Antioxidant capacity of hydrolyzed animal by-products and relation to amino acid composition and peptide size distribution

Enzymatic processing of animal by-products: production of antioxidant hydrolysates with Bacillus sp. CL18 crude protease

Protein hydrolysates might display diverse bioactivities with potential relevance to human and animal health and food technology. Enzymatic hydrolysis of agro-industrial by-products is increasingly focused. In this study, a crude protease from Bacillus sp. CL18 was applied to obtain antioxidant protein hydrolysates from porcine, bovine, poultry, and fish by-products. The crude enzyme hydrolyzed all the twelve investigated by-products, as detected by increased soluble protein contents after 4 h of proteolysis. Hydrolysates exhibited higher radical-scavenging, Fe2+-chelating and reducing power capacities than non-hydrolyzed by-products. Hydrolysis times (0-8 h) and enzyme-to-substrate (E/S) ratios (384, 860, and 1,400 U/g) were assessed to produce antioxidant bovine lung hydrolysates. The highest E/S ratio accelerated both hydrolysis and increases in antioxidant activities; however, it did not result in bioactivities higher than hydrolysates obtained with the intermediate E/S ratio. Optimal antioxidant activities could be reached after 6 h of hydrolysis using 860 U/g. Animal by-products are interesting sources of bioactive protein hydrolysates, which could be produced with a non-commercial bacterial protease. This might represent a promising strategy for the valorization of animal by-products generated in large amounts by the agri-food sector.

Antioxidant properties of bovine liver protein hydrolysates and their practical application in biphasic systems

BACKGROUND

The influence of protein hydrolysate produced from bovine liver protein hydrolysate (LPH) by enzymatic hydrolysis, using Alcalase/Protamex (1:1), on lipid dispersions was investigated. LPH production was optimized to maximize the antioxidant activity (at 45, 50, and 55 °C for 12, 18, and 24 h). Different concentrations of LPHs (1, 3, and 5 mg/g) were added to emulsions and to liposomes. Lipid oxidation level and particle size of the lipid dispersions were monitored for 14 days of storage at 25 °C.

RESULTS

Radical scavenging activity and reducing power were the highest at 45 °C after 24 h of hydrolysis. Electrophoresis pattern showed that the antioxidant activity was arising from the peptides with molecular weight around 10 kDa. Lipid oxidation occurred more rapidly in samples without LPH during storage. In emulsions, lower thiobarbituric acid-reactive substance and conjugated diene values were measured with increasing concentrations of LPH at day 14. Accordingly, particle size of the samples containing 5 mg/g of LPH was smaller than those of other groups. Phase separation was observed only in lecithin emulsion without LPH at day 14. The use of LPH in liposome limited the lipid oxidation and maintained the size of the particles independently from the concentration.

CONCLUSION

This study highlights the potential applications of animal by-products as natural antioxidants in complex food systems. The results demonstrate that LPH, particularly when hydrolyzed at optimized conditions, can effectively inhibit lipid oxidation. The findings suggest that biphasic systems incorporating LPH have promising prospects for enhancing the stability and quality of food products. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Bioprocess to valorise fleshing produced in the tanning industry

This study focuses on circular bioeconomy and how to reduce the management of solid by-products in tannery facilities. To achieve this, double enzymatic hydrolysis has been developed, which allows the integrated management of both limed and fresh fleshing that are classified as category 3 animal by-products (ABPs). Fleshing has an average content of 15% fat, 20% protein and 65% water. To process these components independently, the fat fraction is separated from the protein and liquid protein fractions. This bioprocess has been developed from fleshing, yielding up to 78% mass recovery as biostimulants that are suitable for formulation and use in the fertiliser market. The efficacy of the protein fraction as a biostimulant was validated through laboratory tests, specifically by cabbage germination, which exhibited a notable improvement by 25%.

