Food & Nutrition

Arab Journal of Food & Nutrition
32. Level of Solanine in Potatoes in Local Market and Effect of Light Exposure
during Storage on its Development in Two Potato Cultivars (1998)
Fathi Ahmad Qaroot
Supervisor: Dr. M. Ali Humied
Co-Supervisor: Dr. Malik Haddadin
Solanine is a naturally occurring toxin found in all parts of potato plant, and have
been shown to play a role in the disease and pest resistance mechanism of the plant.
The tubers are considered toxic and unfit for human consumption if solanine
concentration exceeds 20mg/100g fresh weight.
The aim of this study was to evaluate solanine content in potato samples in local
markets as well as to investigate the effect of storing tubers under direct and indirect
exposure to sunlight on solanine development in two locally planted cultivars (Sponta
& Draga). The variation of solanine concentration in three consequent layers of a tuber
at the depth 1, 2-4 and 5-14 mm respectively was also investigated.
The study revealed that solanine content of 20 samples of marketed potatoes
ranged between 94 to 32.3 mg/100g with an average of 19.5 mg. Storing potatoes in
darkness gave the minimum increase in solanine content followed by the samples
exposed to indirect then direct sunlight. In the whole tuber of Sponta cultivar the
solanine content increased from the l.4mg/100g initially to 4.8, 18.1, 29.7 mg/100g
during the six weeks of storage period respectively. The average solanine content of
the peel (1mm depth) increased from 5.2 mg initially to 18.6, 44.6, 47.9 mg/100g and
in the (2-4 mm) layer, the increase was from 3.6 mg to 6.8, 18.7, 29.8 mg, and in the
third layer (5-14 mm) the increase was from 0.5 mg to 2.9, 3.2, 6.2 mg/100g. No
significant increase was observed during the last three weeks of storage.
Draga was found to be more susceptible to light exposure for solanine formation
compared to Sponta. In the whole tuber, the average solanine concentration increased
from 4.0 mg initially to 9.2, 22.8, 46.l mg/100g; in the peel, the solanine content
increased from 5.9 mg to 21.8, 41.8, 159.1 mg/100g, and in the next layer (2-4 mm
depth) the content increased from 5.5 to 11.7, 29.7, 94.9mg/100g, and in the third layer
(5-14 m depth) the content increased from 1.1 mg to 3.6, 4.2, 13.9 mg/100g in the
three treatments-darkness, indirect and direct exposure to sunlight, respectively.
Generally, there was no significant increase of solanine during the last four
weeks of storage. This indicates the presence of a control mechanism, which inhibits
solanine formation when reaching certain levels.
The results pointed out that solanine content in one third of market potatoes
exceeded the safety limit of 20mg/100g, and that there is a difference in cultivar
response to light regarding induction of solanine biosynthesis.
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Volume 11, No. 25, 2011
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