# Mexican Bee Honey Identification Using Sugar Crystals' Image Histograms
###### Abstract  
Second harmonic generation (SHG) microscopy is applied to image honey sugar crystals, with the advantage of avoiding the surrounding signal of the liquid honey. It is a non-contact method where the specialized preparation of the honey is not required. Since the crystallization process of honey depends upon its floral origin, among other conditions, analyzing its crystallographic behavior results in a challenging task as the crystals are mixed and overlapped. This work introduces a simple, multi-variable data analysis requiring only one SHG image, where its gray-level histogram was retrieved and processed from eight Mexican bee honey samples. These honey samples represent a broad range of regions from the central-east part of Mexico, describing different environments and climates. The results obtained with this simplified methodology can differentiate among the botanical origin of the honey samples at different crystallization times and storage conditions. A repeatability test was performed using three honey samples with different crystal morphologies to expand the method to all of the samples. The results show that the proposed methodology could be a helpful alternative to identifying the botanical origin of honey despite its crystallization time. second harmonic microscopy; principal component analysis; bee honey; image processing; optical metrology +
Footnote †: journal: applied sciences  
Article  
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arises predominantly from a single botanical origin, with more than 45% of the total pollen content coming from the same plant, and it is named after that plant, i.e., orange, mangrove, or mint honey. Honey is a complex mixture of supersaturated carbohydrates (a sugar solution with fructose and glucose as the main ingredients). The exact ratio between fructose and glucose in any honey depends mainly on the nectar source. The honey taste, color, and other physical properties like crystallization are contributed to by the non-volatile compounds in it, like sugar, amino acids, minerals, and phenolic compounds, while the aroma of honey is mainly contributed to by the volatile components [7]. The crystallization of honey is a natural process due to its supersaturated nature, so monitoring this process could also provide information on the authenticity and botanical origin of the honey. The crystallization process does not modify the honey's nutritional value if it is adequately crystallized. Glucose is the principal component that crystallizes in honey, as it exists in a supersaturated state. The factors influencing crystallization include the fructose/glucose ratio, glucose/moisture ratio, the presence of crystallization centers, and the storage temperature [8]. Honey consumption has increased rapidly, generating a growing demand for it. To satisfy this demand, diverse types of commercialized honey exist internationally [9]. However, honey production depends on favorable climatic conditions to have an available volume; otherwise, the demand is satisfied by adulterated honey [10]. Discrimination between pure and adulterated honey is a critical and continuous task; therefore, producers, retailers, consumers, and regulatory authorities should identify new methodologies for its authentication [11]. Several techniques have already been applied to this purpose in the optical field, such as microscopy, chromatography, near-infrared spectroscopy, and Raman spectroscopy [12; 13; 14; 15; 16]. The techniques mentioned above consume time to retrieve relevant information to identify or classify the honey samples. Some techniques use attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) combined with multivariate statistical analysis to establish the authenticity of wild honey [17].