POTATO

Family: Solonaceae

Genus: Solanum

Species: tuberosum

(i) General background on the plant

The potato is the only member of the Solonaceae of outstanding agricultural importance. The genus Solanum comprises some 2000 species and is very variable in habit, about 170 species produce underground stem tubers. A few other species are horticultural crops, but many Solonaceous plants are poisonous. The potato is a native of South America, originating in the Andes at high altitude where it has been cultivated since pre-Colombian times. The cool damp conditions in which the potato evolved made it particularly well suited to the European climate. Potatoes were first taken to Spain in 1570 but it was not until two centuries later that they were appreciated as a food plant, except in Ireland where they had become a staple diet, being particularly suited to the cool wet climate there. Elsewhere in Europe the potato only became widely established in the early 19th century, this was largely due to the efforts of French agronomist Parmentier. In the 20th century potatoes are cultivated worldwide, except in the lowland tropics. Europe (including the Soviet Union) accounts for 90% of the world's crop.

The potato is cultivated for its tubers which are stem structures formed by the enlargement of the tips of underground stems (stolons). The poisonous alkaloid solanine is widely distributed through the green parts of the plant which are therefore not suitable for fodder. Solanine is absent from tubers except when they are greened by exposure to light.

The potato is a perennial herb with weak trailing or more or less erect branching stems 0.3 - 1m high. Leaves are pinnate with smaller leaflets between 3 - 4 pairs of main lobes. Flowers are white, red or purple, approximately 2.5cm across with yellow anthers joined into a cone-like structure. The fruit is a small inedible green or yellowish tomato-like berry approximately 2cm across. Tubers are very variable in size shape and skin colour according to cultivar. Several hundred cultivars exist differing in the quality of the tubers, suitability to different climates and soil types. Cultivars may be classed as first earlies, second earlies, main or late crop depending on when they mature.

(ii) Details of quality characteristics

Potatoes are the most important 'vegetable' in the world today - after cereals the tubers provide the main source of carbohydrate in the European diet. Secondary uses include the production of starch and dextrose, industrial alcohol by fermentation, and spirits. Potatoes yield 17 - 21% fresh weight of starch and 0.5 - 1.2% of pure protein.

(iii) Current production and yields

Source: FAO 1997

(iv) Constraints upon production

Phytophthora infestans can cause serious losses, it was the cause of the great famine in Ireland in 1845. Control with fungicides is possible with careful monitoring of climatic conditions.

In Europe, the seasonal character of potato cultivation and the geographical location restrict the prospects of growth of the potato starch industry.

(v) Markets and market potential

Today, in volume and value the potato exceeds all other crops worldwide, including wheat.

Starch is a carbohydrate polymer that occurs in granular form in the organs of higher plants and is composed almost exclusively of anhydro-a-D-glucose units. It is the most abundant storage polysaccharide in the plant kingdom. Its digestibility in the human and animal intestine makes it the most important nutritional component in food and feed. Industrially, starch consists of starch polysaccharides, minor constituents and moisture and is obtained by industrial wet milling, refining and drying. The paper and board industries are the largest non-food starch-using sector, using approximately 60% of the total industrial starch.

Potato starch is obtained by continuous wet-milling processes with low input of fresh water applied to farina potatoes as the starting material. The world production of potato starch exceeds 2x10⁶ mt per annum, it is traditionally regarded as having superior properties to cereal starches. Potato starch is the preferred starch for paper/pulp surface sizing which accounts for more than 50% of the use in this particular industry, however wheat and maize starch are usually used as they are a lower cost option.

Applications of Starch and its Derivatives:

Source: Jacques Michaud, Cerestar, Belgium.

The amino acid content of potato protein has a highly balanced physiological value in contrast to many other plant proteins. Soluble and insoluble protein complex from the fresh potato tuber is derived as a by-product of potato starch production. The resulting granules have the following composition:

The fibrous and starchy by-product of potato starch production is used as potato pulp feed. This represents 11 - 13% of the potato input and becomes a low-protein, medium-energy feed.

There are also attempts to use the highly fibrous material as bulk filters for plastics.

(vi) Other information

The agronomy of potato growing is well researched and documented.

The manufacture of native starch in the EU is dependant on the payment of production refunds to allow EU starch to compete with imports. Potato starch production receives additional support in the form of 'fixed premiums', this is limited to about 1.6 million tonnes and is distributed principally to Germany, Holland and France. In the UK currently no potatoes are grown specifically for starch so all potato starch is imported.

See the following pages in the NF-2000 Database

FAIR-CT95-0568 - Genetic Tailoring of Novel Starch Polymers

National Activities - UK - UK Government Funded R on Crops for Industrial and Energy Uses: Section 3 - Starches

FAIR-CT96-1780 - Sustainable Production in Biodegradable Polyesters in Starch-Storing Crop Plants

FAIR-0837 - Novel Polyol Intermediates Derived from Biosustainable Starch for Polymer Technologies - STARPOL

AGRE-0001 - The Research Development and Production of Low Temperature Storage Tolerant Chipping (Crisping) Potato Cultivars

FAIR-PL97-3527 - Exploitation of the unique genetic variability of peas in the production of food and non-food ingredients

FAIR-1633 - Genetic Engineering of Carotenoid Metabolism: a Novel Route to Vitamins, Colours and Aromas for the European Market

FAIR-1201 - Liquid Products and Hydrogen from Biomass (the ABE fermentation) - European Integration

FAIR-CT96-1780 - Sustainable Production in Biodegradable Polyesters in Starch-Storing Crop Plants

(vii) Contacts

See the following pages in the NF-2000 Database

Organisation Description - Germany - Emsland-Starke GmbH

Starch and Potato Products Research Laboratory (Poland)
ul. Zwierzyniecka 18, 60 - 814 Poznan, Poland
Tel: + 48 61 8668045
Fax: + 48 61 8417610
Email: clpz@man.poznan.pl
Email: lewal@man.poznan.pl

(viii) References

Gill, N.T., Vear K.C. (1980). Agricultural Botany 1. Dicotyledonous Crops. Duckworth.

Halley, R.J (1983). The Agricultural Notebook 17th Edition. Butterworths.

Michaud, J. (1998). Starch: Non-food Uses. In Production and Uses of Starch International Conference, Association of Applied Biologists.

Zoebelein, H. (1997). Dictionary of Renewable Resources. Weinheim.