The rationale for combining quercetin with bromelain rests on complementary pharmacology. Quercetin is a plant-derived flavonoid with documented anti-inflammatory, antioxidant, and immunomodulatory properties; in preclinical work it has been reported to interfere with viral replication and to dampen the exaggerated inflammatory responses that drive severe COVID-19. Bromelain, a mixture of proteolytic enzymes extracted from pineapple stem, has been studied for its mucolytic, anti-edema, and anti-inflammatory effects, and laboratory evidence suggests it may enhance the intestinal absorption of quercetin, which is otherwise poorly bioavailable. The pairing is therefore intended to deliver both a bioactive polyphenol and an enzyme that improves its uptake while contributing its own anti-inflammatory activity.

In the trial, participants were randomly assigned in a 1:1 ratio to receive either the quercetin–bromelain formulation or a placebo, in addition to standard supportive care. Each capsule contained 400 milligrams of quercetin and 100 milligrams of bromelain with an enzymatic activity exceeding 2,000 gelatin digesting units. The dosing schedule called for 800 milligrams of quercetin per day for the first 10 days, followed by a maintenance dose of 400 milligrams per day for 30 days. The primary outcome measure was respiratory deterioration, with secondary outcomes including cardiac complications, in-hospital mortality, and length of hospital stay.

The primary result favored the supplement. Respiratory deterioration occurred in 9.0 percent of patients in the quercetin–bromelain group compared with 21.3 percent of those receiving placebo, a relative risk of 0.42 with a 95 percent confidence interval of 0.22 to 0.81 and a p-value of 0.007. In practical terms, patients given the formulation were less than half as likely to experience worsening of their respiratory status during hospitalization as those given placebo. For a condition in which respiratory decline is the central driver of intensive care admission and death, an intervention that halves that risk—even in a single trial—commands attention.

The secondary outcomes told a more restrained story. The researchers did not observe statistically significant differences between the groups in in-hospital mortality or in the length of hospital stay. This pattern is not unusual for trials of this size: mortality differences in particular require very large sample sizes to detect, and a 244-patient study is powered mainly for more frequent endpoints such as clinical deterioration. The absence of an effect on hospital stay suggests that any benefit of the supplement, if real, is concentrated in preventing escalation of disease rather than in accelerating recovery among those who remain stable.

Two exploratory subgroup analyses added nuance. Among patients with less than 40 percent pulmonary involvement on baseline chest computed tomography, the overall complication rate was 18.4 percent in the treatment group versus 40.5 percent in the placebo group, a statistically significant difference with a p-value of 0.03. And among patients with pre-existing comorbidities—the group at highest baseline risk of cardiovascular events—the rate of cardiac complications was 4.4 percent with the supplement versus 14.0 percent with placebo, again a significant difference with a p-value of 0.02. The authors emphasize that these subgroup findings are exploratory and should be interpreted with caution, since subgroup analyses in trials of this scale are prone to chance findings and were not the primary focus of the study design.

The cardiac signal deserves particular note. COVID-19 is now well recognized as a disease with substantial cardiovascular consequences, including myocardial injury, arrhythmias, and thrombotic events, especially in patients with hypertension, diabetes, or other chronic conditions. If the observed reduction in cardiac complications among patients with comorbidities is confirmed in larger studies, it would suggest that the quercetin–bromelain combination may act on inflammatory and oxidative pathways relevant beyond the lung. Bromelain’s fibrinolytic and anti-edema properties have been proposed as potentially relevant to the microvascular complications of COVID-19, though this remains speculative at the current stage of evidence.

The trial has limitations that the authors acknowledge transparently. Most notably, the study was registered retrospectively in the Pan African Clinical Trial Registry on 6 June 2024, under a registry initiative that permits inclusion of studies already in progress or completed. Retrospective registration weakens the guarantee that outcomes were analyzed exactly as prespecified, a common concern in supplement trials. In addition, because the intervention combined two active compounds, the effects cannot be attributed to quercetin alone; bromelain may have contributed independently or through enhanced quercetin absorption. The authors call for larger, prospectively registered multicenter randomized controlled trials to confirm the findings and to disentangle the individual and combined contributions of the two components.

Context matters when weighing these results. Quercetin and bromelain have been marketed and self-administered extensively during the pandemic, often on the basis of laboratory and observational evidence far weaker than what this trial provides. A properly randomized, double-blind, placebo-controlled design is the gold standard for establishing causal treatment effects, and this study meets that standard for its primary endpoint. At the same time, a single-center trial in one country, with a modest sample size and retrospective registration, cannot settle the question of whether quercetin–bromelain should become part of standard supportive care for hospitalized COVID-19 patients. The appropriate reading is that the trial provides credible preliminary evidence of benefit on respiratory deterioration and justifies larger confirmatory studies.

For clinicians and the public, the practical takeaway is measured. The trial does not support abandoning established COVID-19 therapies or replacing vaccination and antiviral treatment with supplements. Nor does it establish safety and efficacy across all patient populations, disease severities, or dosing regimens. What it does establish is that a defined quercetin–bromelain formulation, given at a specific dose and schedule alongside standard care, was associated with a substantially lower rate of respiratory worsening in a hospitalized cohort, with hints of benefit for cardiac outcomes in comorbid patients. Whether that signal survives replication in adequately powered, prospectively registered multicenter trials will determine whether this inexpensive and widely available combination earns a place in clinical guidelines or remains an intriguing footnote in the long search for adjunctive COVID-19 therapies.

