Preventing food contamination from heat transfer fluids

IT IS CRITICAL that the heat transfer fluids (HTFs) used in the manufacturing sector are used appropriately and managed safely. Food grade HTFs are highly refined petroleum mineral oils that are non-toxic, non-irritating and lack an odour. If a food grade HTF has been certified for use in food processing it carries a HT-1 certificate, for example Globaltherm^Ò FG. Food grade HTFs are commonly referred to as being non-fouling which means that as they thermally degrade they produce small carbon particles that are suspended in the HTF. This means the carbon formations are less sticky and this reduces the extent of adhesion to the internal surfaces of a HTF system. The current report analysed the test reports from HTF systems and showed carbon residue was lower for food grade HTFs than mineral-based HTFs. This demonstrates the non-fouling nature of food grade HTFs. The report concludes by recommending the independent assessment of HTFs to ensure food manufacturers are using food grade HTFs in the manufacture and processing of foods.

It is estimated that the value of the HTF market in 2011 was worth $1,684.0 million and by 2017 it will be worth $2,557.2 million. Heat transfer refers to the transfer of thermal energy and fluids are used to transfer heat energy from a heat source to processing equipment where heat is needed. This is a basic requirement in a wide variety of industrial processes including the processing of food stuffs such as crisps or any foods that come in a packet.

Food grade HTFs are non-toxic, odourless and appear transparent like water, but clearly should not be confused with water ^[1]. Indeed, a food grade HTF is a highly refined petroleum mineral oil and consists of a complex combination of hydrocarbons obtained from the intensive treatment of a petroleum fraction with sulphuric acid and oleum, by hydrogenation or by a combination of hydrogenation and acid treatment.

Taking a sample of HTF

Food grade HTFs are the most likely HTF to be used in the processing of foods provided they are judged to be safe for incidental contact with food. This certification is governed by two well-known bodies – the NSF and InS. In the case of the NSF, the components comprising a fluid are assessed for safety by a toxicologist and, if judged safe, are awarded a HT-1 certification and can be used for incidental contact. In some cases, but not in all, the use of so-called food grade HTFs is stipulated by insurers and food retailers, and certain manufacturers will be routinely audited to ensure that an appropriate HTF is being used in the processing of food. Another advantage of a HT-1 certification is that it is associated with fewer handling complaints than other fluids.

In the case of the United Kingdom, Global Heat Transfer, part of the Global Group of Companies, estimates that around 20 percent of all HTF systems are involved in the processing of food. The use of a food grade HTF is recommended, but its use is not regulated. However, HTF leaks do occasionally occur. In 1998 more than 490,000 pounds of smoked boneless hams were recalled by Smithfield Foods after several customers reported a ‘bad taste’ and ‘burning in their throat’ which lasted anywhere up to three hours. The cause was incidental contact with a non-food grade gear lubricant.

In the context of food processing, good manufacturing practice (GMP) prerequisites combined with the application of risk based Hazard Analysis Critical Control Points (HACCP) according to Codex Alimentarius principles  alongside first, second and third party quality audits in the supply chain are used to ensure food is managed safely both during processing and then when being distributed to the consumer. An additional safety measure is provided by trade bodies such as the British Retail Consortium, which promotes responsible retailing. Finally, industrial insurers work closely with manufacturers to make sure that commercial operations are adequately insured and as part of this may stipulate the use of a food grade HTF and how it should be maintained.

Whilst there is no specific legislation to ensure that food grade HTFs are used in the processing of food, regulation EC852/2004 in Europe sets out the responsibilities of the food business owner to ensure food safety throughout the supply chain and more pointedly to design plant, equipment and premises such as to protect against the accumulation of dirt, contact with toxic materials and the shedding of particles into food.

Even though, as outlined in the Smithfield Foods case, there is the potential for the food to come into contact with a HTF during processing. However, let’s consider a few scenarios where a food may be contaminated with a HTF:

cenario 1 - The HTF may be managed by the manufacturer according to HACCP if directly involved in the processing of a product or by GMP prerequisites if the HTF forms part of the facility and services to the production line. Either system will not allow any amount of HTF to be present in food. In the event of incidental contact with food, the manufacturer may choose to dispose of all food. In this scenario, a mineral-based HTF may be used rather than a food grade HTF.

Scenario 2 – The HTF is managed according to the stipulations from the retailer. In this scenario the retailer may stipulate that a food grade HTF is used. The HTF would be checked during auditing. However, this would be a paper-based audit and so the HTF would never be physically sampled and analysed.

Scenario 3 – The insurer stipulates the use of a food grade HTF. Like scenario 2, adoption would be assessed during audits of a facility and paper-based checks would be conducted. Like scenario 2, however, the HTF would never be physically sampled and analysed. In this case the insurer may be more concerned with the safety of the system and may be more interested in the sampling reports and parameters such as annual sampling frequency, flash point temperature of the HTF.

The gap highlighted in scenarios 2 and 3 is that a food grade HTF would never actually be physically analysed onsite. Even though HTF sampling and chemical analysis are quick and easy to conduct, and can be done by professional companies, such as Global Heat Transfer, without interrupting production.

Independent sampling could be conducted and shared with: the insurer to show the HTF is being managed and the HTF system is safe; the retailer to demonstrate that an appropriate food grade HTF is being used during the processing of food; and, external auditors could be provided with these results to demonstrate that production is focused on consumer safety.

^[1] Wright CI, Bembridge T, Picot E, Premel J, Food processing: the use of non-fouling food grade heat transfer fluids. Applied Thermal Engineering 2015: 84; 94-103.  (Please contact the author for reference materials cited in this article.)

About the authors

Chris Wright is a research scientist, graduating from the University of Leeds in the UK with a BSc and PhD. 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. Dr Wright can be contacted by email, chrisw@globalgroup.org and at this address: Global Group of Companies, Cold Meece Estate, Cold Meece, Staffordshire, United Kingdom

Martin Anderson is Senior Lecturer in Food Science and Management at Harper Adams University. His research and teaching focus around food quality management and food and drink retail management. Prior to becoming an academic he worked in some of Europe’s largest food and drink manufacturers in technical and operational roles.

Acknowledgements

The authors would like to acknowledge the writing support provided by Red Pharm communications, which is part of the Red Pharm company (please see @RedPharmCo on Twitter).