Alkaline Solubilization Research Articles

Enzymatic and extrusion pretreatments of defatted rice bran to improve functional properties of protein concentrates

SummaryThis study evaluated effects of enzymatic, extrusion and combined pretreatments on functional and thermal properties of protein concentrates from defatted rice bran to improve their applicability to food formulations. After the pretreatments, protein concentrates were recovered by alkaline solubilisation and isoelectric point precipitation. Water absorption capacity, oil absorption capacity, emulsifying and foaming properties, and thermal stability were determined in protein concentrates. Yields of each pretreatment were above 62% protein. Enzymatic hydrolysis increased all functional properties studied, mainly for emulsifying activity index (an increase of 71.1%) and foaming capacity (an increase of 60.3%). The extrusion affected positively the oil absorption capacity, emulsifying activity index and foaming capacity. The combined process was able to raise the functional properties. The principal component analysis confirmed that 95.5% improvement in functional properties of concentrates had a strong positive correlation with the pretreatments. However, the pretreatments affected thermal stability and the enthalpy of denaturation negatively.

Antioxidant and antibacterial properties of Monodora myristica (Calabash nutmeg) seed protein hydrolysates

The purpose of this study was to investigate some of the properties (antioxidant, antibacterial and functional properties) of Monodora myristica seed protein hydrolysates. Monodora myristica protein was extracted using alkaline solubilization, followed by acid precipitation to its isoelectric point. Monodora myristica seed protein isolate was hydrolyzed using three enzymes separately (pepsin, trypsin and pancreatin). Antioxidant activities (2,2-diphenyl-1-picrylhydrazyl (DPPH)-radical scavenging and ferrous ion (Fe2+)-chelating) were determined using standard procedures. Antibacterial activities of protein hydrolysates were done using zone of inhibition test. All protein hydrolysates of Monodora myristica had significantly high DPPH radical scavenging and Fe2+-chelating properties and were soluble over a wide pH range with more than 30% solubility. Pepsin hydrolysate had the highest foam expansion and stability of 117.4% and 98%, respectively and trypsin hydrolysate showed the lowest foam expansion and stability of 97.8% and 78.2%, respectively. Only proteins hydrolyzed with pepsin (regardless of the duration of hydrolysis) demonstrated potent antibacterial activity on test bacteria (Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis and Proteus vulgaris). It could be deduced from this study that enzymatic hydrolysates of Monodora myristica protein has potential application among functional foods, and may be a promising source of natural antioxidants and antibacterial drugs.

Solubilization Processing of Ashes Power Plant

Abstract The paper presents the attempts of acid and alkaline solubilization of the power plant ashes, using different chemical reagents, at different concentrations. Due to the mineralogical content of these ashes, was elaborated a technological flow for the recovery the iron minerals, resulting an ferrous concentrate containing noble metals. For their recovery from ferrous concentrate, were studied properties of gold, silver and platinum, the conclusion being that these chemical elements can be extracted, in economic conditions, with sodium hypochlorite.

Chickpea Protein Isolation, Characterization and Application in Muffin Enrichment

The aim of this study was to enhance the nutritional value and the functional characteristics of muffins by enriching with chickpea protein isolate, while keeping their rheological characteristics. Chickpea Protein isolate (CPI) was prepared by alkaline solubilization (pH 11), followed by isoelectric precipitation at pH 4.5. SDS-PAGE revealed three subunits with molecular weights of 47, 30 and 85 kDa; representing the globulin fractions, legumin-like and vicilin-like proteins. Maximum protein solubility (83.32%) was obtained at pH 11. CPI exhibited an emulsifying activity index of 25.17 m2 g-1, emulsion stability index of 14.09 min. The foaming capacity and stability were 62% and 94.49%, respectively. Water and oil absorption were 3.65 and 2.30 mL g-1, respectively. CPI was added to muffin batter at 0, 2.5, 5, 7.5 and 10%. CPI fortifieded muffins showed reduction in moisture content, which influenced texture profile analysis through increasing hardness, gumminess and chewiness values. Additionally, both protein content and protein digestibility of muffins increased to 22.2 and 94.08%, respectively. CPI-enriched muffins were darker (lower L) with yellowish crumbs (higher b). Finally, preliminary sensory evaluation showed high consumer acceptance for CPI-enriched muffins.

