Humidity Control

Moisture (humidity) control is of utmost importance in a meat plant or a sausage kitchen. Any moisture that will show on meats as water droplets will create perfect conditions for the development of bacteria. The products will also feel "slimey". The recommended humidity levels for meat processing rooms are:

meat cutting room	45 - 60% relative humidity at 10° - 12° C (50 - 54° F)
coolers	85 - 95% relative humidity at 0° - 4° C (32 - 36° F)

In coolers the higher humidity is required to prevent the drying of the meat products as that will lead to weight loss and cut in profits. The humidity control in a meat plant is based on dew point control. Dew point is the temperature at which condensation forms. When air comes in contact with a surface (often metal or glass surfaces) that is at or below its Dew Point temperature, condensation will form on that surface. In a meat plant the item that is at risk is meat taken out from the cooler as its temperature will be about 2° C (35° F). In the processing room the temperatures are about 10° - 12° C, though they may reach even up to 16° C (60° F) if the meat will not remain there longer than one hour. By adjusting the room temperature and its humidity levels we can control the temperature of the dew point.

In a well designed meat plant the temperature will stay more or less the same. If the facility is climate controlled the amount of relative humidity should also remain at the same level. The meat taken out of the cooler for processing should also have the same temperature. In the kind of "improvised" facility without automatic control the relative humidity can be controlled by any of the following factors:

• meat temperature - the worst solution as the meat's temperature will have to be increased which will lead to bacteria growth and shorter shelf life of the product
• room temperature - will have to be lowered which is acceptable in a cutting and processing room. Bad idea in coolers where air dried and fermented sausages must be kept for a long time at precise temperatures and humidity.
• room humidity - the best idea as it allows moisture removal (dehumidifier) or moisture introduction (humidifier) by separate devices. Those simple units will control the relative humidity without the need for room temperature adjustments or worrying about meat temperature.

It is very unlikely that an average sausagemaker will ever bother with humidity control but for those interested the following table will show how it is done. Only a part of the table that contains temperatures that might be encountered in a meat processing facility is quoted. Tables that include all temperature and humidity readings can be obtained on the Internet.

Dew Point Table in ° F

Note: numbers in red color denote the Dew Point. For example if the temperature in the sausage factory is 60° F (16° C) and the relative humidity is 50%, the intersection of the two shows that the Dew Point is reached at the temperature of 41°F (5° C), or below. This means that the moisture that is present in the air at 60° F (16° C) will condense on any surface that is at or below the Dew Point temperature of 41° F (5° C). This also means that if the meat having a temperature of 35° F (2° C) was brought from the cooler into this room (60° F, 16° C) the moisture would condense on its surface. The meat's temperature of 35° F (2° C) is below the Dew Point limit of 41° F (5° C).

If the meat's temperature (35° F, 2° C) and room's humidity (50 %) remain constant, the only way to correct the problem will be to lower the room's temperature to 52° F (11° C). At the intersection of air temperature of 52° F (11° C) and 50 % relative humidity the Dew Point becomes 33° F (0.5° C) which is below meat's temperature of 35° F (2° C).

If we decide not to change the room temperature and leave the meat temperature at 35° F (2° C) the only way to correct the problem would be to lower relative humidity in the room. Going to the right at 60° F (16° C) air temperature we look for the Dew Point which is below the temperature of the meat (35° F, 2° C). It is found below the 35% relative humidity column and its temperature is 32° F (0° C). At 60° F (16° C) and 35 % relative humidity we will not have problems with moisture condensing on the meat.

Looking at the table we can see that when processing meats at 50° F (10° C) and humidity of 60 % or less, we should not have any problems with moisture control. Meats are normally processed at 50° - 53° F (10° - 12° C). Although processing meats at lower temperatures will be even better, lower temperatures will present too much of a hardship for people that would work many hours under such conditions.

Dew Point Table in ° C

For more information on humidity:

• Meat smoking and humidity
• Fermented sausages equipment and humidity
• Humidity and smokehouse design