Treatment of cattle hides with Shellac-in-ethanol solution to reduce bacterial transferability--a preliminary study

A solution of natural, food-grade resin (Shellac) in ethanol was evaluated to treat samples of visually clean and dry cattle hides with the aim to reduce bacterial removability from the hides by swabbing. Hide treatment by 23% Shellac-in-ethanol solution reduced sponge-swabbing recoveries of general microflora (TVC) by a factor of 6.6 logs (>1000-fold larger than the 2.9 log reduction observed by ethanol alone), and of generic Escherichia coli and Enterobacteriaceae by factors of at least 2.9 and 4.8 logs, respectively. These reductions were superior to those achieved by a sanitizer rinse-vacuum hide treatment. Significantly greater reductions of TVC recoveries from hides were achieved when using higher Shellac concentrations (23 and 30% rather than 4.8-16.7%) and when Shellac solution temperatures were 20-40 degrees C rather than 50-60 degrees C. Furthermore, the Shellac-based treatment also markedly reduced the E. coli O157 prevalence (3.7-fold reduction) on natural, uninoculated hides, as well as the counts of E. coli O157 on artificially inoculated hides (2.1 log reduction). This preliminary study indicated that a "bacterial on-hide immobilisation" approach to reducing transmission of microorganisms from cattle hide is promising and so will be further explored.