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Functional and physiochemical properties of protein isolates from different body parts of North Atlantic sea cucumber (Cucumaria frondosa)
... Wild populations of these species are declining due to extensive commercial exploitation in coastal waters, driven by high demand from both domestic and international markets (Yaghmour & Whittington-Jones, 2018;Kamaruddin & Rehan, 2015). From a nutritional point of view, sea cucumbers are low in sugar, fat, and cholesterol, but rich in proteins and essential amino acids (Senadheera et al., 2023). Additionally, sea cucumbers contain various essential nutritional components, including vitamins, minerals, collagen, and polyunsaturated fatty acids . ...
... In most forms of trade, only the body wall and muscle bands of sea cucumbers are harvested and sold off (Senadheera et al., 2023), while the intestines, gonads, and other organs (termed viscera), which can account for up to 50% of the sea cucumber's total Babji et al. (2020), consumption of relatively small amounts of sea cucumber viscera hydrolysate may satisfy various vitamin needs in both animal and human nutrition. As sea cucumber viscera are known to contain various nutrients and bioactive compounds, further research should be conducted to valorise them for the industrial production of high-value nutritional products while addressing the issue of harmful heavy metal content. ...
Sea cucumbers have high economic value, and in most forms of trade, their body wall is typically the only part that is harvested and sold. The organs of the sea cucumber, collectively known as the viscera, are frequently discarded, contributing to land and water pollution. However, discarded sea cucumber viscera contain various nutrients that can be used in many applications. Therefore, this review highlights the biological and economic aspects of sea cucumbers, followed by a critical discussion of the nutritional value of their internal organs and possible applications, including as functional feed additives in the aquaculture industry, sources of natural testosterone for application in sex reversal and production of monosex population, of neuroprotective agents against central nervous system disorders and of cosmetic ingredients, especially for skin whitening and anti-ageing products. The review further highlights the valorisation potential of viscera to maximize their economic potential, thus providing an enormous prospect for reusing sea cucumber waste, thereby reducing the negative impact of the sea cucumber fishery sector on the environment.
... These findings suggest that the protein content and solubility have positively affected the foaming properties of protein extracts from A. mollis. This pattern was also observed in other studies, where high solubility increased protein chain flexibility, facilitating rapid dispersion in water and effective adherence at the water-air interface, demonstrating superior foaming properties [51,52]. Compared to commercial protein isolates, the FC of all extracts was comparable under acidic, neutral, and moderately alkaline conditions but declined significantly above pH 9. ...
This study investigated the physicochemical properties, functionalities, and antioxidant capacities of protein extracts from wild sea cucumber Australostichopus mollis collected from four distinct locations in New Zealand. Protein was extracted from sea cucumber body walls using trypsin enzymatic extraction, followed by cold acetone precipitation. The amino acid analysis revealed high glycine (189.08 mg/g), glutamic acid (119.45 mg/g), and aspartic acid (91.91 mg/g) concentrations in all samples. The essential amino acid indexes of the protein extracts (62.96, average) were higher than the WHO/FAO standard references, indicating the excellent protein quality of A. mollis. Furthermore, protein extracts from A. mollis demonstrated superior emulsifying activity (202.3–349.5 m2/g average) compared to commercial soy and whey protein isolates under all tested pH conditions, and enhanced foaming capacity (109.9–126.4%) and stability (52.7–72%) in neutral and acidic conditions. The extracts also exhibited good solubility, exceeding 70% across pH 3–11. Antioxidant capacities (ABTS and DPPH free radical scavenging activity and ferric reducing antioxidant power) were identified in A. mollis protein extracts for the first time, with clear variations observed among different locations. These findings elucidate the advantageous functional properties of protein extracts from wild New Zealand A. mollis and highlight their potential application as high-quality antioxidant food ingredients.
