A thermal or “heat transfer fluid” is an agent, a gas or liquid used to carry heat from one part of a processing plant to another. Heat transfer fluids are commonly used on an industrial scale in the processing of food. Such fluids need to be certified by a body, such as NSF International, for incidental contact with food. This is to safeguard consumers purchasing processed foods. Indeed, consumer trust dictates the highest standard, and failure to protect the product from harm, resulting in customer harm, is something no food and drink manufacturer can afford to do, either ethically or financially. This article outlines the safeguards in Europe and North America and presents a case calling for the independent sampling of food-grade heat transfer fluids as a measure to uphold consumer safety and improve consumer confidence.

The food and beverage industry is highly regulated and as the globalization of the global food and beverage market expands, worldwide producers are met with increasing requirements to meet the demands. In European law, EC Food Hygiene Regulation 852/2004 sets out the basic clauses requiring food businesses to protect food and drink products from anything that could be hazardous to human health. In principle, these can be categorized as biological, physical, chemical and allergenic agents. Within this regulation, the adoption of a risk-based approach to controlling these hazards is stipulated, that is to adopt a system of Hazard Analysis via Critical Control (HACCP), according to Codex Alimentarius principles.

Beyond the requirement of regulation, many food and beverage manufacturers will adopt private quality systems to ensure supply. The British Retail Consortium 3rd party certification system is one such standard that many food and drink manufacturers will adopt to supply most major U.K. multiple retailers. The latest version 7 addition clause 4.7.6 states, “Materials used for equipment and plant maintenance and that pose a risk by direct or indirect contact with raw materials, intermediate and finished products, such as lubricating oil, shall be food grade and of a known allergen status.”

International organizations not engaged in the supply of food and drink to the U.K./Europe may adopt other standards such as ISO 22000, which again has HACCP as a key theme for the control of food and drink safety. ISO 21469 certification for lubricants in food and pharmaceutical applications can be useful for key stakeholders to understand.

Other standards to ensure the use of food-grade fluids

Food-grade HTFs are highly refined mineral fluid composed of saturated hydrocarbons with carbons in the range C15 to C50 and an example of a food-grade HTF that carries an HT-1 certificate. It is recommended for incidental contact with food, is non-fouling, is easy to handle, nontoxic, nonirritating and odorless.

A research paper1 recently published about the use of non-fouling food-grade heat transfer fluids in food processing highlighted five key points:

  • Food-grade HTF is colorless, nontoxic and nonirritating.
  • This HTF is nonfouling and less carbon forms.
  • Such HTFs can be safely used in food processing if they are HT-1 certified.
  • A number of food safety management systems (e.g., HACCP) are used to ensure such fluids are safe.
  • An additional check is to sample fluids to ensure food-grade fluids are being used.

The most common approach for checking the HTF used is to assess the material safety data sheet (MSDS) supplied with the HTF and to check HTF maintenance reports. An HTF supplier should provide an MSDS on delivery of an HTF or they can be consulted to provide an updated MSDS. This will contain product-related information on the chemical structure of the fluid, how to handle the fluid, how to store the fluid and what precautions should be taken when handling and transporting the fluid. An HTF approved for incidental contact with food should be accompanied by a HT-1 certificate. If it does not, get the appropriate paperwork and do not assume it is approved for this use.

The service history of the HTF can also be checked and will provide an overview of the fluid’s physical and chemical properties at discrete points in time. However, the objective of this report is to gain insight into the condition of the fluid more than to assess the type of fluid used. Although, the text report will confirm the details of the plant sampled, when it was sampled, what fluid is in the HTF system and how parameters relating to condition (e.g., carbon residue, total acid number and accumulation of ‘light-ends’) are changing against time and how they compare with the typical values for that type of HTF. The objective of such reports, however, is to evaluate the condition of the fluid and to assess and slow the rate of thermal cracking and oxidation, which accelerate with prolonged use at high temperature.

Another check that could potentially be performed is the on-site live sampling of an HTF by an independent company, which this could form part of a supplier or retail audit. This would enable the HTF’s chemistry to be analyzed and, in the case of a food-grade HTF, confirm it is a highly refined mineral fluid. This is not currently part of an audit trail in Europe or North America, but can easily be added as a further safeguard. Indeed, manufacturers are routinely audited by insurance companies to ensure there is no breach of the terms of the policy. This approach could be of benefit to an auditor because it is an additional tool to ensure companies comply with existing standards. It is also different from the previously mentioned approaches since fluid is physically taken and sent to a laboratory for chemical testing.

Do companies offer independent sampling & testing of HTFs?

The answer is yes. Specialist companies such as Global Heat Transfer in Europe can sample an HTF while in use – meaning it is in operation and being taken at the operational temperature, typically up to 326°C for a food-grade HTF. These samples are taken by engineers who have been trained to sample the fluid into a specifically designed sampling container. Standard operating procedures ensure a representative sample is taken and then sent to the laboratory for chemical testing according to international test standards and procedures.


The independent sampling of food-grade HTFs is not used in industry at the present time, but the technology is available to do this and to confirm a food-grade fluid is being used. This test enables companies to further safeguard consumers from any safety issues arising from incidental contact of a HTF with foods or drinks. It also enables auditors to enforce companies to comply with standards of supply and the terms and conditions of their insurance. This can be done while the HTF is in operation and can be done by specialist engineering companies that already conduct similar assessments in Europe and North America.

Author’s note: The author would like to acknowledge the writing support provided by Red Pharm communications, which is part of the Red Pharm company (see @RedPharmCo on Twitter). Please contact the author for reference materials cited in this article.


  1. Wright, C.I., Bembridge, T., Picot, E., Premel, J. (2015). “Food processing: the use of non-fouling food grade heat transfer fluids.” Applied Thermal Engineering. 84; 94-103. Accessed from http://www.sciencedirect.com/science/article/pii/S1359431115002562.

Christopher Wright is a research scientist with a Bachelor of Science and doctorate from the University of Leeds in the U.K. His research focuses on the use and maintenance of heat transfer fluids in manufacturing and processing, which includes food, pharmaceutical, specialist chemicals and solar sectors.