Copper chelating protein hydrolysate from Salvia hispanica L. by pepsin-pancreatin treatment

Salvia hispanica L. (Chia) seeds are good source of proteins with diverse health benefits. The seed protein was extracted through alkaline solubilisation followed by acid precipitation to separate fibres and are digested sequentially by pepsin and pancreatin. Enzyme-substrate ratio, temperature and contact time had high impact on degree of hydrolysis affecting their chelating ability. Maximum degree of hydrolysis (14.06%) and maximum copper chelation (74.98%) was obtained at 4% w/w enzyme-substrate ratio at 37 °C for 4 h. Copper chelating enzymatic hydrolysate was isolated by HiTrap chelating column and purified further by rpHPLC. Out of nine fractions obtained by rpHPLC the sixth fraction with 93.09 ± 0.16% of copper chelating activity and 82.91 ± 0.52% of antioxidant activity was further characterized as Copper chelating Chia Protein Hydrolysate (CCPH). Ultraviolet spectroscopy and fluorescence spectroscopic studies revealed the interaction of the major chelating sites of the CCPH with the copper divalent ion. The purified CCPH was subjected to LC-MS/ESI-TOF analysis from which six major intense peaks obtained with m/z value ranging from 0.4 kDa to 2.5 kDa were identified and sequenced using Mascot database. The functional behaviour and the binding capacity of these peptides were analysed by their amino acid composition. The CCPH was stable in a simulated gastric condition and its chelating ability remained unaltered. These results explored an informative bioactive peptides with varied activity and one valuable among is the copper chelating with antioxidant property. Furthermore, these Chia seed protein hydrolysates can be useful as dietary supplements to enhance mineral bioavailability.

Antioxidant and enzyme-inhibitory properties of sesame seed protein fractions and their isolate and hydrolyzate

ABSTRACT Sesame seed was defatted and subsequently fractionated into albumin, globulin, glutelin and prolamin. The defatted flour was also subjected to alkaline solubilization and acid precipitation to obtain protein isolate. The sesame seed protein isolate was hydrolyzed using a combination of pepsin and pancreatin to produce the protein hydrolyzate. The defatted flour, protein fractions, isolate and hydrolyzate were evaluated for their amino acid profiles as well as in vitro antioxidant and enzyme inhibitory activities. The results showed that the glutelin fraction had higher amounts of essential amino acid (38.1%) when compared with albumin (35.6%), globulin (31.3%), prolamin (37.1%), protein isolate (37.1%) and protein hydrolyzate (36.7%). The defatted flour exhibited the strongest DPPH radical scavenging activity while only the globulin, isolate and hydrolyzate exhibited superoxide radical scavenging activity. The defatted flour also had the strongest hydroxyl radical scavenging activity of 91.79%, although lower than the 95.93% for the control peptide (glutathione). The hydrolyzate had the strongest metal chelating activity (75.53%), while the isolate had the highest ferric antioxidant reducing power. The albumin was the most effective inhibitor of angiotensin converting enzyme and α-amylase with values of 30.04% and 29.44%, respectively. In contrast, renin activity was strongly inhibited (89.87%) by the isolate but acetylcholinesterase was weakly inhibited by the hydrolyzate (16.89%) and prolamin (16.29%). We conclude that the defatted flour and protein products are potential ingredients that could be incorporated into foods to extend shelf-life but also with potential bioactive properties.

