Complex sentence: HFCS is 24% water, the rest mainly fructose and glucose with 0--5% unprocessed glucose oligomers, but also 0.3--1.1 grams/liter reactive degradation products, including 3-deoxyglucosone and other α-dicarbonyls, plus HMF (see below).
Split into simpler sentences: HFCS is 24% water and the rest sugars--mainly fructose and glucose with 0--5% unprocessed glucose oligomers. However, there are also 0.3--1.1 grams/liter reactive degradation products, including 3-deoxyglucosone and other α-dicarbonyls, plus HMF (see below).