Honey
Enzymes Honey
can contain a number of different enzymes. Some of these are
introduced by bees, and some are found in the nectar. As with
most aspects of honey, different nectar/honey sources have widely
varying enzyme activity. Typically enzymes are proteins of complex
structure that catalyse a specific chemical reaction. They are
sensitive to heat, visible and UV light and other forms of energy
such as microwaves Glucose
Oxidase The
activity of GOX is reduced by heat, light and other forms of
energy such as microwaves. Some honeys appear to lose GOX activity
with even small amounts of visible light while other honeys
can retain their GOX activity with exposure to stong sunlight.
© 1999
Airborne Honey Ltd
Last
updated
26-Jan-2010
Of all the enzymes in honey, Diastase and Invertase have received
the most attention. They are introduced to honey by
bees but their presence [in fresh honey] is variable. Factors
that affect their presence are thought to be nectar composition
and concentration, the age of the bees, and the intensity of
the nectar flow. e.g. an intense flow of nectar with a high
concentration usually yields low values for diastase and invertase
activity.
Diastase
In simplistic terms,
this enzyme is responsible for converting starch to dextrins
and sugars and is introduced into honey by the bees. Its main
point of interest is as an indicator of heating - much like
HMF and is usually used in conjunction
with HMF. It is measured with an empirical scale - the Gothe
scale. Some honeys are naturally very low in Diastase. The Codex
standard
has a minimum of 8 on the Gothe scale for Diastase and a special
category for honeys low in Diastase of 3. However in the case
of honeys low in Diastase, the HMF must not be more than 10
mg/kg (compared with the more normal 80 mg/kg).
20°C
1,480
days
The
"half life" is the time taken for half of the
activity of the enzyme to disappear.
30°C
200
days
40°C
31
days
50°C
5.38
days
60°C
1.05
days
70°C
5.3
hours
80°C
1.2
hours
Invertase
Invertase is the most significant enzyme in honey in relation
to the amount of work done, and is primarily responsible for
converting sucrose in nectar to glucose and fructose. Since
most ripe honey has very little sucrose (usually less then 5%)
this enzyme's work is done very early on in the life of honey.
20°C
820
days
Invertase
becomes inactivated more quickly than diastase at the
same temperatures.
30°C
83
days
40°C
9.6
days
50°C
1.28
days
60°C
4.7
hours
70°C
47
minutes
80°C
8.6
minutes
Glucose Oxidase (GOX) is of interest in relation to antibacterial
properties in honey. It catalyses glucose to form gluconic acid
and Hydrogen Peroxide (H2O2)
- the main agent responsible for antibacterial activity in most
honeys. GOX activity (usually measured by its production of
H2O2) is highly
variable in differing honeys. It appears that GOX activity is
related to specific honey sources e.g. beech honeydew
usually has a high level of activity.
GOX is thought to be mostly added to honey by bees. There is
some evidence that there are at least two variants of this enzyme
coming from different parts of the bee - and this may explain
the apparent variance in some GOX's sensitivity to heat/light
etc. GOX is also produced by various other sources (e.g. Aspergillus
niger is a common source of commercially available GOX)
and it is possible that some of these may find their way into
honey under some circumstances.
Gluconic acid is the main acid found in honey and usually accounts
for most of a honey's acidity. The production of gluconic acid
and H2O2 is
very slow in ripe honey and most of this production takes
place as the honey is being ripened and dried by the bees. If
honey is diluted then this reaction speeds up again. This is
an important factor that greatly affects the antibacterial property
of a honey. At this time we have no published data on the half
life of GOX, but references to its stability indicate that this
is highly variable.
Catalase
Catalase is recorded in some honeys and its presence is thought
to be derived from the nectar i.e. a plant source. Catalase
decomposes H2O2
so its presence will produce a decrease in the antibacterial
activity produced from GOX activity. It is possible that
some of the variability of apparent H2O2
production is due to the presence or absence of catalase in
the nectar from a particular plant species.
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