Fermentation in meat production
General introduction for meat fermentation
This is done to avoid condensation which favours rapidly forming moulds. The principle two subgroups of fermented sausages are semidry or quickly fermented and dry or slowly fermented (semi-fermented) sausages. There are both hard and soft types in both subgroups.
- The length of production (smoking and fermentation) of these sausages depends upon their type but rarely exceeds several days. The pH of semidry sausages is explicitly acid (4.8 to 5.2–5.4); although they are often finely chopped and spreadable, many of them can be cut in thin slices; their water content reaches 35 percent or more. Semidry sausages are regularly smoked and only exceptionally slightly cooked by the heat applied in the smokehouse at various temperatures, mostly not exceeding 45°C and very occasionally rising to nearly 60°C for a strictly limited time; after smoking the sausages are usually air-dried for a relatively short time.
- This category of sausages is popular in many European countries and North America. As these sausages need only little refrigeration, they can be successfully produced in many subtropical countries.
- Overall processing time may require up to 90 days. The final pH of dry sausages is usually somewhat higher (5.0–5.5) than in semidry sausages. Dry sausages are made from selected, mainly coarsely chopped, meat (some Italian salamis, some types of sucuk); often they are moderately chopped (majority of small-diameter dry sausages) and very occasionally finely chopped. They are cut in thin slices, their water content is under 35 percent, but normally less than 30 percent. Most varieties of dry sausages are subjected to cold smoking (12 to 18°C) but sometimes not; in some countries they are often heavily spiced with red pepper or garlic or sometimes heavily smoked and strongly salted. In principle, they are processed by long, continuous air-drying, sometimes after a comparatively short period of smoking.
- Dry sausages are usually sold as new dry sausages (about 20 percent weight loss from original weight), moderately dry (about 30 percent of weight loss) and dry sausages (about 40 percent of weight loss).
In the traditional production process, fermentation is accomplished by natural flora. In order to achieve safe fermentation of the raw sausage, it is of importance to give the microflora the proper growth conditions as well as the appropriate type of the meat. The inherent bacterial sausage microorganisms use various sugar substances as energy sources, whereby they produce acids and contribute to the flavour of the raw sausages. While dextrose is degraded by almost all kinds of bacteria, lactose or starch products of higher molecularity are converted only by some of them. In the second case, the speed of acidification is delayed.
Acidification, i.e. with a sufficiently low pH (below 5.2–5.3) is indispensable for adequate binding and colour development in the sausage. A pH value of 4.8 or below influences the taste, but does not contribute to better binding properties of the final product. However, this low pH gives fermented sausages excellent keeping qualities. In general, addition of sugar varies from 0.3 to 2.0 percent. If dextrose or other easily degradable sugars are used, acidification is fast and the amount of sugar added should be somewhat lower. In opposition, corn syrup solid must be added at somewhat higher levels in order to compensate for its lower acidification properties.
A sufficient level of acidification can also be obtained by the addition of glutamine or some other acids and particularly by the addition of glucono-delta-lactone (GDL). When GDL is used, acidification (release of gluconic acid) occurs at 21–23°C. At GDL levels under 0.5 percent, the curing agent should be nitrate, but at GDL levels higher than 0.5 percent nitrite is preferred since too high a rate of acidification does not permit the process of denitrification performed by microorganisms.
In modern fermentation, bacterial starter cultures used in the production of dry sausages are lactic acid producing and belong mainly to the general Lactobacillus, Pediococcus and Streptococcus. The reason for applying these bacteria in the production of raw sausages is their ability to produce a consistent and controlled acidification able to inhibit growth of undesirable microorganisms and as an aid in obtaining the desired structure and colour of the final product. Using starter cultures in current production practices, desired acidity can be achieved within 24 hours at a high (35–41°C) incubation temperature. This is in contrast to traditional manufacturing processes which utilized the natural flora of the meat as the source of lactic bacteria and required extended incubation times.