|MadSci Network: Agricultural Sciences|
Many factors influence the color of maple syrups. You can find many information about maple syrup in The North American Maple Syrup Producers Manual (Bulletin 856), produced by The Ohio State University Extension in Cooperation with The North American Maple Syrup Council. You can browse it at:
Here are the main factors (text quoted from cited reference except when noted):
- Biochemistry of the sap: It is the main factor influencing the color and flavor grade of the maple syrup produced. Sap not affected by microorganism activity will produce lighter grades of syrup with a subtle maple bouquet flavor. Sap affected by higher concentrations of microorganisms will produce darker grades of syrup. (JB: Microorganism will hydrolyse the sucrose to glucose and fructose, which will caramelize when the sap is boiled. You will get more microorganism if you keep your sap too long before boiling or if your tubing becomes too much contaminated);
- Storage time and Temperature (JB: More time, more temperature equal more caramelization);
- Type of storage container: Plastic containers cause syrup to darken after only three months of storage. However, new materials and/or treatment of plastic containers are proving beneficial in improving the shelf-life of syrup packaged in plastic containers. The syrup packed in tinned steel containers gets lighter in color over time because of increased leached tin and develops a metallic flavor because of high iron content, after the tin coating dissolves. Glass containers also cause darkening of syrup, but not nearly as much as plastic;
- Filtering and packing techniques;
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