Subject of Research: A randomized controlled trial of quercetin–bromelain supplementation for clinical outcomes in hospitalized COVID-19 patients

Article Title: Quercetin–bromelain supplementation and clinical outcomes of COVID-19: a randomized, double-blind, placebo-controlled trial in hospitalized patients in Tunisia

Article References: Gargouri, M., Gargouri, H., Jedidi, J., Issaoui, N., Ketata, I., Ghorbel, H., Zrelli, L., Azouzi, H., & Boukhchina, M. A. (2026). Quercetin–bromelain supplementation and clinical outcomes of COVID-19: a randomized, double-blind, placebo-controlled trial in hospitalized patients in Tunisia. BMC Pharmacology and Toxicology. https://doi.org/10.1186/s40360-026-01257-2

Image Credits: AI Generated

DOI: 10.1186/s40360-026-01257-2

Keywords: quercetin, bromelain, COVID-19, randomized controlled trial, respiratory deterioration, cardiac complications, hospitalized patients, Tunisia, clinical trial, supplements, pharmacology, SARS-CoV-2

The active ingredient at the heart of the study is zingibain, a cysteine endopeptidase designated EC 3.4.22.67. Like papain and bromelain, zingibain cleaves peptide bonds in proteins, but it shows a particular appetite for myofibrillar proteins, the contractile machinery of muscle, and for connective tissue proteins. Because myofibrillar proteins, chiefly myosin and actin together with regulatory proteins such as troponins and tropomyosin, account for 50 to 60 percent of total muscle protein, an enzyme that targets them efficiently can reshape the texture of a steak or a chicken breast from the inside out.

To test how such an enzyme behaves across different animals, the team prepared crude aqueous extracts from fresh ginger at three concentrations and compared them against commercial bromelain and papain preparations standardized to identical protein levels. The substrates were purified myofibrillar proteins extracted from chicken breast and pork loin, two muscles chosen as models with distinct structures and functional properties. Reactions ran at 4 degrees Celsius and pH 6, mimicking the refrigerated conditions of real marination, and proteolytic activity was tracked spectrophotometrically over time.

The kinetic data revealed a striking asymmetry. Ginger extract displayed its highest catalytic performance against chicken myofibrils, reaching the greatest maximum reaction velocity of any enzyme tested at the highest concentration, with a Vmax of about 84.77 units per milligram of enzyme protein. On pork myofibrils, the same extract was considerably less active. Bromelain, by contrast, performed comparatively better on pork, where lower apparent Km values at higher enzyme concentrations drove its catalytic efficiency sharply upward. The authors attribute these differences to the intrinsic architecture of the two muscles: in chicken, disruption of Z-disks and actin-myosin cross-bridges occurs relatively rapidly after slaughter, whereas porcine muscle weakens more slowly and resists enzymatic attack longer.

Having identified the most efficient preparations, the researchers moved from the model system to whole meat. Cubes of chicken breast and pork loin, all cut to identical dimensions, were marinated for 6 or 12 hours in water, bromelain, papain, or ginger extract, then cooked. A key measurement was the myofibrillar fragmentation index, or MFI, which rises as myofibrils are broken into smaller pieces. All three enzymes raised MFI in both meats, and chicken fragmented faster and more extensively than pork. But the temporal patterns differed: papain and bromelain kept fragmenting the tissue as marination lengthened, while ginger produced its most pronounced relative increase in fragmentation during the first 6 hours, then plateaued, behaving as a milder, self-limiting tenderizer.

That restraint proved technologically important. Excessive proteolysis can wreck the protein network that holds water in meat, and the cooking yield data showed exactly that trade-off. Papain-treated chicken consistently lost the most weight during cooking, indicating that aggressive enzymatic breakdown destabilized the protein matrix during heating. Ginger-treated samples of both species, meanwhile, achieved the highest or near-highest cooking yields after 12 hours of marination, statistically comparable to the water controls and significantly better than papain or bromelain. Water-holding capacity told a complementary story: in chicken, moderate proteolysis after 6 hours improved water entrapment, while prolonged treatment eroded it, and pork showed a blunted response overall, consistent with its tougher myofibrillar scaffolding.

Color measurements added another dimension. In raw chicken, ginger-marinated samples retained redness better than controls or samples treated with the other enzymes, an effect the authors link to the antioxidant phenolic compounds that ride along in the crude ginger extract and help protect myoglobin from oxidation. After cooking, enzymatic marination produced large treatment-dependent color shifts in both meats, with papain causing the most dramatic alterations. Ginger-treated samples partially preserved reddish tones after cooking, particularly in pork, suggesting that the extract modulates pigment chemistry as well as protein structure.

The final test was whether any of this registers on the palate. A 25-member sensory panel, untrained but experienced in meat evaluation, compared cooked samples marinated for 6 hours in water or ginger extract under blind conditions. Ginger marination lifted scores across the board in both meats, with statistically significant gains in odor intensity, flavor, and overall acceptability in pork, and marked improvements in odor, flavor, sapidity, chewiness, and juiciness in chicken. Notably, the ginger-derived aroma was positively received and introduced no off-notes, while metallic or ferrous perceptions actually declined in the treated samples. The sensory gains tracked the instrumental data: controlled myofibrillar modification and preserved water retention translated directly into juicier, more tender eating.

