EVALUATION OF FUNGI ASSOCIATED WITH GROUNDNUT CAKE (KULIKULI) SAMPLES FROM SELECTED NORTHERN NIGERIAN STATES AND THEIR CONTROL WITH SOME BOTANICALS

Abstract

Groundnut cake (Kulikuli) is a common snack in Nigeria prepared from groundnut (Arachis hypogaea L.). Food contamination by aflatoxin-producing fungi remains a major health challenge in Nigeria. Fungal contamination in Kulikuli occurs during production, handling, storage and transportation. However, research on Kulikuli has focused on microbial characterisation and nutritional value. There is dearth of information on fungal infestation, mycotoxin production in Kulikuli and their control with botanicals having anti-fungal properties. Therefore, this study was aimed at evaluating fungi associated with Kulikuli production, aflatoxin secretion and their control using selected botanicals.

Twenty five Kulikuli samples each were purchased from selected markets with Kulikuliproduction centres in Kano (Rimin Gado, Janguza, Kurmi, Sabongari, Rimi); Kaduna (Bacci, Kaduna Central, Kawo, Sabuwar Gari, Kakuri); Sokoto (Kanawa, Ilaela, Dange Shuni, Jabo, Yan tumatir); Zamfara (Bungudu, Tsohuwar Kasuwa, Dampa Sabuwar Kasuwa, Tudun Wada) and Abuja (Utako, Wuse, Madalla, Dutse, Bwari). Fungi associated with the Kulikuli samples were isolated and identified using morphological and molecular characterisations. Kulikuli with botanicals (MLB) and without botanicals (ML) were also prepared at the Mycology Laboratory Department of Botany as controls. The botanicals used were garlic, ginger and turmeric.Proximate analysis and aflatoxins (AFB1, AFB2, AFG1 and AFG2) contents of the samples were determined using standard procedures. Ten Simple Sequence Repeat primers were used for aflatoxin genes (AT, AN, AP, AFUM and FUS) in each isolated fungus. Data obtained were subjected to descriptive statistics and Analysis of Variance (ANOVA) at α0.05.

One hundred and six fungi were isolated and identified as Aspergillusflavus (n=28), A. parasiticus (n=26), A. niger (n=7), A. tamarii (n=9), A. fumigatus (n=3), Penicillium oxalicum (n=11), P. chrysogenum (n=6), Fusarium oxysporum (n=10)and F.compaticum (n=6). All fungi isolated from market samples, except A. fumigatus and P. oxalicum were also isolated from Kulikuli samples prepared in ML without botanicals. Kulikuli samples with botanicals had no fungal incidence. Kulikuli samples from the markets compared with MLB and ML samples were significantly different in moisture content (11.91, 6.64, and 12.64%), ash (3.91, 4.84, and 4.84%), crude protein (49.23, 59.23, and 50.25%), fibre (3.20, 4.55, and 4.05%), fat (4.83, 3.26, and 3.83%) and pH (6.30, 6.88, and 6.84), respectively. Market samples had the highest AFB1, AFB2, AFG1 and AFG2 of 1.64, 2.10, 0.10 and 0.13 µg/kg, respectively, while samples treated with garlic had the least AFB1 (0.34µg/kg), AFB2 (0.37µg/kg), AFG1 (0.01µg/kg) and AFG2 (0.02µg/kg). Aflatoxin concentrations in MLB and ML samples were within tolerance limits of NAFDAC and European Union 4 µg/kg. The aflR, nor, ver and omt biosynthetic pathway genes found in aflatoxin producing fungi were detected in all fungi isolated from the purchased Kulikuli except strains from Kaduna (Kaduna Central) samples. However, the MLB samples yielded no fungal growth.

Kulikuli samples from the studied areas were infested with nine fungi species. Aspergillus spp were the dominant fungi found to be most prevalent in the market samples. The addition of garlic during production of Kulikulibest suppressed fungal infestation and reduced aflatoxin levels.