Biochemical and microstructural characteristics of meat samples treated with different plant proteases

This study was conducted to compare the efficiency of different plant proteases for changing biochemical and microstructural characteristics in muscle foods. The meat samples from chicken, giant catfish, pork and beef were treated with four types of proteolytic enzymes: Calotropis procera latex proteases, papaya latex proteases, commercial papain and bromelain at the concentrations of 2 × 103 to 6 × 103 activity units/100 g of muscle. The pH, collagen solubility, trichloroacetic acid (TCA) soluble peptides, protein patterns and muscle microstructures of the treated samples were evaluated after 24 h at 4°C. A decrease of muscle pH in chicken, giant catfish and pork was observed when the enzymes were added (p < 0.05). A significant increase in collagen solubility was also found in all of the muscle samples (chicken increased from 37.64 to 83.59%; giant catfish increased from 52.82 to 84.14%; pork increased from 14.34 to 86.78; and beef increased from 26.02 to 86.18%; p < 0.05). An increase in TCA-soluble peptides (from 0.90 to18.53 μmole/g sample), and myofibrillar protein degradation was observed in all of the enzyme treated samples as compared to the control (p < 0.05). The electrophoretic pattern of the muscle proteins also revealed extensive proteolysis and reduction of protein bands in all of the treated samples. At the microstructural level, tissue fibers were broken, and the connections between the sarcolemma and the myofibrils were loosened when each enzyme was applied. When comparing all proteolytic enzymes used, papaya latex proteases showed the highest hydrolysis activity in all muscle types, which was followed by C. procera latex proteases, commercial papain, and then bromelain. The results show that these proteolytic enzymes could be used as an effective meat tenderizer.Key words: Proteases, muscle foods, collagen, tenderization, toughness

Impact Of Pulsed Electric Field Pretreatment On Yield And Quality Of Lipid Extracted From Cephalothorax Of Pacific White Shrimp (Litopenaeus Vannamei) By Ultrasound Assisted Process

Impacts of pulsed electric field (PEF) pretreatment with different electric field strengths (4, 8, 12 and 16 kVcm-1 ) and pulse numbers (120, 160, 200 and 240) on extraction yield of lipid and cell disintegration index (Zc) of Pacific white shrimp cephalothorax were examined. PEF treated samples were subsequently subjected to lipid extraction using ultrasonic assisted extraction (UAE) process at ultrasonic amplitude of 91.2 microns for 25 min in continuous mode. Samples with PEF pretreatment and subjected to UAE rendered the highest lipid yield (30.34% dry basis). PEF pretreatment resulted in suppression of lipid oxidation as affirmed by the decreases in peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). Lipid from PEF pretreated samples had higher content of PUFAs as well as carotenoids, which included astaxanthin, astaxanthin monoester, astaxanthin diester, canthaxanthin and β-carotene. Overall, PEF was a promising pretreatment to increase the yield and maintain the quality of lipid extracted from cephalothorax using UAE

Utilization of wastes from Pacific whiting surimi manufacturing : proteinases and protein hydrolysate

Both liquid and solid wastes from Pacific whiting surimi manufacturing were characterized and value-added products were recovered. A proteinase in surimi wash water (SWW) was determined to be cathepsin L with Mr 54,200 on SDS-substrate gel. Heat treatment and acidification shifted the activity zone to M [subscript r] 39,500. No evidence of calpain, cathepsin B or H activity was found. Cathepsin L from SWW was recovered by ohmic heating (55°C for 3 min), ultrafiltration, and freeze-drying with overall yield of 0.83 g protein/L SWW and 78% recovery of activity. A 5.9 purification fold was achieved by these processes. The recovered enzyme had an optimum activity at pH 4.0 and showed preferable hydrolytic activity towards casein, acid-denatured hemoglobin and myofibrils. β-Mercaptoethanol, dithiothreitol and urea enhanced the enzyme activity. The recovered proteinase showed 18.5% residual activity after 7 wk storage at 4°C. Proteolytic activity in solid waste and digestive organs from Pacific whiting was investigated. Pepsin-like proteinase predominated in solid waste, while trypsin-like proteinase was predominant in viscera. Carboxypeptidase b was found in both viscera and solid waste. Protein hydrolysate was produced from Pacific whiting solid waste (PWSW) using commercial proteinase, Alcalase, under optimum hydrolysis conditions. Enzyme concentration, reaction time and waste/buffer ratio affected the hydrolysis and nitrogen recovery (NR). Correlation between the degree of hydrolysis (DH) and NR was high (R₂=0.978). Freeze-dried hydrolysate contained 79.97% protein and showed similar amino acid composition to PWSW and Pacific whiting muscle but tryptophan was reduced. With different DH (20, 30, 40, 50, 60%), surface hydrophobicity, total and surface sulfhydryl content decreased as the DH increased. The hydrolysate showed a high solubility over a wide pH range. Fat adsorption and fat binding capacity were reduced, while foam expansion was enhanced with an increased DH. Hydrolysate with DH of 30% showed highest emulsifying activity. Low emulsion stability and high foam stability were obtained in all hydrolysates tested. Hydrolysate showed antioxidant activity, but no obvious differences in activity were found with varying DH and hydrolysate concentrations

