PHYSICAL AND CHEMICAL CHARACTERIZATION OF FRESHLY HARVESTED AND FACTORY-PROCESSED MANGROVE HONEY FROM KILIFI COUNTY, KENYA
Loading...
Date
2021-11
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Mangrove honey from the mangrove forests at the Kenyan coastal region has been
in production at the commercial level by beekeepers organized and registered in
self-help groups for more than a decade now. The honey is said to have medicinal
properties but it has not been fully characterized to determine whether it meets the
Kenyan standards on Honey – Specification (KS EAS 36:2020), European Union
(EU) Directive on Honey (2001/110/EC) and International Honey Commission
(2009). The objective of this study was, therefore, to characterize Kenyan
mangrove honey in terms of its physicochemical properties and volatile organic
compounds present. It was also important to correlate the honey VOC profiles
with the mangrove tree flowers extract profiles. Unprocessed honey sampling was
done from selected beekeepers from the four mangrove forest regions of Kilifi
County, namely, Mida, Kilifi, Watamu and Mtwapa creeks while processed honey
samples were obtained from Kwetu Training Centre. Twenty (20) honey samples
weighing approximately 250 g each were collected randomly from farmers and
factory in different locations in Kilifi County, packed in 500 cm3 plastic bottles,
ferried for refrigeration in the lab at a temperature of 4o C. Mangrove flower
volatile organic compounds (VOCs) were collected by static headspace solid
phase microextraction (HS-SPME) fiber while collection of VOCs in honey
samples was done by ultrasound-assisted solvent extraction (USE) method.
Mangrove honey was analyzed for moisture content (by refractometry), colour
index, diastase, proline and hydroxymethylfurfural (by spectrophotometry), pH
and electrical conductivity (by pH/conductivity meters), free acidity (by
titrimetry), sugar content (high performance liquid chromatography) and volatile
organic compounds (by GC-MS). Quantitative data was analyzed using the SPSS
program version 21. The results showed that the mean moisture content ranged
from 23.40±0.00 to 19.23±0.06%, mean pH from 4.45±0.05 to 4.00±0.00, 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 734.36±4.23 to 602.24±2.68 mg/kg. The mean HMF levels were in
the range of 2.86±0.14 to 0 mg/kg. The mean invertase content ranged from
9.55±0.10 to 5.54±0.11 U/kg. The mean diastase content ranged from
11.48.47±0.06 to 8.11±0.64 S/units. In the VOCs profile of mangrove flower,
factory and farm, 119, 90 and 70compounds were identified, respectively. Of the
identified VOCs, 35 were found both in the honeys analyzed and in mangrove
flower. Three compounds docosanoic acid, palmitoleic acid and n-hexadecanoic
were found in large quantities in all samples analyzed and the mangrove flowers
and can be considered to be chemical markers for mangrove honey. The HMF,
diastase and invertase were found to be below the set limits suggesting that the
mangrove honey studied was fresh and had not been heated by farmers during
harvesting and extraction. The high proline content also revealed that nectar and
pollen are produced in great quantities by mangrove plants. The rest of the
physicochemical parameters were found to be within the limits set by the
International Honey Commission, Codex Alimentarius and the Kenya bureau of
standards (through the EAS)