourants, and its intensity depends also on the tissue composition and structure of the raw material and chemical condition of the colourants. The proportions of key ingredients of batter, i.e. meat, fat and water determine the quantity of colourants, first in the batter itself and then in the finished product. Colour is largely determined by the curing, smoking and cooking processes. It should also be remembered that the comminution of raw materials and conformance of this comminution with the consumer’s habits also affects colour assessment. Heme pigments content has a decisive importance for the colouration of meat products. The most important is them is myoglobin, a muscle colourant, as it occurs in approx. 90% of all colourants in meat.

Colour changes are catalysed by activity of native and microbiological enzymes. Oxidation promoting effect of native enzymes is quite slow but difficult to inhibit, as they are more resistant to thermal inactivation than microbial enzymes. The latter ones are more dangerous because their count in the product can grow rapidly and their effects accumulate.

Post-manufacturing colour changes are the more visible the more colourants are in the product. They are always caused by changes in the myoglobin molecule, regardless of its form after the end of processing. The changes always start with oxidation processes which initiate further, irreversible and undesired changes in the colourants. Therefore, protection against storage changes is based on the same principles as are applicable during the technological process. The simplest way to inhibit colourant changes during warehousing and distribution is to maintain the temperature of 0-2°C and keep the products away from the light. Low temperature prevents microbial growth and inhibits the rate of chemical reactions. Lack of light prevents the supply of energy which could initiate oxidation reactions. It is believed, that light energy initiates adverse colour changes more rapidly than increased storage temperature. Presence of electron donors in the product must also be ensured. This role is played by natural compounds and radical groups present in raw meats as well as by chemicals intentionally added in the technological process. In meat products, presence of sulphhydryl radicals from proteins plays an important role in extending colour durability. In their presence, the small amount of nitrates left after curing has a positive, antioxidating effect. Removal of cations of polyvalent metals, such as iron or copper, from the environment also slows down the colourant oxidation processes. Such additives as citric acid, phosphates, and nitrates are capable of forming inactive complexes with metal ions (chelates).

DAN-POL recommends the use of substances promoting colouration of processed meats with composition based on natural substances being extracts of spices, red wine, and natural muscle tissue colourants.