The flavour profiles of my batches of syrup are so predictable and consistent that it's ridiculous. Batches 1 and 2 are always really light and always have vanilla and marshmallow notes; batch #3 may still be light in colour but the flavour is becoming more maple-y; batches 4-5 are definitely textbook maple both in colour and taste; batch #6 usually starts to develop a dark colour and carry a brown sugar note. Batch #7, if I get one, may be almost molassesy to the taste and near black.
There are exceptions though....I've been lucky enough to never have any severe/noxious flavours (ie industrial or chemical) but I once had batch #4 carrying a light but noticeable smell and flavour of...fresh-cut hay. It was wonderful, but sadly the flavour and scent didn't last long and mellowed out.
Also you may want to check out the following: http://www.agr.gc.ca/eng/science-and...=1231363888838
Been tapping since 2008.
2018 - 17 taps/7 trees...819l sap, approx 28l syrup
2019 - 18 taps/8 trees...585l sap, 28l syrup...21:1 ratio
2020 - 18 taps/8 trees...890.04l sap...gave away about 170l, 30l snafu'd....23l total for me from approx 690l
2021 - 18 taps/8 trees...395l sap, 12 l syrup
2022 - 18 taps/8 trees....7 sugars 1 red due to #2 having surgery so had the season off....582l sap, 18.5l syrup
2023 - 18 taps/8 trees...all sugars again. 807l sap, so far approx 14l syrup