Application of Calcium Hypochlorite for Sanitizing 3/16-Inch Tubing Used in Maple Sap Collection

Despite the widespread empirical adoption of calcium hypochlorite (Ca(ClO)₂) for sanitizing 3/16-inch tubing after the maple sap collection season, there remains a dearth of scientific data on its best practice and effectiveness. To address this gap, we cultivated microbial mass in tubing through continuous maple sap flow at 7 °C for 5 weeks in the lab. The tubing was sanitized with 200, 400, or 600 ppm Ca(ClO)₂ and retained Ca(ClO)₂ for either 10 min, 1 h, 7 days, or 6 weeks. Half of the tubing segments underwent microbial analysis, while the other half were stored for 6 weeks post-flushing of the Ca(ClO)₂ to determine microbial survival/growth. The level and presence of the microbial load were determined, and the inner tubing surfaces were visualized using scanning electron microscopy (SEM). The initial microbial load in the tubing was approximately 4-5 log CFU/cm². A 10-min and 1 h contact time with 200 ppm Ca(ClO)₂, and a 10-min exposure to 400 ppm Ca(ClO)₂, achieved reductions of 2.4-2.8 log for Pseudomonas spp., 1.6-2.5 log for mold and yeast, and 2.3-3.3 log for psychrotrophic microorganisms. Microorganisms were recovered from the enrichment process after retaining 200 ppm Ca(ClO)₂ for 6 weeks, indicating insufficient inactivation. Consequently, the data suggests the use of at least 400 ppm Ca(ClO)₂ for 1 day. The SEM images supported the microbial count results, offering valuable insights for educating maple syrup producers on optimal tubing sanitation practices.