Thermal treatments using heat exchangers, such as pasteurisation, heating and cooling, feature in the manufacture of multiple food and drink products. In this article we look at five of the most challenging foodstuffs in terms of thermal processing, and the heat exchanger solutions to help manufacturers handle them correctly.
1. Highly viscous materials
Highly viscous foods, including nut butters and other fat-based products, can be almost solid at low temperatures. This creates a number of challenges, including moving the material through the heat exchanger. Other considerations include preventing fouling and ensuring an even temperature.
Nut butter can be one of the most difficult products to handle, and so a heavy duty rotating scraped surface heat exchanger (SSHE) is required. With its larger motor, bigger scrapers and extra mounting supports, the HRS RHD Series was specifically designed for such tough materials.
2. Products containing pieces
The challenge when dealing with pieces of product (from small, diced vegetables to large fruit pieces) is ensuring the mixture moves through the process at a constant speed without damaging the physical integrity of the product.
The Unicus Series of reciprocal SSHE is perfect as they separately controlled hydraulic scrapers are available in a range of designs and are fully controllable.
3. Thermally challenging products
Some ingredients, such as eggs or chocolate, are very sensitive to temperature and must be processed at precise temperatures to avoid damaging the product. Liquid egg, for example, is extremely delicate as the proteins in egg are more sensitive to heat than other products, such as milk or juices. The white and yolk are distinct components with different compositions and behaviours: egg white is denatured at 58°C while yolk is denatured at 65°C.
If not handled correctly, thermal pasteurisation can decrease protein content, change physical characteristics such as texture and colour, and increase product viscosity. Depending on the required handling, corrugated tube heat exchangers or gentle SSHEs (like the HRS Unicus Series) are ideal for processing liquid eggs and other egg-based products.
Tempering chocolate is also extremely difficult. Without strict temperature control, the crystals formed are of different sizes and the resulting chocolate will ‘bloom,’ having a matt appearance and waxy texture. The HRS R Series has been successfully used to commercially temper chocolate, raising the temperature, cooling it back down, and then raising it again so the chocolate can be transported and worked elsewhere.
4. Delicate products
Many sauces, and some dairy products, need to be handled delicately in order to avoid splitting or shearing, while careful temperature control is required to avoid the creation of undesirable flavours, such as a burnt taste.
The solution is a gentle yet thermally efficient reciprocating SSHE, such as the HRS Unicus Series.
5. Very dense materials
Globally, there is increasing interest in using heat exchangers to process mechanically deboned meat (MDM), meat slurry and viscera components. One advantage is that heat exchangers have the potential to generate products with better quality, at lower cost and with less waste and lower energy consumption than via traditional methods of heating and cooling MDM.
The HRS RHD Series has been employed commercially to keep meat viscera and similar materials below a specified temperature of 4°C. Because it ensures thorough mixing, slugging does not occur.
Some heat exchanger developers will not offer solutions for certain food products because they are so challenging in terms of physical and thermal handling. HRS Heat Exchangers has spent the last forty years specialising in developing heat exchangers and processing systems for these most difficult products.
(The author is global key account director at HRS Heat Exchangers)