Gone are the days when a simple cone would suffice. And it’s not just the children who are making all the demands. Adult markets have been successfully targeted and reached by a hitherto unsurpassed appetite for new and sophisticated ice-cream brands. These huge successes in this market have prompted manufacturers to constantly reinvent the ice-cream concept and have led – amongst other innovations – to a growth in ice-cream versions of popular chocolate bars.
Ice-cream is primarily an impulse buy, so branding and product appearance is a vital key to success. But ice-cream manufacturers are constantly finding their creative impulses constrained by conventional methods of manufacture. This is because there is a limit to what can be achieved using standard ice-cream production lines.
This has prompted one of the world’s largest ice-cream equipment manufacturers – WCB Ice Cream in Denmark and the multinational supplier of gas technologies – Air Products Plc to think about trying to improve methods of manufacture. The result was the world debut this year – at Anuga Food Tech 2000 – of 3-D ice-cream. But before we go into what it is and how it works, let’s look at why it didn’t work before.
A sticky issue
The problem has been quite literally a very sticky one. Ice sticks. A problem all too familiar to anyone trying to prise ice-cubes out of an ice-tray that has come straight from the freezer. What do you do? The first temptation is to bang the tray and the ice cubes scatter and smash all over the kitchen floor. Or you run the ice-cubes under the tap, causing a partial melting of the ice – and you end up with something half the size of the original. Both of these examples are not far removed from what actually happens on the ice lolly and ice-cream manufacturing production line. The problem for the moulding machine designer is how to break that powerful adhesive bond formed by the ice particles and the mould. The problem is a familiar one in the frozen food industry – but for ice-cream manufacturers the problem is exacerbated as the more liquid the product the greater the bond.
Low temperature bonding
To get some idea of quite how strong that bond is, Air Products conducted research that came up with the startling fact that at a temperature of -30ºC it would require a force of around seven tonnes to extract a lolly from its mould. But even this initial setback did not cause the company to completely deviate from the low temperature path.
Interesting things started to happen when the temperature of the mould was taken down to temperatures around -80ºC before the product was put in it. At these temperatures the ice and mould easily separated. This observation though was not new. Laboratory scientists have been using it as a preparative technique for freezing tissue samples prior to viewing under an electron microscope. The technique is referred to as “slamming”. In the lab the specimen is “slammed” against a block of pure copper that has been cooled to the temperature of liquid nitrogen. The sample is then removed from the cold block and sectioned. No one bothered to ask why the specimen didn’t stick to the block. The lab scientists had inadvertently stumbled across “zero adhesion”.
Quite why this happens, even now remains a bit of a mystery. Ice is a complex molecular mix and what happens when ice is subjected to fluctuations in temperature, is the subject of a university degree course in itself. In a nutshell, the most plausible explanation for the phenomena relies on two effects. Firstly, the bond between the product and the mould is relatively weak because the ice has been formed at very high speed. Secondly, the ice, once formed, contracts and over comes the weak bonding force.
The phenomena was developed into a technology, patented and christened ZAT™ (Zero Adhesion Technology) and it remains one of the lynchpins of many of the company’s cryogenic applications.
Ice-cream, an even stickier prospect
Ice-cream presents substantial challenges to manufacturers because it is a very delicate material. The result of the collaboration between WCB Ice Cream and Air Products is a new way of freezing ice-cream using the principle of zero adhesion.
Many ice-cream manufacturers have got round their “sticky” adhesion problem by heating the surface of the mould prior to removal. For ice-cream though this presents all sorts of problems – not least the hygiene implications of heating a dairy product and refreezing it.
Conventional ice-cream manufacture
Ice-cream is manufactured in a two-stage process. The first step introduces air into the ice cream mix and cools it. This cooling increases the viscosity of the mix to the point where it has to be handled as a solid. At this point it is typically extruded and cut into slices by a wire cutter. If required, a stick is inserted. The result is a not too appealing two dimensional ice cream with a flat bottom and flat top. The best that can be done to liven such products up, is to use a variety of colours and flavours. ZAT™ though, allows a third dimension to be added simply because the 2D slab can be pressed into any desired 3D shape because ZAT™ tools are truly nonstick.
But how exactly is this done?
Zero adhesion technology
Using the Cryo-ZAT™ method, ice-cream mould-ing tools are cooled down to a temperature below -80ºC with liquid nitrogen. Ice-cream mixture at around -6ºC is then deposited onto the bottom half of the mould tool. If necessary a wooden stick is added. Then, the mould moves to the next stage where the top half of the mould is pressed onto the ice cream to form its shape. The ice-cream is then quickly hardened in a cryogenic freezer while still on the bottom tool. The product is then picked up, decorated and wrapped automatically.
There is a further unexpected benefit of Cryo-ZAT™ – the product actually tastes better after the process. This is because the quick freezing process minimises the size of the ice crystals. The milk solids remain “milky”, yielding a more tender texture and a pleasurable “melt in the mouth” feel. What’s more, because there is no need to warm the ice-cream to extract it from the mould, quite intricate pattern details emerge intact. This means that the ice-cream mould can contain 3-D characteristics of facial features or other 3-D shapes.
There are further benefits: No ice-cream residues remain in the moulds – this helps cut down on product wastage. Also, unlike conventional ice-cream making, individual moulds do not have to be cleaned and rechilled. These operations can be laborious and time wasting on lines that need to operate at optimum efficiency.
The benefits of Cryo-ZAT™ technology lie not merely in production efficiencies and capabilities – but in marketing potential. Like the confectionery sector, market branding and product appearance play a huge part in sales success. The ice-cream sector is heavily reliant on the consumer impulse purchase. Brand leaders will have to be imaginative with their product development to stay ahead. This step forward in ice-cream technology will lead to hitherto unimagined branding opportunities. Also products can be linked to the latest craze or film, or portray a brand logo.