The broader significance of the study lies in its demonstration that enzyme effects cannot be divorced from muscle biology. The same extract that excels on chicken may underperform on pork, and the same treatment that improves tenderness at 6 hours may degrade water retention at 12. For a meat industry under pressure to replace synthetic additives with natural, clean-label ingredients, crude ginger extract emerges as a promising middle path, a tenderizer strong enough to restructure muscle protein yet gentle enough to preserve cooking performance, color, and flavor. As the authors conclude, the response of meat to plant proteases depends on the enzyme, the muscle, and the clock, and ginger, it turns out, keeps remarkably good time.

Subject of Research: Proteolytic activity of ginger extract on myofibrillar proteins and meat quality

Article Title: Proteolytic Activity of Zingiber officinale Extract: Interaction With Myofibrillar Proteins of Different Origins and Functional Effects in Meat Systems

Article References: Crinò, A., Fabrizi, C., Menci, A., & Liburdi, K. (2026). Proteolytic Activity of Zingiber officinale Extract: Interaction With Myofibrillar Proteins of Different Origins and Functional Effects in Meat Systems. Food Science & Nutrition, 14(10), Article e72459. https://doi.org/10.1002/fsn3.72459

Image Credits: AI Generated

DOI: 10.1002/fsn3.72459

Keywords: ginger, zingibain, plant proteases, meat tenderization, myofibrillar proteins, papain, bromelain, chicken breast, pork loin, marination, water-holding capacity, sensory analysis

The two ingredients of BromAc attack biofilm in fundamentally different ways. N-acetylcysteine, or NAC, is the N-acetylated derivative of the amino acid L-cysteine, long used clinically as a mucolytic and as the antidote for paracetamol poisoning. Its antibiofilm power comes from a free thiol group that chemically reduces disulfide crosslinks holding together the polysaccharide and protein strands of the biofilm’s extracellular matrix. Bromelain, by contrast, is a cocktail of cysteine proteases extracted from pineapple stem, already used as an anti-inflammatory and wound-debridement agent with regulatory precedent in enzymatic burn treatment. Its proteolytic activity cleaves the peptide bonds of the protein scaffold, including fibrin and collagen, that stabilises biofilm architecture. Because biofilm matrices contain both polysaccharide-stabilised and proteinaceous components in varying proportions, the review’s authors argue that a dual-action agent targeting both simultaneously is mechanistically rational in a way single agents cannot be.

The scale of the clinical problem gives this mechanistic appeal real urgency. Current management of prosthetic joint infection relies on surgical debridement combined with antibiotics and implant retention, a strategy known as DAIR, or on two-stage revision in which the prosthesis is removed, an antibiotic spacer is implanted, and reimplantation follows months later. A recent meta-analysis cited in the review found that DAIR procedures fail in roughly 36 percent of cases on average, with failure rates climbing from about 34 percent in acute infections to nearly 74 percent in late chronic infections. Two-stage revision achieves better outcomes, typically between 54 and 100 percent success, but demands multiple surgeries, prolonged disability, and substantial cost. The fundamental limitation is that mechanical debridement with curettes and pulse lavage cannot reliably strip biofilm from prosthetic surfaces, while systemically delivered antibiotics penetrate the matrix poorly.

The laboratory evidence for each component of BromAc is instructive. A landmark 2013 study by Drago and colleagues tested NAC against Staphylococcus aureus and Pseudomonas aeruginosa biofilms grown on smooth polyethylene and sand-blasted titanium discs, the very materials used in hip and knee prostheses. NAC achieved roughly 50 percent biofilm reduction on polyethylene but only about 20 percent on titanium at minimum inhibitory concentrations after three hours of exposure. Studies outside orthopaedics suggest higher concentrations can do more: in staphylococcal isolates from chronic rhinosinusitis, NAC at eight times the minimum inhibitory concentration eradicated biofilm in 81.5 percent of isolates. Bromelain, meanwhile, reduced biofilm biomass by up to 98 percent in a wound-relevant S. aureus model supplemented with human plasma, and a 2025 study on cortical bone screws contaminated with MRSA found that bromelain powder combined with scrubbing produced the greatest reduction in adherent biomass of any tested regimen.

The pivotal proof-of-concept study for the combination came from Carter and colleagues in 2021, who tested BromAc against biofilms formed by three strains of Pseudomonas aeruginosa on surgical hernia mesh. Intriguingly, NAC alone actually enhanced growth in two of the three strains, while biofilms were more susceptible to bromelain alone. The combination overcame this limitation dramatically, achieving more than 80 percent biofilm removal, quantified by crystal violet biomass reduction, across all three strains, with corresponding one to two log reductions in adherent viable bacteria. Microscopy confirmed physical disruption of biofilm architecture with previously embedded bacteria left exposed. The strongest effects occurred at higher bromelain-to-NAC ratios, and no antagonistic interactions between the agents were observed.

