Heavy metal and microbial safety assessment of raw and cooked pumpkin and Amaranthus viridis leaves grown in Abakaliki, Nigeria

Abstract

In this study, heavy metal and microbial safety assessment of raw and cooked pumpkin and Amaranthus viridis leaves grown in Abakaliki, Nigeria, was examined. The levels of lead (Pb), arsenic (As), chromium (Cr), cadmium (Cd), and mercury (Hg) were evaluated using atomic absorption spectrophotometer. The microbial cells were counted and further identified to species level using 16S rDNA and ITS rDNA sequencing analysis at CABI microbial identification services United Kingdom (UK). The results showed that the heavy metal concentrations of lead (10.5, 12.0), arsenic (7.5, 8.5), chromium (0.9, 0.1), and mercury (13.1, 14.0) in the pumpkin and A. viridis leaves, respectively, were above maximum acceptable limit according to relevant national and international food regulatory agencies (Tables 1 and 2). Cooking significantlyreduced the concentrations of the heavy metals at (p > 0.05) to or below, lead (6.8, 8.4), arsenic (5.1, 6.1), chromium (0.6.0.1), and mercury (9.5, 11.4) in the pumpkin and A. viridis leaves, respectively, but still not to international safe limit. The result of the microbial safety assessment showed that the microbial load of both the pumpkin and Amaranthus viridis leaves were above acceptable limit and the contaminating organisms were identified as Escherichia coli (504743), Klebsiella pneumonia (504744b), and Aspergillus flavus (504740).This study therefore shows that the vegetables (pumpkin and A. viridis leaves) contain unacceptable levels of toxic heavy metals and potentially dangerous pathogenic microorganisms, thus present significant health risk for the consumers.

Occurrence of Trace Metals in Food Crops Grown on the Mbale Dumpsite, Uganda, and Human Health Risks

“…Except for Z. mays seeds, the measured Cr concentrations in crop parts were higher than the WHO/FAO food safety standards of 0.2 mg/kg for vegetables (Nabulo et al 2010). The Cr concentrations measured in most crop parts were below the recommended levels of 1.3 mg/kg for plants (Azi et al 2018) and 1.0 mg/kg for cereals and vegetables (Choi 2011). In other studies (Table 3), the Cr concentrations in Z. mays leaves (Muchuweti et al 2006), Amaranthus leaves (Olowoyo et al 2012), and leafy vegetables (Rahman et al 2014) were higher than those measured at the Mbale dumpsite.…”

“…In this study, the Cd concentrations were lower than the Codex and WHO/FAO food standard limits of 0.1 to 0.2 mg/kg (Nabulo et al 2010; Choi 2011; Azi et al 2018). Hg concentrations were above the limit of 0.001 mg/kg (WHO/FAO) (Azi et al 2018) but within the 0.05 mg/kg (Muchuweti et al 2006) and 0.5 mg/kg (EFSA) limits for solid foods (Choi 2011). Arsenic concentrations (0.05 mg/kg) were lower than the WHO/FAO food limit value of 0.1 mg/kg (Azi et al 2018), but higher than the FSANZ limit of 0.005 mg/kg (Rahman et al 2014).…”

“…Mean Pb concentrations in crop parts ranged from <0.05 mg/kg ( Z. mays seeds) to 0.8 ± 0.6 mg/kg ( Amaranthus leaves) (Table 2). Except Pb concentrations in Z. mays seeds, the other crop parts exhibited levels above WHO/FAO and EFSA food standards of 0.3 mg/kg (Nabulo et al 2010; Azi et al 2018) and 0.1 mg/kg (Choi 2011; Rahman et al 2014; Azi et al 2018), respectively. In other studies, higher Pb concentrations have been reported in Z. mays seeds (Oluyemi et al 2008), roots (Cortez and Ching, 2014), and other crop parts (Muchuweti et al 2006) (Table 3).…”

“…The mean concentrations for Cd, Hg, and As in the 2 crops were <0.05 to 0.06 ± 0.04 mg/kg, <0.05 mg/kg, and <0.05 to 0.06 ± 0.03 mg/kg, respectively. In this study, the Cd concentrations were lower than the Codex and WHO/FAO food standard limits of 0.1 to 0.2 mg/kg (Nabulo et al 2010; Choi 2011; Azi et al 2018). Hg concentrations were above the limit of 0.001 mg/kg (WHO/FAO) (Azi et al 2018) but within the 0.05 mg/kg (Muchuweti et al 2006) and 0.5 mg/kg (EFSA) limits for solid foods (Choi 2011).…”

“…Hg concentrations were above the limit of 0.001 mg/kg (WHO/FAO) (Azi et al 2018) but within the 0.05 mg/kg (Muchuweti et al 2006) and 0.5 mg/kg (EFSA) limits for solid foods (Choi 2011). Arsenic concentrations (0.05 mg/kg) were lower than the WHO/FAO food limit value of 0.1 mg/kg (Azi et al 2018), but higher than the FSANZ limit of 0.005 mg/kg (Rahman et al 2014). Concentrations of Cd and Hg measured in Z. mays leaves and seeds were similar to Cd concentrations in crops from Manilla (Cortez and Ching 2014) and Hg concentrations in crops from Zimbabwe (Muchuweti et al 2006) (Table 3).…”