Allulose lowers the freeze point about 1.9 times as much as table sugar, gram for gram. That means you need roughly half as much of it, not the same amount. Most slush calculators assume table sugar, so they tell sugar-free users to add far more allulose than the batch needs, and the batch never sets.
Every Ninja SLUSHi needs roughly 4% dissolved solids, measured as table sugar, before the auger can shave soft crystals instead of hitting a solid block. These are the allulose equivalents.
| Batch | Sugar it would take | Powdered allulose | By weight |
|---|---|---|---|
| Ninja SLUSHi FS301 88 oz mix |
104 g | 5¾ tbsp | 55 g |
| Ninja SLUSHi Max FS601 128 oz mix |
152 g | 8¼ tbsp | 80 g |
| Ninja SLUSHi XXL FS605 150 oz mix |
178 g | 9¾ tbsp | 93 g |
| A single 24 oz bottle 24 oz mix |
28 g | 1½ tbsp | 15 g |
| One 8 oz cup 8 oz mix |
9 g | ½ tbsp | 5 g |
Powdered allulose, about 12 g per tablespoon. The tablespoon figures include a small margin over the bare minimum, because sitting exactly on the threshold is how a batch fails when your measuring is a little off.
Freezing point depression is a colligative property: it depends on how many molecules are dissolved, not how much they weigh. Table sugar is sucrose, a disaccharide with a molecular weight around 342. Allulose is a monosaccharide, weighing around 180. The same weight of allulose puts roughly 1.9 times as many molecules into the mix, so it pushes the freeze point down roughly 1.9 times as far.
Allulose is also only about 70% as sweet as sugar, which is where people go wrong twice over. They add more to reach the sweetness they expect, which overshoots the freeze point, and the mix stays liquid no matter how long the machine runs. Match the freeze point first using the table above, then adjust sweetness separately with a sugar-free syrup or a little extra allulose.
Alcohol depresses the freeze point as well, and it stacks with the allulose rather than replacing it. A spiked sugar-free batch reaches the limit much faster than either ingredient would alone. Keep the finished mix under the machine's alcohol ceiling, 16% ABV on the Ninja models, and start at the lower end of the allulose range rather than the top.
About 2 tablespoons of powdered allulose per 24 oz of liquid, or roughly 7 tablespoons for a full 88 oz FS301 batch. That is less than the sugar you would use, because allulose depresses the freeze point about 1.9 times as hard as table sugar by weight.
Not in the amount, only in the effect. Allulose is a monosaccharide and table sugar is a disaccharide, so the same weight of allulose puts roughly twice as many molecules in solution and lowers the freeze point roughly twice as much. It is also only about 70% as sweet, so match the freeze point first and adjust sweetness separately.
Usually one of two reasons. Either the sweetener does not lower the freeze point at all, which is the case for stevia, erythritol and most monk fruit blends, so the mix sits below the machine's threshold and it refuses to run. Or you used a calculator built for table sugar, which under-reads allulose by about half and told you to add more than you needed.
No. Erythritol tastes sweet but contributes very little usable freeze-point depression at the concentrations a slush machine needs, and it tends to recrystallise. A zero-sugar mix built on erythritol behaves like water: it either sets into a solid block or stays liquid.
Not on its own. Most monk fruit products sold as a sugar substitute are mostly erythritol with a trace of monk fruit extract for sweetness, so they behave like erythritol. Check the ingredients panel: if erythritol is first, it will not freeze properly.
Yes, but the dose is different because syrup is diluted. Allulose syrups are typically 70 to 80% solids, so you need roughly a third more by volume than the powder figures here. Powder dissolves more evenly in a cold mix.
Alcohol lowers the freeze point too, and it stacks with the allulose, so a spiked sugar-free batch reaches the limit faster than either alone. Keep the finished mix under your machine's alcohol cap, which is 16% ABV on the Ninja models, and start at the lower end of the allulose range.