Rapid cooling system

A rapid cooling technique - spray crystallisation - may result in ingredients with reduced freezing-induced damage and consequently enhanced functional properties, compared with those frozen by other techniques.

The technique involves atomising a liquid product and contacting it with a spray of liquid nitrogen. This results in the formation of small, frozen droplets that will mix easily with other foods and defrost rapidly.

The technique has already been shown to be beneficial for bakery fats.

Recent work, done in collaboration with BOC, investigated the effects of spray crystallisation on the functional properties of liquid egg and the water-in-oil emulsion of tomato soup.

Thawed, spray crystallised egg behaved in a similar manner to both fresh egg and a refrigerated control sample, in a foaming test to assess the ability of the egg to retain air.

Choux pastry baking trials showed that the functional properties of the egg were retained. With the tomato soup, spray crystallisation resulted in a product that was more viscous at room temperature than a control sample, although microscopy tests showed no obvious differences in particle size or distribution.

The increased viscosity may possibly be due to differences in sizes and growth rate of starch crystals.