... Approximately 1500 varieties of sea cucumbers are reported to be found worldwide; however, about 100 species are used for food/ medicinal purposes [2]. Sea cucumbers contain more than 50 types of biomolecules, including proteins (amino acids, collagen, and peptides), lipids (polyunsaturated fatty acids), sulphated polysaccharides (fucosylated chondroitin sulphate and fucoidan), ash, lectins, saponins, glycosides, phenolics (phenolic acids and flavonoids), and sterols, which are well reported for their anticancer, anti-tumour, anti-coagulation, antioxidant, antidiabetic, antihypertensive, antiglycation, and anti-osteoclastogenesis properties [1,[4][5][6][7][8][9]. For instance, sea cucumber processing discards, mainly internal organs along with or without tentacles/aquapharyngeal bulbs/flowers, are rich sources of essential amino acids, polyunsaturated fatty acids, and phenolic compounds, which exhibit potent antioxidant activity [4,6,10]. ...
Sea cucumbers are well demarcated for their valuable role in the food, pharmaceutical, nutraceutical, and cosmeceutical sectors. The demand for well-processed dried sea cucumber retaining quality is prioritized by local markets and industries. There are several techniques for the pre-processing of fresh sea cucumbers, including traditional and modern methods, such as salting, boiling, high-pressure processing, high-pressure steaming, and vacuum cooking, among others, in order to inactivate enzymes and microbial attacks. Further, pre-treated sea cucumbers require post-processing before human consumption, transportation, or industry uses such as hot air, freeze, cabinet, sun, or smoke drying. However, despite the ease, traditional processing is associated with several challenges hampering the quality of processed products. For instance, due to high temperatures in boiling and drying, there is a higher chance of disrupting valuable nutrients, resulting in low-quality products. Therefore, the integration of traditional and modern methods is a crucial approach to optimizing sea cucumber processing to obtain valuable products with high nutritional values and retain bioactive compounds. The value of dried sea cucumbers relies not only on species and nutritional value but also on the processing methods in terms of retaining sensory attributes, including colour, appearance, texture, taste, and odour. Therefore, this review, for the first time, provides insight into different pre- and post-treatments, their perspective, challenges, and how these methods can be optimized for industry use to obtain better-quality products and achieve economic gains from sea cucumber.
... Previous studies [19,40] have highlighted the importance of WHC and OHC in determining the quality and appeal of various food product, especially for enhancing the textural properties and preserving the flavor during food processing. As presented in Fig. 3A, SPI had a high WHC of 4.44 g water /g protein but a low OHC of 1.59 g oil /g protein , which was lower than values reported in the literatures [41,42]. However, after hydrolysis with bromelain at 12 % DH, SPIH showed a decrease in WHC to 1.03 g water /g protein , but an increase in OHC to 3.55 g oil /g protein . ...
High-concentration soy protein isolate was subjected to ultrasonication for viscosity reduction to assist the process of limited enzymatic hydrolysis. Ultrasonication (20 kHz, 10 min, 160 W/L) effectively reduced the viscosity of soy protein isolate at a comparatively high concentration of 14 % (w/v) and promoted the limited enzymatic hydrolysis (controlled degree of hydrolysis of 12 %) with a higher peptide yield than that of the conventional method. The correlations between substrate viscosity and peptide yield, as well as the viscosities of the resulting hydrolysates, were studied. The findings revealed positive correlations between the viscosities of the substrate and hydrolysate, underscoring the potential impact of altering substrate viscosity on the final product. Furthermore, the utilization of ultrasonic viscosity reduction-assisted proteolysis has shown its capability to improve the functional and physicochemical properties, as well as the protein structure of the hydrolysate, while maintaining the same level of hydrolysis. It is worth noting that there were significant alterations in particle size (decrease), β-sheet content (increase), β-turn content (increase), and random coil content (increase). Interestingly, ultrasonication unexpectedly impeded the degradation of molecular mass in proteins during proteolysis, while increasing the hydrophobic properties of the hydrolysate. These findings aligned with the observed reduction in bitterness and improvement in emulsifying properties and water-holding capacity.
... Traditionally, protein hydrolysates are prepared using several chemical extraction methods. However, techniques such as enzyme hydrolysis, microwave-assisted extraction, ultrasound-assisted extraction, high-pressure processing-assisted extraction, supercritical fluid extraction, pressurized solvent extraction, pulsed electric field-assisted extraction, and fermentation are preferred (Cheung et al. 2015;Senadheera et al. 2023). Protein hydrolysates obtained from these processes are used in the food industry as milk replacers, protein supplements, stabilizers in beverages, and flavor enhancers, among others. ...