Yet the review is notably candid about how far this evidence falls short of clinical readiness. The principal proof-of-concept study used hernia mesh rather than orthopaedic implants and Pseudomonas rather than the staphylococci that dominate prosthetic joint infection. It was also funded by the manufacturer of BromAc, and independent replication is lacking. More recent data showing BromAc activity against S. aureus on surgical metal clips and near-complete eradication of S. epidermidis biofilms when combined with vancomycin or rifampicin come from the sponsor and remain unpublished and unpeer-reviewed. The reviewers flag that across the preclinical literature, studies differ in pathogen, substrate, exposure time, and outcome measure, making direct comparison of efficacy figures hazardous. Crystal violet assays, moreover, measure total biomass including dead cells and residual matrix, so they evidence biofilm disaggregation rather than bacterial killing; corroborating viable-count recovery will be essential in future work.

Formulation stability poses a further, less obvious barrier. The same free thiol group that gives NAC its antibiofilm activity is susceptible to autoxidation in aqueous solution, a process accelerated by oxygen, metal ions, elevated pH, and warmth. Reported shelf lives of reconstituted NAC solutions range from a few hours at ambient temperature to 24 hours under refrigeration and light protection, and loss of free thiol translates directly into loss of biofilm-disrupting potency. Bromelain, for its part, loses proteolytic activity in solution through autodigestion. In an operating theatre, this means BromAc cannot be assumed to retain full activity if mixed in advance, and point-of-use reconstitution, preservative-free buffering, and oxygen-protective packaging would likely be required. Nothing is yet known about the pharmacokinetics of either agent inside an infected joint, including residence time, clearance, and protein binding in synovial fluid.

Safety questions specific to the joint environment loom equally large. BromAc has been administered to more than 100 patients by intratumoural and intraperitoneal injection in first-in-human and Phase III trials for pseudomyxoma peritonei, with a manageable safety profile, and across 21 preclinical animal experiments it has shown a favourable safety record via intraperitoneal, subcutaneous, intravenous, and inhaled routes. But none of these routes approximates injection into a weight-bearing joint, where cartilage, synovium, and the bone-implant interface are uniquely vulnerable to a proteolytic enzyme. The safety database for intra-articular BromAc is, as the reviewers put it, empty. Effects on cartilage integrity, synovial inflammation, and osseointegration of the implant are entirely unknown, as are the optimal NAC-to-bromelain ratio, pH, osmolality, dosing, and contact time.

To close these gaps, the authors lay out a structured preclinical programme before any first-in-human orthopaedic trial could be defensible. It begins with small-animal models using implanted titanium or polyethylene carrying established staphylococcal biofilm, with endpoints of viable bacterial recovery and histological assessment of joint tissue, followed by large-animal studies with loaded prostheses and dynamic synovial fluid sampling, ex vivo human cartilage and synovium tolerance studies, and formulation-stability testing under realistic operating-theatre conditions. Only consistent positive efficacy and acceptable safety across all four streams, ideally replicated independently of the sponsor, would justify moving to the clinic.

On present evidence, BromAc stands as a promising but unvalidated adjunct for prosthetic joint infection: mechanistically elegant, cheap relative to revision surgery, and built from two agents with long clinical histories, yet supported almost entirely by preclinical data on non-orthopaedic substrates and partly by unpublished sponsor figures. If the necessary validation succeeds, the combination could improve DAIR success rates, spare thousands of patients prosthesis removal, and potentially extend to other biofilm-associated implant infections. Until then, the reviewers conclude, any clinical use outside a properly designed and regulated trial is not justified.

Subject of Research: Preclinical evaluation of bromelain and N-acetylcysteine combination therapy for disrupting biofilms in prosthetic joint infection

Article Title: Bromelain and N-acetylcysteine (BromAc) as novel adjunctive therapy for prosthetic joint infection: a narrative review

Article References: Parnell, B., & Morris, D. (2026). Bromelain and N-acetylcysteine (BromAc) as novel adjunctive therapy for prosthetic joint infection: a narrative review. Journal of Bone and Joint Infection, 11(4), 441-451. https://doi.org/10.5194/jbji-11-441-2026

Image Credits: AI Generated

DOI: 10.5194/jbji-11-441-2026

Keywords: prosthetic joint infection, biofilm, BromAc, bromelain, N-acetylcysteine, DAIR, joint arthroplasty, antibiofilm therapy, implant infection, Staphylococcus aureus, Pseudomonas aeruginosa, drug stability

Myofibrillar proteins are the workhorses of muscle tissue, accounting for roughly 55 to 65 percent of the total protein in meat. Composed primarily of myosin and actin, they form the structural framework of muscle fibers and govern the qualities that matter most to consumers and processors: solubility, gelation, water-holding capacity, and flavor development. When bromelain cleaves these proteins, the consequences ripple through every one of those attributes. Previous research had shown that the enzyme reduces shear force and hardness, degrades large protein molecules, and nudges ordered protein structures toward more disordered forms, but the dynamic molecular interactions between the enzyme and its protein targets had never been systematically characterized.

The research team, based at an institution supported by the Liaoning Provincial Basic Research Program, extracted myofibrillar proteins from beef longissimus dorsi muscle and treated them with bromelain at four enzyme-to-substrate ratios: 0.10, 0.25, 0.50, and 0.75 percent by weight, alongside an untreated control. Each sample was incubated for 30 minutes at 40 degrees Celsius before the reaction was halted with a protease inhibitor. This concentration range allowed the investigators to trace how escalating doses of the enzyme reshape protein behavior, from gentle depolymerization to outright fragmentation.

