Biological Activities of Soy Protein Hydrolysate Conjugated with Mannose and Allulose

Rare sugars can do more than sweeten

A new study in Foods adds practical evidence for an idea formulators should watch: Maillard conjugation with rare sugars can turn a commodity protein hydrolysate into a more functional ingredient. The researchers tested soy protein hydrolysate conjugated with mannose and allulose. The allulose conjugate, SPHA, showed clear activity in antioxidant, lipase, and ACE assays. Paper DOI: 10.3390/foods13193041.

Why conjugate peptides with rare sugars?

Non-enzymatic conjugation of peptides through the Maillard reaction has gained attention as an effective way to enhance biological functions. Most food technologists know the Maillard reaction for browning and flavor. This study looks at a different output: bioactivity. When you attach a rare sugar like allulose to the amine groups of peptides, you alter the molecule's electron-donating and enzyme-interacting behavior. The result can exceed what the protein hydrolysate delivers alone.

Soy protein hydrolysate is a sensible starting point. It already contains bioactive peptides. Conjugation may amplify those effects or add new ones. For a food manufacturer, the appeal lies in making standard ingredients work harder without a new enzyme or fermentation step.

What the study did

Researchers took soy protein hydrolysate and conjugated it with mannose and allulose under Maillard conditions. They did not use enzymes. Then they measured several biological activities:

• DPPH radical scavenging
• FRAP (ferric reducing antioxidant power)
• Pancreatic lipase inhibition
• ACE (angiotensin-converting enzyme) inhibition

These assays map to oxidative stress, fat digestion, and blood-pressure regulation.

Key findings

SPHA, the allulose conjugate, performed well across the board. Its DPPH radical scavenging activity hit 280.87 ± 16.39 µg Trolox/mL. Its FRAP value reached 38.91 ± 0.02 mg Trolox/mL. Both numbers signal real antioxidant potential in vitro.

The same conjugate inhibited pancreatic lipase at 29.43 ± 1.94%. That level of inhibition suggests a possible role in weight-management or satiety products. No formula can make a clinical claim from this single study, but the mechanism deserves attention.

ACE inhibition appeared in the conjugated mixture and in the rare sugars themselves. That last point matters. Allulose alone may carry ACE-inhibitory properties. In a formulated product, you might get bioactivity from both the sugar and the conjugate.

Assay	Result for SPHA	What it suggests
DPPH radical scavenging	280.87 ± 16.39 µg Trolox/mL	Strong antioxidant activity
FRAP	38.91 ± 0.02 mg Trolox/mL	High reducing power
Pancreatic lipase inhibition	29.43 ± 1.94%	Potential fat-digestion modulation
ACE inhibition	Positive in conjugate and rare sugars alone	Possible blood-pressure-related activity

What it means for formulators and ingredient buyers

You can treat these results as a starting point, not a finished product spec. The data came from lab assays, not sensory panels or clinical trials. Still, the implications are concrete.

If you already source allulose, you have an opportunity to create functional ingredients by reacting it with a protein hydrolysate. No enzyme step is needed. The reaction is non-enzymatic, which simplifies process development. You can control the degree of conjugation through time, temperature, and sugar-to-peptide ratio.

Watch the sensory side. Maillard conjugation changes color and flavor. In some applications, darkening and roasted notes are acceptable or even desirable. In white powders or neutral beverages, you will need to manage it.

Ingredient buyers should also look at allulose differently. The study found ACE inhibitory properties in the rare sugars themselves. That means allulose can contribute directly to bioactivity, not just sweetness and texture.

FAQ

Does SPHA mean allulose-conjugated soy protein hydrolysate? Yes. In this paper, SPHA is the soy protein hydrolysate–allulose conjugate.

Are the antioxidant and lipase results strong enough for product claims? They support research and development decisions, not health claims. You would need dose-response work and actual product testing before claim substantiation.

Did mannose show the same effects as allulose? The paper's title and scope cover mannose and allulose. The reported evidence on SPHA focuses on allulose, so use that for your next formulation screen. Compare mannose conjugates in your own test if the application depends on it.

Closing thought

One reaction step can change the biological profile of a standard soy ingredient. That is valuable for a B2B food market looking for differentiation. The next move belongs to formulators: run your own trials, check the sensory impact, and see where allulose-conjugated peptides fit in your product lineup.