HRS helps orange juice producer with ohmic pasteurisation

HRS Heat Exchangers has supplied a leading Mexican orange juice producer with a complete pasteurisation system that uses a novel electrical heating method. The system maintains the properties of freshly squeezed juice, which are adversely affected during traditional pasteurisation processes, allowing the company to increase its presence in the lucrative North American ‘as fresh’ juice market.

Pasteurisation is a well-established method for increasing the shelf life of juice and reducing the likelihood of microbiological spoilage, but it requires the use of heat, which adversely affects product quality. The popular high-temperature, short-time (HTST) pasteurisation technique aims to limit these adverse effects by cutting the amount of time that the product is exposed to heat. However, it still takes time to evenly heat the product, adding to the total processing time and increasing the risk of adversely altering the product’s organoleptic properties.

By contrast, ohmic heating, which uses electricity to rapidly and uniformly heat the product, has been scientifically shown to be highly effective at inactivating bacteria, yeast and moulds while maintaining the flavours and quality of fruit juice.¹

HRS was approached by a leading Mexican fruit juice producer who wanted to use ohmic pasteurisation. With almost 40 years’ experience installing food and drink pasteurisation systems around the world, HRS was able to supply this technology as the heating section of a complete pasteurisation system that included preheating and cooling elements as per the juice producer’s request.

“The ohmic system works by passing electricity between two electrodes in the product in a 1 m ceramic tube, so the electricity has to pass through the product,” explained HRS Food Business Development Director Francisco Hernández Ortiz. “The result is that the juice is heated up to 105°C within one second. It is then held at this temperature for four seconds before being cooled. Ohmic technology itself is not new, but this system uses the latest electronics to ensure that the temperature curve is very smooth, which not only helps to preserve product quality but also improves process efficiency.”

Maximising efficiency is important as, depending on local electricity prices, ohmic heating can be a more expensive process than traditional methods of heating products for pasteurisation. It also represents a larger capital investment, with the ohmic heating unit accounting for a significant part of the total project cost. However, the customer believed that the proven benefits in terms of quality and the ability to market their product in the lucrative US ‘as fresh’ market justified the additional investment.

The final system designed and installed by HRS has the capacity to treat 18,000 litres of juice each hour. Once the juice has been pasteurised, it is important to cool it as quickly as possible to prevent any additional quality changes. This is achieved using a HRS MI Series stainless steel shell and tube heat exchanger. The product is initially cooled by water, with the recovered energy being used elsewhere in the process, while a final cooling phase with glycol achieves a final product temperature of 2–4°C.

“As a heat treatment specialist, HRS was able to provide a complete system that incorporated the required ohmic heating element,” added Ortiz. HRS Heat Exchangers offers heat transfer solutions worldwide across a diverse range of industries and has almost 40 years’ experience in the food and beverage sector.

1. Beveragedaily.com 2005, Ohmic heating could up juice quality, <<https://www.beveragedaily.com/Article/2005/04/21/Ohmic-heating-could-up-juice-quality>>