The beneficial potential of protein hydrolysates as prebiotic for probiotics and its biological activity: a review

Probiotics are not only a food supplement, but they have shown great potential in their nutritional, health and therapeutic effects. To maximize the beneficial effects of probiotics, it is commonly achieved by adding prebiotics. Prebiotics primarily comprise indigestible carbohydrates, specific peptides, proteins, and lipids, with oligosaccharides being the most extensively studied prebiotics. However, these rapidly fermenting oligosaccharides have many drawbacks and can cause diarrhea and flatulence in the body. Hence, the exploration of new prebiotic is of great interest. Besides oligosaccharides, protein hydrolysates have been demonstrated to enhance the expression of beneficial properties of probiotics. Consequently, this paper outlines the mechanism underlying the action of protein hydrolysates on probiotics, as well as the advantageous impacts of proteins hydrolysates derived from various food sources on probiotics. In addition, this paper also reviews the currently reported biological activities of protein hydrolysates. The aim is a theoretical basis for the development and implementation of novel prebiotics.

Industrial Application of Protein Hydrolysates in Food

Protein hydrolysates, which may be produced by the protein in the middle of the process or added as an ingredient, are part of the food formula. In food, protein hydrolysates are found in many forms, which can regulate the texture and functionality of food, including emulsifying properties, foaming properties, and gelation. Therefore, the relationship between the physicochemical and structural characteristics of protein hydrolysates and their functional characteristics is of significant importance. In recent years, researchers have conducted many studies on the role of protein hydrolysates in food processing. This Review explains the relationship between the structure and function of protein hydrolysates, and their interaction with the main ingredients of food, to provide reference for their development and further research.

Protein Characteristics and Bioactivity of Fish Protein Hydrolysates from Tra Catfish (Pangasius hypophthalmus) Side Stream Isolates

Enzymatic hydrolysis is a novel method to recover highly potent bioactive fish protein hydrolysates (FPHs) from fish processing side-streams. The common way of producing FPHs directly from fish side-streams may be inappropriate due to the excess of lipids and pro-oxidants, especially in lipid-rich streams, as obtained from Tra catfish. This study aimed to optimise the hydrolysis conditions for a commercial enzyme (Alcalase® 2.4 L) (enzyme concentrate, temperature, and time) in FPH production from the fish protein isolate obtained from Tra catfish dark muscle (DM-FPI) using the pH-shift method. The degree of hydrolysis (DH), protein recovery (PR), and antioxidant properties, including DPPH radical scavenging activity (DPPH-RSA) and total reducing power capacity (TRPC), were measured to evaluate the effects of the hydrolysis conditions on the FPHs. Optimal hydrolysis was obtained at an enzyme/substrate protein ratio of 3% (v/w) and a hydrolysis temperature of 50 °C for 3 h. The FPHs obtained from different substrates, including DM-FPI, abdominal cut-off (ACO) FPI, and head and backbone blend (HBB) FPI, had similar DHs under these optimum conditions, ranging from 22.5% to 24.0%. However, the FPH obtained from abdominal cut-off isolate (ACO-FPH) showed the highest PR of 81.5 ± 4.3% and the highest antioxidant properties, with a DPPH-RSA of 86.1 ± 1.6% and a TRPC of 6.4 ± 0.4 equivalent mg vitamin C/g protein. The resulting FPHs present a natural source of antioxidants with great potential for food applications, especially the ACO-FPH. In addition, all FPHs had excellent amino acid profiles, indicating strong potential for their use as supplements. Tra catfish protein-rich side-streams can thus be processed into high-value bioactive FPHs using Alcalase for human consumption.

Valorization of porcine by-products: a combined process for protein hydrolysates and hydroxyapatite production

The meat industry generates large amounts of by-products that are costly to be treated and discarded ecologically; moreover, they could be used to extract high added-value compounds. In this work, we present an innovative combined process which allowed the parallel extraction of both organic and mineral compounds; more specifically protein hydrolysates and single-phase hydroxyapatite were obtained. The protein hydrolysates, extracted through an enzymatic hydrolysis with alcalase, showed a degree of hydrolysis of 53.3 ± 5.1%; moreover, they had a high protein content with peptides with molecular weight lower than 1.2 kDa. Their antioxidant activities, measured with ABTS and ORAC tests, were 21.1 ± 0.5 mg ascorbic acid equivalent/g of dry extract and 87.7 ± 6.3 mg Trolox equivalent/g of dry extract, respectively. Single-phase hydroxyapatite, obtained with a simple calcination at 700 °C on the residues of the hydrolysis process, showed a Ca/P ratio close to the stoichiometric one (1.65 vs. 1.67) and presented a nanometric structure. This study reports a simple and feasible process for the valorization of porcine by-products in a large-scale up generating products with potential applications for environment remediation, biomedicine, nutrition and catalysis/bioenergy.

