Variation and correlation of properties in different grades of maple syrup.

Thirty five commercial maple syrups from twelve producers in Southern Ontario were evaluated for properties including light transmittance, autofluorescence, density, pH, total soluble solids (TSS), glucose and fructose content, total phenol content, antioxidant potential and mineral content (Mg, Mn, P, Zn, Ca, K, Fe and Pb). A high degree of variability was found in many characteristics, often exceeding an order of magnitude. Syrups were categorized based on light transmission at 560 nm into amber (12), dark (13) and very dark (10) using International Maple Syrup Institute (IMSI) guidelines. No statistical differences were found among grades of syrup for density, pH, TSS, glucose, fructose, total reducing sugars, glucose:fructose ratio, magnesium, manganese or potassium. Darker syrups showed significantly higher autofluorescence, total phenol content, antioxidant potential, phosphorous, calcium and total mineral content. Significant negative correlations of percent transmission with total phenol content, antioxidant potential and total mineral content are reported. Significant positive correlations among total phenol content, antioxidant potential and total mineral content are also described. The results from this study suggest that darker syrups tend to contain more beneficial traits and may be applied in developing functional foods and value added products.