The results revealed a striking dose-dependent pattern with a clear optimum at 0.50 percent bromelain. At this concentration, protein solubility peaked at 81.53 percent, turbidity and average particle size fell to their lowest values, and the polydispersity index dropped to 0.338, down from 0.871 in the control, indicating a remarkably uniform dispersion of protein particles. The explanation lies in the balance between two competing processes. Moderate hydrolysis breaks apart myofibrillar bundles and exposes polar, charged groups that were previously buried, strengthening hydration interactions and boosting solubility. But when the enzyme dose climbed to 0.75 percent, excessive cleavage generated a flood of small peptides and exposed hydrophobic patches, which promptly reaggregated into insoluble clumps, dragging solubility back down.

Spectroscopic measurements painted a consistent picture of progressive protein unfolding. Ultraviolet absorption and intrinsic fluorescence both intensified as bromelain levels rose to 0.50 percent, signaling that aromatic amino acid residues such as tryptophan, tyrosine, and phenylalanine were being liberated from the protein interior into the surrounding polar environment. The fluorescence emission maximum also shifted slightly toward longer wavelengths, a hallmark of a more extended protein conformation. Surface hydrophobicity climbed in parallel, confirming that hydrophobic residues once hidden within the folded structure were now accessible at the molecular surface. At the highest enzyme dose, all of these signals reversed, as reaggregation re-buried the exposed groups.

Fourier transform infrared spectroscopy delivered perhaps the most dramatic evidence of structural transformation. The amide A band, sensitive to hydrogen bonding, shifted from 3304 to 3405 wavenumbers as enzyme concentration increased, indicating the progressive dismantling of the hydrogen-bond network that holds the protein together. Curve-fitting analysis of the amide I band showed that ordered secondary structures, alpha-helices and beta-sheets, declined from 70.97 percent of the total to just 50.37 percent, while disordered beta-turns and random coils expanded from 29.03 to 49.63 percent. In effect, bromelain converted a compact, well-ordered protein architecture into a loose, flexible tangle, a transition the authors describe as protease-driven structural disordering.

Scanning electron microscopy and gel electrophoresis corroborated the story at larger scales. Untreated protein displayed dense, block-like aggregates, while the 0.50 percent treatment produced the most dispersed and uniformly distributed microstructure of any group. Electrophoretic profiles showed the myosin heavy chain band, normally a prominent feature at approximately 220 kilodaltons, becoming progressively fainter with increasing enzyme dose, accompanied by diffuse staining at lower molecular weights that betrayed extensive fragmentation. Actin, the other major myofibrillar component, also showed changes at the higher enzyme levels, though the myosin heavy chain proved conspicuously vulnerable.

To probe the enzyme’s target at atomic resolution, the team built a three-dimensional model of the bovine myosin heavy chain by homology modeling, validated it with a Ramachandran plot showing 94 percent of residues in the most favored regions, and docked bromelain onto it. The best docking pose exhibited a binding energy of minus 12.4 kilocalories per mole, stabilized by a multipoint hydrogen-bonding network with bond distances ranging from 1.9 to 3.6 angstroms, involving residue pairs such as GLU211 of bromelain with THR424 of myosin and ASN78 with GLU577. Molecular dynamics simulations running 100 nanoseconds under physiological conditions then revealed what binding actually does to the protein: the complex showed higher root-mean-square deviation, greater radius of gyration, and larger solvent-accessible surface area than myosin alone, all signs of a looser, less compact, more flexible structure primed for further proteolytic attack.

The energetic accounting confirmed the partnership is spontaneous and thermodynamically favorable, with a total binding free energy of minus 59.97 kilojoules per mole calculated by the MM/PBSA method. Van der Waals and electrostatic interactions emerged as the primary driving forces, with electrostatics contributing most significantly, while residue decomposition identified MET549, GLU374, VAL420, LYS368, GLU598, THR547, LYS568, and LYS281 as key contributors to binding. The free energy landscape of the complex displayed multiple rugged low-energy basins, in contrast to the smoother, more concentrated landscape of free myosin, indicating that the enzyme destabilizes its target even as it grips it.

For the meat industry, the practical message is one of precision. The study demonstrates that bromelain’s benefits hinge on hitting a narrow optimal dose, because the same proteolytic power that disperses aggregates and unlocks solubility at moderate concentrations can trigger wasteful reaggregation and quality loss when overdone. By linking macroscopic properties like solubility and turbidity to specific molecular events, hydrogen-bond disruption, secondary-structure loss, and a computationally characterized enzyme-substrate interface, the work provides a rational framework for deploying bromelain in meat tenderization and quality regulation. It also offers a template for studying other enzyme-protein systems in food science, showing how experiments and simulations can converge to explain, at the level of individual residues, why a pineapple enzyme makes steak tender.

