Honeydew
Honey
"Honeydew"
is a classification of honey that
refers to honey produced by honeybees collecting nectar that is exuded from
another insect such as an aphid or scale insect. It is quite common in a number
of countries and the best known is honeydew from the Black Forest in Germany.
World wide honeydew can be referred to variously as "forest honey",
"Pine honey", "Fir honey" etc. and may sometimes be referred
to by the specific species of tree producing the honeydew.
Typically honeydews have lower levels of glucose and fructose and higher levels
of complex sugars due to the extra enzymatic actions in the sap sucking insect's
gut. Honeydews don't normally crystallize due to the reduced levels of glucose
and also have a high mineral content which is measured as a high conductivity
- this measurement being the main tool to differentiate honeydews in the laboratory.
New
Zealand Beech
Honeydew honey
is one of New Zealand's premium export honeys. It has a history of export
to Europe and specifically Germany since the early
1970s. There are several honeydew producing scale insects in New Zealand inhabiting
a variety of plants. However most of these are small honeydew sources or intermittent
production. The beech forests of the South Island are a different story however.
Two species of beech tree inhabited by two species of honeydew insect (the
sooty beech scales) from the Margarodidae family produce New Zealand's largest
single exported honey crop. The beech trees are Black Beech (Nothofagus
solandri) and Red Beech (N. fusca). The two insects
are Ultracoelostoma assimile and U. brittini.
U. brittini tends to inhabit the trunks and larger branches, while U. assimile
is recorded (C.F.Morales) as favouring the upper branches and twigs, thus
U.brittini is the insect most likely to be encountered by the casual
observer wandering in the beech forests.
The black colour of trees and plants with a honeydew source is due to the
growth of a black
sooty mould (Capnodium fungus) on the surplus nectar exuding over the
plant and sometimes even the ground. Particles of this fungus are typically
found in honeydew being referred to as "honeydew elements" and are
used as a part of the identification as honeydew.
Droplets of nectar are highly visible to any observer visiting the beech forest,
but bees are rarely seen collecting these. Mostly they are observed foraging
on the bark and particularly at the base of the tubules extending from the
scale insect buried under the bark.
Colour
Beech honeydew is one of our darker honey types with a Pfund
Scale average of 87.6mm and a Standard Deviation (SD) of 12.9mm (1,125
records). Colour does depend to some extent on area. There are some areas
that do produce darker honeydew. Whether this is due to local conditions or
blends of lighter (non honeydew) honeys is uncertain but we can find no correlation
between conductivity and colour. Honeydew is generally a slower honey flow
than most of the other flower honeys (although there are exceptions of course),
and honeybees prefer to store honeys like this closer to the brood nest, typically
in darker combs. This can darken the colour of the resultant honey.
Conductivity
New Zealand Beech honeydew is typical of most honeydews in having a high conductivity.
This arises from the nature of honeydew production. An insect of the Hemiptera
order of insects (those with sap sucking mouthparts e.g. aphids, scale insects
etc.) sucks sap from the host plant and exudes a sweet sticky nectar which
is essentially slightly modified sap. This is then collected by honeybees
as a nectar source and is "ripened" into honey. This pathway is
quite different from that of normal flower honeys. The direct sucking of the
sap, the additional insect in the production chain with many additional enzymatic
processes taking place, and the presence of sooty moulds, all add up to an
additional mineral content not normally found in flower honeys. This is indirectly
measured by the ability of honeydew to conduct electricity. The average conductivity
for Beech honeydew is 1.19 mS/cm SD .22 mS/cm ( 1,390 records) which is around
10 times the average for flower honeys. This high level of mineral and trace
elements is thought to be of significant nutritional value, one of the key
reasons honeydew is popular in Europe.
Carbohydrate Profile
Honeydews
in general are normally low in glucose and they are also lower in fructose
than flower honeys. This low glucose and fructose
is supplemented by higher levels of more complex sugars sugars such as maltose,
erlose and melezitose. This has the effect of reducing the tendency
to crystallize. Beech honeydew is likewise very slow crystallizing and
in fact some beech honeydews never crystallize. Typical values for Beech Honeydew
are:
Glucose 22.9% - SD 2.0% (400 samples),
Fructose 33.8% - SD 2.1% (400 samples).
Sucrose 0.67% - SD 0.81% (400 samples)
SD = Standard Deviation.
Oligosaccharides
Another feature of New Zealand beech honeydew is the presence
of oligosaccharides (complex sugars) in greater levels than average flower
honeys.
It has been shown that oligosaccharides are helpful in maintaining and promoting
beneficial bacteria in the gut (probiotic bacteria), particularly after treatment
with antibiotics. As such oligosaccharides are classed as "prebiotics"
i.e. a food for probiotics.
Antioxidants
New Zealand Beech Honeydew is similar to other honeydews in having higher
levels of antioxidants than most other flower honeys. In a study at Lincoln
University, Beech Honeydew had the highest levels of polyphenolics, one
of the most significant classes of antioxidant compounds. Additionally, using
the ABTS and ORAC methods for antioxidant calculation, Beech Honeydew consistently
ranked near the top of 10 monofloral honey varieties tested. The results of
these three tests indicates that New Zealand Beech Honeydew has one of the
highest levels of antioxidants of all New Zealand honeys. Other high ranking
honeys include Thyme, Manuka and Rewarewa
- all dark coloured, strong flavoured honeys.
Antibacterial Activity
Honeydew has very high levels of Glucose Oxidase
activity giving a high degree of antibacterial activity that often exceeds
levels found in manuka honey. We are currently
collaborating on further research into Glucose Oxidase activity in Honeydew.
Moisture Content - Presence of Yeast
Normally honeydew is below 17% moisture. In the main production
area, fermentation is not generally a concern, but the environment is such
that large populations of yeast can occur in the honeydew forests. This is
due to the presence of large quantities of a food resource (honeydew nectar)
and, particularly after rain, wet conditions. At times the forest
can smell quite sour with a fermentation smell and wasps can be observed drunk
on the tree trunks. Under these conditions, high levels of yeast may occur
in honeydew honey that come from this environment, rather than from fermentation
of the ripened honey. It is possible that this may be marked against the product
as a perceived quality issue, rather than it being a natural occurrence.
"Oligosaccharides
in New Zealand Honeydew Honey"
K. Astwood, B. Lee, and M. Manley-Harris J. Agric. Food Chem., 46(12), 4958-4962.
Abstract
"A series of oligosaccharides based upon successive addition of glucose
(1->4) to the glucopyranosyl residue of sucrose and another series similar
to the first but with the final residue linked (1->6) have been isolated
from New Zealand honeydew honey and fully characterized. Because the trisaccharide
in this series is erlose, it is inferred that the honeydew of the indigenous
scale insect, Ultracoelostoma assimile, which lives upon the
Southern beech, Nothofagus spp,. is of the erlose type. These oligosaccharides
and others have been quantifed by GC and LC in six New Zealand honedew honeys"
This paper is available online from the publisher at www.acs.org
for US$25.00 in PDF format. The author (to whom correspondence should
be addressed) is manleyha@waikato.ac.nz
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Airborne Honey Ltd
