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In this article:
Temperature considerations
Humidity considerations
The manufacture of dry sausage is probably the oldest form of meat preservation. Dry sausage was undoubtedly discovered by accident and gradually evolved into a popular means of preserving meat in a highly palatable form.
In fact, the development of dry sausage varieties can be traced to geographical areas where natural climatic conditions offered an environment in which temperature, humidity and other factors resulted in a product with distinguishing characteristics. Northern Italy, Hungary and Switzerland are some of the areas in Europe, for example, where dry sausage products have evolved over time to the point of becoming distinct products that are recognized all over the world. Pepperoni, Genoa salami and cervelat are some typical products from this region that are widely recognized. Other parts of the world have produced dry sausage varieties that resulted from environmental and cultural conditions characteristic of those localities.
Production of dry sausage clearly was a poorly understood but well-perfected art form for centuries. It has only been in the past 50 years or so that the physical and chemical changes that occur during dry sausage production have been studied and explained to permit improved control of the process.
While many factors including raw meat quality, salt, cure and pH are critical considerations for dry sausage quality, the very nature of "dry" sausage means that temperature and humidity will be critical during key steps of the process.
Temperature considerations
Temperature considerations for dry sausage are usually focused on temperatures used for the drying process, but it's important to realize that temperature effects on product quality actually begin with the raw meat used for product formulation. Meat must be kept very cold during grinding, mixing and/or chopping to avoid fat smearing, which can form a film of fat over the lean tissue and reduce the movement of water out of the product. Meat should be maintained at -2 degrees C to -4 degrees C (24 degrees F to 28 degrees F) to facilitate good fat/lean distinction and allow effective moisture migration.
Frozen meat is often used as part of the formulation to achieve temperature control. Use good quality frozen meat, because another temperature/quality issue can arise. Frozen meat stored at higher than ideal temperatures (above -20 degrees C/0 degrees F) is likely to develop rancid flavors that will subsequently be magnified by the drying process.
Avoiding fat smearing during stuffing is also important, particularly because a film of fat just under the casing can dramatically slow the migration of water out of the product. So, again, temperature becomes an important consideration and should not exceed -1 degrees C to 0 degrees C (30 degrees F to 32 degrees F) during stuffing. Using large-diameter, short-length stuffing horns can also minimize fat smearing in dry sausage.
Following stuffing, most dry sausage will be fermented, either in a "green room" or a fermentation chamber. Because most traditional dry sausage types are fermented with cultures that do best at relatively low fermentation temperature, a temperature of 22 degrees C to 24 degrees C (72 degrees F to 75 degrees F) is typical. Determining the best fermentation temperature for the culture used is important to producing the desired pH within the targeted time for achieving optimal product quality and safety. Relative humidity becomes important at this point, with 95 percent recommended to facilitate growth of the culture and active production of lactic acid.
Following the fermentation step is drying, which is the most critical step in the production of dry sausage and where temperature (and humidity) will have a major impact on final product quality. To be successful, the drying process must achieve surface evaporation at very nearly the same rate as moisture moves through the product to the surface.
It should be no surprise that the rate of migration within a product will vary with product diameter, pH and texture of the mixture. If drying is too fast, a crust forms on the outside of the product (case-hardening), and additional water removal becomes difficult and slow. This can also contribute to the problem of pepperoni slices "cupping" on pizzas when cooked. If drying is too slow, surface growth of mold and other microorganisms is likely to occur.
Successful drying requires control of conditions within a relatively narrow set of limits for temperature, relative humidity and air-flow rates. Recommended temperature in drying rooms is generally in the range of 10 degrees C to 13 degrees C (50 degrees F to 55 degrees F).
However, the temperature becomes an interactive factor with relative humidity and air flow at this point, and conditions need to be fine-tuned in a given drying facility to achieve the best performance. Air flow must be relatively slow to maintain uniform temperature and humidity, yet uniformity is difficult to achieve with slow air speed, especially in large drying rooms. The air contact with product surfaces will pick up moisture, meaning that relative humidity of the air is changing as the air moves through drying rooms. In large rooms, this means that uniformity is increasingly difficult. Air speeds of 0.15 ft/sec to 0.3 ft/sec (0.05 m/sec to 0.1 m/sec), or about 15 to 25 air changes per hour, are good starting points.
Humidity considerations
Relative humidity first becomes a consideration for fermentation when at least 90 percent is recommended and 95 percent or more is often used. For drying, however, the relative humidity must be reduced to achieve evaporation of water from the product surface. A relative humidity of 72 percent to 75 percent is recommended by many dry sausage experts. This level is usually sufficient to prevent surface mold growth while avoiding case-hardening.
For those products in which surface mold is desired, a higher relative humidity at the beginning of the drying process is necessary. The relative humidity may also be slowly decreased from just below 90 percent to 65 percent or 70 percent as drying progresses, if drying room control is sufficient to achieve these conditions.
