This study evaluated the potential impact of environmental factors and harvesting practices on microbial load of macadamia nuts. Three farms located in the main macadamia nut production regions including Mbombela (A), Barberton (B) and White River (C) areas in Mpumalanga Province, South Africa were sampled over a ,rtwo-year period. A total of 264, irrigation water (54), soil (30) and macadamia nut (180) samples were collected and evaluated for microbial concentrations. All water samples had mean E. coli counts below 1000 CFU/100ml which is the standard regulatory requirement for agricultural water considered fit-for-purpose for irrigation of nut trees in south Africa. Mean total aerobic plate counts of on-tree nut-in-husk samples (3.91 log CFU/g; n=60) increased after harvesting (5.98 log CFU/g; n=60) but decreased with dehusking to 4.89 log CFU/g (n=60) on nut-in-shell. Salmonella spp. were only detected in water samples from two farm B (67 %; n=18) and C(15 %; n=18). However, neither Listeria monocytogenes nor Salmonella spp. were detected in any of the soil samples. Escherichia coli were only detected in 20 % (n=10) of soil samples collected from two farms (A and B). None of the E. coli isolated in this study were positive for the eae, stx 1, and stx 2, enterohaemorrhagic E. coli (EHEC), virulence genes. Information from this study provides basic data that can be used in the development of macadamia nut specific hazard assessment tools within primary production environments.
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