Simple sugars can exist in multiple molecular conformations, some of which have different tastes and optical properties.
Steve Mould's video on optical rotation: https://www.youtube.com/watch?v=975r9a7FMqc
Reaction's video on Mexican Coke: https://www.youtube.com/watch?v=NY66qpMFOYo
Research paper describing enzymatic synthesis of L-glucose: https://nopr.niscpr.res.in/bitstream/123456789/17714/1/JSIR%2061%285%29%20361-365.pdf
D-mannose on Amazon: https://www.amazon.com/Micro-Ingredients-Mannose-Supplement-Soluble/dp/B01L2TFP1Q
My crystals were almost entirely the sweet form, but it is possible that your bag may have the bitter-tasting form to begin with.
D-fructose on Amazon: https://www.amazon.com/Fructose-Fruit-Sugar-16-ZIN/dp/B07DXVSGJT
D-glucose, also known as dextrose, also known as "corn sugar", can be found on Amazon, or beer homebrewing stores.
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