Subject of Research: Bromelain-induced structural and physicochemical changes in beef myofibrillar proteins and their molecular interaction mechanisms

Article Title: Bromelain-induced physicochemical and structural changes in beef myofibrillar proteins and their molecular interaction mechanisms

Article References: Huang, W., Fu, H., Geng, L., Qi, R., Jia, D., & Zhou, W. (2026). Bromelain-induced physicochemical and structural changes in beef myofibrillar proteins and their molecular interaction mechanisms. Food Chemistry: X, 39, Article 104560. https://doi.org/10.1016/j.fochx.2026.104560

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104560

Keywords: bromelain, myofibrillar proteins, meat tenderization, myosin heavy chain, molecular docking, molecular dynamics simulation, protein solubility, protein structure, food chemistry, enzymatic hydrolysis, beef quality, hydrogen bonding

The study, published in Food Chemistry: X, focused on Nam Dok Mai, one of Thailand’s most important commercial mango cultivars and a significant export to Singapore, China, Malaysia, and Japan. Fresh-cut mango deteriorates through three intertwined processes: enzymatic browning, tissue softening, and microbial growth, with yeasts being a particular problem. Browning arises when the enzyme polyphenol oxidase, or PPO, oxidizes phenolic compounds in the damaged tissue, generating brown pigments on the cut surface. The researchers set out to test whether two natural agents with complementary modes of action could tackle these problems simultaneously, offering an eco-friendly alternative to synthetic antibrowning chemicals such as sulfites.

The first ingredient, pineapple core extract, was prepared from Smooth Cayenne pineapple fruit selected at 16 to 18 percent total soluble solids. The cores were blended, squeezed, filtered, and pasteurized at 70 degrees Celsius for 10 seconds before being diluted to a 50 percent solution. Notably, previous work by the same research group had shown that the core of the pineapple, often discarded as waste, is actually more effective at inhibiting browning than the pulp, likely because of its higher bromelain activity. Bromelain is a sulfhydryl protease, a protein-digesting enzyme that has been shown to suppress enzymatic browning, and pineapple also contains organic acids, chiefly citric and malic acids, along with sulfur-containing amino acids and phenolic compounds, all of which contribute to antibrowning and antioxidant activity.

The second ingredient, fresh Aloe vera gel from one-year-old Barbadensis leaves, was similarly blended, filtered, and pasteurized. Aloe vera has earned a reputation in postharvest science as an edible coating: when applied to cut produce, its polysaccharides form a semi-permeable film that limits oxygen diffusion to the surface, reduces moisture loss, and modulates oxidative metabolism. The gel also carries bioactive compounds, including anthraquinones and saponins, with documented antibacterial and antifungal properties. Ripe mangoes, harvested 85 days after anthesis and ripened uniformly with calcium carbide fumigation, were peeled, cut into six-centimeter pieces, and immersed for two minutes in one of three treatment solutions: 50 percent pineapple core extract, 50 percent Aloe vera gel, or a 1:1 mixture of the two. Untreated slices served as the control, and all samples were stored in clear PET trays at 4 degrees Celsius for six days.

The visual results were striking. After just two days of storage, obvious browning had developed on the untreated control slices, while the Aloe vera-treated samples showed slight discoloration. In contrast, the slices dipped in pineapple core extract or the combined treatment showed no visible browning at all. By day six, the control and Aloe vera-only samples were extensively browned, whereas the pineapple-treated and combined-treatment slices displayed only slight browning. Quantitative measurements backed up what the photographs showed: browning intensity, measured as absorbance of ethanol extracts at 420 nanometers, rose steadily in all samples but remained lowest in the pineapple-containing treatments. A panel of fifty tasters scored browning severity on a nine-point scale, and by day six the control and Aloe vera samples had crossed the acceptability threshold of a score above five, while the pineapple core extract and combined treatments remained at approximately 2.8, comfortably within the acceptable range.

Colorimetry told a consistent story. Surface lightness, the L* value, dropped sharply in the control during the first two days, while the treated slices stayed significantly brighter. On day four, the combined treatment achieved the highest L* value of all groups, and by the end of storage the pineapple-containing samples retained significantly better lightness than the control or Aloe vera alone. Hue angles stayed within the range of 88 to 95 degrees, confirming that the slices kept their characteristic yellow color, and the combined treatment held chroma, a measure of color saturation, significantly higher than the control in later storage while maintaining the smallest overall color difference from the initial sample. The researchers attribute the dominant antibrowning effect to the pineapple extract, whose organic acids lower tissue pH and directly suppress PPO activity, while bromelain and sulfur-containing compounds add further inhibition; the Aloe vera layer contributes by physically restricting oxygen delivery to the cut surface.

Texture proved to be where the combination genuinely outperformed either ingredient alone. Firmness declined in all samples over the six days, as expected, since softening in mango is driven by the enzymatic degradation of pectic polysaccharides in the cell wall and by the loss of cell membrane integrity. But from day two onward, the combined treatment consistently maintained significantly higher firmness than every other group, including the individual treatments, while the control was the softest. The authors propose two mechanisms for this synergy. Both pineapple and Aloe vera are rich in calcium, which can cross-link demethylated pectin chains into calcium pectate, strengthening cell-to-cell adhesion and stabilizing the wall. Meanwhile, the Aloe vera coating restricts oxygen diffusion, reducing oxidative stress and membrane lipid peroxidation, which was reflected in lower accumulation of malondialdehyde, a standard marker of membrane damage, in all treated samples compared with the control. Importantly, neither total soluble solids nor titratable acidity changed significantly in any treatment, meaning the dips preserved the fruit’s balance of sweetness and acidity untouched.

