Influence of Degree of Hydrolysis on the Functional Properties of Cowpea Protein Hydrolysates

Application of experimental design as a statistical approach to recover bioactive peptides from different food sources

Bioactive peptides (BAPs) derived from samples of animals and plants have been widely recommended and consumed for their beneficial properties to human health and to control several diseases. This work presents the applications of experimental designs (DoE) used to perform factor screening and/or optimization focused on finding the ideal hydrolysis condition to obtain BAPs with specific biological activities. The collection and discussion of articles revealed that Box Behnken Desing and Central Composite Design were the most used. The main parameters evaluated were pH, time, temperature and enzyme/substrate ratio. Among vegetable protein sources, soy was the most used in the generation of BAPs, and among animal proteins, milk and shrimp stood out as the most explored sources. The degree of hydrolysis and antioxidant activity were the most investigated responses in obtaining BAPs. This review brings new information that helps researchers apply these DoE to obtain high-quality BAPs with the desired biological activities.

Emulsifying Capacity of Cowpea Protein Isolates. Effect of Thermal and Hydrolytic Treatment

In this work, modifications due to the effect of thermal treatments (TT 70 and 90 °C) and partial hydrolysis by digestion with alcalase (LH) on the emulsifying properties of cowpea protein isolates (CPIs) extracted at pH 8 and 10 were analyzed. In addition, the influence of protein concentration [0.1 and 1% (w/v)] was evaluated. Emulsions (O:W) were prepared and particle size, stability, interfacial composition, and microstructure were studied. Fresh emulsions formulated with TT CPIs presented lower values of volume-weighted mean droplet size (D4.3), with the increase in temperature and treatment time, compared to the untreated CPIs. After seven days of storage, D4.3 and the indexes of flocculation (FI) and coalescence (CI) increased, mainly at 90 °C. On the other hand, the emulsions with LH CPIs presented lower D4.3 values compared to all the conditions tested, remaining unchanged during the storage time. The destabilization process in the TT CPIs emulsions revealed coalescence at 0.1% (w/v) and cremated-flocculation at 1% (w/v). The presence of polypeptides of low molecular mass (MM) at the interface would be responsible for the better stability found in emulsions with LH CPIs, compared to those formulated with untreated and TT CPIs. Increasing the protein concentration resulted in a significant improvement of all emulsifying properties.

Comparison of Functional Properties of Blood Plasma Collected from Black Goat and Hanwoo Cattle

Slaughterhouse blood is a by-product of animal slaughter that can be a good source of animal protein. This research purposed to examine the functional qualities of the blood plasma from Hanwoo cattle, black goat, and their hydrolysates. Part of the plasma was hydrolyzed with proteolytic enzymes (Bacillus protease, papain, thermolysin, elastase, and α-chymotrypsin) to yield bioactive peptides under optimum conditions. The levels of hydrolysates were evaluated by 15% sodium dodecyl sulfate polyacrylamide gel electrophoresis. The antioxidant, metal-chelating, and angiotensin I-converting enzyme (ACE) inhibitory properties of intact blood plasma and selected hydrolysates were investigated. Accordingly, two plasma hydrolysates by protease (pH 6.5/55°C/3 h) and thermolysin (pH 7.5/37°C/3-6 h) were selected for analysis of their functional properties. In the oil model system, only goat blood plasma had lower levels of thiobarbituric acid reactive substances than the control. The diphenyl picrylhydrazyl radical scavenging activity was higher in cattle and goat plasma than in proteolytic hydrolysates. Ironchelating activities increased after proteolytic degradation except for protease-treated cattle blood. Copper-chelating activity was excellent in all test samples except for the original bovine plasma. As for ACE inhibition, only non-hydrolyzed goat plasma and its hydrolysates by thermolysin showed ACE inhibitory activity (9.86±5.03% and 21.77±3.74%). In conclusion, goat plasma without hydrolyzation and its hydrolysates can be a good source of bioactive compounds with functional characteristics, whereas cattle plasma has a relatively low value. Further studies on the molecular structure of these compounds are needed with more suitable enzyme combinations.

Improving emulsification properties of alkaline protein extract from green tea residue by enzymatic methods

Alkaline extraction is an important process in the integrated biorefining of leafy biomass to obtain protein, but the resulting alkaline protein extract (APE1) may have poor emulsification properties for food applications. In this study, the components in the APE fractionations obtained by size exclusion chromatography were determined. The emulsification properties of APE were determined using oil/water with a ratio of 7:3. Whey protein and soybean protein isolate were used as controls while enzymes were used to improve APE's emulsification properties. The results showed that the APE could be divided into three fractions with protein content of 83, 56, and 34%. Carbohydrates mainly derived from homogalacturonan pectin were mostly in Fraction 2, while Fraction 3 consisted of peptides, oligosaccharides, and free polyphenols. The APE had similar emulsification capacity and emulsification stability as those of whey protein and soybean isolate. The emulsion made by the APE had a creaming index of 92% with emulsification activity index value of 44 m² g⁻¹, and these numbers could retain after storing at 25 °C for 15 days. The emulsification properties of the APE can be further improved by carbohydrate degradation. With the use of Viscozyme® L, the emulsification activity index value of treated APE was increased by 60%, and then still retained at 67 m² g⁻¹ after storing for 15 days. Treated by either pepsin or alkaline protease, the emulsification properties of APE were decreased, suggesting the key role of protein in APE for emulsification.

