Fish is a perishable food product, making it easily susceptible to microbial attacks. Therefore, adequate drying becomes paramount to make fish shelf-stable. In the quest for food safety, the Nigerian Stored Products Research Institute developed a rotary smoking kiln to reduce product-human contact and contamination. This study, therefore, evaluated the performance of the new kiln and the existing model-B, concerning some quality attributes of smoked fish. Catfish (Clarias gariepinus) was used for the evaluation, and charcoal and gas were used as an energy source. Quality assessments were conducted on the fish products using standard methods. The proximate qualities of the samples in the two kilns were not significantly or negatively affected. The two kilns lowered the level of heavy metals in the fish within the global permissible limits. Additionally, the PAHs of the products from the two kilns, regardless of the energy source, were lower than the global permissible limit. Out of the total PAHs recorded in the fish dried in the rotary kiln powered with charcoal (8.43 µg/kg) and gas (18.08 µg/kg), only 0.42 and 0.26 µg/kg, respectively, were carcinogenic. Similarly, 0.40 and 0.26 µg/kg were carcinogenic out of the total PAHs recorded in the samples dried in the model-B kiln powered with charcoal (9.19 µg/kg) and gas (16.54 µg/kg), respectively. The products from both kilns received good overall acceptability. Therefore, considering the addressed challenge of opening the model-B kiln before trays could be changed, resulting in reduced risk of product contamination, the rotary kiln is an improved version/model of the NSPRI smoking kiln.
As a possible substitute for synthetic insecticides, ethanolic extract of Gliricidia sepium seeds was used as a biopesticide to test its insecticidal activity against the infestation of Callosobruchus maculatus and Sitophilus zeamais in stored cowpea and maize. Four concentrations (0.1, 0.2, 0.3 and 0.4 mL of seed extract/200 g cowpea and maize) were employed in laboratory bioassays with cypermethrin as a standard check, to evaluate contact toxicity to adults, adult emergence and seed viability. Untreated grains were set up as a negative control. Treatments were in triplicate, and all experimental data were analysed using SPSS. Results showed the efficacy of gliricidia seed extract was dose-dependent. Adult S. zeamais and C. maculatus mortality increased with higher concentrations of the extract and more prolonged exposure periods. Gliricidia extract (0.4 mL/200 g) caused 75% mortality to C. maculatus 48 hours (2 days) after application, which was significantly different (p<0.05) from the 100% mortality caused by cypermethrin at the same period. Also, gliricidia extract (0.4 mL/200 g) caused 78.3% mortality to S. zeamais, significantly different from the 100% mortality caused by cypermethrin at 48 hours. Gliricidia extracts at concentrations 0.3 mL and 0.4 mL/200 g cowpea (37.0 % and 24.33% respectively) were better than the control 56.33% in reducing the number of emerged adult C. maculatus while extracts at concentrations 0.3 mL and 0.4 mL/200 g maize (22.33% and 27.67% respectively) were more effective than the control 64.3% in reducing the number of emerged adult S. seamais. The mean percentage germination of the cowpea and maize seeds in each treatment did not vary significantly (p > 0.05). The efficacy of this plant extract serves as scientific evidence to argue for employing the gliricidia extract as a botanical substitute for synthetic insecticides, which stakeholders commonly use to protect grains stored after harvest.