On the microbiological front, the roles reversed. Aloe vera immersion proved more effective than pineapple core extract at suppressing total aerobic bacteria, coliform bacteria, and yeasts and moulds, an effect credited to its anthraquinones, saponins, and barrier-forming polysaccharides. Coliform bacteria appeared in the control, pineapple, and combined treatments after four days but were not detected in the Aloe vera samples until day six, and Aloe vera consistently maintained the lowest yeast and mould counts. Throughout the entire storage period, all samples stayed within the microbiological guideline limits for ready-to-eat foods set by the Thai Food and Drug Administration and the Department of Medical Sciences, with total aerobic bacteria below 6 log10 colony-forming units per gram and yeasts and moulds below 4. The combined treatment delayed bacterial proliferation effectively, though the data showed no synergistic antimicrobial interaction beyond what Aloe vera achieved on its own.

To integrate all these threads, the researchers applied principal component analysis to the full dataset of quality attributes. The first two principal components captured 62.2 percent of the total variance, and the resulting biplot cleanly separated the untreated control, which clustered with microbial growth, browning enzymes, lipid peroxidation, and color loss, from all treated samples. The combined treatment sat closest to the desirable attributes of hue angle, chroma, and acidity, and farthest from the deterioration-related variables, confirming its status as the strongest overall preservative strategy. The authors are candid about the study’s limits: sensory attributes such as flavor and aroma, respiration rate, weight loss, and the precise chemical composition of the extracts were not measured, and future work should characterize the bioactive compounds involved. Even so, the message is compelling. Two agricultural byproducts and garden plants, one usually thrown away and the other grown in backyard pots, together kept one of the world’s favorite tropical fruits fresh, firm, golden, and safe for twice its usual shelf life, pointing toward a future where the freshest-cut fruit on the shelf owes its glow to nothing more exotic than pineapple and aloe.

Subject of Research: Natural antibrowning and antimicrobial preservation of fresh-cut mango using pineapple core extract and Aloe vera gel

Article Title: Combined application of pineapple core extract and Aloe vera gel for browning inhibition and quality preservation of fresh-cut ‘Nam Dok Mai’ mangoes

Article References: Keawmanee, N., Techavuthiporn, C., Suo, X., Boonyaritthongchai, P., & Supapvanich, S. (2026). Combined application of pineapple core extract and Aloe vera gel for browning inhibition and quality preservation of fresh-cut ‘Nam Dok Mai’ mangoes. Food Chemistry: X, Article 104571. https://doi.org/10.1016/j.fochx.2026.104571

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104571

Keywords: fresh-cut mango, pineapple core extract, Aloe vera gel, enzymatic browning, polyphenol oxidase, bromelain, edible coating, food preservation, postharvest quality, Nam Dok Mai, food microbiology, natural preservatives

The research team, led by Van-Ba Hoa and colleagues at the National Institute of Animal Science in Wanju, Korea, set out to develop cost-effective methods for converting livestock bones into value-added biomaterials. Their target molecules were collagen, the most abundant protein in the animal body and a mainstay of the nutraceutical and cosmetics industries, and chondroitin sulfate, a sulfated glycosaminoglycan recommended by the European League Against Rheumatism as a symptomatic slow-acting drug for osteoarthritis. Both compounds are traditionally extracted using commercial proteases such as pepsin and Alcalase, enzymes that cleave the chemical cross-links holding these molecules within the bone matrix. The problem, the authors note, is that these enzymes are expensive, driving up extraction costs and, ultimately, the price of the final products on the shelf.

The logic behind the pineapple approach rests on bromelain, a cysteine protease found throughout the pineapple plant but concentrated in the core, which makes up roughly sixteen percent of the fruit’s processing by-products. Pineapple is cultivated extensively across the globe, guaranteeing a stable and abundant supply of the raw material for enzyme production. To prepare their extract, the researchers ground fresh pineapple cores, filtered the pulp through cheesecloth, and centrifuged the liquid to obtain a crude preparation they call pineapple extract, or PE. Colorimetric assays revealed that the extract’s proteolytic activity rose from 1.18 units per milligram of protein at four degrees Celsius to 3.33 units per milligram at fifty-five degrees, confirming that the enzyme remains active across the temperature ranges relevant to industrial extraction.

For the collagen experiments, the team ground pork leg and backbone into a fine powder, stripped away non-collagenous proteins with sodium hydroxide, demineralized the bones with EDTA, and then soaked them in acetic acid before adding either pepsin at 0.5 percent or the pineapple extract at five percent by weight. After forty-eight hours of enzymatic digestion at four degrees Celsius, the released collagen was salted out with sodium chloride, centrifuged, dialyzed, and freeze-dried. The results were striking: the pineapple-extract-derived collagen, designated PESC, yielded 3.77 percent of the original bone weight, whereas pepsin-soluble collagen, or PSC, managed only 1.42 percent. That difference, statistically significant at p below 0.05, translates into more than two and a half times the collagen recovered from the same quantity of bone.

The researchers attribute this yield gap to the distinct cleavage specificities of the two enzymes. Pepsin preferentially cuts peptide bonds in the telopeptide regions at the ends of collagen molecules, a relatively restricted mode of attack. Bromelain, by contrast, hydrolyzes peptide bonds at multiple sites, including those adjacent to aromatic, basic, and hydrophobic residues, giving it a broader capacity to dismantle the intra- and intermolecular cross-links that lock collagen chains into the bone matrix. Previous studies have likewise shown that bromelain exhibits higher enzymatic activity than pepsin under identical hydrolysis conditions. For chondroitin sulfate extraction, performed at fifty-five degrees Celsius with either Alcalase or the pineapple extract, the two approaches proved essentially equivalent: PE yielded 11.98 milligrams of CS per gram of bone compared with 11.37 milligrams per gram for the commercial enzyme.

