Bioactivities of Soy Protein Hydrolysates Conjugated with Mannose and Allulose

What formulators need to know first

Soy protein hydrolysates are workhorse ingredients, but their bioactivity can be modest. This paper puts a new option on the table. Conjugating those hydrolysates with mannose or allulose through the Maillard reaction creates peptides with stronger antioxidant and enzyme-inhibiting activity. The work appears in Foods with DOI 10.3390/foods13193041.

Background: Maillard conjugation as a functional tool

The Maillard reaction is often discussed in terms of flavor and color. This paper uses it for a different purpose. Non-enzymatic conjugation of peptides with reducing sugars modifies the peptides' biological functions. That makes a familiar food reaction into a functional ingredient strategy.

Most protein-sugar work uses glucose or lactose. Rare sugars like allulose and mannose behave differently. They still participate in Maillard chemistry, but their structure changes the resulting conjugates. The study asks whether those differences translate into useful bioactivities.

What the researchers did

The researchers reacted soy protein hydrolysate with both mannose and allulose. Then they tested the conjugates for antioxidant activity, pancreatic lipase inhibition, and ACE inhibition. ACE inhibition matters for blood pressure management. Pancreatic lipase inhibition matters for fat metabolism. Antioxidant activity matters for oxidative stability in food systems.

The headline results focus on the allulose conjugate, labeled SPHA.

Key findings

SPHA delivered strong radical-scavenging activity. Its DPPH value was 280.87 ± 16.39 µg Trolox/mL. Its FRAP value reached 38.91 ± 0.02 mg Trolox/mL. Both numbers point to a real antioxidant capacity, not just a trace effect.

The conjugate also inhibited pancreatic lipase by 29.43 ± 1.94%. That is a meaningful signal for weight-management or satiety products. On top of that, both the conjugated mixture and the rare sugars themselves showed ACE-inhibitory properties.

Assay	What it indicates	Reported value
DPPH radical scavenging	Free-radical neutralization	280.87 ± 16.39 µg Trolox/mL (SPHA)
FRAP	Total antioxidant reducing power	38.91 ± 0.02 mg Trolox/mL (SPHA)
Pancreatic lipase inhibition	Potential fat-digestion modulation	29.43 ± 1.94% (SPHA)
ACE inhibition	Blood-pressure modulation	Present in conjugated mixture and rare sugars alone; no specific value in the evidence

What this means for formulators and buyers

This is in vitro data. That does not make it useless. It makes it a starting point.

For a formulator, the appeal is clear. Soy protein hydrolysate is an established, cost-effective protein source. A Maillard step with allulose adds bioactivity without requiring a new protein isolate. The process uses equipment and heat already common in food manufacturing. That should simplify scale-up.

For ingredient buyers, this suggests a new way to evaluate supplier capabilities. You can ask whether a hydrolysate supplier offers rare-sugar conjugation. You can also use the assay numbers as screening criteria when comparing prospective ingredients.

The ACE inhibition deserves special attention. Here, the rare sugars themselves contribute to the effect. That means formulators might not need as much hydrolysate to hit a target activity. They can let the sugar do part of the work.

FAQ

What exactly is SPHA? SPHA is the soy protein hydrolysate–allulose conjugate tested in the study. It is the sample behind the antioxidant and lipase-inhibition numbers.

Does mannose still matter if the data focus on allulose? The study’s stated focus includes both sugars. The evidence provided centers on allulose, so we have fewer clear numbers for mannose. Treat the allulose results as the strongest available signal.

Can these results support a label claim? Not yet. These are lab assays, not clinical endpoints. They can guide product development, but they do not justify a health claim.

Where to go from here

Try the reaction in your own lab. Start with a standard soy protein hydrolysate and allulose. Measure antioxidant activity and lipase inhibition. See whether the conjugates hold up in your finished product. The data from this paper give you a benchmark. Your matrix will tell you the rest.