Effect of Boiling on the Nutritional Value, Phytochemical Contents, and Antioxidant Activity of Commonly Consumed Potato (Solanum tuberosum L.) Varieties in Bangladesh

Potatoes (Solanum tuberosum L.) are one of the common vegetables in Bangladesh. The present study was aimed to assess the effect of boiling on the nutritional value, phytochemical contents, and antioxidant activity of two commonly consumed potato varieties in Bangladesh; Lal Sheel and Diamant. Our results show that boiling increased moisture and crude fiber contents while ash, crude lipid, carbohydrate, and protein contents decreased in both potato varieties. Both Lal Sheel and Diamant potatoes contained considerable amounts of polyphenols (expressed as gallic acid equivalents, mg GAE per 100g sample), flavonoids (expressed as catechin equivalents, mg CE per 100g sample) and tannins (expressed as tannic acid equivalents, mg TAE per 100g sample) and all those significantly decreased after boiling. However, boiled Lal Sheel potato retained higher amounts of these phytochemicals [368.23±13.05 mg GAE/100g, 351.91±31.45 mg CE/100g, and 3946.54±298.72 mg TAE/100g, respectively] than those of boiled Diamant variety [329.12±3.72 mg GAE/100g, 312.51±12.18 mg CE/100g, and 2897.72±454.54 mg TAE/100g, respectively]. Like phytochemicals, antioxidant activity also decreased after boiling, as measured by ferric reducing antioxidant power (FRAP), phosphomolybdate reduction, and total reducing power assays, as well as, 1,1-diphenyl-2-picrylhydrazyl- (DPPH)-radical scavenging activity. Vitamin C content was good but β-Carotene, vitamin A, vitamin B1, B2 and essential minerals including iron, zinc, copper contents were relatively low, all of which also decreased after boiling. Despite the negative impacts of boiling, both Lal Sheel and Diamant boiled potatoes retained good amounts of nutrients, as well as, phytochemicals possessing antioxidant activity and thus are beneficial foodstuffs for health.