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How Pasteurization in a Laboratory Glassware Washer Works

With the PG 8536 from Miele, temperatures can be raised step-by-step, then held for a specific time interval and reduced.

by Miele
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how pasteurozation in a laboratory glassware washer worksMiele's PG 8536 laboratory glassware washer.Problem: Pasteurization is a thermal treatment applied to foods to destroy pathogens and prevent spoilage. In the food and beverage industry, tunnel washers are often used to pasteurize beverage bottles in a production line. Within R&D flavors laboratories, new flavors and additives are tested for heat stability prior to being used in new formulations and production. Typically, pasteurization here is performed with a benchtop pasteurization system in a stove-top immersion bath. Bottles are immersed in boiling water and held at temperature for a given amount of time. The immersion process, while inexpensive, is neither accurate nor controlled, and the benchtop equipment can be expensive and complicated to install and operate. 

Solution: A laboratory glassware washer simulates tunnel washer conditions— i.e. the bottles are sprayed with water at a certain temperature. With the PG 8536 from Miele, temperatures can be raised step-by-step, then held for a specific time interval and reduced. This temperature ramping can be customized for a particular liquid and flavor. For example, the program can be written with a number of steps, with each step raising the temperature by 10 degrees (variable) then holding a temperature designated by the researcher. At first, the temperature/hold can be estimated for each step until the pasteurization temperature is reached—then it needs to be determined exactly.

Miele has been customizing programs for this function for more than two decades. For a global spice manufacturer looking to test the heat stability of spices, Lisa Choplo, Miele application specialist, created a program that held the temperature at 63 degrees for 12 minutes. For a global food ingredients developer, she created a program that allowed water temperatures to be held at 82°C for two minutes. Temperatures and holding times can be customized, allowing researchers to optimize for flavor. For example, if the material is heat-sensitive, the water temperature can be held at a lower level for a longer period of time. Once the temperature is held, it must then be ramped down to cool the bottles. Using the programming function of the G 7836, the incoming tap water can be mixed from the hot and cold taps so the system can circulate ambient temperature water for a few minutes. This eliminates bottle breakage due to direct cold spray, which would shock the bottles.

Sample program:

Step One: Fill with hot water and heat to 82°C. Circulate for three minutes at 82°C. Drain (this is the main step of pasteurization, where beverage temperature is held for a specific amount of time).

Step Two: Fill with two parts hot water and one part cold water. Circulate for 20 seconds and drain (this begins the cool down step, which is gradual at first to avoid thermal shock to bottles).

Step Three: Fill with equal parts hot and cold water. Circulate for 20 seconds and drain (adjustable for more cool down).

Step Four: Fill with two parts cold water and one part hot water. Circulate for 10 seconds and drain (repeat).

Step Five: Fill with cold water. Circulate for 30 seconds and drain (bottles should be totally cool at the end of this step—timing may need to be adjusted appropriately).

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