Biological Activities of Soy Protein Hydrolysates Conjugated with Mannose and Allulose

Conjugation changes what a protein hydrolysate can do

Conjugation changes what a protein hydrolysate can do. That is the core message of a new paper on soy peptides and rare sugars. The research, published in the journal Foods (DOI: 10.3390/foods13193041), looks at what happens when mannose or allulose is attached to soy protein hydrolysate through the Maillard reaction. For formulators, the results point to more than a sweetness advantage.

Why the Maillard reaction matters here

The Maillard reaction is usually discussed in terms of color and flavor. Bread crust. Roasted coffee. Grilled meat. But the same chemistry can be used deliberately. Non-enzymatic conjugation of peptides through the Maillard reaction is a known way to improve biological functions. Soy protein hydrolysates are already common in food formulations. Conjugating them with rare sugars can shift their activity in measurable ways.

Allulose is one of the rare sugars in the study. Mannose is the other. The researchers used both as conjugation partners.

What the study did

The team conjugated soy protein hydrolysate with mannose and allulose. Then they ran a set of laboratory assays. They measured radical scavenging with DPPH. They measured antioxidant reducing power with FRAP. They tested pancreatic lipase inhibition. They also tested ACE inhibition. ACE is the angiotensin-converting enzyme involved in blood pressure regulation.

The allulose conjugate appears in the paper as SPHA. The reported data on antioxidant and lipase activity focus on SPHA. The ACE results are broader. Both the conjugated mixtures and the rare sugars themselves showed ACE inhibitory properties.

Key findings

SPHA produced clear antioxidant responses in the lab. Its DPPH radical scavenging activity came in at 280.87 ± 16.39 µg Trolox/mL. Its FRAP value was 38.91 ± 0.02 mg Trolox/mL. These are standard ways to measure antioxidant capacity. The values are expressed as Trolox equivalents, which gives formulators a reference point.

Pancreatic lipase inhibition was 29.43 ± 1.94%. That is not a pharmaceutical-strength block. But it is a real effect for a food ingredient. Slowing lipase by about 29% could matter for formulations aimed at fat digestion.

ACE inhibition appeared in the conjugated mixtures and in the rare sugars alone. That is worth attention. The sugar is not just a passive carrier. It contributes to the bioactivity.

Assay	Finding	What it indicates
DPPH radical scavenging (SPHA)	280.87 ± 16.39 µg Trolox/mL	Ability to neutralize free radicals
FRAP (SPHA)	38.91 ± 0.02 mg Trolox/mL	Ferric-reducing antioxidant power
Pancreatic lipase inhibition (SPHA)	29.43 ± 1.94%	Modest interference with fat digestion
ACE inhibition	Present in conjugated mixtures and rare sugars	Potential support for blood pressure regulation

What it means for manufacturers

Rare sugars can act as functional partners for protein ingredients. That is especially relevant for allulose, which already has a role in reduced-sugar product development. If you source allulose for sweetness, this paper adds another angle. The same sugar may help you build a peptide-based ingredient with antioxidant or enzyme-inhibiting activity.

Ingredient buyers should ask suppliers for data, not just declarations. When a supplier offers a soy protein hydrolysate, ask whether it has been conjugated with a rare sugar. Ask for the assay results. The SPHA data here gives you a benchmark for what a conjugated ingredient can show.

The ACE finding is broader. If the rare sugar itself carries ACE inhibitory activity, formulators can consider it even without a protein conjugate. That opens up simpler formulations for blood-pressure-oriented concepts. But keep expectations in check. These are laboratory assays. They do not prove clinical outcomes. Product claims will require human studies and regulatory review.

FAQ

What does SPHA stand for?

SPHA is the soy protein hydrolysate-allulose conjugate used in the study. The paper reports its antioxidant and lipase inhibition results.

Is allulose only providing sweetness in this application?

No. The rare sugars themselves showed ACE inhibitory properties in the conjugated mixtures. Allulose contributed to the measured bioactivity, not just to taste.

Can formulators use these findings right away?

For concept development, yes. For claims, no. The data come from lab assays. You need human data and regulatory approval before making functional claims.

Closing

The paper adds another reason to treat allulose and mannose as functional ingredients, not just sugar replacements. Soy protein hydrolysates are already familiar to food formulators. Conjugating them with rare sugars could give that ingredient a new job. The antioxidant numbers are solid. The lipase inhibition is modest but real. The ACE activity appears in both sugars and conjugates. That is enough to start pilot work and supplier conversations.