Pretreatment of spent coffee grounds with alkaline soju bottle-washing wastewater for enhanced biomethanation

The production of spent coffee grounds (SCG) is steadily increasing, and its proper treatment has become an increasingly challenging task. This study explored the potential use of alkaline bottle-washing wastewater (BWW) from a soju (a Korean hard liquor) manufacturer as an alternative pretreatment agent to enhance the biodegradability and thus the biomethanation of SCG through anaerobic digestion. Thermo-alkaline pretreatment with BWW was effective in increasing the soluble organic fraction of SCG (i.e., improved bioavailability) at all temperatures tested (23–70 °C). The disintegration degree of the particulate organic matter in SCG ranged from 8.6 to 13.1% and increased with increasing pretreatment temperature. The 30-day methane yield (per g chemical oxygen demand (COD) of SCG fed) was significantly higher for the BWW-pretreated SCG (342.4–361.2 mL/g COD) than for the raw SCG (284.7 mL/g COD) and even for the NaOH-pretreated SCG (at the same pH as BWW, pH 12.3) tested for comparison (299.7–320.9 mL/g COD). This significant increase in methane production can be attributed to the presence of readily biodegradable ethanol derived from waste soju in BWW and the alkaline solubilization of SCG. Our results suggest a straightforward way to manage SCG and BWW together in a sustainable and economical manner.

Potential use of human hair shaft keratin peptide signatures to distinguish gender and ethnicity.

BackgroundMost human hairs collected at old crime scenes do not contain nuclear DNA and are therefore of less value for forensic investigations. In the present study, hair shaft proteins were extracted from 40 healthy subjects between the ages of 21 to 40 years and profiled using gel electrophoresis-based proteomics to determine if they can be used to distinguish gender and ethnicity.MethodsExtraction of the human hair shaft proteins was performed using a newly developed alkaline solubilisation method. The extracts were profiled by 2-dimensional electrophoresis and resolved protein spots were identified by mass spectrometry and queried against the human hair database. The study was then followed-up by immunoblotting of the identified hair shaft keratin of interest using commercially available antibodies.ResultsSeparation of the human hair shaft proteins by 2-dimensional electrophoresis generated improved and highly resolved profiles. Comparing the hair shaft protein profiles of 10 female with 10 male subjects and their identification by mass spectrometry and query of the human hair database showed significant altered abundance of truncated/processed type-II keratin peptides K81 (two spots), K83 (one spot) and K86 (three spots). The 2-dimensional electrophoresis profiling of 30 hair shaft samples taken from women of similar age range but from three distinctive ethnic subpopulations in Malaysia further showed significant altered abundance of one type-I and four type-II truncated/processed keratin peptides including K33b, K81, K83 and K86 (2 spots) between at least two of the ethnic groups. When a followed-up immunoblotting experiment was performed to detect the relative expression of the K86 peptides using commercialised antibodies, similar trends of expression were obtained. The present data, when taken together, demonstrated the potential use of keratin peptide signatures of the human hair shaft to distinguish gender and ethnicity although this needs to be further substantiated in a larger scale study.

Antioxidant activities of peptide hydrolysates obtained from the seeds of Treculia africana Decne (African breadfruit)

Protein hydrolysates usually possess higher nutritive value than an equivalent mixture of free amino acids. This study was aimed at determining the antioxidant activities of protein hydrolysates of Treculia africana seeds. Soluble protein was isolated from Treculia africana seed flour by alkaline solubilization and acid precipitation, and further hydrolyzed with three proteases (trypsin, pancreatin and pepsin) individually and in a sequential two- and three-protease systems. Antioxidant activities (DPPH, FRAP and lipid peroxidation) of the hydrolysates were investigated. Hydrolysates from Treculia africana seed protein showed varying degree of hydrolysis, pancreatin hydrolysates had the highest (94.92%) and pancreatin-pepsin hydrolysates had the least (6.59%). Pancreatin proved to be the most efficient protease for hydrolyzing Treculia africana protein with a high protein recovery of 156.06 mg/ml. Its hydrolysates exhibited the highest DPPH scavenging activity (71.02%) and had a high radical-mediated peroxidation of oleic acid. Likewise, pancreatin hydrolysates as well as trypsin-pancreatin hydrolysates showed the highest FRAP activity (37.17 and 38.52 µg/ml BHA, respectively). Pancreatin hydrolysates showed significant higher (p < 0.05) antioxidant potentials than other hydrolysates of T. africana seed protein. These findings showed the potential use of Treculia africana hydrolysates as antioxidants in reducing food spoilage and management of oxidative stress-related metabolic disorders.

