The sugars of honey—A review

Abstract Surveys of floral honey composition have established that the three major components are fructose, glucose, and water, averaging 38.2, 31.3 and 17.2%, respectively. Glucose and fructose are the only monosaccharides in honey and it is these sugars, combined in various forms, that comprise the di‐ and trisaccharide fractions of floral honey. Several laboratories, utilising various chemical and physical methods, have been responsible for the isolation and characterisation of ten disaccharides, ten trisaccharides, and two higher sugars from floral honey. Several of these occur only rarely in nature, and the trisaccharide erlose, produced by the action of honeybee invertase on sucrose, was first discovered as a component of honey. Honeydew honey is produced by the honeybee from honeydew deposits left by various hemipterous insects on their host plant. Honeydew contains a more complex mixture of sugars than does nectar, and honeydew honey is appreciably higher in reducing disaccharides and higher sugars than is floral honey. The trisaccharide melizitose, not found in floral honey, is often present in levels exceeding 10% in honeydew honey. The precipitation of glucose from honey, termed granulation, is often technologically undesirable as it is sometimes followed by fermentation. Indices such as the glucose/water ratio have been used to predict granulation tendency. Small amounts of hydroxymethylfurfural (HMF) occur naturally in honey, resulting from the acid catalysed dehydration of the hexoses, particularly fructose. High levels of HMF suggest adulteration of honey with acid inverted invert syrup and several methods are available for its determination. The conversion of nectar and honeydew to the complex array of honey sugars by the honeybee involves a variety of chemical and biochemical processes, some of which are now understood, while others remain to be elucidated.