Invertobee 66-C: Cold-Process 2:1 Syrup for Bee Winter Stores

Invertobee 66-C at a glance:

€120 for a 350 g sachet, enough to invert 1,000 kg of dense 2:1 winter-stores syrup (660 kg sugar + 340 kg water) — cold at room temperature (~20 °C) in about 36 hours, with no heating and no HMF; or warm at 50–60 °C in about 8 hours, up to ~70% solids. Real material cost: about €0.55/kg.

Inverted syrup is already split into glucose and fructose, so bees absorb it with less metabolic effort than plain sucrose syrup — and research on intestinal health shows a measurable lifespan benefit from inverted feed over plain sugar syrup (2013 Apimondia study). At the same time, the dense 2:1 syrup you build is a strong winter-stores feed: more sugar per litre than a light 1:1 mix, less water for the bees to evaporate, and better resistance to fermentation. Below about 10 °C, bees stop taking liquid feed — that is when you switch to Invertase Invertobee 73-Z, the sugar-paste option.

Why 2:1 — dense syrup for winter stores

The 2:1 ratio is the autumn standard for one reason: it concentrates the feed. Run at room temperature you get roughly 66% sugar; heat the tank to 50–60 °C and the same enzyme takes you to about 70% — both are the dense winter-stores feed.

• More feed per litre. A 2:1 syrup packs roughly a third more sugar into each litre than the light 1:1 spring syrup — so every feeder run stores more energy.
• Less water for the bees to ripen. Bees ripen syrup by evaporating the water off. A denser syrup means less moisture to fan out, and less humidity added to the hive in autumn as the cluster forms.
• Takes less space. For the same stored energy, dense syrup occupies less comb — comb your bees will need for the cluster and for brood come spring.
• Better microbiological stability. At 66–70% solids the syrup resists fermentation far better than a light 1:1 mix, so it keeps through the feeding window.

This is the feed for building winter stores — not the light spring stimulant. The same dense 2:1 syrup is also used in queen rearing, where cell-raising and mating colonies need a reliable energy feed whenever fresh nectar is scarce.

Cold or warm — 66-C vs 66-W

Invertobee makes two dense-syrup products, and each works across roughly the same 66–70% concentration range. The real difference is how you run them — the temperature you can hold, the time you have, and the equipment on hand.

• Invertobee 66-C (this page) is the flexible option. Run it cold and you need no heating at all: dissolve, add the enzyme, leave it at room temperature (~20 °C) for about 36 hours, and you get a ~66% syrup with zero energy cost. Have a tank you can warm? The same enzyme also runs at 50–60 °C, finishes in about 8 hours, and handles a higher sugar load — up to around 70%. Cold or warm, it is one product and one dosage: 350 g per 1,000 kg of syrup.
• Invertase Invertobee 66-W is the warm-process workhorse. It is designed to run at 50–60 °C, finishes in about 12 hours, and reaches the top of the dense range (68–70%). It suits commercial operations with a heated tank that want a single, fast, repeatable warm batch for bulk production and storage.

Which one fits you? If you already heat your tanks and want the dedicated warm-process product, see the 66-W page. If you want one enzyme that works cold or warm — with no heating as the default and higher concentration available when you do heat — 66-C is the one.

How to use 66-C — dosage and process

One 350 g sachet of Invertase Invertobee 66-C inverts 1,000 kg of dense syrup. Operating conditions:

Step by step — cold process:

1. Weigh the ingredients. For 1,000 kg of finished syrup: 660 kg white granulated sugar + 340 kg clean water. Use only white beet or cane sugar — avoid raw sugar, brown sugar or syrups containing molasses.
2. Combine sugar and water. Pour the water into the tank first, then add the sugar and stir until dissolved. No heating is needed.
3. Add the enzyme. Dissolve 350 g of Invertase Invertobee 66-C in a little water separately, then mix it into the batch.
4. Wait for inversion. Cover the container and leave it at room temperature for about 36 hours.
5. Feed. The syrup is 100% inverted, at ~66% solids, with zero HMF — ready to feed as winter stores.

Prefer a denser, faster batch? Run the same steps warm: raise the sugar to ~700 kg per 1,000 kg, warm the mix to 50–60 °C to dissolve it, add the 350 g of enzyme, and hold it covered at 50–60 °C for about 8 hours to reach up to ~70% solids.

The autumn feeding window — and the below-10 °C switch

Winter stores are built between September and November. That is the window to feed the dense 2:1 syrup while the colony is still active and the weather still allows liquid feed.

Below about 10 °C, bees stop taking liquid feed altogether — no matter how good the syrup. When the temperature drops, switch to a solid feed: Invertase Invertobee 73-Z turns 200 kg of syrup plus 600 kg of powdered sugar into about 800 kg of sugar paste, placed directly on the frames above the cluster.

What it costs — and what you save

Costs assume sugar at €0.65/kg, the current European market reference — your actual cost depends on your local sugar price, and the comparison scales with it. The point: you mix the feed yourself from your own sugar and water, so your cost is the sugar price plus one sachet of enzyme — not the price of a ready-made drum.

Against ready-made syrup. A ready-made low-cost bulk syrup runs around €1.10/kg, and premium invert syrups start near €1.60/kg. At ~€0.55/kg for the finished mix, that is a saving of roughly €550 per tonne against low-cost bulk (~50%), and €1,050+ per tonne against premium — before you add the transport and margin a ready-made drum carries. (Comparison figures from the market reference prices in our how-to guide; the full working is there under Option 1.)

Why beekeepers trust Invertobee

Here's why beekeepers choose it:

• Cold process — zero heating cost. Works at room temperature (~20 °C): make the dense 2:1 syrup in an unheated room — no tank heater, no energy bill.
• One enzyme, cold or warm. No heating setup? Leave the batch at ~20 °C for about 36 hours and it is done. Have a heated tank? The same 350 g sachet runs at 50–60 °C, finishes in about 8 hours and pushes the syrup up to ~70% solids.
• Zero HMF by design. The low-temperature enzymatic process produces no hydroxymethylfurfural (HMF), a substance toxic to bees — run cold it stays at zero, and even run warm at 50–60 °C it stays below 5 mg/kg, far under the levels that acid-and-heat inversion produces.
• In use since 2015. Chosen by thousands of professional beekeepers in 29 countries.
• 15 days to change your mind. Returns accepted on unopened products within 15 days of delivery.

Every ingredient is food-grade for human consumption: acidity regulators (lemon powder, tartaric, malic and citric acid) and texture regulators (glucose, maltose and other sugars). The low-temperature inversion technology behind it was granted a patent in 2016 — confirmation of an original in-house formulation, not a generic one.

Further reading

• Invertase Invertobee 66-W — warm process, 68–70% syrup in 12 hours
• How to make invert syrup for bees — Option 1: cold, 66%, no heating
• Healthy and productive beehives — Building Winter Stores
• Invertase Invertobee 73-Z — sugar paste for feeding below 10 °C