Effect of pulsed electric field treatments on melanosis and quality changes of Pacific white shrimp during refrigerated storage

Polyphenoloxidase (PPO) from Pacific white shrimp was subjected to Pulsed electric field (PEF) at varying specific energy (54-483 kJ/kg) and pulse number (200-600). PPO activity was decreased as both parameters increased (P < 0.05). Among shrimp treated with PEF, those subjected to PEF-T3 (483 kJ/kg, 600 pulses) had the lower melanosis score than other PEF treatments and the control, packaged in polystyrene trays and wrapped with shrink film, during 10 days of storage at 4 °C (P < 0.05). Highest shear force values were noticed with PEF-T3 treated sample at the end of storage period (day 10) (P < 0.05). Microstructural gaping between shrimp muscle fibers was notably higher in PEF-T3. No protein degradation was observed for all samples, regardless of PEF treatments. Lower mesophilic and psychrophilic microbial counts in shrimp were obtained when PEF-T3 was implemented. After 10 days of storage, higher sensory scores of PEF-T3 treated samples were also attained, as compared to others (P < 0.05). Quality deterioration of shrimp was retarded with the aid of PEF

Antimicrobial activity of some potential active compounds against food spoilage microorganisms

Antimicrobial activities of six potential active compounds (acetic acid, chitosan, catechin, gallic acid, lysozyme, and nisin) at the concentration of 500 g/ml against the growth of Escherichia coli, Staphylococcus aureus, Listeria innocua, and Saccharomyces cerevisiae were determined. Lysozyme showed the highest antimicrobial activity against L. innocua and S. cerevisiae with an inhibition zone of 19.75 and 17.37 mm, respectively. Catechin was strongly active against E. coli, L. innocua, and S. aureus with 15.37, 19.38, and 17.00 mm of inhibition zone diameter, respectively. The minimum inhibitory concentration (MIC) value of catechin for E. coli and for S. aureus was the same at 640 μg/ml, while the minimum bactericidal concentration (MBC) values were 640 and 1,280 μg/ml, respectively. The MIC and MBC values of lysozyme for L. innocua were 160 and 640 μg/ml, respectively. S. cerevisiae was the most susceptible microorganism to lysozyme among others, since both its MIC and MBC were the lowest (2.5 μg/ml). However, catechin and lysozyme were combined in equal amounts; all tested microorganisms were effectively inhibited as indicated by both qualitative and quantitative antimicrobial activities. This study thus revealed the potential application of some active compounds such as catechin and lysozyme for their usage in food products.Keywords: Antimicrobial activity, catechin, lysozyme, agar disc diffusion, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC

Cosmetic potential of marine fish skin collagen

Many cosmetic formulations have collagen as a major component because of its significant benefits as a natural humectant and moisturizer. This industry is constantly looking for innovative, sustainable, and truly efficacious products, so marine collagen based formulations are arising as promising alternatives. A solid description and characterization of this protein is fundamental to guarantee the highest quality of each batch. In the present study, we present an extensive characterization of marine-derived collagen extracted from salmon and codfish skins, targeting its inclusion as component in cosmetic formulations. Chemical and physical characterizations were performed using several techniques such as sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier Transformation Infrared (FTIR) spectroscopy rheology, circular dichroism, X-ray diffraction, humidity uptake, and a biological assessment of the extracts regarding their irritant potential. The results showed an isolation of type I collagen with high purity but with some structural and chemical differences between sources. Collagen demonstrated a good capacity to retain water, thus being suitable for dermal applications as a moisturizer. A topical exposure of collagen in a human reconstructed dermis, as well as the analysis of molecular markers for irritation and inflammation, exhibited no irritant potential. Thus, the isolation of collagen from fish skins for inclusion in dermocosmetic applications may constitute a sustainable and low-cost platform for the biotechnological valorization of fish by-products.The authors would like to acknowledge to European Union for the financial support under the scope of European Regional Development Fund (ERDF) through the projects 0687_NOVOMAR_1_P (POCTEP (Programa Operacional de Cooperação Transfronteiriça España-Portugal) 2007/2013) and 0302_CVMAR_I_1_P (POCTEP 2014/2020) and the Structured Project NORTE-01-0145-FEDER-000021 (Norte2020) and under the scope of the European Union Seventh Framework Programme (FP7/2007-2013) through grant agreement ERC-2012-ADG 20120216-321266 (ERC Advanced Grant ComplexiTE). The Portuguese Foundation for Science and Technology is also acknowledged for the grant of A.L.A (Ana Luísa Alves.) under Doctoral Programme Do* Mar (PD/BD/127995/2016).info:eu-repo/semantics/publishedVersio

