Fungal species isolated from peanuts in major Kenyan markets: Emphasis on Aspergillus section Flavi

Abstract

A survey was conducted in Nairobi, Nyanza and Western provinces in Kenya between March and July 2009 with 1263 peanut products sampled out of which 705 samples underwent microbial analysis. The study aimed at determining the incidence of fungal species e emphasis on Aspergillus section Flavi e associated with peanut products. A 0.5 kg representative sample was obtained from each surveyed vendor and the colony forming units (CFU) of fungal species determined. The samples were also analyzed for total aflatoxin level while isolates of Aspergillus flavus and Aspergillus parasiticus were screened for production of aflatoxin B1, B2, G1 and G2. Eight fungal species were detected in the samples and were in decreasing order of CFU/g of sample: A. flavus S-strain (467), A. flavus L-strain (341), Penicillium spp. (326), Aspergillus niger (156), Aspergillus tamari (27), Aspergillus alliaceus (21), A. parasiticus (10), and Aspergillus caelatus (5). The overall incidence of A. flavus S-strain in samples from Nairobi was 92 and 1425% higher than samples from Nyanza and Western regions, respectively. The combined incidence of A. flavus and A. parasiticus was varied significantly (p 0.05) with peanut product: peanut flour (69%), shelled raw peanuts (53%), spoilt peanuts (49%), boiled podded peanuts (45%), podded peanuts (39%), peanut butter (31%), fried peanuts (22%) and roasted peanuts (20%). Seventy three percent of A. flavus and A. parasiticus isolates produced at least one of the aflatoxin types, with 66% producing aflatoxin B1. The total aflatoxin level among peanut products ranged from 0 to 1629 mg/g; and there was a positive correlation (r ¼ 0.2711) between the incidence of A. flavus and A. parasiticus, and total aflatoxin level. The high incidence of aflatoxin producing fungi in peanuts traded in Kenyan markets implies a risk of aflatoxin contamination, highlighting the need for stakeholders to promote sound practices at all stages of the peanut value chain in order to minimize market access by non-complying products.

Changes in Fungal Population and Aflatoxin Levels and Assessment of Major Aflatoxin Types in Stored Peanuts (Arachis hypogaea Linnaeus)

“…Previous studies have reported isolation of diverse fungal pathogens from peanuts in Kenya (Mutegi et al 2012;Wagacha et al, 2013). Although A. flavus and A. parasiticus are the species most frequently implicated in aflatoxin contamination (Cotty, 2006), the wide fungal species diversity poses a health risk of exposing peanut consumers to other secondary metabolites.…”

“…Peanuts in Kenya are frequently infected by A. flavus and A. parasiticus (Mutegi, Ngugi, Hendriks, & Jones, 2012;Wagacha, Mutegi, Karanja, Kimani, & Christie, 2013) and this infection can occur at all stages in the peanut value chain (Waliyar et al, 2005). Determination of the level of fungal infection of a foodstuff as well as establishing the occurrence of common species is important as the fungal population and diversity could give an indication of the food quality and the presence and types of mycotoxins (Suanthie, Cousin, & Woloshuk, 2009).…”

Susceptibility of locally cultivated groundnut (Arachis hypogaea) varieties to aflatoxin accumulation in Homa Bay County, Kenya

“…These findings do not resonate provisions by Wagacha et al (2013). According to Wagacha et al (2013), the incidence and population of A. flavus S-strain significantly and positively correlate with the levels of total aflatoxin in groundnuts. This may be due to sample size.…”

“…High aflatoxin contamination levels (above the 10 ppb limit set by KEBS) have also been reported in raw and processed groundnuts from different regions in Kenya (Gachomo et al, 2004;Mutegi et al, 2012Mutegi et al, , 2013Wagacha et al, 2013). In a recent study Mutegi et al (2012), 37% of groundnuts including products like groundnut butter and groundnut flour sampled from Nairobi, Nyanza and Western Kenya failed to meet the 10 ppb total aflatoxin limit set by the Kenya Bureau of Standards (KEBS, 2007).…”

Determination of aflatoxin B1 in food products in Thailand

“…Several researchers have investigated peanuts for the presence of Aflatoxins, particularly AFB1 (Bankole et al, 2005;Barro et al, 2002;Mutegi et al, 2009). Iqbal et al (2013) reported the level of AFB1 ranging from 2.4 to 12.3 µg/kg but Wagacha et al (2013) reported AFB1 level in peanut products ranging from 0 to 1629 µg/kg. Therefore, our study is in agreement with other previous studies in other countries on the natural occurrence of AFB1 in peanut samples.…”