Potato with skin

Availability and types: Potato with skin

The potato originates from the Andes in South America. Wild potatoes were gathered there thousands of years ago and later cultivated intentionally. From South America the potato reached Europe and from there spread to almost all parts of the world. Today potatoes grow on almost every continent — they are a very important and widespread crop.

Where does the potato grow?
Potatoes are grown in many countries. Major growing regions include, for example:

The potato is very adaptable: it grows in cooler regions as well as in warmer areas, provided the soil is well managed and there is sufficient water and sunlight.

When can you buy potatoes?
Fresh 'early potatoes' or 'new potatoes' are usually available in spring and early summer. Most potatoes are harvested and then stored cool, so you can find them in shops year-round — similar to apples, which can be stored for a long time. When buying potatoes with the skin, check that they are firm and not shriveled and that they have no green spots. Green spots can contain a bitter compound that should not be eaten.

Which varieties and types exist?
Potatoes differ in shape, size, color and in how they behave when cooked. The main types are:

Purchasing options
You can find potatoes at supermarkets or markets as conventional produce or as organic potatoes. 'Organic' means they were grown without certain chemicals. They are also available pre-washed or unwashed — unwashed potatoes often have more soil on the skin but tend to keep longer.

If you prepare potatoes with the skin you save time and often preserve vitamins, because many nutrients sit just under the skin. Simply wash, scrub and then boil, fry or roast — with the skin they often taste more intense and rustic.

Potato with skin refers to the whole, intact tuber of the cultivated plant Solanum tuberosum, as it typically appears in the kitchen or in processing before peeling. Botanically it is a storage organ that stores starch in the form of starch granules. The skin (periderm) is a thin but chemically and functionally significant layer that reduces water loss, mechanical damage and microbial attack while also containing a notable proportion of nutrients and secondary plant compounds.

Chemical composition and nutritional values (typical per 100 g, raw with skin): Composition varies with variety, maturity and storage conditions; values given are averages. Energy about 70–90 kcal; water content 75–80%; carbohydrates 15–20 g (starch makes up the main share, sugars <1 g to a few grams); fiber 1.5–3 g; protein 2–3 g; fat <0.2 g. Minerals are especially potassium (approx. 300–450 mg), plus phosphorus, magnesium and traces of iron. Significant vitamins are vitamin C (typically 10–25 mg) and vitamin B6. The skin contains a higher share of fiber, phenolic compounds and minerals than the inner tissue.

Starch and starch structure: Starch consists of amylose and amylopectin; the ratio is variety-dependent and affects cooking behavior, texture and glycemic effect. On heating starch gelatinizes; on cooling retrogradation can occur forming resistant starch (resistant starch type 3), which escapes digestion in the small intestine and can be fermented in the colon, lowering glycemic load and producing prebiotic effects.

Secondary constituents and safety: In the skin and in green or sprouted areas glycoalkaloids such as solanine and chaconine can occur. Light exposure, stress and variety traits increase concentrations. High levels are considered a health concern because they can have gastrointestinal and neurological effects; therefore green, damaged or heavily sprouted parts should be removed. Other secondary plant compounds include phenolics, which contribute to antioxidant activity.

Processing and impact on nutrients: The method of preparation substantially influences nutrient content and contaminant formation:

Technical and analytical aspects: Various analytical methods are used for quality and safety testing. HPLC with UV/FL detection or MS is used to determine glycoalkaloids; GC-MS and LC-MS are standard methods for acrylamide analysis. Starch composition is examined by enzymatic hydrolysis or size analysis (e.g. gel-permeation chromatography). Thermal properties are tested with differential scanning calorimetry (DSC).

Practical significance and recommendations: Potatoes with skin are nutritionally valuable because the skin provides fiber, minerals and secondary plant compounds. To minimize health risks, green or sprouted areas should be removed, storage should be cool and dark, and for high-temperature preparations (frying, intense baking) suitable varieties and control measures should be chosen. Appropriate processing improves digestibility, reduces nutrient losses and can be used to influence functional properties such as the proportion of resistant starch.