Identification of novel antioxidant peptide from porcine plasma hydrolysate and its effect in in vitro digestion/HepG2 cells model

A novel antioxidant peptide EDEQKFWGK from porcine plasma hydrolysate (PPH) was separated by chromatography, HPLC, and identified by LC-MS/MS. Results showed that EDEQKFWGK had better antioxidant ability (Hydroxyl RAS 32.19%, ABTS RAS 92.93% and DPPH RAS 26.76%) compared with glutathione (30.11%, 82.01%, 26.44%) due to the presence of hydrophobic, aromatic acids (F, W) and acidic amino acids (E, D), decreasing ROS by providing hydrogen atom and chelating metal ions. Furthermore, the antioxidant properties of synthetic EDEQKFWGK still significant despite in vitro digestion because of the production of smaller active peptide. Additionally, it could increase SOD, CAT, GSH-Px to resist oxidative damage in HepG2 cells by inhibiting ROS (O₂ ^- , OH·), forming complexes to prevent OH· from destroying DNA and binding to ARE to promote antioxidase expression. Thereby, the novel peptide EDEQKFWGK from porcine plasma had much stable antioxidant properties and hade great potential in formulating functional foods. PRACTICAL APPLICATIONS: This research isolated a novel antioxidant peptide. Moreover, the antioxidant effects of peptide were confirmed under the in vitro digestion model and oxidative damage HepG2 cells model. The results showed the antioxidant peptide could play better effect after digestion and protect the cells from oxidative damage. These data could expand the sequence data of antioxidant peptides and promote the high-value utilization of PPH.

A Review on Health-Promoting, Biological, and Functional Aspects of Bioactive Peptides in Food Applications

Food-derived bioactive peptides are being used as important functional ingredients for health-promoting foods and nutraceuticals in recent times in order to prevent and manage several diseases thanks to their biological activities. Bioactive peptides are specific protein fractions, which show broad applications in cosmetics, food additives, nutraceuticals, and pharmaceuticals as antimicrobial, antioxidant, antithrombotic, and angiotensin-I-converting enzyme (ACE)-inhibitory ingredients. These peptides can preserve consumer health by retarding chronic diseases owing to modulation or improvement of the physiological functions of human body. They can also affect functional characteristics of different foods such as dairy products, fermented beverages, and plant and marine proteins. This manuscript reviews different aspects of bioactive peptides concerning their biological (antihypertensive, antioxidative, antiobesity, and hypocholesterolemic) and functional (water holding capacity, solubility, emulsifying, and foaming) properties. Moreover, the properties of several bioactive peptides extracted from different foods as potential ingredients to formulate health promoting foods are described. Thus, multifunctional properties of bioactive peptides provide the possibility to formulate or develop novel healthy food products.

Effect of Gelatin Coating Enriched with Antioxidant Tomato By-Products on the Quality of Pork Meat

The use of edible biopolymers and natural additives obtained from food processing by-products is a sustainable strategy for food packaging applications. Gelatin is a biopolymer with great potential as a coating due to its low cost, high availability, and technological and functional properties. Among them, gelatin can be used as a carrier of bioactive compounds such as antioxidants, which can retard oxidation processes and thus extend the shelf-life of highly-perishable products. This study evaluated the effect of gelatin coating enriched with antioxidant tomato by-products hydrolysate (TBPH) on the quality of pork meat during cold storage. Results showed that TBPH obtained from Alcalase hydrolysis presented antioxidant activity with good stability against cooking. Additionally, chromatographic and mass spectrometry techniques, as well as in silico analysis, were used for the peptidomic characterisation of TBPH. The application of enriched gelatin coating on meat led to some physicochemical changes including increased weight loss and colour differences; however, the pH and water activity, which control meat spoilage, were maintained during storage. Moreover, coating prevented lipid oxidation of meat, and enriched-coated meat presented high antioxidant activity after cooking. These results suggest the positive role of gelatin coating enriched with TBPH in extending the shelf-life of meat during storage.

