Smoke for treatment of meat products is produced from raw wood. Smoke is generated through the thermal destruction of the wood components lignin and cellulose. The thermal destruction sets free more than 1000 desirable or undesirable firm, liquid or gaseous components of wood.
These useful components contribute to the development of the following desirable effects on processed meat products:
- Meat preservation through aldehydes, phenols and acids
- (anti-microbial effect)
- Antioxidant impact through phenols and aldehydes
- (retarding fat oxidation)
- Smoke flavour through phenols, carbonyls and others
- (smoking taste)
- Smoke colour formation through carbonyls and aldehydes
- (attractive colour)
- Surface hardening of sausages/casings through aldehydes (in particular for more rigid structure of the casing)
The most known undesirable effect of smoking is the risk of residues of benzopyrene in smoked products which can be carcinogenic if the intake is in high doses over long periods. With normal eating habits, a carcinogenic risk is normally not associated with moderately smoked food such as smoked meat products.
Depending on the product, smoke is applied at different temperatures. There are two principal smoking techniques:
- Cold smoking
- Hot smoking
The principle of both methods is that the smoke infiltrates the outside layers of the product in order to develop flavor, color and a certain preservation effect.
Cold Smoking – This is the traditional way of smoking of meat products and was primarily used for meat preservation. Nowadays it serves more for flavor and color formation, for example in sausages made from precooked materials such as liver sausage and blood sausage (see page 153, 161).
The combination of cold smoking and drying/ripening can be applied to fermented sausages (see page 124) and salted or cured entire meat pieces (see page 176), in particular many raw ham products. In long-term ripened and dried hams, apart from providing colour and favour, the cold smoking has an important preservative effect as it prevents the growth of moulds on the meat surfaces.
The optimal temperature in “cold” smoking is 15 to 18°C (up to 26°C). Sawdust should be burned slowly with light smoke only and the meat hung not too close to the source of the smoke. Cold smoking is a long process which may take several days. It is not applied continuously, but in intervals of a few hours per day.
Hot Smoking – Hot smoking is carried out at temperatures of +60 to 80°C. The thermal destruction of the wood used for the smoking is normally not sufficient to produce these temperatures in the smoking chamber. Hence, additional heat has to be applied in the smoking chamber.
|Fig. 69: Hotdogs are placed in the smokehouse for hot smoking (pale colour before smoking)|
|Fig. 70: After completion of the smoking process (brown-red colour after smoking, see also Fig. 42)|
The relatively high temperatures in hot smoking assure a rapid color and flavor development. The treatment period is kept relatively short in order to avoid excessive impact of the smoke (too strong smoke color and flavor).
Hot smoking periods vary from not much longer than 10 minutes for sausages with a thin calibre such as frankfurters to up to one hour for sausages with a thick calibre such as bologna and ham sausage and products like bacon and cooked hams.
Products and smoking – Cold smoking is used for fermented meat products (raw-cured ham, raw-fermented sausage) and precooked-cooked sausage (liver and blood sausages). Hot smoking is used for a range of raw-cooked sausages, bacon and cooked ham products. Smoke treatment can only be applied, if meat the products are filled in casings permeable to smoke (see page 248, 261). All natural casings are smoke permeable, as are cellulose or collagen basis synthetic casings.
Smoke permeable casings can also be treated using a new technology, where a liquid smoke solution is applied on the surface. This can be done by dipping in solution, showering (outside chamber) or atomization (spraying inside chamber). Polyamide or polyester based synthetic casings are not permeable to smoke. If smoke flavour is wanted for products in such casings, small quantities of suitable smoke flavour (dry or liquid) are added directly to the product mix during manufacture.