Processing

Snack foods are made from a wide range of raw materials and the preparation differs from product to product. Frying, however, is the main process by which many are made and this is considered in detail here. (It should also be noted that concentrated milk solids or fruit pulps are also used for snacks in some countries.)

Principles of frying

Frying alters the eating quality of food. It also provides a preservative effect as the heat treatment destroys microorganisms and enzymes, and there is a reduction in moisture at the surface of the food.

Choice of oil

Most oils used for frying are of vegetable origin, but there is no reason why animal fats cannot be used. The oil used has a great impact on the taste, texture, and keeping-quality of the final product.

Fats and oils are subject to a type of deterioration known as rancidity. This produces disagreeable odours and flavours and makes the fried foods unpalatable. Some oils are more prone to rancidity than others, and this is important when considering which oil to use. In many countries, however, there is only one type of oil widely available at the lowest cost, and processors will use this, despite rancidity problems, if it gives a flavour that is acceptable.

Raw material preparation

Cutting

Cutting into slices or cubes is often the only preparation needed for many snack foods. An ordinary kitchen knife can be used, or one of the many gadgets on the market (both manual and powered), make this stage easier and faster.

Slicing potatoes

Forming

Some snack foods are prepared by forming a dough and then shaping it into pieces. These doughs are usually cereal or pulse-based and may be mixed manually or by using a powered mixer. Shaping can take place by either rolling out and cutting or by extruding the dough into strands before frying Small hand-held extruders are widely available in some countries and can be fabricated locally from materials such as wood or metal. They may be fitted with dies of different shapes and sizes to add variety to the products made.

Extruding dough

Some doughs can be prepared from milk solids. This involves evaporating milk until it forms a thick granular mass. This is then mixed with flour and sugar to produce a dough which is subsequently shaped into balls and fried. Examples are 'Mhisti' in Bangladesh and 'Rasangolla' in India, both of which are served floating in sugar syrup.

Frying

The amount of oil required for frying will vary according to whether the product is to be shallow-fried or deep-fried.

The temperature to which the oil is heated is not limited by a boiling point as with water. Heated oil does however reach a stage at which it breaks down to fumes, which is known as the smoke-point. It is important that oils do not reach the smoke-point when used for frying as this will cause the oil to deteriorate more rapidly and increase the danger of it catching fire. Suitable temperatures for frying are between 180 and 200°C.

Frying can take place using a simple pan heated by an open fire or other heat source. Alternatively, for deep-frying, an electrically powered fryer, fitted with a thermostatic control, gives more control over heating for larger quantities of food.

Draining

Fried products need to be drained adequately in order to remove any excess oil. If this is not achieved the excess oil can make the product soggy, which is particularly important if snack foods are characterized by their crispness. In addition, poorly-drained products are likely to leave a film of oil on the inside of polythene packs. Not only does this look unappetizing, but it will also promote more rapid rancidity.

Leaving the product to drain is rarely sufficient to remove excess oil. Fans may help remove more oil or it can be absorbed into paper. In general, higher temperatures during frying cause less oil to be retained on the product. New oil also sticks to the product less than old oil.