Hypolipidemic and anti-inflammatory effects of aorta and heart tissues of cattle and pigs in the atherosclerosis rat model

The aim of this study was to investigate the effects of aorta and heart tissues obtained from cattle and pigs on atherosclerosis disorders. Atherosclerosis model rats were provided with the respective diets consisting of aorta and heart tissues. Administration of each tissue suppressed body weight gain as compared to that of the control. In particular, the aorta tissues of pigs and cattle demonstrated significant suppressions in body weight gain in the model rats. The aorta tissues of pigs and cattle showed a significant increase and decrease in the serum high-density lipoproteins and atherogenic index, respectively, which was correlated with the increase in apolipoprotein A1. Hematological analysis revealed that aorta tissues of pigs and cattle clearly reduced the ratio of granulocytes/lymphocytes in the atherosclerosis rats. Serum vascular cellular adhesion molecule-1 levels in the atherosclerosis rats, which were administered these aorta tissues, were also significantly reduced. Additionally, there was an increase in von Willebrand factor in the rat serum. Based on the results obtained, the aorta tissues of pigs and cattle, in particular, demonstrated positive effects in the atherosclerosis rats due to the alteration of lipid metabolism and reduction in inflammation related to atherosclerosis.

Interfacial Antioxidants: A Review of Natural and Synthetic Emulsifiers and Coemulsifiers That Can Inhibit Lipid Oxidation

There has been strong interest in developing effective strategies to inhibit lipid oxidation in emulsified food products due to the need to incorporate oxidatively labile bioactive lipids, such as ω-3 fatty acids, conjugated linoleic acids, or carotenoids. Emulsifiers or coemulsifiers can be utilized to inhibit lipid oxidation in emulsions. Both of these molecular types can adsorb to droplet surfaces and inhibit lipid oxidation, but emulsifiers can also stabilize droplets against aggregation whereas coemulsifiers cannot. There are a host of existing emulsifiers, covalent conjugates, or physical complexes that have the potential to inhibit lipid oxidation by a variety of mechanisms. Existing emulsifiers with antioxidant potential consist of surfactants, phospholipids, proteins, polysaccharides, and colloidal particles. Conjugates and complexes are typically formed by covalently or physically linking together a surface-active molecule with an antioxidant molecule. This article reviews the molecular and physicochemical basis for the surface and antioxidant activities of emulsifiers and coemulsifiers, highlights the important properties of interfacial layers that can be engineered to control lipid oxidation, and outlines different kinds of existing emulsifiers, conjugates, and complexes that can be used to inhibit oxidation.

Effect of cooking and in vitro digestion on the antioxidant activity of dry-cured ham by-products

Dry-cured ham by-products have been traditionally used in Mediterranean household cooking of broths and stews. The aim of this work was to evaluate the effect of cooking treatments and in vitro gastrointestinal digestion on the antioxidant activity of natural peptides found in bones from Spanish dry-cured hams. The antioxidant activity was tested using five different assays and results demonstrated that cooking using conventional household methods increased the antioxidant activity of ham by-products when assessed using different antioxidant assays with the exception of the ABTS radical scavenging measurement assay. Simulated gastrointestinal digestion showed no significant effect on the antioxidant activity of ham by-products and antioxidant activity decreased when assessed using the ORAC and β-carotene bleaching assays. Analysis by MALDI-TOF MS revealed a considerable breakdown of peptides due to the action of gastrointestinal enzymes, mainly in samples cooked at 100°C for 1h. In addition, 459 peptides derived from 57 proteins were identified and quantified using mass spectrometry in tandem, evidencing that peptides derived from collagen protein were responsible for the differences in antioxidant activities observed between the uncooked and cooked samples after digestion. The results show the potential of dry-cured ham bones as a source of antioxidant peptides that retain their bioactivity after household cooking preparations and gastrointestinal digestion.