Simple Preparation of Pacific Cod Trypsin for Enzymatic Peptide Synthesis

Trypsin from the pyloric caeca of Pacific cod (Gadus macrocephalus) was easily prepared by affinity chromatography on Benzamidine Sepharose 6B and gel filtration on Superdex 75. Pacific cod trypsin was composed of three isozymes, and their molecular masses were estimated 23,756.34 Da, 23,939.62 Da, and 24,114.81 Da by desorption/ionization time-of-flight mass spectroscopy (MALDI/TOF-MS) and their isoelectric points (pIs) were approximately 5.1, 6.0, and 6.2, respectively. The isolated Pacific cod trypsin showed high similarity to other frigid-zone fish trypsins. The kinetic behavior of tryptic hydrolysis toward N-p-tosyl-L-arginine methyl ester hydrochloride (TAME), N-benzoyl-L-arginine p-nitroanilide hydrochloride (BAPA), and p-amidinophenyl ester were also analyzed. In addition, the cod trypsin-catalyzed dipeptide synthesis was investigated using twelve series of “inverse subdtrates” that is p- and m-isomer of amidinophenyl, guanidinophenyl, (amidinomethyl)phenyl, (guanidinomethyl)phenyl, and four position isomers of guanidinonaphtyl esters derived from N-(tert-butoxycarbonyl)amino acid as acyl donor components. They were found to couple with an acyl acceptor such as L-alanine p-nitroanilide to produce dipeptide in the presence of the trypsin. All inverse substrates tested in this study undergo less enantioselective coupling reaction. The p-guanidinophenyl ester was most practical substrate in twelve series tested. The enzymatic hydrolysis of the resulting products was negligible

Characteristics and Gel Properties of Gelatin from Goat Skin as Influenced by Alkaline-pretreatment Conditions

Characteristics and properties of gelatin from goat skin pretreated with NaOH solutions (0.50 and 0.75 M) for various times (1 to 4 days) were investigated. All gelatins contained α-chains as the predominant component, followed by β-chain. Gelling and melting temperatures of those gelatins were 23.02°C to 24.16°C and 33.07°C to 34.51°C, respectively. Gel strength of gelatins increased as NaOH concentration and pretreatment time increased (p<0.05). Pretreatment for a longer time yielded gelatin with a decrease in L*-value but an increase in b*-value. Pretreatment of goat skin using 0.75 M NaOH for 2 days rendered the highest yield (15.95%, wet weight basis) as well as high gel strength (222.42 g), which was higher than bovine gelatin (199.15 g). Gelatin obtained had the imino acid content of 226 residues/1,000 residues and the gelatin gel had a fine and ordered structure. Therefore, goat skin gelatin could be used as a potential replacer of commercial gelatin

Preparation and characterization of squid pen chitooligosaccharide-epigallocatechin gallate conjugates and their antioxidant and antimicrobial activities

Chitooligosaccharide (COS) and epigallocatechin-3-gallate (EGCG) at various concentrations were used for the preparation of COS–EGCG conjugates. The highest total phenolic content (TPC), representing the amount of EGCG conjugated, was obtained for 1 wt% COS together with EGCG at 0.5 wt% (C1-E0.5- conjugate) or 1.0 wt% (C1-E1.0-conjugate) (66.83 and 69.22 mg EGCG per g sample, respectively) (p < 0.05). The 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,20 -azino-bis(3-ethylbenzothiazoline-6- sulfonic acid) (ABTS) radical scavenging activities (DRSA and ARSA, respectively) and ferric reducing antioxidant power (FRAP) of all the samples showed similar trends with TPC. The C1-E0.5-conjugate had higher DRSA, ARSA, FRAP and oxygen radical absorbance capacity (ORAC) values than COS (p < 0.05). Similarly, the antimicrobial activity of COS increased when conjugated with EGCG (p < 0.05). FTIR, 1 HNMR and 13C-NMR analyses confirmed the successful grafting of EGCG with COS. Therefore, 1 wt% COS and 0.5 wt% EGCG were used for the production of a conjugate with augmented antioxidant activity, which could be used to retard lipid oxidation of fatty foods

Ethanolic Noni (Morinda citrifolia L.) leaf extract dechlorophyllised using sedimentation process: Antioxidant, antibacterial properties and efficacy in extending the shelf-life of striped catfish slices

Antioxidant and antimicrobial activities of ethanolic noni leaf extract (ENLE) without and with chlorophyll removal by sedimentation method were comparatively investigated. Total chlorophyll content was reduced by 82% in the top fraction (CR-ENLE) collected after 24 h at 4 °C as compared to that of ENLE. Antioxidant and antimicrobial activities were lower in the bottom fraction rich in chlorophyll (Chlo-ENLE) than others (P < 0.05). Based on the microbiological limit, the shelf-life of striped catfish slices pre-treated with 400 mg kg⁻¹ C-R-ENLE was extended to 9 days as compared to the 3 days recorded for the control (without pre-treatment). Slices treated with CR-ENLE had lower lipid oxidation than those treated with ENLE during refrigerated storage (P < 0.05). The sedimentation process was therefore a potential green method for producing ENLE having improved antioxidant and antimicrobial activities without green colour. It can be used as a natural additive for shelf-life extension of fish slices