Canada has a "Enhanced Surveillance Database" to detect adulteration of  honey using 240 retail and wholesale samples,  domestic and imported, taken in 2018-19.
Available for download at:   https://open.canada.ca/data/en/dataset/7ecfee4c-b6f5-45f8-9fd4-16976f55f8d9

I subset this sample into "satisfactory"  and "unsatisfactory"  subsets.

I sorted the subsets by the reported "Calculated C4 Sugar Addition".    A very compelling pattern emerged at the bottom of the "Satisfactory" subset emerged --  New Zealand Manuka honey samples completely dominated the bottom of the sort.

Is there an innocent explanation why Manuka honey  is characteristically 5-10% C4 Sugar addition ??  C4 sugar are produced by the C4 photosynthetic pathway and are characteristic of Rice, Corn and Sugar Cane syrups.

It appears to me that Manuka honey, generically,  is being adulterated (in an undetected manner) by 5 -10% sugar syrup.   Note there are, 4 Manuka samples below this list (0-4.4%) and one "unsatisfactory" one above (at 12.1 %)

My data from the sort of Satisfactory samples by C4 sugar concentration --  ( I inserted an • character as a separator so this table can be moved to spreadsheet columns)
Country of Origin    •     Declared Floral    •     C4 Sugar %
New Zealand    •     Manuka                   •     4.7
New Zealand    •     Manuka                   •     5
New Zealand    •     Manuka                   •     5
New Zealand    •     Manuka                   •     5.1
New Zealand    •     Manuka                   •     5.3
New Zealand    •     Manuka                   •     5.5
India          •     wildflower               •     5.7
Thailand       •     undeclared               •     5.7
India, Thai    •     undeclared               •     5.8
New Zealand    •     Manuka                   •     5.9
New Zealand    •     Manuka                   •     6.1
New Zealand    •     Manuka                   •     6.2
New Zealand    •     Manuka                   •     6.3
New Zealand    •     Manuka                   •     6.6
New Zealand    •     Manuka                   •     6.7
Australia      •     undeclared               •     6.8
New Zealand    •     Manuka                   •     7.1
New Zealand    •     Manuka                   •     8.4
New Zealand    •     Manuka                   •     9.1
New Zealand    •     Manuka                   •     9.3

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