Squeezing the most from your orange juice

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Demandfor fruit juice amongst Malaysian consumers shows no signs of slowing down.Some estimates suggest the country is now drinking more than 150 million litres of juicedrinks a year1, with many consumers preferringthem to fizzy drinks.Not surprisingly, orange juice is the most popular variety.

Although three manufacturers account for over half the Malaysian juice market,2there is still a large market for smaller brands and niche manufacturers, with many concentrating on fresh and unpasteurised products. Chilled productsare particularlypopular with premium customers and, likemany other manufacturersaround the world, Malaysian manufacturers can now use ‘flashpasteurisation’ in order to appeal to discerning consumers, while prolonging the life of their products.

The dash for flash

With or without pulp, the challenge for manufacturers of fresh orange juice is the speed at which the flavour and quality alters and deteriorates after the orange is squeezed. Like any fruit, oranges are perishable commodities and need to bepasteurised to stop the product spoiling. If there is to be an acceptable shelf life, the juice has to be pasteurised to destroy microorganisms and stop enzymatic activity.

There are various ways to delay these chemical changes. At HRS Heat Exchangers, thermal treatment, also known as ‘flashpasteurisation’, is the preferred techniquefor 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 asthejuice 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’s flashpasteurisation treatmentis assisting juice production plants to optimise juice quality and taste.

Preserving taste and quality

HRS has significant experience in juice production facilities around the world and when designing an orange juice processing plant the company is guided by four key objectives:1.Maximising the quality and taste of the juice2.Maximising energy consumption3.Exploiting by-products such as dried orange peel4.Exploiting digital control and product recovery technology

The HRS series of MI/MRPasteurisers use food-grade,multi-tube,corrugated heat exchangersto 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 topasteurisation temperature much faster –typically by 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 mediacan affect quality,too -the hotter the heating media, the more damage the hot tubes inside thepasteuriser will have on product quality.”

Benefits of high heat transfer

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 the system footprint can be reducedbyusing 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%.

System lifespan is also greater using the HRS technology. The corrugated design/profile of the inner tube helps reduce product fouling –it disrupts the fluid boundary layer and creates higher velocity and turbulence. As the juice travels around the system,it’s less likely to stick to the tube wall and causecorrosion and reducedperformance (leading to increased downtime and maintenance costs, expensive replacement parts and reduced system lifespan).

In the system, water carrying the recycled heat energy travels in the space between the inner and outer tubes and flows in the opposite direction to the juice. The fact that the two liquids are travelling in opposite directions boosts the maximum amount of heat transfer due to a mechanism called counter-current exchange,as Matt explains: “Counter-current creates a declining difference in temperature (helping heat transfer) whereas in concurrent (where heated and heating elements are side by side, as in a tank and jacket system) the initial difference is higher but quickly levels off. The HRS system pumps the juice and heating and cooling water around the exchanger, which further boosts the maximum heat transfer achievable.”

Perfect pulp processing

As well aspasteurisers, HRS provides systems for treating and aseptically filling pulp. One of the key aspects of this is the ability to move the pulp and the HRS BP Series of piston pumps are particularly suited to this purpose. The BP pump is hygienic yet can still develop pressures of up to 40 Bar. For the thermal treatment of pulp we suggest the HRS AS Series of heat exchangers, which uses three concentric tubes, with the pulp flowing through the annulus between the outer and inner tubes, so that it is thermally treated from both sides. Finally,the pulp treatment process uses a ‘Bag-in-Drum’ or ‘Bag-in-Box’ AF Series aseptic filler designed by HRS, which allowsthe product to be packedinto aseptic containers. Pre-formed and pre-sterilised containers of between 5 and 1,000 litres are normally used, depending on market requirements.

Matt Hale concludes: “With experience in fruit juice plants around the world, we can provide solutions not only to provide high quality juice products from a wide range of fruits and vegetables, but also equipment to process the resulting by-products. Thismeans that as well as maximising energy efficiency to reduce running costs, we extract the greatest possible value from every stage.”