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The majority of Alberta’s potato crop is grown for processing potatoes into French fries and chips and other potato products such as shredded potato patties. Specific potato varieties are grown for processing into frozen foods. Potatoes destined to be French fries must have a long, cylinder shape.

To determine French fry quality the following factors are important: high dry matter, reduced sugars, minimal defects and good flavour. One of the most important qualities of French fry potatoes is high dry matter, which is measured as specific gravity or percent solids. As the specific gravity increases, the water content of the potato decreases. French fry processing removes water from the potato, so the higher water content of the potato, means more water or weight lost during processing resulting in a lower yield of fries. Potatoes with a high specific gravity produce a greater yield of fries than potatoes with low specific gravity. Specific gravity also has a direct bearing on the amount of oil absorbed by the potato slices during the deep frying process. Fries made from tubers with low specific gravity absorb more oil than fries from tubers with high specific gravity. Although some oil absorption during deep frying is desirable for flavour development, too much results in limp, greasy fries. Low specific gravities increase production costs because more oil is used in the frying process.

 

 French fries should have a uniform light cream to golden colour. French fry colour is largely determined by the reducing sugar content of the potato tuber: potatoes with high sugar levels make dark fries. When potatoes are fried, the sugars react with amino acids in the tuber to form dark fries which is undesirable. The level of sugars in potatoes depends on variety, growing conditions, maturity, and storage conditions. The processor can make some adjustments to fry colour during processing, primarily by manipulating blanching conditions. Processors prefer the lightest fry colour.  Defects such as sunburn, net necrosis, sugar ends, bruises, carbon spots and light and dark brown areas negatively influence the appearance of the finished French fry and reduce its value on the market.

 

Types of potatoes grown for processing as potato chips also have a high proportion of dry matter (as opposed to water), and a low sugar content. Reducing sugars is critical for light coloured chips. Even low levels of sugar cause chips and fries to turn dark brown when frying. Sugar levels typically make up less then three per cent of total tuber (potato) dry matter. Chipping varieties all have a round shape. Good quality potato chips have a light colour with little vascular discolouration. Potato chip processors have slightly less control over reducing sugar levels because blanching is not an option in the chipping process. High specific gravity is particularly important in the production of potato chips because of greater surface area to volume ratio in chips compared to fries. Chip crispness and lack of oiliness increases with increasing specific gravity.
 

Potato chips must have a pleasing and desirable flavour, thus potatoes used in chipping must not be bitter or have other off-flavours. The flavour of potato chips is more complex than that of boiled, baked or mashed potatoes, since the cooking temperatures are higher, and the absorbed oil contributes to the overall flavour profile of the product.