Quality control was central to the study, because a cheaper extract is worthless if it produces an inferior product. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that collagen from both extraction routes displayed the characteristic two-band pattern of type I collagen, with alpha-1 chains at roughly 130 to 120 kilodaltons and alpha-2 chains at 120 to 110 kilodaltons. The PESC sample also showed several lower-molecular-weight bands between about 75 and 20 kilodaltons, evidence that bromelain cuts not only within the telopeptide domain but also at specific sites inside the triple-helical region. Amino acid analysis confirmed that both products were dominated by glycine, at approximately 23.7 to 24.2 percent of total amino acids, followed by proline and glutamic acid, a profile consistent with authentic collagen and with no significant differences between the two extraction methods.

The chondroitin sulfate products passed equally rigorous scrutiny. Agarose gel electrophoresis revealed a single band for both PE- and Alcalase-derived CS, migrating in the same position as a commercial CS standard, and the bands disappeared entirely after digestion with chondroitinase ABC, indicating that the extracts consisted of pure glycosaminoglycans free of contaminants such as dermatan sulfate. Proton nuclear magnetic resonance spectroscopy at 600 megahertz then probed the sulfation patterns of the molecules. Both products showed the diagnostic signals for N-acetylgalactosamine methyl protons near 2.0 parts per million and, crucially, peaks at approximately 4.15 and 4.63 parts per million corresponding to the H4 and H6 protons of GalNAc-4-sulfate and GalNAc-6-sulfate. This confirmed that the pork bone CS contained both CS-A and CS-C structural units, the same forms found in commercially sourced products, which today come overwhelmingly from marine organisms processed in China.

Perhaps the most intriguing findings emerged when the researchers digested their two collagen products with the pineapple extract to generate peptide hydrolysates. Using ultra-performance liquid chromatography coupled with high-resolution tandem mass spectrometry, they identified 28 peptides, seventeen of which appeared in both hydrolysates. Seven peptides, including Gly-Arg, Glu-Gly-Arg, Ala-Val-Gly, Leu-Ala, Leu-Val-Gly, Phe-Ala-Gly-Gly, and a longer proline-rich sequence, were found exclusively in the pepsin-derived material, while four others, including Leu-Pro, Leu-Thr-Gly, and two glycine-proline-rich sequences, appeared only in the pineapple-extract-derived hydrolysate. These differences trace directly back to enzyme specificity: pepsin favors bonds next to leucine and phenylalanine, whereas bromelain cuts beside aromatic, basic, and hydrophobic residues such as glycine. All identified peptides contained glycine, proline, or hydroxyproline, the structural backbone of collagen, and most fell within the two-to-twenty-residue range associated with strong biological activity.

Those structural differences translated into measurable functional advantages. In DPPH free radical scavenging assays, the PESC-derived hydrolysate achieved an EC50 of 0.76 milligrams per milliliter, outperforming the PSC-derived hydrolysate at 0.82 milligrams per milliliter. The same pattern held for ferrous ion chelation, where the PESC hydrolysate recorded an EC50 of 0.77 milligrams per milliliter against 0.83 for the pepsin product. Both fell short of the synthetic antioxidant butylated hydroxyanisole, which posted EC50 values between 0.65 and 0.69 milligrams per milliliter, but the researchers point out that the enhanced activity of the pineapple-derived peptides likely stems from their richer content of hydrophobic amino acids such as leucine, glycine, alanine, proline, and valine, which donate electrons or hydrogen atoms to neutralize radicals and bind metal ions that catalyze oxidative damage.

The implications extend well beyond the laboratory bench. Free radicals generated through normal metabolism and environmental exposure can overwhelm the body’s antioxidant defenses, contributing to oxidative stress and a range of chronic diseases, so natural antioxidant peptides from food sources are attracting growing commercial interest. By demonstrating that a crude, inexpensive extract from pineapple cores can outperform pepsin on collagen yield, match Alcalase on chondroitin sulfate recovery, and deliver collagen peptides with superior antioxidant activity, the Korean team has outlined a genuinely circular economy: fruit waste becomes an enzyme source, and bone waste becomes a biomaterial feedstock. The authors caution that further studies are needed to validate the biological activities of the identified peptides and CS and to assess their suitability for functional food and pharmaceutical applications, but the economic case is already compelling. For an industry that discards both of these raw materials by the millions of tons each year, the study suggests that two waste problems may, together, be the solution to one another.

Subject of Research: Extraction of collagen and chondroitin sulfate from pork bones using pineapple by-product bromelain extract as an alternative to commercial proteases

Article Title: Extraction and characterization of biomaterials from pork bones: a potential alternative of pineapple by-product extract for commercial proteases

Article References: Hoa, V.-B., Park, W.-S., Ham, J.-S., & Bae, I.-S. (2026). Extraction and characterization of biomaterials from pork bones: a potential alternative of pineapple by-product extract for commercial proteases. Food Science of Animal Resources, 46(1), Article 58. https://doi.org/10.1007/s44463-026-00066-9

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00066-9

Keywords: pork bones, collagen, chondroitin sulfate, bromelain, pineapple by-products, proteases, pepsin, Alcalase, antioxidant peptides, food waste valorization, biomaterials, functional foods