Honey crystallization the formation and growth of sugar crystals in a container of honey. Crystallization is a natural process and not a sign of adulteration or spoilage. Due to its physical properties, honey initially tends towards natural crystallization, as it is a supersaturated sugar solution. Honey is mainly comprised of two sugars: fructose and glucose.
The starting point of a crystallization depends on various factors. The main reasons involve the fructose/glucose ratio (F/G) and the glucose/water ratio (G/W). A high F/G and a low G/W generally have a slow crystallization process. When the level of glucose increases, it becomes insoluble in the water, and crystallization will happen.
Another common reason for crystallization involves the storage temperature, which contributes significantly to the formation of crystals. Ideally, honey should be stored in either a cool location (lower than 4°C) in order to reduce the mobility of sugar molecules or at a high temperature (greater than 25°C) in order to ensure the crystals liquify and the degree of the supersaturation of glucose decreases.
There are many further external factors influencing the tendency of a honey to crystallize. The treatment of honey during processing and bottling plays an important role for the crystallization behavior of the finished product. Even the packaging type and material affects the long-term stability of honey with regard to crystallization. Plastic bottles boost the process of crystallization more than glass.
Lastly, crystallization can also depend on how honey is processed. Raw honey with zero preservatives is a desired product, as today's consumers are becoming more aware of how their food is made and what may be added. But, when honey is sold raw, it can still have small, honey-typical particles that are present in the liquid, such as plant components, pollen, yeasts, sugar crystals, and beeswax. While these are all safe and edible, they provide starters to the crystallization process.
Unfortunately, crystallization is not a desired outcome. When honey crystallizes, it stops the ability for technological processing and increases the turbidity of the product. Even though crystallized honey is safe, a cloudy-looking jar of honey is more difficult to sell to consumers. Furthermore, a separation into a crystalline and a liquid phase reduces the microbial stability of the honey due to the elevated moisture content in the upper layer.
Source : Meixner & Bellesen. 2021. Honey Crystallization: A Natural Process.