Understanding potatoes and processing

By Theresa Siebert, Agricultural Research Council

Faced with current economic realities, farmers worldwide are seeking new options to survive and expand their businesses. One of the many opportunities to grow turnover and profits is by adding value to farm produce through processing.

Potatoes are cultivated across South Africa in areas ranging from Marble Hall in Limpopo, to the Sandveld in Mpumalanga. Potatoes South Africa classifies potatoes into three categories:

Waxy: This type of potato includes the cultivars Mondial, Fabuka, and BP13, and is characterized by high moisture and low starch content. During boiling, waxy potato varieties remain firm and retain their shape, making them suitable for applications where one does not want the potato to break up. As such, they are not suitable for mashing. When used for making chips, they produce a “slap” chip instead of a crisp chip.
Waxy-floury: Waxy-floury potato cultivars include BP1, VDP, Fianna, Valor, and Sifra (Bianca), which are somewhat moist with a mildly floury texture. Waxy or floury potatoes retain their shape well during the cooking process and are suitable for all cooking methods. This is also the type of potato most often available in supermarkets.
Floury: This type of potato includes the cultivars Caren, Darius and Avalanche and has a low moisture and high starch content. Floury-type potatoes do not retain their shape well when boiled and are therefore preferred in applications that require mashing of the potato. These potato cultivars are also best suited for making crisps and chips.

Understanding the distinct characteristics of different potato varieties enables you to choose the best potato for your production and market it accordingly. Photo: CHIPS Magazine

Various processing options

Fresh cut peeled potatoes: Fresh cut produce is any fresh fruit or vegetable that has been physically altered from its original form but remains fresh. It has been trimmed, peeled, washed, and cut to make a product that is 100% usable, with no wastage. The product is packaged for consumer convenience. Peeled potatoes fall into this category and have become very popular due to their convenience and fresh characteristics. This is a ready-to-use product that requires no further preparation prior to cooking. Young potatoes are used for fresh-cut peeled potatoes. The product is preserved by surface treatments, refrigerated storage and protective packaging and has a very limited shelf-life, which should be marked with an expiry date.
Canned potatoes: Potatoes best suited for canning are small new potatoes with smoothshoulders and free from contours, with a creamy-white flesh colour. Potatoes can be canned in several forms, including whole, diced, sliced, strips, and julienne. Potatoes can also be canned as pieces in mixtures with other vegetables, curries, or meat dishes. However, whole potatoes, usually smaller than 38mm diameter, make up the largest part of the potatoes that are canned. One of the primary requirements of a good canning potato is that it should not disintegrate during processing.
Frozen diced potato is used for the preparation of hash browns or stews and casseroles. The potatoes should be large tubers with smooth shoulders and free from contours with creamy white flesh. The specific gravity should be 1.080 – 1.120, and the reducing sugar content approximately 0.3%.
Frozen mashed potato: Mashed or whipped potatoes can be shaped into various shapes and sizes before being frozen. It is used as a casing for other products, such as sauces or fillings. Mash is seldom made from fresh, whole potatoes. Off cuts separated from the potato chip/crisp processing line are usually used as well as any other potatoes that are too small, have irregular shapes or have been trimmed too much.
Frozen hashbrowns are made from grated potato that is blended with complementary ingredients. The mixture is shaped and fried prior to freezing and packaging. Hash browns are seldom made from fresh, whole potatoes. Off cuts separated from the potato chip processing line are usually used as well as any other potatoes that are too small, have irregular shapes or have been trimmed too much.
Potato starch is extracted from pulped potatoes through a washing process. The starch slurry is then dehydrated. Potato starch is widely used in the food industry in its native form but can also be modified to obtain special characteristics.
Frozen potato croquettes are extruded products made from mashed potato that is blended with optional ingredients and seasoning. The seasoned mash is extruded into any desired shape, deep-fried in fat, and then frozen. Mashed products are seldom made from fresh, whole potatoes; instead, off-cuts separated from the potato chip processing line are usually used, as well as any other potatoes that are too small, have irregular shapes, or have been trimmed excessively for high-priority potato products such as chips or crisps.
Potato flour is used in the baking industry to enhance the keeping quality of baked products. The dried potato powder may also be used as a flavouring and thickening agent in food. The flour may be seasoned and rehydrated by adding boiling water and/or milk to produce instant mashed potatoes.