Validating the Efficacy of Cleaning Procedures Used to Reduce Microbial Loads on Wooden Boards Used for Cheese Aging

Introduction: Artisanal cheesemakers follow traditional European practices of aging cheeses on wooden boards. The Food and Drug Administration’s current regulations mandate that utensils and other surfaces that contact food must be adequately cleanable and properly maintained. Development of simple methods to assess the efficacy of board cleaning and sanitizing regimens will assist cheesemakers in providing food safety assurance.

Purpose: To develop a method to assess and validate the efficacy of cleaning procedures used to reduce microbial loads on wooden boards used for cheese aging.

Methods: Six sponge samples per board (3M Sponge stick moistened with Dey-Engley Neutralizing Broth) were taken from previously used wooden boards, where a 4”x 4” area was swabbed at random.  Swabs were obtained prior to and following cleaning and sanitizing procedures. The wooden boards studied were used to age three different cheese varieties: Alpine style, Blue, and Cheddar; and counts following treatments were compared to determine if cheese type influenced results. Sponges were analyzed by removing 1 ml aliquots and plating using 3M APC Petrifilm, where levels of bacteria were enumerated pre-and post-board washing and drying. ANOVA was performed to determine statistical significance (P < 0.0001).

Results: Analysis of 150 samples revealed average microbial loads on boards prior to washing of 6.6 log CFU/cm². By cheese type, counts were 5.94 log CFU/cm² for Alpine, 7.16 log CFU/cm² for Blue, and 6.93 log CFU/cm² for Cheddar. Cleaning regimens consisting of hot water bath (46.5°C 30 seconds), sanitizing with 200-250 ppm Peroxyacetic acid for 2 minutes, and manual scrubbing, resulted in counts averaging 3.37 log CFU/cm², 4.21 log CFU/cm², and 3.58 log CFU/cm², respectively. The cleaning regimens analyzed showed a consistent 3.75 log/cm2 reduction in count, regardless of cheese type.

Significance: These results indicate that the outlined method can be easily, reproducibly and cost-effectively used by cheese makers to validate the efficacy of wooden board cleaning/sanitizing procedures.