Effect of Magnesium Supply and Storage Time on Anti-Nutritive Compounds in Potato Tubers

Abstract

The nutritional quality of potato tubers is cultivar-specific and depends on climate-soil conditions and agrotechnical practices, as well as the conditions during long-term storage. Studies were performed from 2009–2011 to determine the effects of magnesium fertilisation and storage duration on the contents of the anti-nutritive compound nitrates, nitrites and total glycoalkaloids (TGA) in potato tubers of mid-early cultivar “Bila” (Solanum tuberosum L.). Magnesium (Mg) was applied in doses of 0, 20, 40, 60, 80 and 100 kg MgO ha−1, respectively, in the form of kieserite–magnesium sulphate (26% MgO). Potato quality after harvest and after three and six months of storage was determined. The content of nitrates in tubers after harvest ranged from 303 to 356 mg kg−1 FW and nitrites from 1.59 to 1.67 mg kg−1 FW. Increasing magnesium fertilisation reduced the nitrate and nitrite content of tubers but increased TGA content. Possible explanations for the TGA increase after Mg supply are discussed. Tubers that contained less TGA after harvest also had less glycoalkaloids after storage. However, physical damage during harvest or transportation, exposure to light and bad storage conditions increase the concentrations of glycoalkaloids in tubers. The consumption of cultivar “Bila” would not exceed the acceptable daily intake of harmful substances.