# Mexican Bee Honey Identification Using Sugar Crystals' Image Histograms
## 2 Materials and Methods  
### Bee Honey Samples  
Eight different honey samples from certified beekeepers were used to carry out this proof-of-principle. The selected honey represents several geographical regions of the central-east region of Mexico. They also have economic relevance due to their production volume, such as orange, avocado, and citrus honey. Twenty-one samples for each selected honey were collected directly from the extraction tanks and stored in bottles to prevent exposure to sunlight and environmental moisture absorption [25]. Once at the laboratory, each bottle was labeled for floral and geographical identification and stored at room temperature. Several samples were transferred to 1.5 mL Eppendorf tubes to be transported for moisture control and SHG imaging tests at different times. Sterilized materials were used during transportation, and the honey was kept away from direct sunlight.  
The samples were collected from different regions of Mexico, each with a distinct floral source and geographical origin. A common practice is to measure the refractive index of each sample in order to determine its moisture. This value estimates the crystallization rate that may have the honey. For this purpose, a commercially available refracometer (Hanna Instruments, Model HI96801, Smithfield, RI, USA) was used within the honey exporters' facilities (see Table 1).  
Once each sample was measured, all of the honey samples were manually stirred to ensure homogeneity before they were observed in the microscope. For the SHG microscopy, 0.5 g for each honey sample was uniformly distributed and placed between two microscope slides to produce a thin layer, and then positioned and imaged using the microscope. Samples (S) from the same honey but with a different crystallization time were labeled with consecutive numbers, i.e., MQ-S1, MQ-S2, MQ-S3, and so on.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Geographical Origin** & **Floral Origin** & **Brix [\%]** & **Moisture [\%]** & **Refractive Index** & **Label** \\ \hline \multirow{2}{*}{Veracruz} & Mangrove & \multirow{2}{*}{75.7 \(\pm\) 0.2} & \multirow{2}{*}{22.9 \(\pm\) 0.2} & \multirow{2}{*}{1.4792} & \multirow{2}{*}{MG} \\  & _(Rhizophora)_ & & & & \\ \hline \multirow{2}{*}{Guerrero} & Red Powder Puff & \multirow{2}{*}{77.3 \(\pm\) 0.2} & \multirow{2}{*}{20.8 \(\pm\) 0.2} & \multirow{2}{*}{1.4842} & \multirow{2}{*}{RP} \\  & _(Callandra grandiflora)_ & & & & \\ \hline \multirow{2}{*}{Veracruz} & Coffee & \multirow{2}{*}{78.1 \(\pm\) 0.2} & \multirow{2}{*}{19.3 \(\pm\) 0.2} & \multirow{2}{*}{1.4880} & \multirow{2}{*}{CF} \\  & _(Coffea arabica)_ & & & & \\ \hline \multirow{2}{*}{Michoacan} & Avocado & \multirow{2}{*}{80.8 \(\pm\) 0.2} & \multirow{2}{*}{17.4 \(\pm\) 0.2} & \multirow{2}{*}{1.4930} & \multirow{2}{*}{AV} \\  & _(Persea americana)_ & & & & \\ \hline \multirow{2}{*}{Estado de Mexico} & Mint & \multirow{2}{*}{81.0 \(\pm\) 0.2} & \multirow{2}{*}{17.2 \(\pm\) 0.2} & \multirow{2}{*}{1.4934} & \multirow{2}{*}{MT} \\  & _(Mentha canadensis)_ & & & & \\ \hline \multirow{2}{*}{Nuevo Leon} & Orange & \multirow{2}{*}{81.4 \(\pm\) 0.2} & \multirow{2}{*}{16.9 \(\pm\) 0.2} & \multirow{2}{*}{1.4943} & \multirow{2}{*}{OG} \\  & _(Citrus sinensis)_ & & & & \\ \hline \multirow{2}{*}{San Luis Potosi} & Citrus & \multirow{2}{*}{81.8 \(\pm\) 0.2} & \multirow{2}{*}{16.4 \(\pm\) 0.2} & \multirow{2}{*}{1.4960} & \multirow{2}{*}{CB} \\  & _(from citrus flowers)_ & & & & \\ \hline \multirow{2}{*}{Tamaulipas} & Mesquite & \multirow{2}{*}{82.3 \(\pm\) 0.2} & \multirow{2}{*}{16.0 \(\pm\) 0.2} & \multirow{2}{*}{1.4966} & \multirow{2}{*}{MQ} \\  & _(Prosopis glandulosa)_ & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Honey samples information and labels.