• E.O. ONI Department of Microbiology; Federal University of Agriculture, Abeokuta, Nigeria
  • A. ALADESIDA Department of Pure and Applied Zoology, Federal University of Agriculture, Abeokuta, Nigeria
  • T.M. OBUOTOR Department of Microbiology; Federal University of Agriculture, Abeokuta, Nigeria
  • F.O. ALDER Department of Microbiology; Federal University of Agriculture, Abeokuta, Nigeria
  • A.O. BADMOS Department of Microbiology; Federal University of Agriculture, Abeokuta, Nigeria
  • ADELEYE TOLULOPE MODUPEOLA Department of Microbiology; Federal University of Agriculture, Abeokuta, Nigeria
  • A.O. TAIWO Department of Pure and Applied Zoology, Federal University of Agriculture, Abeokuta, Nigeria
  • A.J. ADELEKE Department of Microbiology, Modibbo Adamawa University. Yola, Nigeria.



Aflatoxin, Fungi, Mycoflora, Proximate, Walnut


Aflatoxin levels in nuts and fruits pose a great threat to food storage and availability. This study aimed at determining the mycoflora and aflatoxin level in stored walnut under various conditions.  Freshly harvested walnuts were stored for 90 days  in three different media: jute bags, Plastic containers and sterile polythene bags under room (37ᵒC) and refrigeration (4ᵒC) temperature. After 90 days of storage, the stored walnuts were examined for fungal growth at one month interval after which colonial and morphological characterization were carried out to identify the fungi present. Proximate analysis and aflatoxin content of the walnut samples were determined by standard methods. Fungi isolated from the walnuts include; Aspergillus niger, Saccharomyces cerevisae, Penicillum notatum, Aspergillus sydowi, Fusarium oxysporium, and Rhizopus stolonifer. Walnuts stored in plastic container at room temperature had the lowest aflatoxin level of 0.002 ng/kg while that stored in polythene bags had the highest (0.054 ng/kg).  Proximate analysis also revealed that walnuts stored in polythene bag reduced significantly (p<0.05) in protein, ash content, fat, fibre, moisture and carbohydrates while samples stored in jute bag and plastic container remained unchanged. This study shows that storage methods contributed to the overall quality, shelf life and aflatoxin content of walnut and hence care should be taken during post harvesting process.




Amnah, M.A., Alsuhaibani 2018. Effects of storage periods and temperature on mold prevalence and aflatoxin contamination in nuts. Pakistan J. Nutrition. 17:219 – 227.

AOAC, Official Methods of Analysis, 1990. In: Association of Official Analytical Chemists (1990) AOAC Press; Gaithersburg, Washington D.C, USA. 15th Edition: 71–92.

Bankole, S.A., Ogunsanwo B. M, Eseigbe D.A. 2005. Aflatoxins in Nigerian dry – roasted groundnuts. Food Chemistry 89:503 – 506

Barnett, H.L., Hunter, B.B. 1972. Illustrated genera of imperfecti fungi, 3 ed. Burgess Publishing Company, Minnesota, U.S.A, pp: 273.

Bruhn, C., Harris, L. J., Giovanni, M., Metz, D 2010. Nuts: Safe Methods for Consumers to Handle, Store and Enjoy Almonds, Chestnuts, Pecans, Pistachios, and Walnuts. UCANR Publication 8406.

Christopoulos, M.V., Tsantili, E. 2011. Effects of temperature and packaging atmosphere on total antioxidants and colour of walnut (Juglans regia L.) kernels during storage. Sci. Hortic., 131, 49–57.

Gong, Y.Y., Cardwel, l K., Hounsa, A., Egal. S., Turner, P.C., Hall, A.J., Wild, C.P. 2002. Dietary aflatoxin exposure and impaired growth in young children from Benin and Togo: cross sectional study. British Medical Journal. 325, 20-21.

Harris, L.J. (ed.) 2013. Improving the safety and quality of nuts. Woodhead Publishing Series in Food Sciences, Tech. and Nutrition Number250, Woodhead Publishing, Cambridge, UK. 405 pp.

Iqbal, S.Z., Bhatti, I. A.. Asi, M.R., Bhatti, H.N., Sheikh M.A. 2014. Aflatoxin contamination in chillies from Punjab Pakistan with reference to climate change. International Journal of Agriculture and Biology. 13: 261 – 265.

Jimoh K.O., Kolapo A.I. 2008. Mycoflora and aflatoxin production in market samples of some selected Nigerian foodstuffs. Res Journal of Microbiology 3(3): 169-174.

Kaaya, A.N., W. Kyamuhangire, 2006. The effect of storage time and agroecological zone on mould incidence and aflatoxin contamination of maize from traders in Uganda. International Journal of Food Microbiology 110: 217 – 223.

Kader, A. A., Hussein, A. M. 2009. Harvesting and Postharvest Handling of Dates. Aleppo: International center for Agriculture Research in the dry areas. 15.

Markuszewski, B., Kopytowski, J 2015. Effects of storage conditions on the quality of unripe hazelnuts in the husk. Journal of horticultural research. 23: 59 – 67.

Mexis, S.F., Kontominas, M.G. 2010. Effect of oxygen absorber, nitrogen flushing, packaging material oxygen transmission rate and storage conditions on quality retention of raw whole unpeeled almond kernels (Prunus dulcis). LWT‐Food Science and Technology 43: 1‐11.

Milind P., Deepa, K. 2011. Walnut: Not a hard nut to crack. International Research Journal of Pharmacy 2(5) :8 – 17.

Njobeh, P.B., Dutton, M. F., Koch, S. H., Chuturgoon, A., Stoev, S., Selfert, K. 2009. Contamination with storage fungi of human food from Cameroon. International Journal of Food Microbiology 135: 193 – 198

Oluwafemi, F. 2012. Aflatoxin M1 levels in lactating mothers in two Nigerian cities. Archives of Clinical Microbiology 3(4:3), 1-6.

Ozcan, M.M. 2009. Some nutritional characteristics of fruit and oil of walnut (Juglans regia L.) growing in Turkey. Iranian Journal of Chemistry and Chemical Engineering 28; 57 – 62

Ozcan, M.M., Iman, C., Arslan, D. 2010. Physicochemical properties, fatty acid and mineral content of some walnuts (Juglans regia L.) types. Agricultural Sciences 01; 62 - 67

Stroka, J., Reutter, M., Van Holst, C., Anklam, E., 2004. Immuno affinity column clean-up with liquid chromatography using post-column bromination for the determination of Aflatoxin B1 in cattle feed: Collaborative Study. Journal of AOAC International. In press.

Reddy, B. N., Raghavender, C. N. 2010. Outbreaks of aflatoxicoses in India. African Journal Food Agric. Nutrition Dev. 7,1–15