Chemical Composition, Amino Acids, Phenolic Profiles and Bioavailability of Minerals in Livingstone Potato ( Plectranthus esculentus ) as Affected by Different Processing Techniques

ABSTRACT The purpose of this study is to assess the impact of cooking methods on the chemical composition and bioavailability of minerals in Plectranthus esculentus tubers. Analysis of the chemical composition and bioavailability of minerals in Plectranthus esculentus tubers was performed using standard protocols. Boiling increased the moisture and decreased the total protein, total amino acids and some minerals but did not affect the ash, crude fibre, fat, total carbohydrates, energy value, phytates, tannins, oxalates, trypsin inhibitor, saponin, Pb, Cd, Ar, Mg, Ni, Mo, Al, vanadium, Be and Au; frying increased the total fat content; decreased the total proteins, amino acids and some minerals; and depleted Be but did not affect the moisture, ash, crude fibre, carbohydrates, energy value, phytates, tannins, oxalates, trypsin inhibitor, saponin, Pb, Cd, As, Ni, Mo, Al, vanadium and, Au; roasting decreased the total protein, total amino acids and some minerals; depleted Pb, Ni and Be but did not affect the moisture, ash, crude fibre, fat, total carbohydrates, energy value, phytates, tannins, oxalates, trypsin inhibitor, saponin, Cd, As, Mo, Al, vanadium and Au contents of the tuber compared to the raw tubers. Raw and processed Plectranthus esculentus tubers were good sources of some important nutrients, phenolic and flavonoid compounds. Boiling retained the nutrients and polyphenol compounds in the tubers better than frying or roasting. A bioavailability study showed that the phytates and oxalates in the tuber may not affect the bioavailabilities of calcium, zinc or iron in it when eaten. Consumption of raw and processed Plectranthus esculentus tubers could be relevant in curbing nutrient deficiency for people in tropical regions where this tuber is eaten as food. For the purpose of processing, boiling may be more useful than frying or roasting, for utilization of the nutrient and bioactive compounds of this tuber.