Effect of the Rare Sugar D-Allulose on the Hardening of Starch Gels during Refrigerated Storage

Starch gels turn hard in the fridge. That is a real problem for bakers, sauce makers, and prepared food manufacturers. A new study published in Foods (DOI: 10.3390/foods13142183) shows that the rare sugar D-allulose can slow that hardening. It works even better than sucrose.

The study’s title translates to English as “Effect of the Rare Sugar D-Allulose on the Hardening of Starch Gels during Refrigerated Storage.” The findings matter because refrigerated starch-based products often lose quality quickly. Texture changes, water weeps out, and the product feels stale or tough. Most formulators reach for sugar or other humectants to manage this. Allulose offers a different route.

What happens when starch gels age

Starch gels are not static systems. When cooked starch cools, amylose molecules set quickly into a network. Later, amylopectin chains slowly realign. That process is called retrogradation. It drives gel hardening, firmness increase, and syneresis. Refrigerated storage speeds it up. This is why rice puddings, pie fillings, and custard-based products harden after a day or two in the cold.

Sugars interfere with retrogradation. They change water availability and hydrogen bonding. But sucrose comes with calories. Allulose is different. It is a rare sugar with about 10 percent of the calories of sucrose and roughly 70 percent of its sweetness. It also has anti-hyperglycemic and anti-obesity effects in animal and human studies. The FDA recognizes it as GRAS. That makes it an attractive tool for formulators who want to cut sugar without sacrificing shelf life.

What the study actually did

The researchers made starch gels from an amylopectin-rich starch source. They added D-allulose and compared it against sucrose, then stored the gels under refrigerated conditions. They measured hardening over time and analyzed hydrogen bonding patterns to understand the mechanism behind the texture changes.

The results were clear. Allulose suppressed the hardening of amylopectin-rich starch gels. It did so significantly better than sucrose. That is a practical finding, not just a lab curiosity.

The mechanism is also useful. Allulose reduced the proportion of intermolecular hydrogen bonds in the gel network. At the same time, it increased the number of loose hydrogen bonds. This shift made it harder for amylopectin chains to pack tightly and recrystallize. Less recrystallization means less hardening.

Sucrose vs. D-allulose: the difference at a glance

Factor	Sucrose	D-allulose
Effect on starch gel hardening	Moderate suppression	Stronger suppression
Hydrogen bond effect	Standard sugar behavior	Reduces intermolecular bonds, increases loose bonds
Amylopectin recrystallization	Slowed somewhat	More effectively inhibited
Calories	4 kcal/g	~10% of sucrose’s calories
Sweetness	100%	~70% of sucrose

The table tells the story. Sucrose helps, but allulose helps more in this system. And it does it with fewer calories.

What this means for manufacturers

If you formulate refrigerated starch-based products, allulose is worth testing. It could be a partial replacement for sugar, or a full replacement in systems where sweetness can be adjusted. The anti-hardening effect is not just a side benefit. It attacks the core mechanism of quality loss: amylopectin recrystallization.

You can also combine the texture benefit with label benefits. Allulose supports calorie reduction. It does not spike blood glucose the way sucrose does. Since it is GRAS, it can be used in many applications without the approval delays that some novel ingredients face.

Start with a simple bench trial. Make your standard gel, replace part of the sugar with allulose, and check hardness after one, three, and seven days of cold storage. The hydrogen bond data from this study suggest the texture should hold up better. But your formulation will determine the exact dose. Starch type, solids content, and other ingredients all matter.

FAQ

Is allulose a direct replacement for sucrose?
Not exactly. It is about 70 percent as sweet, so you may need to blend it with high-intensity sweeteners or adjust flavor systems. In terms of texture, this study suggests it can perform better than sucrose in refrigerated starch gels.

Does this apply to all starch-based foods?
This study focused on amylopectin-rich starch gels. That model is relevant to many puddings, fillings, and baked goods, but it is not proof for every formulation. Test your own system.

Is allulose allowed for food use?
The FDA considers D-allulose to be GRAS. Check local regulations if you sell outside the United States, because approval status can vary.

The evidence here gives formulators a clear reason to look beyond sucrose. Allulose changes hydrogen bonding in the gel. That simple shift keeps amylopectin from recrystallizing, and the gel stays softer under refrigeration. Fewer calories, comparable sweetness, and better texture. That is a rare combination in food ingredients.