title: Evaluation of microbial loads and the effects of antimicrobial sprays in postharvest handling of California walnuts.
abstract: Changes in aerobic plate count (APC) and Escherichia coli/coliform count (ECC) of inshell walnuts and walnut kernels were evaluated during commercial harvest and postharvest handling. APC and ECC for inshell walnuts collected from the tree were 6 and 4 log CFU/nut, respectively; counts increased by 1 log during harvest and hulling and decreased by 1 log during drying. Application of up to 200 ppm peracetic acid after hulling with or without a subsequent 2% lauric arginate spray reduced APC and ECC by less than 1 log CFU/nut; counts were not significantly different from the water control. A decrease in shell integrity was evident after drying: visible shell damage increased from 4 to 47% of walnuts after drying. Counts on kernels extracted from visibly intact walnuts from the tree were near the limit of detection (1.7 log CFU/nut). These counts increased by at least 1.4 log CFU/nut after hulling for both thin- and hard-shell cultivars. Microbial populations were 1.6-2.2 log CFU/nut higher for kernels from walnuts with broken shells than for kernels from walnuts with visibly intact shells before, but not after, drying. A better understanding of how microbial populations are affected by postharvest handling practices is important in the development of walnut-specific food safety programs.
authors: Department of Food Science and Technology, University of California, One Shields Avenue, Davis, CA 95616-5270, USA.
authors: John C
authors: JC
authors: Frelka
authors: Department of Food Science and Technology, University of California, One Shields Avenue, Davis, CA 95616-5270, USA. Electronic address: ljharris@ucdavis.edu.
authors: Linda J
authors: LJ
authors: Harris
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002140:California; D003257:Consumer Product Safety; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development; D005511:Food Handling / Q000379:methods; D005519:Food Preservation / Q000379:methods*; D031324:Juglans / Q000737:chemistry / Q000382:microbiology*; D009754:Nuts / Q000737:chemistry / Q000382:microbiology*; D010463:Peracetic Acid / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; C031371:N(alpha)-lauroylarginine ethyl ester; D001120:Arginine; D010463:Peracetic Acid
keywords: PAA; Peracetic acid; Postharvest; Walnuts