Effect of floral origin on the physicochemical and microbial characteristics

Introduction: Honey is one of the most economically important bee products (Apismellifera) that is produced as a natural chemical from plants. Honey quality is mainly determined by its physicochemical and microbial properties, and the physicochemical properties of honey are specified in national and international standards. Honey ripening, harvest season, production and processing methods, climatic conditions, storage time and storage location and source of nectar (single or multiple flowers) have important effects on the quality, composition and biochemical properties of honey. These factors can have different physico-chemical properties. The main properties of honey are moisture, electrical conductivity, ash, reducing and non-reducing sugars, acidity, diastatic activity, hydroxymethylmorphoreal and proline content. In other words, the standards of honey in terms of microbial and health contamination of this product are deficient. In fact, many studies have been reported on the physicochemical properties of honey, but studies on microbial contamination are scarce. In this study, physicochemical properties (moisture, acidity, pH, soluble solids, diastase activity, electrical conductivity, ash, reducing sugars before and after hydrolysis, fructose to glucose ratio, sucrose, proline and hydroxymethylmfurfural), and microbial properties ( Mold, Yeast, and sulphite reducing Clostridium) in 30 honey samples of different plant origin (Milkvetch , Jujube, Thymes, Orange blossom, Multi flower) were analysed and compared with the Codex standard in order to classify different honeys and to specify the characteristics of each honey.
Material and methods: In this study, 30 samples of honey with different plant sources (24 single flower and 6 multi flower) produced by Karnica bee were collected from Alborz province with the assistance of the Ministry of Agriculture's Ministry of Agriculture during 2017-2018. For this purpose, 10 beekeepers were selected from the Alborz Agricultural Jihad Organization. Honey samples were then harvested by random sampling and packed in glass bottles (500 g) and stored    at -18⁰C in the dark until the test. Physicochemical properties (moisture, soluble solids, pH, acidity, electrical conductivity, ash, reducing sugars, sucrose, fructose to glucose ratio, diastatic activity, hydroxymethylfurfural and proline) and microbial properties (Mold,Yeast, sulphite reducing Clostridium) were evaluated from various plant sources (Milkvetch , Jujube, Thymes, Orange blossom, Multi flower) and compared with the characteristics defined in the International Codex Standards.
Results and discussion: There was no significant difference in soluble solids content of Milkvetch and Multi flower samples (P>0.05). While other samples showed significant differences (p <0.05).Honey samples beside the highest soluble solids and Orange blossom honey had the least soluble solids. The amount of soluble solids is related to the amount of sugar in honey and is an important indicator in the diagnosis of fraud. There was a significant difference between pH and acidity in different honey samples of different plant origin (P<0.05). Orange blossom had the lowest pH and acidity and the honey had the highest pH and acidity. High acidity is the indicator of fermentation of sugars to organic acids. Electrical conductivity was significantly different in honey samples of different plant origin (P<0.05). The electrical conductivity of Jujube was above the permissible limit (0.8 ms/cm) and other samples were within acceptable range. The electrical conductivity of Jujube was higher than the permitted limit (0.8 ms/cm) and other samples were within acceptable range, indicating that the honey samples were rich in flower pollen. Ash content in honey of different plant origin was not significantly different (P> 0.05). The amount of ash was related to total minerals in honey and it was dependent on environmental, geographical and vegetative conditions. There was a significant difference in the amount of sugars before and after hydrolysis of the studied honey samples (P<0.05). Orange blossom honey had the highest and the Jujube honey had the least amount of reducing sugars. The Orange blossom hony had the lowest sucrose content and the Jujube honey had the highest sucrose content. Sucrose content of Milkvetch, Jujube, Thymes, Orange blossom, and Multi flower honeis was exceeded as specified in Codex standard (maximum 5%). Fructose to glucose ratio was not significantly different in Milkvetch, and Jujubehoneies (P>0.05), while the other samples had significant differences (P<0.05). The ratio of fructose to glucose was lower than the standard level (0.9) in Milkvetch, and Jujubehoneies. The results show that Orange blossom honey with higher fructose to glucose ratio has fewer tendencies to crystallization than other types of honey. Sucrose content in Milkvetch, Jujube, Thymes, andMulti flower honey samples exceeded the International Standard Codex limit (maximum 5%) (Codex 2001) and may be indicative of honey bee feeding or premature harvesting. Hydroxy methyl furfural content was not significantly different in Milkvetch, and Thymes honeis (P>0.05), while other samples showed significant differences (P<0.05). In all honey samples with the exception of Orange blossom the levels of hydroxymethylfurfural were higher than the maximum (40 mg / kg). Diastatic activity of the up and down specimens were not significantly different (P> 0.05), while the other samples had a significant difference (P<0.05). Samples of Astragalus, Quercus, Thyme and Multi flower had lower diastase activity than standard (minimum G0 8) and only the samples of spring honey were within acceptable range. Proline content in honey samples of different plant origin was significantly different (P<0.05). Honey samples except of Milkvetch, and Jujube honeis had the proline content within the allowed range (minimum 180 m /kg). The amount of mold, and yeast in the analyzed honey samples was generally low, and the amount of sulphite reducing Clostridium was negative in all samples. Microbial contamination of honey samples was not dependent on plant origin and no significant differences were observed between the samples.
Conclusion: The physicochemical properties (moisture, soluble solids, acidity, pH, electrical conductivity, ash, sucrose, fructose to glucose ratio, hydroxymethylfurfural and proline) were dependent on the plant origin of the honeycomb but, the microbial properties (Mold, Yeast, and sulphite reducing Clostridium) was not dependent on the origin of honey. Based on the results, it is recommended to review the standards regarding the physicochemical properties of honey with regard to its plant origin and to determine the acceptable limit standards for each of the attributes, to consider the origin of honey samples.