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11/8/2012

Storing cheese at the right temperature

Storing cheese at the right temperature

Before cheese can develop the right flavor, it must be stored for several months at the right temperature and air humidity. Owing to the high air humidity, not every sensor is suitable for regulating the air conditioning system. Also, the sensors must be calibrated at the right operating point.

 

Kirchberg in Bern stores 18,000 Emmental cheese wheels each weighing about 95 kilograms. After aging for three months, they are transported from the local cheese dairies that make them to the Swiss corporation Emmi AG in Kirchberg. There the wheels mature for six months under precisely defined conditions before they are delivered to outlets in Switzerland and abroad. Every week, the Emmental wheels are brushed and turned in the stores. It is important that the temperature in the hall and the air humidity are just right to prevent the  cheese from sweating or exuding fat. In order to safeguard the right temperature and humidity, the cellarers at Emmi use a range of temperature and humidity sensors made by Rotronic. These keep the temperature constant at 11.5 °C and the relative air humidity at 74%.

New sensors

Replacement parts were no longer available for its old sensors, so Emmi decided in favor of the new transmitters from the Rotronic HygroFlex5 Series. Daniel Wüthrich, shop mechanic responsible for the air conditioning system in the store rooms, has come to appreciate the new transmitters, above all because he can easily replace the sensors without having to take off the whole housing. For example, he needs only to remove the old sensors and plug in the new ones, and the system is already calibrated. He does not have to unscrew the whole transmitter. This saves valuable time.

Calibration at high air humidity

Sensor calibration is vital for a cheese store. Temperature sensors are normally calibrated at 23 °C for a relative air humidity of 10%, 35%, and 80%. In other words, the sensor exhibits its greatest precision around this operating point. At this point, it can measure temperature to a precision of ±0.1 °C and the relative air humidity to ±0.8%. The more the temperature departs from 23 °C, the greater the difference in the sensor readings. Above all the air humidity is critical. This soon gives rise to errors on incorrectly calibrated systems. The cheese store has a temperature of 11 °C and a relative air humidity of 74% (which is over 90% in the second large cheese store for Gruyère), so Daniel Wüthrich regularly calls on the Rotronic technicians to calibrate the sensors at each of the operating points.

Gruyère emits ammonia

When Emmi decided to order the new sensors from Rotronic, the developers were faced with yet another challenge: Gruyère tends to emit ammonia during maturation. The engineers feared that the ammonia could attack and affect the sensors. After a long series of analyses, the developers could give the all clear: the sensors work reliably despite the high concentration of ammonia in the air. One further advantage of the Rotronic meters is the continuous monitoring of temperature and air humidity, even when the technician is absent.

When the values exceed the tolerance for longer than an hour, an alert is sent to his cellphone. When, for instance, the drive for an air valve failed, the system reliably signaled the rise in temperature even before the cellarers noticed anything. By analyzing the trend values, Daniel Wüthrich could even pinpoint precisely when the air valve failed.

 

Emmi AG

Emmi is the largest Swiss milk processor and one of the most innovative premium dairies in Europe. In Switzerland, Emmi focuses on the development, production, and marketing of a full range of dairy and fresh products, including the production, maturation, and sale primarily of Swiss cheeses. Abroad, Emmi utilizes its brand concepts and specialties to target markets in Europe and North America. On highly promising markets abroad, the range is supplemented with specialties produced locally. The listed corporation achieved a net turnover of CHF 2,721m in 2011. It employs 3890 people in Switzerland and abroad.