Inhibiting Tyrophagus putrescentiae orientation to and reproduction on dry cured hams: The impact of acetic acid-treated ham nets

Dry-cured hams are often infested by Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae) during aging. Recent studies have highlighted the potential for liquid smoke infused nets to control Tyrophagus putrescentiae infestations on dry-cured hams, as a potential alternative replacement to methyl bromide. This research aims to investigate acetic acid (CH3COOH), one of the three predominant components of liquid smoke, for its efficacy in mite control when applied to ham nets. Solutions with acetic acid concentrations ranging from 0% to 2% in 0.5% increments, and 1% xanthan gum (XG), were infused into nets, which were then applied to ham cubes. The twochoice orientation assay demonstrated that mites exhibited a preference for the untreated control ham cubes over any of the tested treatments (P < 0.0001). In the reproduction assay, all treatments reduced mite numbers in comparison to the untreated control (P < 0.0001). There was no significant difference (P = 0.72) among the treatments and the positive control, which was a net infused with 40% propylene glycol (PG), 1% carrageenan, and 1% propylene glycol alginate. The positive control with 40% PG had no living mites present after two weeks of incubation, demonstrating the complete inhibition of mite feeding and reproduction. The XG + acetic acid (0.5%-2.0%) treatments, which had no PG, resulted in mean mite counts ranging from 20 to 26. However, XG alone without acetic acid led to a similar small number of mites (16) (P > 0.05); indicating that addition of acetic acid was not needed to control mites. Scanning electron microscopy revealed that the liquid smoke treatment forms a more robust physical barrier than acetic acid treatments. The effectiveness in previous liquid smoke treatments is likely due to physical properties imparted by liquid smoke in conjunction with the components that make up liquid smoke.