Simple GFAAS Method for Determination of Pb, As, and Cd in Cannabidiol Extracts Used for Therapeutic Purposes

Cannabis sativa has many promising medicinal applications for the mitigation, or even cure, of chronic diseases. The high bioaccumulation potential of C. sativa enables its use for the phytoremediation and detoxification of soil, may increase the levels of inorganic elements in products such as cannabidiol (CBD) extracts being necessary the evaluation/monitoring of the level of inorganic components, mainly the toxic species in these formulations. An analytical method employing graphite furnace atomic absorption spectrometry (GFAAS) was developed for the quantification of Pb, As, and Cd in commercial CBD extracts and homemade samples. The alkaline solubilization was employed in agreement with the external analytical curve, in a robust method. The limits of quantification were 0.26 (Pb), 0.067 (As), and 0.011 µg g-1 (Cd), with satisfactory accuracy (80-120%) and relative standard deviation (RSD) values < 7%. The CBD extracts presented levels of Pb, As and Cd below the maximum limits established by regulatory agencies.

Método de Solubilização Alcalina Aplicado à Amostras de Pão Industrializado Para Subsequente Determinação de Cu, Fe, K, Mg, Na e Zn Por Espectrometria Atômica

Foi desenvolvido um metodo de preparo de amostras de pao do tipo bisnaguinha utilizando o TMAH para a solubilizacao alcalina. O objetivo desse trabalho foi avaliar a concentracao de Cu, Fe, K, Mg, Na e Zn apos a solubilizacao das amostras a temperatura ambiente, em overnight. A solubilizacao alcalina se apresentou como um metodo simples e rapido, alem de ser uma melhor alternativa frente aos procedimentos de mineralizacao convencional, permitindo a solubilizacao completa das amostras usando pequenas quantidades de TMAH. Utilizou-se um metodo de decomposicao acida e adicao de analito para avaliar a exatidao do metodo. Obtiveram-se baixos limites de deteccao 0,073; 0,051; 0,021; 0,008; 0,003 e 0,043 mg kg-1 para Cu, Fe, K, Mg, Na e Zn, respectivamente, alem de bons valores de recuperacao, variando de 80 a 120 % para os analitos. Dentre os resultados obtidos todos apresentaram concentracoes de acordo com a legislacao pra Na e abaixo do DRI para os demais mais elementos. A comparacao de metodo nao apresentou diferenca significativa, assim o metodo se mostrou adequado para as analises.

Análise Comparativa de Elementos Traços em Tecidos Animais Cancerosos e Não Cancerosos Usando Regressão Logística

Essential metals are important in the normal functioning of the body. However, tissues or organs can be affected when there are inappropriate concentrations of these elements. In the literature, there are works indicating that essential elements may be related to the emergence of neoplasms. Therefore, it is important to determine the metal species in biological samples in order to relate the concentration of these species to the emergence of neoplasms. This study reports the application of the Flame Atomic Absorption Spectroscopy (FAAS) for the quantification of Cu, Fe, Mn and Zn in 31 samples of canine tissue (11 mammary glands, 4 pancreas, 3 skin and 13 testicles) with and without neoplasms, using alkaline solubilization of the tissues. The concentration of these metals was used as co-variables for the construction of models of logistic regression. The concentration of Zn in breast and Fe in pancreas was significant (p < 0.05) in the logistic models. The findings of this study describe that the elements Fe and Zn play a major role in the development of carcicoma, since high levels of these metals were observed in neoplastic tissues.

