The 'pure maple syrup' includes: (from Wikipedia)
The basic ingredient in maple syrup is the sap from the xylem of sugar maple or various other species of maple trees. It consists primarily of sucrose and water, with small amounts of the monosaccharides glucose and fructose from the invert sugar created in the boiling process. Organic acids, the most notable one being malic acid, make the syrup slightly acidic. Maple syrup has a relatively low mineral content, consisting largely of potassium and calcium, but also contains nutritionally significant amounts ofzinc and manganese. Maple syrup also contains trace amounts of amino acids, which may contribute to the "buddy" flavour of syrup produced late in the season, as the amino acid content of sap increases at this time. Additionally, maple syrup contains a wide variety of volatile organic compounds, including vanillin, hydroxybutanone, and propionaldehyde. It is not yet known exactly what compounds are responsible for maple syrup's distinctive flavour, however its primary flavour contributing compounds are maple furanone, strawberry furanone, and maltol.
Maple syrup is similar to sugar with respect to calorie content, but is a source of manganese, with 13 grams containing about 0.44 milligrams, or 22 percent of the US Food and Drug Administration Daily Value (DV%) of 2 milligrams. It is also a source of zinc with 13 grams containing 0.55 milligrams or 3.7 percent of the DV% of 15 milligrams. Compared to honey, maple syrup has 15 times more calcium and 1/10 as much sodium.
Scientists have found that maple syrup's natural phenols inhibit two carbohydrate-hydrolyzing enzymes relevant to type 2 diabetes. A number of new compounds have been identified in maple syrup, one of which is quebecol, a phenolic compound created when the maple sap is boiled to create syrup.
Cane sugar is: (again from Wikipedia):
Since the 6th century BC, cane sugar producers have crushed the harvested vegetable material from sugarcane in order to collect and filter the juice. They then treat the liquid (often with lime (calcium oxide)) to remove impurities and then neutralize it. Boiling the juice then allows the sediment to settle to the bottom for dredging out, while the scum rises to the surface for skimming off. In cooling, the liquid crystallizes, usually in the process of stirring, to produce sugar crystals. Centrifuges usually remove the uncrystallized syrup. The producers can then either sell the sugar product for use as is, or process it further to produce lighter grades. The later processing may take place in another factory in another country.
Sugarcane is a major component of Brazilian agriculture; the country is a top producer of sugarcane products, such as crystallized sugar andethanol (ethanol fuel). The sucrose found in sugarcane produces ethanol when fermented and distilled. Brazil has implemented ethanol as an alternative fuel on a national scale.
As you can see, there is a whole lot more in maple syrup than in cane sugar, and ingredients that, in maple syrup, that are fermentable, and not so much in cane sugar. Fermentation is much more possible in maple syrup, and that is what the odor was from. I would stick with cane sugar or its' derivatives, such as sucrolose.