Cheese Maturing

Cheese manufacturing in general

Since humans began to domesticate milk-producing animals around 1,000 BC, they have known about the propensity of milk to separate into curds and whey. It is the curds that are used to produce cheese .

The cheese manufacturing process

Cheese making involves a number of main stages that are common to most types of cheese.

Preparing the cheese milk:

Either pasteurised or non pasteurised cheese milk can be used. Non pasteurised cheese milk contains the necessary bacteria to produce lactic acid, one of the agents that triggers curdling. Pasteurised cheese milk requires a culture of bacteria in order to produce this lactic acid.

If non pasteurised cheese milk is used, the cheese must be ripened for at least 60 days at a temperature of not less than 4 °C to ensure safety against pathogenic organisms.

Separating the curds from the whey:

Animal or vegetable rennet is added to the cheese milk. The enzyme activity of the rennet causes the milk to coagulate producing curd. The remaining liquid is the whey.

There are various ways to help accelerate the separation:

– Cutting the curd,

– Stirring the curd,

– Heating the curd.

The curd is eventually put into moulds and placed on draining boards. Once in the moulds, the curd is then ready for pressing.

Aging the cheese:

The cheese is stored in a suitable room at the required temperature and humidity to age. Some cheeses are aged for a month, some for up to several years.

 

Why the need to measure the relative humidity?

Storage

For centuries, caves which are usually cool and have a constant humidity, have provided a suitable environment to age and store cheese. Caves are still used today, Roquefort for example is a cheese aged in the natural Combalou caves in France. Nowadays though most storage areas are man made structures with a highly controlled environment.

The treatment during curd making and pressing determines the characteristics of the cheese. The actual flavour of the cheese is determined during the ripening of the cheese.

The ripening of the cheese is characterised first and foremost by the decomposition of protein. The degree of protein decomposition affects the quality of the cheese to a very considerable extent, most of all consistency and taste.

The purpose of storage is to create the external conditions that are necessary to control the ripening cycle of the cheese as far as possible. For every type of cheese, a specific combination of temperature and relative humidity must be maintained in the different storage rooms during the various stages of ripening.

The climatic conditions are of great importance to the rate of ripening, loss of weight, rind formation and development of the surface flora: the total characteristic of the cheese!

The optimum conditions

Here are a few examples of storage conditions for a few cheeses:

Cheddar Cheese family: low temperature: 4 to 8 °C; Relative humidity lower than 80 %rh. The cheese is often wrapped in plastic in order to prevent excessive water loss. The ripening time may vary between a few months up to 8 to 10 months.

Cheeses like Emmentale have a more complex maturing process: 3 to 4 weeks between 8 and 12 °C followed by 6 to 7 weeks at 22 to 25 °C. The final stage is ripening over several months between 8 and 12 °C. The relative humidity is maintained at 85…90 %rh.

Semi hard cheeses like Tilsiter or Havarti are held for a period of 2 weeks in a fermenting room at 14 to 16 °C with a relative humidity of about 90 %rh. During the fermenting process, the cheese is covered with a special cultured mix with a salt solution. After 2 weeks, the cheese is transferred to the ripening room for another 3 weeks at 10 to 12 °C and 90 %rh. The final stage is storage in a cold room at 6 to 10°C at 70 to 75%rh.

Another example are other hard and semi hard cheeses like Gouda. These cheeses are stored at 10 to 12 °C for a few weeks at 75 %rh, then for a few weeks at 12 to 18°C and 80 %rh. The final stage is a storage room at 10 to 12 °C at 75 %rh where the final characteristics are developed.

Air conditioning:

During the maturing process, moisture must be removed from the cheese. This moisture will move from the cheese to the air (equilibration): the air in the room or chamber must not have a high humidity.

The air in the chamber is frequently exchanged with air from outside which is typically warmer. As the temperatures are rather low during the ripening process, the air in the maturing chamber can hold less humidity than the air from outside. The air in the chamber will become saturated and condensation will form, thus there is a need to dehumidify the incoming air.

What solutions can Rotronic offer?

The measurement of relative humidity in the maturing chambers is not an easy task due to:

The relative humidity being high during the cheese ripening process.

Additionally, each cheese emits ammonia into the air. Ammonia is a compound of nitrogen and hydrogen with the formula NH3. It is a colourless gas with a characteristic pungent odour.

The result of the stress that both of these factors place on the humidity sensor is drift! The sensor will drift much faster than expected!

In order to maintain perfect conditions in the chamber, Rotronic offers a range of products that will control air conditioning systems and a humidity sensor that is resistant to both the high humidity and ammonia!

Rotronic products:

Humidity and temperature probes:

• HC2-S

Standard humidity sensor,

-50…100 °C,

0…100 %rh,

±0.8 %rh and ±0.1 K…

• HC2-S-HH

Ammonia resistant humidity sensor,

-50…100 °C,

0…100 %rh,

±0.8 %rh and ±0.1 K…

• HC2-IM

Stainless steel Industrial probe,

-100…200 °C,

0…100%rh,

±0.8 %rh and ±0.1 K…

Transmitters:

• HF5 series

For interchangeable probes,

2-wire or 3/4 wire configuration,

Various analogue and digital outputs,

Display,

All psychrometric calculations available…

• HF7 series

Stainless steel probe,

-100…200 °C,

2-wire or 3/4 wire configuration,

Various analogue outputs,

Display…

 

Dataloggers:

• HL-NT range

For interchangeable probes (up to 7 probes with docking station)

32 MB flash card,

Display,

Conform to FDA21 CFR Part 11 and GAMP4…

• HL-20

20,000 measurement pairs,

Display,

±0.8 %rh and ±0.2 K,

Conform to FDA21 CFR Part 11 and GAMP4…

Customer benefits:

Accuracy:

Choosing Rotronic gives you the best available accuracy on the market. Precise humidity measurements can be obtained: meaning that as soon as the required relative humidity level is reached, the dehumidifier can be switched off.

How is this better for the maturing process?

Since the humidity level is critical and defines the characteristics of the cheese, then the more accurate the measurement, the better the end result!

The sooner the dehumidifier is switched off, the less power will be consumed.

Communication:

With various analogue and digital interfaces available from RS-485, Wireless & Ethernet RJ-45, Rotronic can provide the perfect solution.

Long term stability:

Excellent long term stabilitywith drift less than 1%rh peryear (depending on the environment).

Calibration and sensor adjustment:

Calibration is easy with the Rotronic product range. A calibration can be performed by the user using traceable calibration standards. Rotronic also offers UKAS accredited temperature and humidity calibration with a certificate which is typically required to meet quality management standards .