Once the sausage batter is packed into casings, the material is moved into specially designed ripening chambers where the fermentation occurs. These facilities, often referred to as the green room or smoke house or simply the house have controls for maintaining temperature, humidity, and air movement. Moreover, control systems in modern facilities are fully programmable so conditions can be ramped or adjusted depending on how the fermentation is proceeding or on the particular specifications of the manufacturers. Thermocouples and pH probes inserted directly into product samples can feed the appropriate information into a computer to provide constant monitor ing, record-keeping, and feed-back control. Thus, the entire fermentation can proceed in the absence of a full-time operator.

Fermentation parameters vary depending on the culture and the desired product qualities. In general, lower incubation temperatures require longer fermentation times. For example, at the low temperature range of 21°C to 24°C (70°F to 75°F), which is very near ambient, fermentation can take as long as two to three days. At 29°C to 32°C (85°F to 90°F), twelve to sixteen hours of fermentation will be required. In the United States, where faster overall production times are preferred, the incubation temperature can be as high as 37°C to 40°C (98°F to 102°F) for as little as twelve to eighteen hours.

Box 6-5. Ensuring Meat Safety Through HACCP

In July 1996,the Pathogen Reduction/Hazard Analysis and Critical Control Point system became regulatory law for all USDA-regulated facilities.This system, abbreviated as HACCP, was designed to apply scientific principles to process control in food production.

The processing steps for manufacture of a representative fermented sausage product are illustrated in a flow diagram (Figure 1). Through careful analysis all hazards that are considered reasonably likely to occur are then identified (Table 1). Control measures designed to prevent hazards are applied at specific points in the manufacturing process; these are called critical control points.

Fermentation Flow Diagram
Figure 1. Generic process flow diagram for fermented dry sausage. The main critical control points (CCP) are shown.

Box 6—5. Ensuring Meat Safety Through HACCP (Continued)

In the fermentation step, for example, the pH must attain 5.3 or below within six hours. Control of this step may have the greatest impact on assuring the safety of the final product. Critical limits are established and then continuously monitored and recorded to verify that the process is under control.

Corrective actions are developed for each critical control point and documented in the HACCP plan.These corrective actions are applied whenever deviation from a critical limit occurs; specific and exacting records are kept.A separate HACCP program is designed and documented for each manufacturing process used in an establishment.

The HACCP method accompanied by proper prerequisite programs such as Good Manufacturing Practices and Sanitation Standard Operating Procedures can be an effective means of assuring the safety and quality of food products.

Table 1. Identification of critical control points during the manufacture of fermented semi-dry sausage.

Critical Control Point



Control Measure

Receiving Raw Meat

Cold Storage




Salmonella E.coli 0157:H7 Listeria monocytogenes

Salmonella E.coli 0157:H7

Staphylococcus aureus


Staphylococcus aureus

Listeria monocytogenes

Reasonably likely to be present in raw meat ingredients

Salmonella and E. coli 0157:H7 may grow if temperature is not maintained below minimum growth requirement

Potential for growth and toxin production due to fermentation failure

Potential for growth and toxin production due to drying failure

Potential for contamination from environment or handling

Supplier certification to guarantee laboratory analysis indicating absence of Salmonella and E.coli 0157:H7

Refrigeration temperature not to exceed 40°F; freezer temperature not to exceed 30°F

Must attain pH of 5.3 or below within 6 hours

Attain established moisture to protein ratio (1.6:1 for pepperoni and 1.9:1 for sausage)

Sanitizer effective against L. monocytogenes applied to food contact surfaces every 4 hours

Since individual culture strains may have different temperature optima and tolerances, selection of cultures that perform under the selected conditions is critical. It is also important, for some applications, that the fermentation rate not proceed too fast.This is particularly relevant when flavor- or color-producing organisms (e.g., Micrococcus) are used, because they may be inhibited by fast lactic acid producers. However, if the fermentation is too slow, there may be sufficient opportunity for pathogens or spoilage organisms to grow. Ultimately, the pH

at the end of fermentation should be less than 5.1, which, by itself, will not make the product shelf-stable, but which does provide a reasonable protective barrier against most foodborne pathogens. In addition, fermented sausages at pH 5.0 to 5.1 will have only a slight tart flavor that may actually be indistinguishable from non-fermented products.

Alternatively, depending on the culture, the incubation conditions, and the amount of substrate (i.e., fermentable sugar) provided, much higher acidities can be achieved.Typically, sum mer sausage has a pH around 4.9 but can be as low as 4.7.When the pH reaches 4.8 or less, a definite "tangy" flavor becomes apparent.

Fermentation rooms are also equipped with air movement devices and humidistats to maintain the relative humidity (RH) at desired levels. Since the RH in the atmosphere surrounding a food directly influences the water activity of that food (where aw X 100 = RH), as RH is decreased, the more moisture is lost to the atmosphere and the lower will be the aw in the sausage.Typically, the RH should be about 10% less than the aw X 100 of the finished product.

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