Epsilon Archive for Student Projects

Abstract

The potato (Solanum tuberosum ssp. tuberosum) is today the fourth most important food crop species in the world. The potato tuber is a storage organ rich in nutritious substances such as starch, vitamin C and minerals. However, tubers also contain steroidal glycoalkaloids (SGAs), which in excessive doses can be toxic to consumers. SGAs are present also in other members of the Solanaceae, e.g. in tomato, eggplant, and pepper, but also occur in some species within the Liliaceae. In the cultivated potato, more than 95 % of the SGAs are in the form of α-solanine and α-chaconine. The basal SGA level in tubers at harvest varies strongly between cultivars, and certain stresses such as light and/or damage can increase the SGA levels well above the basal one. The toxicity of SGAs is due both to their interaction with cell membranes and an inhibition of acetylcholinesterase activity. Signs of acute toxicity are abdominal pain, diarrhoea, and vomiting. More severe signs of poisoning are coma, paralysis and even rare cases of death have been reported. To avoid these problems, it is in many countries recommended that potatoes for human consumption should contain less than 200 mg/kg (fresh weight) of SGAs. In Sweden, this limit is legally binding.
Despite the SGA hazard, relatively little is known about SGA levels in tubers that are sold in retail stores, and to what extent the forms of package and display influences the SGA levels. In the present study, the levels of α-solanine and α-chaconine were analysed in table potato cultivars of common use in Sweden. The tubers were purchased in different sorts of packages from food stores in the Uppsala area, or obtained from plants grown outdoors. SGA levels were analysed by liquid chromatography-mass spectrometry (LC-MS).
Results from potatoes grown outdoors at Ultuna in year 2020 showed that the basal SGA level differed between cultivars. Also, the SGA-promoting effect of a light treatment was shown to differ between cultivars. None of the over 50 samples from retail stores contained SGA levels over the upper safe limit of 200 mg/kg.
The knowledge about how cultivars react differently to light treatments can be used by the potato industry to adapt suitable tuber package, display and post-harvest conditions. For example, if some cultivars are more sensitive to light, they might not be suitable for transparent bags but more suitable to sell in dark paper bags to prevent SGA levels from rising. Information about which cultivars that are more prone to maintain low levels of SGAs might also be of importance for potato breeders to breed potatoes with lower levels of SGAs. Finally, results also indicate that the occurrence of tuber batches with high SGA levels is very low under retail conditions (less than 1 in 50; or below 2 %). Future attempts to monitor SGA levels in table potatoes will thus need to be designed accordingly, and include sample numbers well above the 50 used here, to be able to detect a high-SGA sample with reasonable probability.

Potatis är en av världens viktigaste grödor som odlas som livsmedel och är rik på en rad näringsämnen så som stärkelse, C-vitamin och mineraler. Potatis innehåller inte bara nyttigheter utan även glykoalkaloider vilket kan vara giftigt om man får i sig en stor mängd. Symptom på att man har fått i sig för stora mängder glykoalkaloider kan vara kräkningar, diarré och illamående. Det finns fall där personer har fått i sig så mycket glykoalkaloider att de har hamnat i koma, drabbats av förlamning och det exempel på att människor har dött av stora mängder glykoalkaloider. Potatis är del av familjen Solanaceae och flera andra grödor i samma familj innehåller glykoalkaloider, till exempel tomat, aubergine och spanskpeppar. Glykoalkaloider finns också i vissa medlemmar i familjen liljeväxter. Mängden glykoalkaloider i potatis vid skörd varierar mellan olika sorter och kan sedan öka om knölarna utsätts för stress som ljusexponering och/eller skada. För att undvika problem med glykoalkaloider finns det i många länder en högsta rekommenderade dos på 200 mg/kg (färsk vikt) glykoalkaloider som potatis får innehålla. I Sverige finns denna gräns och den får inte överstigas enligt lag.
I den här studien undersöktes mängden glykoalkaloider i olika vanligt förekommande potatissorter. Potatisen som undersöktes köptes antingen in från olika butiker i Uppsalaområdet eller odlades utomhus i krukor på Ultuna. Resultatet visade att glykoalkaloidnivån varierade mellan olika potatissorter vid skörd och att inga av de över 50 inköpta potatisarna hade nivåer över 200 mg/kg.