As a general rule, the drying rate should not exceed about 1 percent per day during the early phases of green room curing and fermentation, and should not be more than 0.7 percent per day during drying. However, keep in mind that when it comes to dry sausage, every drying process should be fine-tuned for each product and drying environment that is used in order to maximize product quality.
Production of dry sausage clearly was a poorly understood but well-perfected art form for centuries. It has only been in the past 50 years or so that the physical and chemical changes that occur during dry sausage production have been studied and explained to permit improved control of the process.
While many factors including raw meat quality, salt, cure and pH are critical considerations for dry sausage quality, the very nature of "dry" sausage means that temperature and humidity will be critical during key steps of the process.
Temperature considerations
Temperature considerations for dry sausage are usually focused on temperatures used for the drying process, but it's important to realize that temperature effects on product quality actually begin with the raw meat used for product formulation. Meat must be kept very cold during grinding, mixing and/or chopping to avoid fat smearing, which can form a film of fat over the lean tissue and reduce the movement of water out of the product. Meat should be maintained at -2 degrees C to -4 degrees C (24 degrees F to 28 degrees F) to facilitate good fat/lean distinction and allow effective moisture migration.
Frozen meat is often used as part of the formulation to achieve temperature control. Use good quality frozen meat, because another temperature/quality issue can arise. Frozen meat stored at higher than ideal temperatures (above -20 degrees C/0 degrees F) is likely to develop rancid flavors that will subsequently be magnified by the drying process.
Avoiding fat smearing during stuffing is also important, particularly because a film of fat just under the casing can dramatically slow the migration of water out of the product. So, again, temperature becomes an important consideration and should not exceed -1 degrees C to 0 degrees C (30 degrees F to 32 degrees F) during stuffing. Using large-diameter, short-length stuffing horns can also minimize fat smearing in dry sausage.
Following stuffing, most dry sausage will be fermented, either in a "green room" or a fermentation chamber. Because most traditional dry sausage types are fermented with cultures that do best at relatively low fermentation temperature, a temperature of 22 degrees C to 24 degrees C (72 degrees F to 75 degrees F) is typical. Determining the best fermentation temperature for the culture used is important to producing the desired pH within the targeted time for achieving optimal product quality and safety. Relative humidity becomes important at this point, with 95 percent recommended to facilitate growth of the culture and active production of lactic acid.
Following the fermentation step is drying, which is the most critical step in the production of dry sausage and where temperature (and humidity) will have a major impact on final product quality. To be successful, the drying process must achieve surface evaporation at very nearly the same rate as moisture moves through the product to the surface.
It should be no surprise that the rate of migration within a product will vary with product diameter, pH and texture of the mixture. If drying is too fast, a crust forms on the outside of the product (case-hardening), and additional water removal becomes difficult and slow. This can also contribute to the problem of pepperoni slices "cupping" on pizzas when cooked. If drying is too slow, surface growth of mold and other microorganisms is likely to occur.
Successful drying requires control of conditions within a relatively narrow set of limits for temperature, relative humidity and air-flow rates. Recommended temperature in drying rooms is generally in the range of 10 degrees C to 13 degrees C (50 degrees F to 55 degrees F).
However, the temperature becomes an interactive factor with relative humidity and air flow at this point, and conditions need to be fine-tuned in a given drying facility to achieve the best performance. Air flow must be relatively slow to maintain uniform temperature and humidity, yet uniformity is difficult to achieve with slow air speed, especially in large drying rooms. The air contact with product surfaces will pick up moisture, meaning that relative humidity of the air is changing as the air moves through drying rooms. In large rooms, this means that uniformity is increasingly difficult. Air speeds of 0.15 ft/sec to 0.3 ft/sec (0.05 m/sec to 0.1 m/sec), or about 15 to 25 air changes per hour, are good starting points.
Humidity considerations
Relative humidity first becomes a consideration for fermentation when at least 90 percent is recommended and 95 percent or more is often used. For drying, however, the relative humidity must be reduced to achieve evaporation of water from the product surface. A relative humidity of 72 percent to 75 percent is recommended by many dry sausage experts. This level is usually sufficient to prevent surface mold growth while avoiding case-hardening.
For those products in which surface mold is desired, a higher relative humidity at the beginning of the drying process is necessary. The relative humidity may also be slowly decreased from just below 90 percent to 65 percent or 70 percent as drying progresses, if drying room control is sufficient to achieve these conditions.
As a general rule, the drying rate should not exceed about 1 percent per day during the early phases of green room curing and fermentation, and should not be more than 0.7 percent per day during drying. However, keep in mind that when it comes to dry sausage, every drying process should be fine-tuned for each product and drying environment that is used in order to maximize product quality.
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