Evaluation of acidogenic sludge from anaerobic reactors running at low solids retention times to reduce sludge generation and enhance biogas production

ABSTRACT&#x0D; &#x0D; Sludges generated in the biological processing of sewage are complex mixtures, the constituents of which pose risks to public health and the environment. Anaerobic digestion is considered the most sustainable option for treating sludge because it offers the possibility of generating biogas. The aim of this study was to compare the quantities, properties, biodegradabilities and biochemical methane potentials (BMP) of primary sludge (PS) generated by a primary decanter with acidogenic sludges produced by upflow anaerobic (UA) reactors operating at solids retention times (SRTs) of 2, 4, 6 and 8 days (Samples S2, S4, S6 and S8, respectively). Sludges from both pre-treatments were submitted to alkaline solubilization in order to determine the efficiency of the process in disrupting extracellular complexes. Based on the levels of total solids (TS) present, the primary decanter was found to generate higher quantities of excess sludge (yield of 3.1 gTS∙d-1) than UA reactors operating at low SRTs (yields in the range 1.69 to 0.64 gTS∙d-1). The concentrations of dissolved materials in PS and Samples S2 and S8 were considerably higher after alkaline solubilization, with respective increases of 8, 14 and 28-fold in dissolved organic carbon, 12, 20 and 40-fold in chemical oxygen demand, 25, 31 and 59-fold in proteins, and 17, 21 and 63-fold in carbohydrates. In addition, the BMP value for S8 was some 13% higher than that recorded for PS while the kinetic constant for gas production by S8 was 1.8-fold greater than that of PS. It is concluded that a pre-treatment combining anaerobic digestion at low SRT and alkaline solubilisation would lead to improved performance in subsequent stages of anaerobic digestion and, consequently, increased efficiency in biogas production.

Chemical and Nutritional Evaluation of Protein-Rich Ingredients Obtained through a Technological Process from Yellow Lupin Seeds (Lupinus luteus).

In recent years, interest in plant-based proteins has been rising due to ethical and sustainability issues. In this context, the production of protein concentrates and isolates from new plant sources have increased enormously because of their nutritional and techno-functional properties. Therefore, this work describes a pilot process for obtaining protein-rich ingredients from a yellow lupin variety (Lupinus luteus) developed by the Agriaquaculture Nutritional Genomic Center (CGNA). A protein alkaline solubilisation followed by isoelectric precipitation was used as a method for obtaining a protein concentrate (LPC) and isolate (LPI) with 75 and 95% protein, respectively. The changes in the protein quality and chemical composition during the protein concentration process from lupin flour were evaluated. Thus, nutritional parameters such as the amino acids (AAs) profile, essential amino acid index (EAAI), chemical score (CS), the protein efficiency ratio (PER), and digestible indispensable amino acid score (DIAAS) were determined to evaluate the nutritional quality of LPC and LPI. The facile and scalable protein isolation method without a defatting process proposed in this study showed a great protein separation efficiency (PSE), while the amino acids profile was not affected during both the concentration as well as the isolation of proteins. In addition, SDS-PAGE showed that both LPC and LPI mainly contained the high-molecular-weight proteins α and β-conglutins. Both LPC and LPI had a balanced amino acids profile, and arginine was the most predominant amino acid. These results are useful for increasing the use of lupin based-protein ingredients as a potential functional ingredient in the food industry.

