Public Servant Lifestyle

A favourite for seaside consumption (in the sun, if you can get some) ice cream is actually a complex product engineered for the best attributes.

Sweet and cold with a wonderful in-the-mouth feel, ice cream is a British favourite, but far from the soft, icy home-made product, today's commercial ice cream is a complex product designed and engineered for the best attributes.

"There are no secrets in ice cream formulations, there are a variety of formulas which are used to derive recipes," says Dr Robert Roberts, professor of food science.

Fat?

In general, most ice creams contain 10-16% fat and 9-12% non-fat milk solids with 11-15% sucrose or equivalent for sweetness. Then, of course there are the flavourings and the emulsifiers and the most important, and often forgotten component, air.

So, what's the difference between ice-creams? On most supermarket shelves, you'll find economy, and premium ice cream. "Many people think that the higher the quality of the ice cream, the higher the fat content, since fat makes the ice cream feel unctuous and creamy," says Roberts. "Fat is also a cold insulator and is involved in trapping air and perhaps most importantly, it tastes good."

So What is It?

In essence, ice cream is a frozen foam. During the freezing and whipping process, proteins in the ice cream mix encircle the air bubbles incorporated in the liquid and then the fat stabilises the bubbles.

"Protein traps the air, but cannot hold it, much like skimmed milk foams," says Roberts. "The fat in ice cream partially destabilises and traps the air. In ice cream, in contrast to other products, emulsifiers are added to destabilise the fat."

During ice cream mix manufacture, the ingredients are measured by weight, then mixed, pasteurised and homogenised. "The pasteurisation process is required by law to destroy any potential pathogens and make the product safe for consumption," says Roberts. "Homogenisation, a high pressure process designed to reduce the size of the fat globules and increase 'whipability' is very important. Without homogenisation, the mix might over destabilise during the freezing process leading to a defect known as buttery, which is definitely not what people want in ice cream."

The pasteurised, homogenised mix is cooled and allowed to age for at least four hours to create some fat crystals. Allowing time for the fat to assume the appropriate form is a critical step. After ageing, the mix is ready to be frozen.

Freezing

Commercial ice cream freezers, though much larger, operate on the same principle as home ice-cream-making machines. The outside wall of the freezer gets cold and a series of blades removes the ice crystals from the wall and moves them toward the centre, also incorporating air.

While freezing under agitation, only about half of the water in the ice cream mix freezes, leaving the other half liquid. The proteins, salts and sugars in the mix lower the freezing point enough to require further freezing. The hardening stage, when the rest of the mix solidifies, must be done rapidly to avoid the formation of large ice crystals.

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