Proximate analysis and phytochemical and mineral constituents in four cultivars of yams and tuber crops in Sri Lanka

Abstract

A study was carried out to determine the levels of starch, protein, crude fat, crude fibre, ash and a few phytochemical constituents (saponins, flavanoids and alkaloids) and mineral elements (Calcium, Magnesium, Iron, Potassium and Zinc) in four cultivars of yams and tubers cultivated under similar agro-climatic conditions in Sri Lanka. Tubers of Dioscorea alata (Rajala and Hingurala), Dioscorea esculenta (Kukulala) and Xanthosoma sagittifolium (Kiriala) were subjected to the above analyses. The total starch percentage in crude flours ranged between 74.66 ± 0.66 to 80.46 ± 0.62% on dry weight basis and no significant difference found in total starch (P <0.05) between the studied varieties. The protein level ranged from 2.66 ± 0.21 to 10.16 ± 0.64% whereas D. alata was found to contain a higher protein level. The crude fat levels in tubers varied ranging from 1.5 ± 0.2 to 2.3 ± 0.1% and the highest level was observed in Xanthosoma sp. The crude fibre content in tubers was found to range from 1.8 ± 0.1 to 2.33 ± 0.15% and the highest level was observed in D. esculenta and the ash level ranged from 1.66 ± 0.21 to 2.33 ± 0.21%. There was no significant difference (P<0.05) between the total starch in the extracted starch from the tubers and ranged from 86.3 ± 1.2 to 89.85 ± 1.11%. Crude saponin levels were significantly higher (P<0.05) in yams while D. alata and X. sagittifolium contained a level which was comparable (P> 0.05; 12.98 ± 0.61 and13.11 ± 0.52 mg/100g. High amount of flavonoids were observed in D. esculenta and X. sagittifolium (12.4 ± 0.46 and 11.26 ± 0.46 mg/100g). A considerable level of alkaloids was present in D. alata and D. esculenta (1.64 0.04 ± mg/100g and 1.89 ± 0.02 mg/100g). All three cultivars of yams were rich in Calcium and Iron while a high level of Magnesium was observed in Xanthosoma sp (45.27± 0.31 mg/100g). High levels of Potassium were observed in all the samples.