Maple syrup contamination

The published range of pH of maple syrup varies from somewhat acidic (4.7) to slightly basic (8.7), but typically is near neutral, with reported mean values around pH 6.3-6.8 (Chenard and Gagnon, 1997 Perkins et al, 2006). The pH of the syrup is related to several factors, including collection and storage of sap, the methods employed to process the sap into syrup, time of season, and microbial contamination. 

Because sap is a perishable product, it is generally processed relatively soon after collection to minimize microbial contamination and the accompanying reduction in syrup quality. Sap is often filtered and UV-sterilized after collection to reduce microbial loads in order to maintain sap quality. Ozone treatment, although useful in water treatment, does not appear to be effective in maple applications, presumably due to the strong protective effect of sugars on microbial populations (Labbe et al, 2001). 

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