Heating and Filtering Honey
The processing of honey may be very simple e.g. in the case of a hobby operation, or extremely complex involving a great deal of technology tailored to each individual honey type. Most processing however is concerned with liquefying and straining (or filtering) honey. Both of these operations usually require some application of heat to the honey. The heat has the dual effect of removing crystallization in natural honey, and to reduce the viscosity. Both of these things are required to provide a product that can be cleaned and further processed for creamed honey or just filled into jars as liquid honey.
Heating is one of the most discussed topics relating to honey "quality". Most of this stems from days long before modern processing systems when considerable change occurred in honey due to application of heat needed to extract and process the honey. e.g. the separation of beeswax from honey was often done by melting the beeswax in the honey which then floated on top as a liquid. This required raising the honey above 63.5°C (the melting point of beeswax) with little or no accurate control, for considerable periods of time. Today, modern pumps, extraction plants, filtering and straining systems, flash heat exchangers and coolers controlled by highly accurate electronic sensors coupled to computerized systems etc. make this excessive heating a thing of the past. But marketing claims that were once extremely valid, are still emphasized when their relative importance to honey quality is now significantly reduced.
When confronted by statements relating to heat, it is important to remember two things:
Heat is relative. E.g. 30 degrees Celsius is "cool" to someone from tropical climates while the same temperature in a temperate climate is "hot".
- Nearly all changes in honey are a function of temperature AND time. i.e. long times at low temperatures can have a similar outcome to higher temperatures for a short time (see HMF example - 30°C for 6 months is more damaging for HMF than 70°C for 2 hours).
To have any meaning, statements about heating should therefore contain a temperature that the honey is heated to, the length of time held at that temperature, and whether it is cooled quickly or allowed to cool naturally (which may take hours or even days depending on the size and thermal properties of the container(s)). Quality claims such as "unheated" or "raw" honey that have no qualifying time or temperature, may be quite misleading. E.g. poor storage of bulk honeys, or a long shelf time of slow moving retail lines in a warm climate, will produce changes many times greater than the brief periods of accurately controlled heating during processing.
Effects of Heating
"Honey" is a generic name for an extremely varied product produced by honey bees. This huge variability is in all aspects of its makeup. It is therefore virtually impossible to record or predict the effect of heat on every possible component of every honey. However there are a number of things that do regularly happen to most honeys when they are heated. In order of importance these are:
- Change in flavours
- Sugar crystals "melt" (warming the honey actually re-dissolves the glucose crystals in honey but most people just call it melting)
- Decrease in enzyme activity
- Change in sugar compositions
- Decrease in Yeast activity
- Increases in HMF
This order may change depending on the final usage of the product.
Straining or Filtering
The difference between straining and filtering is mainly one of size of the filter/straining elements. Filtering usually refers to removing very small particles, often with pressure while straining refers to larger particles often without pressure. Filtering can remove particles down to 1 micron in size (0.001mm) while pollen we encounter in New Zealand honeys range in size from 10 to 60 microns (0.01mm - 0.06mm).
Filtering of honey is routinely used to remove pollen and all visible impurities. At Airborne we strain though a mesh size that removes visible impurities such as insect parts (bees' wings, legs etc.) and larger beeswax particles left over from the extraction process but retains all the natural pollen as shown below.
Many honey companies filter to remove all pollen and microscopic particles, thus damaging the natural composition. They do this because these particles can act as a nucleation point that starts crystallization. But this is because honeys that are fast crystallizing have been used to produce a liquid honey. At Airborne we solve this problem with HPLC analyses enabling us to select slow crystallizing honeys - eliminating the need for filtering the pollen out of the honey - and leaving it Undamaged! We then use the fast crystallizing honeys for creamed honey.