A-Z of making tasty chips at home from potatoes

The need to preserve potatoes and reduce waste, add variety to diet, make money, facilitate transportation and reduce price fluctuations due to seasonal availability cannot be over-emphasised.

Price fluctuations due to too much supply in the market are a constant frustration to farmers, majority who rely on rain.

Value addition, in particular by making chips is the way to go. Let us do the math. A 70kg bag of potatoes can yield 21-30kg of chips, which requires five litres of cooking oil to fry.

A plate of chips goes at an average price of Sh70 for 300g, which means one ends up with a gross income of between Sh4,900-Sh7,000 for the bag as opposed to Sh3,000 for the unprocessed produce when supply is high.

Making good quality chips starts with the choice of potatoes, which must have no disorders such as hollow hearts, dark spots, greening caused by exposure to sunlight before or after harvest, bacterial or fungal infected or bruised.

Laboratory tests can be done to determine dry matter and reducing sugars in the flesh of the potatoes. High dry matter, which is usually a characteristic of mature potatoes, has been found to give good quality chips.

On the other hand, lower concentration of reducing sugars is preferred because it does not darken chips.

The potatoes should be regular in shape (oval) and have shallow eyes to avoid wastage in the process of digging them out. Store your potatoes in good conditions to prevent them from absorbing smells such as those of a musty store, parrafin or pesticide.

WASHED PRIOR TO TRIMMING

Storage for prolonged periods at 6oC will result in the potatoes having high reducing sugars. Prolonged storage at 6oC should be mitigated by keeping the product at 15-20oC for two to three weeks.
Varieties commonly used in processing chips include Nyayo, Roslin Tana and Kerr’s Pink.

Proper making of chips starts with washing and preheating to allow lye or steam peeling, which would take a minute or two. The peels are then removed and potatoes washed prior to trimming off the eyes and patches of unpeeled areas.

The potatoes are then size graded and left under water to prevent them from darkening before they are cut using a strip or wedge cutter. The offcuts or small pieces are removed before the shapely pieces are blanched (a mild heat treatment).

This heating (60-85OC in water for about two minutes) may include treatment with chemicals like sodium pyrosulfite to improve colour or salts (calcium and magnesium) or starch to improve texture. The hot water partially cooks the potato and reduces the total frying time, which cuts fat absorption in the final product.

WATER WOULD DESTROY THE FAT

The water is then drained and the chips dried by blowing over warm air. This is because if left, the water would destroy the fat and less time will be needed to fry the chips.

The product will also have a uniform colour and absorb less oil during frying. Temperature ranges used to fry potatoes are 135-185oC.

It is necessary to heat the chips at 180oC to avoid residual enzyme activity even after blanching. Instead of salting, one may add a package of salt and flavour for the consumer to determine if they would like to use the contents.

Some processors use microwave for drying after frying and this is beneficial especially if the potato had high reducing sugar content. Packaging made of polyethylene and polypropylene is preferred as it is inexpensive, flexible, waterproof, can be thermo-sealed and doesn’t have flavour.

Frozen chips can be kept for up to six months. The chips will be thawed and fried before being served hot. Some people bake the frozen or chilled potatoes. It is also possible to microwave the mildly heated and frozen or chilled potatoes.

NUTRITIONAL VALUE

Nutritional value for chips is more or less the same as for the fresh potato but richer in salt (if salted) and fat (4-15 per cent) and flavour. However, there will be loss in N, non-protein nitrogen and amino acids. The moisture content should be less or equal to 38 percent.

Good quality chips should have a light, golden colour but this can be subjective as some consumers prefer darker colour. The chips should also not have any blemishes like dark spots or traces.

The texture should be crispy on the outside and mealy or tending to crumble after cooking on the inside. The oil should not be in excess (>15 per cent) in the finished product because besides it being wasteful, it worsens flavour of the potatoes and may reduce the shelf-life due to rancidity.

The odour and flavour of the chips should be free of bitterness, pronounced burnt or sweet taste besides other off flavours. The interior should be like that of boiled potatoes.

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Dr Ngoda works in the department of Dairy and Food Science and Technology,

Egerton University.