A common justification for the ultrafiltration of honey is “it lasts longer on the shelves.” In other words, the ultrafiltration process—which removes all debris, including any pollen grains—delays crystallization, making the honey more attractive on the store shelf.
In spite of that practice, you cannot assume that pollen causes crystallization. In fact, honey crystallizes based on the type of sugars that are present in the nectar. Honey high in fructose crystallizes slowly; honey high in glucose crystallizes quickly.
That said, crystals form more quickly when they have a nucleus or seed to get them started. The nucleus is just a foundation that gives the crystal a place to build. The seed can be another crystal (a principle used in the Dyce process for making creamed honey) or it can be a speck of dust or a grain of pollen.
But if your honey is very high in fructose, the pollen will not cause the honey to crystallize. Just ask the producers of non-crystallizing honey such as tupelo, gallberry, and chestnut. They’ve been producing honey for generations—since long before ultrafiltration was invented—yet their honey didn’t crystallize. I filter my own honey through a food mesh large enough for aphids to pass through, yet my honey doesn’t crystallize either. It’s all in the nectar.
However, if your honey is high in glucose, you can delay the crystallization process by removing all the pollen grains. With no platforms on which to build a crystal, the honey can remain stable and liquid for extended periods of time—or at least long enough to sell it.
Honey packers buy honey from many different sources and blend it in gigantic batches. Some of the honey will be high in fructose, but most will be high in glucose. Once mixed, the only effective way to slow the crystallization is to remove of all the particulates.
What is sad is the almost universal disdain for crystallized honey. By demanding clear liquid honey with no floaters, consumers have created a market for the over-processed, adulterated, pollen-free “honey” we see on store shelves. If only we could create a demand for the real thing.