Blood is a surprisingly protein-dense material. Whole blood typically contains 17 to 22 percent protein, split between the cellular fraction dominated by hemoglobin and a plasma fraction rich in albumins, globulins, and fibrinogen. These compositions vary by species: bovine and porcine blood contain the highest total protein concentrations at 7.9 to 8.7 and 7.7 to 8.9 grams per 100 milliliters respectively, while goat blood sits lower at 6.8 to 7.2 grams per 100 milliliters. Avian blood, particularly from ducks, is lower still at 12 to 13 percent total protein. These differences matter because the starting protein mix determines which peptides emerge during enzymatic hydrolysis, and the review shows that species-specific peptide profiles translate directly into distinct bioactivities.

The core technology is proteolysis. Enzymes such as alcalase, trypsin, chymotrypsin, pepsin, and papain cleave blood proteins into short peptide chains, each enzyme leaving its own signature. Alcalase, a serine protease with a Ser-His-Asp catalytic triad, broadly generates antioxidant, ACE-inhibitory, and DPP-IV inhibitory peptides. Trypsin cuts specifically after lysine and arginine residues, producing C-terminal basic peptides that often bind well to the angiotensin-converting enzyme active site. Papain, a cysteine protease with a Cys-His catalytic dyad, has been used to extract antioxidant peptides from poultry hemoglobin, while pepsin’s aspartic protease mechanism cleaves preferentially at hydrophobic and aromatic residues under acidic conditions that mimic the stomach. Chemical hydrolysis with acids or alkalis is faster and suited to industrial scale, though it sacrifices the sequence precision that enzymatic cleavage provides.

The resulting peptides display a remarkable range of biological activities. Bovine hemoglobin-derived peptides such as LRVSV inhibit ACE with an IC50 of just 0.15 micromolar, while the chicken blood cell peptide VSKRLNGDA showed antihypertensive effects in vivo in a rat model at 26.46 micromolar. Antioxidant sequences abound as well: duck plasma peptides RCLQ and EVGK showed strong ferric reducing power and iron chelation, and chicken blood peptides achieved metal chelation rates of 65 to 80 percent at 1.0 milligram per milliliter. For type 2 diabetes, blood-derived peptides such as AAATP and LPVPQ from bovine blood inhibit dipeptidyl peptidase IV, the enzyme that degrades the incretin hormones GLP-1 and GIP, with IC50 values in the range of 100 to 150 micromolar. Anti-inflammatory peptides from goose and Siamese crocodile blood act through the TLR4/NF-kB/iNOS pathway and shift macrophages from pro-inflammatory M1 to anti-inflammatory M2 phenotypes.

One of the review’s most significant contributions is its treatment of gastrointestinal stability as a structural question rather than an afterthought. Peptides face a brutal journey: gastric pH of 1.5 to 3.5, pepsin cleavage, pancreatic enzymes in the alkaline intestine, brush border peptidases, and finally plasma peptidases after absorption. Overall bioavailability of most food peptides is estimated at less than 1 to 2 percent of the administered dose. The authors identify proline as a key protective residue. Its unique pyrrolidine ring constrains rotation around the peptide backbone, creates kinks that block enzyme binding, and its capacity to switch between cis and trans configurations confounds aminopeptidases. Peptides rich in hydrophobic amino acids like leucine, isoleucine, and valine also show superior resistance to gastric digestion compared with sequences dominated by polar residues. These structural markers allow researchers to predict, from sequence alone, which peptides are likely to survive digestion and reach their targets intact.

Some peptides are even designed to be activated by digestion. Certain blood-derived sequences act as pro-peptides that release their bioactive fragments only after partial enzymatic breakdown in the gut, a sequential activation mechanism that inverts the conventional view of digestion as purely destructive. Absorption occurs mainly through peptide transporters PEPT1 and PEPT2, with peptides below 1000 daltons showing absorption rates of roughly 5 to 15 percent in Caco-2 cell models. Once in circulation, interaction with albumin can shield peptides from plasma peptidases and extend their half-life, and blood-derived peptides may enjoy enhanced circulation stability because their structures resemble endogenous blood proteins.