Evaluation of gels made with different commercial pea protein isolate: Rheological, structural and functional properties

The gelling of two commercial pea protein isolates (PPI) at 20% and 23% PPI concentration, and the effect of microbial transglutaminase (-0- and -5- U/g protein), were analysed. The final aim was to get PPI gels with textural properties enough to make meat and seafood analogues. The first PPI (-A-), was made by alkaline solubilization and isoelectric precipitation from pea flour. The second one (-B-), was obtained by aqueous dispersion of the pea flour and concentration of the soluble protein. The water and oil holding capacities of PPI-A suggested a higher degree of protein denaturation which was assessed by Dynamic thermo mechanical analysis (DMTA) and Fourier transform infrared spectroscopy (FTIR). FTIR data showed lower intermolecular β-sheet aggregates in PPI-B gels than in PPI-A. This result was consistent with the reticulated and well-interconnected network from scanning electron microscopy (SEM) of PPI-B gels in line with the higher strain amplitude (γmax), and the lower loss factor (tanδ) in PPI-B gels vs PPI-A gels. The MTGase enzyme significantly improved the structural quality of the PPI-B gels (high Q-factor) at 20% and 23% PPI. For all these reasons PPI B is more suitable for achieving consistent gels as bases for meat and seafood analogues.

Comparative Biological Activities Determination of Aqueous Extracts of Hempseed Oil and Hempseed Protein Isolate Production Coproducts

AbstractIndustrial hempseed is an important agricultural crop with increasing potential for food applications. The objective of this study was to determine the different biological activities of hempseed coproducts after hempseed oil extraction and hempseed protein isolate precipitation. Hempseed oil was extracted by n‐hexane and the defatted meal was dried. The hempseed protein isolate was prepared by alkaline pH solubilization followed by isoelectric precipitation. Two coproducts were obtained by freeze drying the precipitate after alkaline solubilization and freeze drying the supernatant after isoelectric precipitation. The coproducts were called hempseed meal after protein isolation (HM‐PI) and hempseed supernatant after protein isolation (HS‐PI). The biological activities of HM‐PI and HS‐PI were determined by measuring their antioxidant properties, antiproliferative properties against two human colon cancer cell lines, and anti‐inflammatory activities in lipopolysaccharide‐induced RAW 264.7 macrophages. The results showed that HS‐PI has better biological activities than HM‐PI, which correlated positively with the concentrations of soluble proteins, soluble polyphenols, tannins, and flavonoids. Our results showed for the first time that coproducts of hempseed processing can be potential sources of food ingredients with health‐promoting properties.

Potential of pulse‐derived proteins for developing novel vegan edible foams and emulsions

SummaryChefs around the world strive to go beyond ordinary and garnish dishes with edible foams and emulsions, generally made using proteins derived from soy or animal sources. However, the increasing number of consumers following a vegan diet has led to a higher demand for novel foods formulated using plant‐derived proteins. The current study evaluated the functional properties of proteins obtained by alkaline solubilisation from common pulses. Water‐ and oil‐holding capacities varied within the ranges 2.39–6.78 and 3.46–6.37 g of water or oil per g or protein concentrate, respectively. Emulsifying capacity and stability was higher at pH values 2.0 and 10.0. A similar trend was observed for foaming capacity and stability. Proteins isolated from fava beans showed the highest foaming capacity, calculated as 56.7 ± 2.9 and 56.7 ± 2.7% when measured at pH 2.0 and 10.0, respectively (P &lt; 0.05). Overall, studied proteins showed potential for their use in edible foams, emulsions and other innovative products.

Food functionality of protein isolates extracted from Yellowfin Tuna (Thunnus albacares) roe using alkaline solubilization and acid precipitation process.