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Alkaline protein extract (APE) had 3 fractions with a fraction of 83% protein. .

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APE had a creaming index of 92% with EAI of 44 m² g⁻¹ could store for 15⁺ days.

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APE, whey protein, and soybean protein isolate had similar emulsification property.

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Emulsification property of APE was attributed from protein and inhibited by pectin.

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Using Viscozyme® L, EAI of APE emulsion increased by 60% with better stability.

Antibacterial Peptides Produced by Alcalase from Cowpea Seed Proteins

Cowpea seed protein hydrolysates (CPH) were output from cowpea seeds applying alcalase® from Bacillus licheniformis. CPH with an elevated level of hydrolysis was fractionated by size exclusion chromatography (SEC). Both CPH and SEC-portions showed to contain antimicrobial peptides (AMPs) as they inhibited both Gram-positive bacteria, such as Listeria monocytogenes LMG10470 (L. monocytogenes), Listeria innocua. LMG11387 (L. innocua), Staphylococcus aureus ATCC25923 (S.aureus), and Streptococcus pyogenes ATCC19615 (St.pyogenes), and Gram-negative bacteria, such as Klebsiella pnemoniae ATCC43816 (K. pnemoniae), Pseudomonas aeroginosa ATCC26853 (P. aeroginosa), Escherichia coli ATCC25468) (E.coli) and Salmonella typhimurium ATCC14028 (S. typhimurium).The data exhibited that both CPH and size exclusion chromatography-fraction 1 (SEC-F1) showed high antibacterial efficiency versus almost all the assessed bacteria. The MIC of the AMPs within SEC-F1 and CPHs were (25 µg/mL) against P. aeruginosa, E.coli and St. pyogenes. However, higher MICsof approximately 100-150 µg/mL showed for both CPHs and SEC-F1 against both S. aureus and L. innocua; it was 50 µg/mL of CPH against S.aureus. The Electro-spray-ionization-mass-spectrometry (ESI-MS) of fraction (1) revealed 10 dipeptides with a molecular masses arranged from 184 Da to 364 Da and one Penta peptide with a molecular mass of approximately 659 Da inthe case of positive ions. While the negative ions showed 4 dipeptides with the molecular masses that arranged from 330 Da to 373 Da. Transmission electron microscope (TEM) demonstrated that the SEC-F1 induced changes in the bacterial cells affected. Thus, the results suggested that the hydrolysis of cowpea seed proteins by Alcalase is an uncomplicated appliance to intensify its antibacterial efficiency.

Degree of Hydrolysis Affects the Techno-Functional Properties of Lesser Mealworm Protein Hydrolysates

Protein hydrolysates from lesser mealworm (Alphitobius diaperinus, LM) were obtained by enzymatic hydrolysis with protease from Bacillus licheniformis. A preliminary test performed for five hours of hydrolysis generated an insect protein hydrolysate with 15% of degree of hydrolysis (DH), optimum solubility property and oil holding capacity, but emulsifying and foaming ability were completely impaired. In order to investigate the potential implication of DH on techno-functional properties, a set of protein hydrolysates with a different DH was obtained by sub-sampling at different time points during three hours of enzymatic hydrolysis process. An increase in DH% had positive effects on the solubility property and oil holding ability, while a reduced emulsifying ability was observed up to five hours of hydrolysis. These results demonstrated that the enzymatic hydrolysis, if performed under controlled conditions and not for a long period, represents a valid method to extract high quality protein from insects with tailored techno-functionality, in order to produce tailored ingredients for feed and food purpose.

Peptides: Production, bioactivity, functionality, and applications

Production of peptides with various effects from proteins of different sources continues to receive academic attention. Researchers of different disciplines are putting increasing efforts to produce bioactive and functional peptides from different sources such as plants, animals, and food industry by-products. The aim of this review is to introduce production methods of hydrolysates and peptides and provide a comprehensive overview of their bioactivity in terms of their effects on immune, cardiovascular, nervous, and gastrointestinal systems. Moreover, functional and antioxidant properties of hydrolysates and isolated peptides are reviewed. Finally, industrial and commercial applications of bioactive peptides including their use in nutrition and production of pharmaceuticals and nutraceuticals are discussed.