A major practical barrier to using hemoglobin in food has always been its intense red color. The review devotes detailed attention to decolorization strategies, ranging from solvent extraction of heme to enzymatic degradation of the porphyrin ring to chemical oxidation with food-grade hydrogen peroxide, peracetic acid, or ozone. Oxidation works by converting the heme iron from Fe2+ to Fe3+ and destroying the conjugated porphyrin system responsible for visible-light absorption. The authors caution, however, that because blood color resides in the heme-porphyrin itself, decolorization necessarily exposes globin and plasma proteins to oxidative conditions that can crosslink alpha-globin and oxidize sensitive amino acids, so mild, dose-controlled treatment with prompt catalase quenching is essential. Importantly, ACE- and DPP-IV-inhibitory activity depends on primary sequence rather than tertiary structure, so mild decolorization is not expected to diminish those potencies, though antioxidant peptides built on oxidation-sensitive residues such as cysteine, methionine, and tryptophan require experimental verification after treatment.

Purification and delivery technologies round out the industrial toolkit. Membrane filtration achieves 80 to 95 percent recovery of target peptides, chromatographic methods reach 60 to 90 percent with higher selectivity, and electrophoresis offers superior resolution for analytical work. Encapsulation technologies can improve stability of bioactive compounds by up to 80 percent during processing and storage, and microencapsulation of blood-derived peptides in maltodextrin carriers has maintained ACE-inhibitory and antioxidant activities over six-month storage periods. Spray-dried blood protein ingredients with neutral flavor and shelf life exceeding 12 months are already commercially feasible under controlled temperature and humidity.

The regulatory and commercial hurdles remain substantial. Blood is a high-risk substrate for pathogens including Salmonella and E. coli O157:H7, and ruminant blood carries transmissible spongiform encephalopathy risk that demands age- and tissue-restricted sourcing. Allergenicity is a further complication: the alpha-gal carbohydrate on mammalian blood glycoproteins survives both heat and proteolysis, making hydrolysis alone insufficient to eliminate allergy risk for sensitized consumers. Halal and kosher dietary law categorically prohibits blood consumption, excluding those markets entirely, and consumer perception of blood-derived ingredients constrains adoption elsewhere. Economic analyses suggest that production costs of purified blood peptides still exceed those of plant-derived alternatives, though integrated abattoir collection and high-throughput purification could narrow the gap.

Despite these challenges, the review positions blood-derived peptides as a cornerstone technology for circular economy food production. Proof of concept for oral antihypertensive peptides already exists in clinical data for milk-derived lactotripeptides, which consistently reduced systolic blood pressure in randomized trials across European and Asian populations. What remains is dedicated clinical validation of blood-derived preparations, scale-up of pilot processes such as the duck blood hydrolysate platform demonstrated by the same research group, and rational design pipelines that use proline content and hydrophobicity as predictive markers for peptide performance. If those pieces come together, the red liquid that slaughterhouses currently pay to dispose of could become a sustainable raw material for cardiovascular support, diabetes management, and next-generation functional foods.

Subject of Research: Bioactive peptides derived from slaughter blood proteins and their structure-function relationships, gastrointestinal stability, and applications in functional foods

Article Title: Slaughter blood-derived bioactive peptides: structure-function relationships, species-specific bioactivities, gastrointestinal stability, and sustainable applications in food systems

Article References: Laosam, P., Yue, Y., Rouabhia, M., Suwanangul, S., Pinyo, J., Katemala, S., Paengkoum, P., Nakharuthai, C., Pongsetkul, J., Pongsamai, N., & Sangsawad, P. (2026). Slaughter blood-derived bioactive peptides: structure-function relationships, species-specific bioactivities, gastrointestinal stability, and sustainable applications in food systems. Food Science of Animal Resources, 46(1), Article 104. https://doi.org/10.1007/s44463-026-00107-3

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00107-3

Keywords: slaughter blood, bioactive peptides, enzymatic hydrolysis, ACE inhibition, DPP-IV inhibition, gastrointestinal stability, proline, hemoglobin decolorization, functional foods, circular economy, food science, protein hydrolysates