Abstract:
Neem seed is known to serve as antimicrobial agent on agricultural commodities. However, the
consumption of its high dosage pose a health risk due to presence of other antinutritional factors.
There is limited information on appropriate treatments for reduction of the antinutrients in neem
seed to safe consumption level. There is need to further determine effects of some treatments on
neem seed chemical properties to ensure safety for consumption. Thus, this study was designed
to investigate the effects of steeping in water, alkaline solution and roasting on neem seed and
toxicity of using its oil as a food preservative.
Neem seeds were subjected to three treatments based on preliminary studies such as; steeping in
water, and 40% NaOH solution for 24 h, and roasting for 10 min at 60oC. Proximate (crude
protein, oil, crude fibre, ash, moisture and carbohydrate contents), minerals (Ca, Na, Mg, P, K,
Cu, Zn, Fe, Mn and Se) and anti-nutrients contents (cyanide, nitrate, oxalate, phytate, tannin and
azadirachtin) ofun-treated and treated seeds were determined using AOAC methods. Oil was
extracted from raw and roasted seeds using hydraulic press.Fatty acid profile and bioactive
compounds of the oil were determined using standard method. Weevil infested grains (maize,
beans and rice), Fermented Locust Beans (FLB), and mouldy onions were treated with different
concentrations (0.6. 0.7, 0.8, 1.0, 2.0 and 3.0 mL/200g) of oil extracted from roasted seed. The
samples were stored at ambient conditions (26.0±2.0oC, RH 70%) for 45 days.Weevils
population in grains and microbial growth on FLB and onions were determined weekly, using
established procedure. Toxicity of roasted seed oilwas conducted using male and female rats
(100.0±5.0g) in a group of three (n = 5), fed with FLB (control, 1.0, 2.0 and 3.0µL/100g) for 13
days. Haematology and histopathology of kidney, liver, heart, testes and ovaries for rats were
done. Data were analysed usingANOVA at α0.05.
Crude protein, oil, crude fibre, ash, moisture and carbohydrate contents of untreated seed were
18.6±0.07, 41.2±0.03, 3.6±0.04, 2.6±0.05, 6.0±0.02 and 28.1±0.02%; while treated were 16.9-
19.1, 40.4-41.8, 3.5-3.6, 2.4-2.6, 5.9-12.1 and 24.4-28.1%, respectively. The seeds had high
contents (mg/100g) of Fe (16364.0-16482.0), Zn (2463.0-2398.0) and Mn (1164.3-1182.0).
Steeping in water significantly reduced cyanide (45.0%), nitrate (12.5%), tannin (50.0%) and
Azadirachtin (16.7%) contents. Major fatty acids in neem oil were oleic (39.10±0.03), linoleic
(18.60±0.03), stearic (17.70±0.02) and palmitic (14.5±0.01%) acids. Roasting significantly
affected the oil profiles. Fourteen bioactive compounds were detected with dominants being nHexadecanoic acid (28.62%), 9,12, 15-Octadecatrienoic acid (17.1%), Neophytadiene (13.7%),
Hexadecanoic acid (10.0) and 9,12-Octadecadienoic (8.3%). Highest percentage weevils’
mortality of 59.2% in maize, 41.25% in beans and 36.67% in rice were recorded at 0.6, 0.7 and
0.8 mL/200g, respectively. E-coli, Pseudomonas, Staphylococcusaureusand Bacillus sp were the
organisms detected in stored FLB. The microbe populations were significantly reduced by the
oil. No spoilage was recorded from treated onions. Reduced erythrocytes and degradation of
hepatocyte were observed in rat tissues fed with 3 µL/100g dose, an indication that the
concentration was outside the safe limit for rat.
The treatments reduced antinutritional factors in neem seed. Oil from roasted neem seed reduced
weevils in grains and retarded microbial multiplication on fermented locust beans and onion.
Low oil dosage is recommended.
