Evaluation of selected food properties of white yam (Dioscorea rotundata) in Papua New Guinea.

Abstract

White yam, Dioscorea rotundata Poir., has recently been introduced for cultivation in Papua New Guinea to increase yam production and provide varieties for yam consumers and potential processors. Physical, chemical, functional, and sensory properties of the introduced yam species, TDr-90-1-1 cultivar, were assessed in relation to popular cultivars, Takua Yavu and Glame, respectively of D. alata and D. esculenta. D. rotundata was the most difficult to peel (manually and mechanically) and gave the highest dry matter. The pH of its water-extract was slightly acidic as were for others (5.7-6.7) but the extract had the lowest solids content. D. rotundata slices (6 mm) absorbed less water but slightly more oil. It exhibited the slowest rehydration behaviour and its 4% slurry was the most viscous at 20 revmin in a rotational viscometer as a cold (35°C, 1.56 Nsm2) or hot (75°C, 0.83 Nsm'2) paste. Sensory evaluation revealed that it was essentially as acceptable as D. esculenta when cooked or fried as chips but better than D. alata. The perceived bitter after-taste and irritation upon chewing and swallowing products from D. rotundata suggested that its content of anti-nutritional (oxalates, tannins and phytic acid) components may be higher than normal and should be quantified for complete acceptability of the yam as a food material. The potential of D. rotundata for food production in PNG is good and ought to be pursued.