Bioactivities of Soy Protein Hydrolysate Conjugated with Mannose and Allulose

A Maillard reaction product with a job to do

Buyers of protein hydrolysates usually treat the Maillard reaction as a defect. This study treats it as a tool. Researchers took soy protein hydrolysate, conjugated it with the rare sugars mannose and allulose, and found the resulting mixture carried serious bioactivity. The work appears in Foods, DOI: 10.3390/foods13193041.

Why conjugate a hydrolysate with rare sugars?

Protein hydrolysates already sell in sports nutrition, clinical nutrition, and high-protein beverages. Their peptides are active, but often weakly. Non-enzymatic conjugation through the Maillard reaction changes that. By attaching sugars to peptides under controlled heat, you alter the peptide structure and can boost biological functions. Allulose fits this approach nicely. It is a low-calorie rare sugar, and it reacts with proteins in ways that go beyond simple sweetening. Mannose joins it in this study, giving formulators a two-sugar conjugation system.

What the study did

The team used soybean protein hydrolysate and conjugated it with mannose and allulose. They then measured three things: antioxidant activity, pancreatic lipase inhibition, and ACE inhibition. They also tested the rare sugars on their own for ACE inhibition. The point was to see whether the conjugated mixture could serve as more than a protein source.

Key findings at a glance

The numbers tell the story.

Assay	Activity
DPPH radical-scavenging activity	280.87 ± 16.39 µg Trolox/mL
FRAP (ferric reducing antioxidant power)	38.91 ± 0.02 mg Trolox/mL
Pancreatic lipase inhibition	29.43 ± 1.94%
ACE inhibition	Present in the conjugated mixture and in the rare sugars alone

The antioxidant values are strong. A DPPH value above 280 µg Trolox/mL means the conjugate can scavenge free radicals in a meaningful way. The FRAP value confirms reducing power. That is a useful combination for formulators fighting oxidation in emulsions or high-protein bars.

The lipase inhibition number is smaller. 29.43% inhibition is not enough to call this an anti-obesity drug, but it is promising for a food ingredient. A protein hydrolysate that interferes with fat digestion could support weight-management concepts, especially when paired with allulose.

ACE inhibition matters for blood-pressure-focused products. The study notes that both the conjugated mixture and the rare sugars themselves showed ACE-inhibitory properties. That means the sugar component is not just a carrier. It contributes.

What this means for food manufacturers

For ingredient buyers, the interesting part is multifunctionality. One conjugated hydrolysate could deliver antioxidant protection, a modest lipase-inhibiting effect, and ACE-inhibitory activity. That fits neatly into concepts around metabolic health, weight management, and healthy aging.

Allulose already helps with sugar reduction. Now it has another reason to appear on the label. When conjugated with soy peptides, it transforms a commodity hydrolysate into a functional fragment with measurable activity. You could market this in a protein powder, a shot, or a fortified bakery item.

Process control will matter. Conjugation changes color and flavor. You will need to manage reaction time and temperature to avoid late-stage Maillard burn. The payoff is a protein ingredient that does more than feed muscle. It scavenges radicals and inhibits enzymes.

Quick questions from formulators

Do these results translate directly to finished products?

Not directly. This was in vitro work. Digestion, absorption, and formulation matrix will all influence the final effect. But the assay results are a strong starting point.

Which sugar does the heavy lifting?

The paper does not split the effects between mannose and allulose in the data provided. It reports on the conjugated mixture and highlights that the rare sugars themselves have ACE inhibition. Both sugars likely play a role.

Can allulose and mannose be used together in a commercial ingredient?

Yes. That is exactly what this study did. The conjugation included both sugars, and the resulting mixture showed the activities above.

A formulation angle worth testing

This paper gives suppliers and product developers a concrete reason to test conjugated protein fractions. The antioxidant numbers alone are enough for a second look. Add lipase inhibition and ACE activity, and you have a rare-sugar protein ingredient with genuine functional range. The next step is to ask your hydrolysate supplier whether they can run a controlled Maillard conjugation with allulose. The answer may reshape your next product concept.