Four types of roe protein isolates (RPIs) were prepared through the alkaline solubilization and acid precipitation (ASAP) process, and their functional properties and in vitro bioactivities were evaluated. Higher buffer capacity in pH‐shift range of 8–12 was found in RPI‐1 (pH 11/4.5), required average 94.5 mM NaOH than that of other RPIs to change the pH by 1 unit. All the samples of 1% dispersion (w/v) showed the lowest buffering capacity near the initial pH. The water‐holding capacities (WHC) of RPIs and casein as controls without pH‐shift were in range of 3.7–4.0 g/g protein, and there were no significant differences (p > 0.05). At pH 2 and 8–12 with pH‐shift, WHC and protein solubility of RPIs were significantly improved compared to those of controls. Foaming capacities of RPI‐1 and RPI‐3 were 141.9% and 128.1%, respectively, but those of RPI‐2 and RPI‐4 were not detected. The oil‐in‐water emulsifying activity index of RPI‐1 and RPI‐3 was 10.0 and 8.3 m2/g protein, which was not statistically different from casein (7.0 m2/g), but lower than that of hemoglobin (19.1 m2/g). Overall, RPIs, casein, and hemoglobin exhibited lower food functionality at pH 4–6 near isoelectric points. Through the pH‐shift treatment, the food functionalities of RPIs were improved over the controls, especially in the pH 2 and pH 8–12 ranges. RPI also showed in vitro antioxidant and antihypertensive activities. Therefore, it has been confirmed that RPI extracted from yellowfin tuna roe has high utility as a protein‐ or food‐functional‐enhancing material or protein substitute resource for noodles, confectionery, baking, and surimi‐based products.

Utilization of freshwater mussel (Lamellidens marginalis) for the isolation of proteins through pH shift processing: characterization of isolates.

Study was conducted touse underutilized freshwater mussel (Lamellidens marginalis) for the recovery of proteins using pH shift method and to study the functionality and characteristics of the recovered isolates. From the pH range tested (pH2.0-13.0), maximum protein yields were obtained during solubilization at pH2.0 and pH13.0 (p < 0.05). During the protein recovery process, pH13.0 was found to have minimal effect on proteins resulting in higher protein yields compared to pH2.0. Isolates obtained by both acidic and alkaline solubilization processes had low stability and poor gel network. Total lipid content, total myoglobin, and pigment contents were reduced significantly (p < 0.05) during pH shift processing, resulting in whiter protein isolates and protein gels. All the essential amino acids were present in the isolates recovered by acid and alkaline solubilization, indicating the complete recovery of amino acids. No microbial counts were observed in any of the isolates prepared using acid and alkaline-aided processing. Acid and alkaline solubilization (pH shift) process was found to be promising for the recovery of proteins from underutilized freshwater mussel thus by reducing the supply demand gap.

Purification and antioxidant activities of peptides from sea squirt (Halocynthia roretzi) protein hydrolysates using pepsin hydrolysis

Sea squirt (Halocynthia roretzi) are widely used as a food material in Korea. Sea squirt protein (SSP) were isolated by alkaline solubilization followed by acidic precipitation. SSP were further hydrolyzed using pepsin hydrolysis at pH 2 for 2 h to release antioxidant peptides. SSP hydrolysates (SSPH) showed DPPH radical scavenging activity of 31 ± 1% at 1 mg/mL, ORAC of 576 ± 1 μM trolox equivalent (TE)/mg SSPH, and ABTS+ radical scavenging activity of 38 ± 1 μM TE/mg SSPH. Three antioxidant peptides LEW, MTTL, and YYPYQL were purified and identified from SSPH using chromatography and tandem mass spectrometry (LC-MS/MS). The antioxidant activities of LEW, MTTL, and YYPYQL were evaluated using DPPH and ABTS+ radical scavenging activity, Fe2+ chelating activity, ORAC, and reducing power. Among the three peptides, LEW showed the highest DPPH radical scavenging activity of 75% at 5 mM. The ORAC value of LEW (77.1 μM TE/50 μM LEW) and YYPYQL (84.6 μM TE/50 μM YYPYQL) are higher than glutathione (18.5 μM TE/50 μM GSH), as a positive control. The three antioxidant peptides showed higher Fe2+ chelating activity than GSH, but ABTS+ radical scavenging activity and reducing power of LEW, MTTL, and YYPYQL were lower than GSH. Taken together, these results suggest that SSPH and/or the purified antioxidant peptides may be useful as a functional food additive.