Effects of processing methods on nutrient retention and contribution of white yam (Dioscorea rotundata) products to nutritional intake of Nigerians

Abstract

Consumption of indigenous foods is being encouraged globally as a means of meeting dietary needs of people. Yam products constitute staple source of energy to many Nigerians but little is documented on their nutrient composition. This study was carried out to determine the effects of processing methods on nutrient retention and possible contribution of some diets prepared from yam to nutrient intake of consumers. Fresh yam tubers were purchased from Sango market in Ibadan, peeled and cut into small pieces, then divided to eight portions. One portion was treated as raw sample while others were processed into roasted, fried, boiled, pounded yam (two samples), amala and porridge. All samples were analysed for proximate, energy and mineral composition using standard methods of AOAC and atomic absorption spectrophotometric methods. Raw yam was very low in crude protein (2.3 g), lipid (0.8 g), and fibre (1.4 g) moderate in ash (3.4 g), iron (4.1 mg) and zinc (5.6 mg), high in carbohydrates (33.3 g), energy (369.6 kcal), sodium (580 mg) and potassium (470 mg) /100 g edible portion. Roasting and frying brought significant improvement on crude protein, lipid and energy content of the products (p<0.05). Boiling yam caused significant reduction in all nutrient content except fibre, while boiling and pounding yam significantly improved its crude lipid, ash and energy content (p<0.05). Frying and using water for boiling yam in pounded yam preparation brought significant retention of nutrients in yam. Processing yam to amala and porridge resulted in significant improvement in nutrient content of the diets. Diets from yam can serve as good source of energy and minerals, and their 100 g portion can contribute between 12.4 to 20.9% gross energy, 11.0 to 46.0% iron and 17.3 to 48.7% zinc to recommended dietary allowances (RDAs) of consumers.

A comparative assessment of nutrients and anti-nutrients contents of varieties of fried yam (<i>Dioscorea specie</i>) commonly consumed in Nigeria

“…On the other hand, Polycarp et al (2012) reported that carbohydrate in different yam varieties range from 77.5 to 87.3 g/100g. However, the carbohydrate content in fried yams in this study were lower than the reported carbohydrate content (53.8 g/100g) obtained in fried yam (Adepoju, 2012) previously. The lower carbohydrate content in this study could be due to pre-boiling of samples prior to frying.…”

“…It is obvious that differences in yam samples and processing methods play significant role in determining nutrient content of various yambased meals commonly consume in Nigeria and other African countries. The low fibre content in fried yam samples (0.9 -2.0 g/100g) concur with previous findings of 1.2 g/100g in fried yam (Adepoju, 2012). Other studies showed fibre content of between 0.39 g/100g and 7.69 % in yams processed in various ways ranging from raw, boiled, pounded, porridge, etc.…”

“…Other studies showed fibre content of between 0.39 g/100g and 7.69 % in yams processed in various ways ranging from raw, boiled, pounded, porridge, etc. (Lawal et al, 2012;Marfo et al, 1990;Udensi et al, 2008 and2010;Ezeocha and Ojumelukwe, 2012;Polycarp et al, 2012;Adepoju, 2012;Shajeela et al, 2011). These results suggest the effect of processing methods on fibre content of yam.…”

Nutrient Composition and Adequacy of two Locally Formulated Winged Termite (Macrotermes Bellicosus) Enriched Complementary Foods

“…The fermented flour were low in moisture and fat content, which is an indication that they can be kept for a period of time before they go bad. They were moderate in protein content compared with that of other plant-based staples used for complementary foods such as yam and rice (Adepoju, 2012;Otegbayo et al, 2001). However, the two fermented flour were high in ash, total carbohydrates and gross energy content.…”

“…The fermented flour were however low in all the water soluble vitamins except vitamin B 12 . The low level of these vitamins is believed to be due to the extent of soaking of the fermented sample, as it has been reported that soaking food samples for a period of time leads to leaching of the water soluble micronutrients into the soaking water (Adepoju et al, 2010, Adepoju, 2012. Addition of M. bellicosus powder led to remarkable increase in the β-carotene content of the enriched foods, the increment being due to the vitamin A content of the insect, which has been previously reported to be a good source of vitamin A (330.42±0.12 µg/100g, Adepoju & Omotayo, 2014).…”