Department of Plant and Soil Sciences, University of Pretoria, Lynnwood Road, Pretoria 0001, South Africa, and Private Bag X20, Hatfield, Pretoria 0028, South Africa.
J Food Prot. 2021 Jun 1;84(6):1088-1096. doi: 10.4315/JFP-20-238.
This study evaluated the potential impact of environmental factors and harvesting practices on the microbial load of macadamia nuts. Three farms located in primary macadamia nut production regions, the Mbombela (A), Barberton (B) and White River (C) areas in Mpumalanga Province, South Africa, were sampled over a 2-year period. A total of 264 irrigation water (54), soil (30), and macadamia nut (180) samples were collected and evaluated for microbial load. All water samples had mean Escherichia coli loads below 1,000 MPN/100 mL, which is the standard regulatory requirement for agricultural water considered fit for irrigation in South Africa. Mean total aerobic plate counts of nut-in-husk on-tree samples (3.91 log CFU/g; n = 60) were higher after harvesting (5.98 log CFU/g; n = 60) but were lower after dehusking (to 4.89 log CFU/g; n = 60) on nut-in-shell samples. Salmonella spp. were only detected in water samples from farm B (67%; n = 18) and farm C (15%; n = 18). Neither Listeria monocytogenes nor Salmonella spp. were detected in the soil samples. E. coli was only detected in 20% (n = 10) of soil samples collected from two farms (farms A and B). None of the E. coli isolated in this study was positive for the eae, stx1, and stx2 enterohemorrhagic E. coli virulence genes. This study provides basic data that can be used in the development of macadamia nut-specific hazard assessment tools within primary production environments.
本研究评估了环境因素和收获实践对澳洲坚果微生物负荷的潜在影响。在南非姆普马兰加省的主要澳洲坚果生产区，包括姆波姆贝拉（A）、巴伯顿（B）和怀特河（C），对三个农场进行了为期两年的采样。共采集了 264 个灌溉水（54 个）、土壤（30 个）和澳洲坚果（180 个）样本，并对微生物负荷进行了评估。所有水样的大肠杆菌负荷均值均低于 1000MPN/100mL，这是南非适合灌溉的农业用水的标准监管要求。带壳坚果树上样本的总需氧平板计数（3.91logCFU/g；n=60）在收获后（5.98logCFU/g；n=60）较高，但在去壳后（至 4.89logCFU/g；n=60）较低。在农场 B（67%；n=18）和农场 C（15%；n=18）的水样中仅检测到沙门氏菌。土壤样本中未检测到李斯特菌和沙门氏菌。仅在两个农场（农场 A 和 B）采集的 20%（n=10）土壤样本中检测到大肠杆菌。本研究中分离的大肠杆菌均未携带肠出血性大肠杆菌的 eae、stx1 和 stx2 毒力基因。本研究提供了基础数据，可用于开发初级生产环境中针对澳洲坚果的特定危害评估工具。
