Evaluation of colour in white and yellow trifoliate yam flours in relation to harvesting periods and pre-processing methods

Colour is one of the important sensory properties that determine the acceptability of food products. Therefore, this work determines the colour in white and yellow trifoliate yam flours in relation to harvesting periods and pre-processing methods. Freshly harvested trifoliate yam tubers were prepared into flour using four pretreatment (untreated, soaking at ambient temperature, soaking at 60 oC and parboiling at 98 oC±2) methods. The flour colour was analyzed and the whiteness index was determined. L？ (brightness) value ranged from 68.90 in parboiled yellow trifoliate yam harvested at 8 months to 96.57 in the raw white trifoliate flour harvested at 9 months. Parboiled trifoliate yams from the two cultivars harvested at 11 months were darker in colour than other flour. Parboiled yellow trifoliate yam flours were significantly (p>0.05) different from other samples in colour. The intensity of colour of the parboiled yellow trifoliate yam flour was more pronounced than others. However, the colour of the flour became deeper with prolonged harvesting periods and prominent in parboiled samples at 11 months.