Low-dose oral cadmium increases airway reactivity and lung neuronal gene expression in mice

Inhalation of cadmium (Cd) is associated with lung diseases, but less is known concerning pulmonary effects of Cd found in the diet. Cd has a decades-long half-life in humans and significant bioaccumulation occurs with chronic dietary intake. We exposed mice to low-dose CdCl2 (10 mg/L in drinking water) for 20 weeks, which increased lung Cd to a level similar to that of nonoccupationally exposed adult humans. Cd-treated mice had increased airway hyperresponsiveness to methacholine challenge, and gene expression array showed that Cd altered the abundance of 443 mRNA transcripts in mouse lung. In contrast to higher doses, low-dose Cd did not elicit increased metallothionein transcripts in lung. To identify pathways most affected by Cd, gene set enrichment of transcripts was analyzed. Results showed that major inducible targets of low-dose Cd were neuronal receptors represented by enriched olfactory, glutamatergic, cholinergic, and serotonergic gene sets. Olfactory receptors regulate chemosensory function and airway hypersensitivity, and these gene sets were the most enriched. Targeted metabolomics analysis showed that Cd treatment also increased metabolites in pathways of glutamatergic (glutamate), serotonergic (tryptophan), cholinergic (choline), and catecholaminergic (tyrosine) receptors in the lung tissue. Protein abundance measurements showed that the glutamate receptor GRIN2A was increased in mouse lung tissue. Together, these results show that in mice, oral low-dose Cd increased lung Cd to levels comparable to humans, increased airway hyperresponsiveness and disrupted neuronal pathways regulating bronchial tone. Therefore, dietary Cd may promote or worsen airway hyperresponsiveness in multiple lung diseases including asthma.

Reformulated meat products protect against ischemia-induced cardiac damage

The protective effects of the antioxidants present in food are of great relevance for cardiovascular health. This study evaluates whether the extracts from reformulated meat products with a reduction in fat and/or sodium content exert a cardioprotective effect against ischemia-induced oxidative stress in cardiomyocytes, compared with non-meat foods. Ischemic damage caused loss of cell viability, increased reactive oxygen species and lipid peroxidation and decreased the antioxidant activity. Pretreatment for 24 h with digested or non-digested extracts from reformulated meat products led to protection against ischemia-induced oxidative damage: increased cell viability, reduced oxidative stress and restored the antioxidant activity. Similar results were obtained using extracts from tuna fish, but not with the extracts of green peas, salad or white beans. These results suggest that reformulated meat products have a beneficial impact in protecting cardiac cells against ischemia, and they may represent a source of natural antioxidants with benefits for cardiovascular health.

Influence of Sorghum Kafirin on Serum Lipid Profile and Antioxidant Activity in Hyperlipidemic Rats (In Vitro and In Vivo Studies)

The aim of this study was to compare in vitro the antioxidant potential of sorghum kafirin and sorghum flour and their influence on lipids and antioxidant capacity in rats. The antioxidant activity in sorghum kafirin extract measured by the DPPH and TEAC methods was increased 30 and 65 times, respectively, compared to that of its counterpart, sorghum flour. According to electrophoresis assay, the kafirins tert-butanol extract showed a high proportion of α-kafirin monomers, and its amino acid composition revealed higher hydrophobic amino acid content such as alanine, isoleucine, leucine, tyrosine and phenylalanine than sorghum flour extract. Diets supplemented with sorghum kafirin extract have improved lipid metabolism and increased the serum antioxidant potential (67%) especially in rats fed with added cholesterol. The bioactive peptides generated from kafirin in vivo hydrolysis appear to be associated with the positive effect on serum lipids and antioxidant activity. According to these results, sorghum kafirin extract at the levels used in this study apparently could be used for prevention of atherosclerosis and other chronic diseases.