Baths and Chillers in the Food Sciences

Brandoch Cook, PhD, is a freelance scientific writer. He can be reached at: [email protected].

Food science is a broad discipline that encompasses at least three related principles. The first is to understand the biological, chemical, and physical properties of food and the mechanisms by which they function. The next is to understand the external factors that can result in spoilage or contamination and leverage those mechanisms to mitigate it. The third is to optimize food processing to maximize the available calories to humanity, and the market return to all aspects of production, from primary agriculture to the grocery store shelf. Inherent in all three fields is a need to control temperatures, both warm and cold.

Food research science often dictates the use of standard laboratory water baths on a small scale to control reactions that can be studied from the perspectives of gene expression, protein chemistry, and microbial infection and growth. With food items specifically, there is perhaps an even greater need than otherwise to control the environments in which reactions proceed. This underscores a premium on cleanliness to avoid unwanted contamination and to initiate and promote microbial invasion in a calibrated manner.

Baths should be regularly cleaned and properly prepared for samples. Most bath receptacles are made of stainless steel. They should be drained of water and cleaned gently with detergents conforming to user manual specifications, rather than with bleach, brushes, or steel wool that can corrode the bath. Abrasive materials can flake apart, score surfaces, and create substrates for microbial growth. Users should carefully select a water source to fall within a middle range of sterility, avoiding both tap and double-distilled, deionized water. Regular tap water contains too many particulate impurities, and system water that is too pure is another vector of metal corrosion.

The applied science of food processing requires moisture removal, identifying the ideal pressure and temperature conditions for preparation and storage, and scaling of both to maximize long-term yield. There are more than 40,000 food processing facilities in the United States, and in addition to standard laboratory-type chillers there is a variety of sophisticated, application-specific food processing chillers designed to fit facilities of different scales and configurations.

A chiller’s most basic function is to replace the unpredictable and costly ice chest with a reliable cycle of air or water to modulate and control temperature through vapor compression. These chillers are defined by their compressors, which can use positive displacement to control refrigerant vapor pressure via pistons or screw rotors, or employ dynamic centrifugal motion to transfer kinetic energy to impellers. Air-cooled chiller compressors and condensers can be separated to conform to specific layouts. Additionally, food processing concerns drive different applications to accommodate coolants particular to their given processes. Water chillers are often the most economical compromise for middle-temperature operations, such as processing meat and cheese products. For lower-temperature operations involving perishable food items prone to melting or dissociation, chillers can use propylene glycol as a refrigerant and antifreeze, with secondary heat exchangers and variable-frequency drives for an added layer of consistency.

Although food research science and food processing require temperature control solutions, their different needs and scales promote an array of different choices for baths and chillers.