Biopreservative Effect of Neem Extract and Storage Methods on the Nutritional Composition of White Yam (Dioscorea rotundata)
Alex Aduojo Iyaji
*
Rev. Fr. Moses Orshio Adasu University, Makurdi, Nigeria.
Moses O. Obasi
Joseph Sarwuan Tarkaa University, Makurdi, Nigeria.
Sonter Samuel Teryila
Rev. Fr. Moses Orshio Adasu University, Makurdi, Nigeria.
Ukaa Gilbert Terna
National Root Crops Research Institute, Umudike, Abia State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Yam (Dioscorea rotundata) is an important staple crop of high food value but suffers considerable postharvest losses. This study investigated the biopreservative effect of neem (Azadirachta indica) extract and storage methods on the nutritional composition of white yam. Yam tubers and neem samples were collected from farmers in Makurdi for a preservative experiment set up as a 3 × 3 factorial in a completely randomised design with three replicates. Three treatments were used (neem leaf, neem bark and a control), along with three storage methods (racks, barns and trench silos). A total of 540 yam tubers was used for a storage duration of six months. Proximate composition was determined using standard analytical methods. Data were analysed using analysis of variance (ANOVA), and Fisher’s least significant difference was used at the 5% significance level. Results showed no significant differences (P > 0.05) in all nutritional parameters before storage; however, significant declines were observed across all parameters after storage (P < 0.05). Neem leaf and bark treatments recorded lower post-storage moisture contents (50.20% and 54.40%, respectively) than the control (58.10%). Higher ash, fat, protein, carbohydrate and fibre contents were recorded in yam treated with neem leaf extract (1.38, 0.13, 1.30, 26.80 and 3.82, respectively) than in neem bark-treated samples (1.22, 0.12, 1.12, 23.91 and 3.05, respectively) and the control (1.05, 0.10, 0.96, 20.42 and 2.14, respectively), and the differences were significant (P < 0.05). Yams stored on racks also showed significantly better nutrient retention (1.41, 0.14, 1.34, 27.22 and 3.96 for ash, fat, protein, carbohydrate and fibre, respectively) (P < 0.05). The interaction of neem bark extract and rack storage recorded higher values for ash, fat, protein, carbohydrate and fibre (1.29, 0.13, 1.22, 26.13 and 3.94, respectively), whereas moisture content was highest in the control-rack combination (61.20%). The study concluded that neem extract exhibits biopreservative properties, particularly when combined with well-ventilated storage systems such as rack storage. Neem leaf extract displayed higher preservative ability for yam storage than neem bark extract when used alone. It is therefore recommended that farmers adopt the combined use of neem extract and rack storage to minimise postharvest losses and preserve yam nutritional quality.
Keywords: Yam, neem, Biopreservation, storage, nutrition, composition, postharvest loss