Dry thoughts on quality

Soup mixes, noodle flavourings and instant coffee all have one thing in common. They're subject to harsh yet cost-effective drying processes. Manufacturers of dried foods often find it tough to balance quality with cost control. But dehydrating techniques have developed considerably - and a new Norwegian process, in particular, is proving a cheaper way to produce better products.

After years of research, the Foundation for Scientific and Industrial Research at the Norwegian Institute of Technology (SINTEF) has come up with a technique (see schematic above) which it hopes will slash the cost of dehydrating food, while approaching vacuum freeze-dry quality.

"The technique uses a patented combination of a fluidised drying bed with a heat pump system," says Professor Ingvald Strommen, who is behind the new procedure. "The first stage uses an upwards gas flow to dry the product at sub-zero temperatures. The second stage uses two dryers: one above and one below. One is cold and one is warm, so the humid air from the warm dryer condenses on the cool surface. The air is dehumidified and then heated again on the warm surface, which operates at 30-40°C."

Although warm, this temperature is significantly cooler than that found in traditional dehydrating operations, where a product is dried on a belt or a fluidised bed, at between 60-80°C. But this is by no means the only benefit of the innovation.

"The heat pump operates in a closed cycle," says Strommen. "So there is much lower energy consumption than is used in typical vacuum processes. But the advantage is, by drying at temperatures below freezing, the shrinkage is quite low - if any - in comparison to traditional methods."

However, while the process is cheaper, quality is not compromised. Early assessments estimate the quality could even exceed that from vacuum freezing, while providing a significantly more cost effective process.

"In terms of quality it's very, very close to vacuum freezing," says Strommen. "Some people would even say better. With vacuum freezing the quality is excellent; with possibly a slight loss of colour. We've had people say that food preserved with this technique tastes better than vacuum frozen products, but obviously taste is a subjective thing, and we haven't yet had the scientific research to back that up fully."

Compared to existing drying methods, Strommen's technique offers the potential for greatly enhanced dehydrated foods. "With the traditional technique of drying on a belt, the reduction in the ability to rehydrate the product is really quite considerable," he says. In comparison, this technique keeps the food porous and easy to rehydrate quickly.

The innovation has already found large-scale backing, and a new factory has been opened in central Europe to cater for the first orders. "We're at the first commercial stage with it, but we're really quite proud to have a fairly large plant begin operations in Hungary," says Strommen. "At the moment we're using it on corn and peas because the orders are there. This is to cater to the large market for 'just-add-water' products. But we might also be looking to use it on other vegetable products - fruits, berries - things like that. The research hasn't yet been done for these products, so we need to look further into this area.

"This technology brings something new, and techniques like freeze-drying are well established. It certainly offers great opportunity for commercial success, and price reductions. Personally I'm very curious to see how the market will react."

UK food dehydration

Strommen isn't the only one keen to see how the market will react to the new process. Lincolnshire-based food dehydrator JLP Foods has spent the last five years waiting for the new developments to become available.

JLP Foods supplies dehydrated fruits and vegetables like garden peas to large producers of dehydrated meals such as Pot Noodle. For decades the dehydration process it has used has remained virtually unchanged, although there have been some developments in terms of computerising the drying machines. Food is washed, peeled, and blanched (if required) to maximise colour preservation. It is then dried in a gas-powered dryer, hand-inspected at the final stage, and packaged ready for sale.

Sourcing of vegetables best suited to dehydrating is also important. "We choose very specific varieties for dehydrating, and that's really on the basis of years of experience," says JLP's commercial director Roger Messenger.

"The varieties we're looking for have a very high solids content, and low moisture, which makes them more suitable to the drying process and yields a better product at the end. In a way the vegetables we use are the complete opposite of what a fresh vegetable seller might be looking for in a product."

Offshoring

Perhaps partly due to the simplicity of the procedure, outsourcing has become common, resulting in the loss of a number of UK and European firms involved in dehydration.

A large proportion of dehydrated products now come from China, while India and Egypt corner the market for dried onions. Even European producers with lower running costs, such as Turkey, have now stopped producing dehydrated foods, leaving the market open to the burgeoning Asian giants.

"We're the last UK firm to deal in dehydrated food," says Messenger. "And we've done it because we've expanded into other areas. We're a big importer of dehydrated foods. This year we've closed our last drying machine. But we've managed to branch out in what we supply, which has enabled us to keep trading."

The company now offers dehydrated roasted vegetables, where the dried food is subjected to an extra roasting process, making it suitable for Mediterranean-style packet foods. "This is a market which is still growing in some areas," says Messenger. "But things like traditional packet soup blends are on the decline." However, he notes that demand for seasonings and flavourings are increasing.

JLP is unsure what impact the Norwegian technology will have on its business. Currently the new Hungarian factory is focusing on corn and peas, which for most food dehydrators are a fairly niche products. In the UK Unilever and Campbells more or less corner demand for these ingredients, so convincing them to change what has previously worked well for them will be a tough proposition, believes JLP.

Dried fruit potential

Where there is real growth potential, however, is in the dried fruit market, which has ballooned under the media barrage of personalities like Gillian McKeith and Jamie Oliver. McKeith, in particular, is a big exponent of dried fruit snacks, and is partially responsible for their sudden mass presence on supermarket fresh produce aisles.

Other factors include a more general UK demand for healthy snacks, and the popular advent of breakfast bars.

"Dehydration can certainly have a negative impact on the vitamin content of foods," says Dr Jinsche Chan, of the University of Leeds' Human Nutrition Department. "Any process that heats fresh food, or preserves it artificially can destroy vitamins, and this is something which the public tend to be more conscious of now. But that's not to say there's not a market for dried food, and certainly new techniques that enhance quality are likely to be popular. Dried fruit and nuts, for example, seem to be very popular at the moment."

Certainly time-pressed UK consumers are likely to snap up anything likely to save them a few minutes in the kitchen. However, with distant memories of the much derided Vesta curries; trends away from instant soups in favour of chilled; and the use of fresh spices, herbs and other seasonings; what hope do dried products have of seeing a renaissance?

"We appreciate that traditional drying processes have a cost benefit and freeze-drying has quality benefits," says Mike Lambert, technical director at Bart Spices. "We currently offer both, so customers could buy, say oregano either dried or freeze-dried. Larger leaves tend to lend themselves better to the freeze-drying process, but it works very well for many herbs. We've definitely seen an increase in consumer demand for quality herb and spice blends, and we're not ruling out the possibility that new developments could deliver quality and cost benefits to our customers - but it's very early days as far as new technology is concerned."

Early days indeed. But the new Norwegian technique certainly offers the possibility of revolutionising an industry that is a long way from drying up. FM