Physicochemical Characterization and Volatile Organic Compounds of Mangrove Honey from Kilifi County, Kenya

Nancy Kwamboka Omori, Robert Bichanga, and Evans Changamu*

Department of Chemistry, Kenyatta University, P.O. Box 43844, Nairobi, 00100, Kenya 

Abstract Characterization of honey is important to the producer, the marketer and the consumer as it assures them of the important characteristics and hence quality of the product. The objective of this study was to characterize mangrove honey from Kilifi County, Kenya, in terms of its physiochemical properties and volatile organic compounds present. Honey sampling was done from the bee keepers (fresh honey) and from the honey processing factory (processed honey) in the region and subjected to determination of its physical and chemical parameters and its volatile organic compounds (VOCs) profile. Mangrove tree flowers were also sampled and their VOCs profile determined and compared with that of the mangrove honey. Twenty (20) honey samples weighing approximately 250 g each were collected randomly from selected farmers in different locations in Kilifi County and from the factory at Kwetu centre, packed in 500 cm3 plastic bottles, ferried for refrigeration in the lab at a temperature of 4 °C. Mangrove tree flower inflorescences were collected from randomly selected trees in the sampled regions of Kilifi county. Flower VOCs were collected by static headspace solid phase microextraction (HS-SPME) fiber while extraction of VOCs in honey samples was done by ultrasoundassisted solvent extraction (USE) method. The VOCs present in honey and flower extracts were identified by Gas Chromatography Mass spectrometry. The physicochemical characterization was done following standard procedures set out by the International Honey Commission. Quantitative data was analyzed statistically using the SPSS program version 21. The results show that the mean moisture content ranged from 19.23±0.06% to 23.40±0.00, the mean pH ranged from 4.00±0.00 to 4.45±0.05 while the mean electrical conductivity ranged from 0.54±0.00 to 0.32±0.00 MS/cm. The mean acidity ranged from 30.21±0.15 to 22.20±0.00 Meq/kg. The mean proline content ranged from 602.24±2.68 mg/kg to 734.36±4.23. The mean hydroxymethylfurfural (HMF) levels varied from 0 mg/kg to 2.86±0.14. The mean invertase content ranged from 5.54±0.11 U/kg to 9.55±0.10. The mean diastase content ranged from 11.40±0.091 to 8.35±0.247 S/units. The volatile organic compounds in honey were extracted, identified and compared with those extracted and identified from the mangrove tree flowers. In the VOCs profile of mangrove flower, factory and farm, 119, 90 and 70 compounds were identified, respectively. Thirty five (35) of the compounds found in mangrove flower were also found in all the honey samples analyzed. Mangrove flowers and honey samples contained high levels of 3-methyl-3-buten-1-ol, 2-pentanone and nhexadecanoic acid followed by other significant compounds like palmitoleic acid, octadecanoic acid, docosanoic and 3-hydroxy-2 butanone. Thus, 3-methyl-3-buten-1-ol, 2-pentanone and n-hexadecanoic acid can be considered characteristic for mangrove honey and highlighted as potential markers useful for mangrove honey.

Keywords: Mangrove honey, chemical markers, SPME, volatile organic compounds, physicochemical properties