Squeezing the myths on OJ pasteurisation
Around the world the demand for premium fresh and not-from-concentrate orange juice is buoyant, with chilled fresh products often bucking a general trend towards reduced juice consumption. With such products depending on the maintenance of high quality to support demand, we look at how the ‘flash pasteurisation technique’ can help satisfy discerning consumers.
Whether fresh or from concentrate, with or without pulp, the challenge for manufacturers is the speed in which the flavour and quality alters and deteriorates after the orange is squeezed. Like any fruit, oranges are perishable and if there is to be an acceptable shelf life, the juice has to be pasteurised to destroy microorganisms and stop enzymatic activity.
At HRS Heat Exchangers, thermal treatment, also known as ‘flash pasteurisation’, is our preferred technique for making premium quality juice. “Oranges are complex fruits,” explains Matt Hale, International Sales and Marketing Director at HRS. “The flavour and quality is determined by hundreds of compounds, among them limonene, pectin methylesterase (PME), hydroxymethylfurfural (HMF) and ascorbic acid (vitamin C). What’s more, the exact composition varies according to the type of orange, climatic conditions and ripeness when picked.”
Chemical changes begin to occur as soon as juice is squeezed. Some compounds react with oxygen in the air; others are affected by enzymes that are released during squeezing. With oranges containing natural yeasts, squeezing triggers fermentation which results in the multiplication of any bacteria present.
Critics of pasteurisation argue that the process destroys the flavour of juice and alters the nutritional value. However, by minimising the thermal treatment time, HRS is assisting juice production plants to optimise juice quality and taste.
The HRS MI and MR Series of heat exchangers use a food-grade multi-tube corrugated tube heat exchanger to speed up the heat transfer in pasteurisation systems. These corrugated tubes create extra turbulence in the fluid as it flows through the tubes.
Matt explains more: “The result of this extra turbulence means that the orange juice can be heated up to pasteurisation temperature much quicker – typically up to 30%. Critically, heat velocity should be carefully considered because the longer it takes the greater the effect on the product and quality will deteriorate. The temperature of the heating media can affect quality too – the hotter the heating media, the more damage the hot tubes inside the pasteuriser will have on product quality.”
Because of the high heat transfer rates of the corrugated tube technique, HRS’s pasteurisation systems use water at a lower temperature to reduce the risk of product damage. Another benefit of higher heat transfer rates is that system footprint can be reduced using shorter heat exchanger pipes. The shorter length of the heat exchanger also results in a reduction in pressure drop, which saves pumping power and further reduces energy costs – often by 40%.
For more information on our MI and MR Series, please click here.