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The benefits of frozen food

19 June 2008 by
The benefits of frozen food

Few caterers would be able to operate without frozen food. Not only is it convenient, it's often more healthy than some fresh fare. Emma White examines the case for freezing

Frozen food has had a raw deal in recent years because of the widely held belief that fresh is best. But with its longer shelf life and versatility, few operators would be able to run an efficient kitchen without frozen. The food service frozen food market is worth £2.5b, increasing at about 4% in value year-on-year and 5% in volume, according to statistics from the British Frozen Food Federation.

"You can be sure it's fresh if it's frozen" is the federation's strapline, and as technical and legislative co-ordinator Ian Farley explains, food that has been frozen properly can be as fresh as when it was first harvested. "Freezing simply slows down the deterioration process of food and the advantage is that it can be done immediately after harvesting so the nutrients are locked in," he says.

By comparison, fresh products may be sitting around for days or weeks before they're cooked and eaten. "By the time some people receive fresh meat and vegetables they've lost nutrients, vitamins and some products are sensitive to light too," Farley says.

The key to effective freezing is starting with a good product and then freezing it as quickly as possible. "Most vegetable and animal products contain between 60% and 80% water and by freezing them quickly smaller ice crystals form. Freezing food slowly results in the formation of larger ice crystals between cells, which can force them apart and rupture the cell walls," Farley explains. This can impact on the taste and texture of the product when it has thawed, and liquid can run out of the ruptured cell walls, resulting in a drier-tasting product.

"The effectiveness of freezing can also be determined by temperature fluctuations," says Farley. "If the freezer cycle's on and off or if the door is frequently opened, the temperature can rise and ice can come off the smaller crystals and join other crystals, resulting in larger crystals, which can result in cell damage." Farley says the best method is to freeze the product down to about -8°C to lock in the quality and then freeze it to the recommended -18°C for storage and distribution.

Food poisoning risk

Nora Asada, process technologist for frozen meal manufacturer Apetito, points out that frozen food also offers caterers convenience and guards against the risk of food poisoning. "Frozen food is convenient and easy to handle. You can take what you need and leave the rest in the freezer. Frozen food gives you a longer shelf life than fresh food and it gives the flexibility of using products that are normally out of season," Asada says.

Apetito meals are frozen to -18°C within 40 minutes, which ensures that biological changes in the products are kept to a minimum, Asada says. "Freezing doesn't kill micro-organisms that cause food poisoning completely but it does slow down enzyme growth significantly," she says. And consuming a product as soon as it's defrosted is paramount. "We recommend that most of our products are cooked from frozen, but caterers can defrost products overnight in the fridge as long as they're consumed immediately to prevent micro-organism activity," she adds.

Most types of food are suitable for freezing, but those with a high water content, such as lettuce, tomato, cucumber and strawberries, are exceptions. "Foods with a high water content are not suitable for freezing because they easily lose their structure and texture during the freezing process," explains Farley. "The best products have cell structures that can effectively resist the freezing process. Fish and seafood freeze well and this is attractive for caterers as they deteriorate rapidly."

Brakes frozen fruit and vegetables are usually grown close to a processing plant so they can be frozen within hours of harvesting. Brakes nutritionist Ruth Casson says some fresh products aren't as fresh as people think. "Fresh vegetables such as carrots and potatoes may be weeks or months old by the time they arrive, while peas really don't last and have a shelf life of just a few days," she says.

Korina Richmond, a dietitian for contract caterer Sodexo, says the company often selects frozen vegetables over fresh. "We use frozen food for consistency of quality, flexibility, waste and nutrient control," she says. "Vegetables frozen within hours of being picked will retain vitamin C for a long time, as opposed to vegetables that are left on the shelf for days."

Nick Vadis, executive chef at contract caterer Compass, often favours frozen peas over fresh. "Frozen items that work well include peas, which can taste better frozen than fresh and also have a higher nutritional content," he says. He finds frozen food is useful when fresh products are not readily available or weather affects the quality of fresh items. "We also use frozen fish so we can source from sustainable stocks," he adds.

Frozen fish suppliers such as Lyons Seafoods, Young's, Whitby Seafoods and Royal Greenland all advocate freezing fish within hours of being caught to retain vitamins and minerals. "Freezing langoustines soon after they're plucked from the sea guarantees locked-in freshness and goodness, such as omega-3 oil," says Whitby Seafoods marketing and sales director Laura Whittle.

Royal Greenland supplies cod and haddock fillets that are frozen at sea on freezer trawlers. The production process from catch to frozen product takes no more than six hours.

Pizza is another popular frozen food. "A pizza is thin and can be defrosted quickly but it also has a flour base that offers stability during the freezing process - you can grill, oven-cook or microwave a frozen pizza," says Unilever Foodsolutions executive chef and culinary controller Ray Lorimer. "Toppings can be frozen too - even pineapple, which has a fibre that protects it from breaking down."

Easy to freeze

With their high starch and low water content, chips are also easy to freeze, says McCain innovations research scientist Matt Yarwood. McCain chips are blanched and fried before freezing and blasted with cold air to remove excess water that can cause the chips to stick together when frozen. They are frozen to -12°C before packing and -18°C afterwards for storage. The process takes 20-40 minutes.

"Preparing chips involves lots of work, but if you buy them frozen they're ready in three minutes," Yarwood says.

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