Moniruzzaman, Mohammed
(2015)
Investigation of chemical components and purities of eight malaysian honeys as compared to manuka honey.
Masters thesis, Universiti Sains Malaysia.
Abstract
Introduction: Malaysia, a tropical country rich with flora and fauna has many
different types of honeys. Although honey is produced and is greatly consumed in
Malaysia, there is a lack of information on the chemical composition of these honeys.
Thus, the present study was aimed to investigate the chemical composition (physical,
chemical, antioxidant parameters, minerals, trace elements, volatile compounds and
sugar content) of eight different Malaysian honeys (acacia, pineapple, gelam, longan,
borneo, rubber tree, sourwood and tualang) compared to manuka honey.
Methods: Different physical and antioxidant parameters were measured using
spectrophotometric techniques while phenolic acid composition was determined by
high performance liquid chromatography. Minerals and trace elements were
determined using atomic absorption spectrometry. Gas chromatography quadrupole
time-of-flight mass spectrometry (GC-QTOF-MS) was used for the first time to
analyse honey volatiles and subsequently a novel dispersive liquid-liquid
microextraction (DLLME) method was developed to analyse volatiles. Sugar
analysis was performed by GC-MS.
Results and discussions: The physical parameters of the investigated honeys were
within the limit recommended by International Honey Commission. The mean
concentration of phenolics (325.59 ± 168.45 mggalicacid/kg) and flavonoids (62.52 ±
56.06 mgcatechin/kg), DPPH radical scavenging activity (43.02 ± 14.03%) and ferric
reducing power was 329.70 ± 209.16 μM Fe (II)/100 g. Benzoic acid was the most
abundant phenolic compounds (75%) among the phenolic acids followed by caffeic
acid, catechin, myricetin, gallic acid and naringenin. High mineral contents were
observed in the investigated honeys with K, Na, Fe and Ca being the most abundant
elements (mean 1466.01, 230.15, 133.39 and 144.48 mg/kg, respectively). Overall,
the trace elements were within the recommended limits with no pesticide residues
detected in any of the honey samples indicating their good qualities. Following
analysis using headspace (HS) solid-phase microextraction (SPME), accurate mass
capabilities of GC-QTOF-MS evaluated for compounds identification showed a
relatively narrow mass window (0.005 Da). Finally, a novel DLLME method was
developed and optimised to analyse honey volatiles. The whole sample preparation
process was completed in only approximately 10 min, with a total
consumption of organic solvents below 4 mL, relative standard deviations
lower than 12% and approximately 78 organic compounds identified in the
obtained extracts. Several sugars were identified and quantified in honeys.
Conclusion: Sourwood, longan and tualang honeys have higher number of phenolic
acids, flavonoids with superior antioxidant potentials when compared to other
Malaysian honeys and manuka honey. Overall, the results of this research indicate
that Malaysian honeys are of good qualities.
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