Salmon aquaculture generates 80% of the total revenue of finfish aquaculture across Canada. Salmon farming is carried out in a multilevel process, and at least 60% of the total production is considered as by-products, including skin, head, viscera, trimmings, frames, bones, and roes. These by-products are an excellent source of protein, which can be converted to protein hydrolysates through enzymatic hydrolysis and non-enzymatic processes such as chemical hydrolysis (acid and alkaline) in order to utilize them into value-added products. Several studies have reported that peptides from salmon protein hydrolysates possess bioactivities, including antihypertensive, antioxidant, anticancer, antimicrobial, antidiabetic, anti-allergic, and cholesterol-lowering effects. Incorporating in silico computational methods is gaining more attention to identify potential peptides from source proteins. The in silico methods can be used to predict the properties of the peptides and thereby predetermine the processing, isolation, and purification steps that can be used for the peptides of interest. Therefore, it is essential to implement robust, standardized, and cost-effective processing techniques that can easily be transferrable and scale up for industrial applications in view of circular economy and upcycling concept. This contribution summarizes the latest research information on Atlantic salmon, production statistics, growth lifecycle, processing, protein production techniques, nutritional and functional properties, peptide production and purification processes, as well as potential health benefits as a nutraceutical product.
Graphical Abstract
... As a typical marine organism in the family of vertebrates and echinodermata [1,2], sea cucumbers are rich in mucopolysaccharides [3], amino acids [4], fatty acids [5], collagen [6], and saponins [7]. Sea cucumber has attracted considerable attention because of its nutritional value [8,9]. ...
To effectively shorten the rehydration time of Apostichopus japonicus and reduce the nutrient loss during the rehydration process, an ultrasound-assisted rehydration method was adopted to rehydrate semi-dry salted A. japonicus in this study. The effects of different ultrasonic powers, temperatures, and times on the rehydration characteristics, textural characteristics, and sensory quality of the semi-dry salted A. japonicus were studied. Box–Behnken response surface analysis was used to study the influence of the interactions among the three factors on the rehydration ratio of the semi-dry salted A. japonicus, and a quadratic multinomic regression model was established to predict the optimal rehydration ratio. The results showed that ultrasound could change the structure of semi-dry salted A. japonicus and form a spatial network structure, thereby improving its water absorption capacity and reducing rehydration time. The optimal rehydration effect could be obtained when the ultrasonic power was 400 W, the ultrasonic temperature was 50 °C, and the ultrasonic time was 83 min. Ultrasonic power, ultrasonic time, and ultrasonic temperature influenced the rehydration ratio of the semi-dry salted A. japonicus. Under the optimal rehydration conditions in this study, the rehydration ratio of semi-dry salted A. japonicus obtained by the test was 2.103, which was consistent with the value predicted by the Box–Behnken response surface method.
... They are rich in proteins, essential amino acids, vitamins, vitamins, minerals, collagen, omega-3, minerals, collagen, and polyunsaturated fatty acids but low in fat, cholesterol, and sugar. They are also used to produce tonic medicines, such as the gamat oil used to treat minor wounds and muscle and joint pain [9,10]. The overharvesting of marine organisms has dire consequences for the environment by reducing its capacity to recycle nutrients and diminishing ocean acidification, lowering symbiont biodiversity, and affecting organic matter recycling. ...
Aquatic organisms comprising various plant and animal taxa represent a wide range of adaptations to a specific environment, but they also share many features with nonaquatic organisms of a given taxonomic group.[...]
... This marine animal possesses a series of biomolecules, showing multiple biological activities. In particular, sea cucumbers are well-known for their protein (collagen, protein hydrolysates, and peptides) [1,2], lipid (polyunsaturated fatty acids, PUFAs) [3,4], polysaccharide (FCS and FS) [5,6], saponins/triterpene glycosides (frondoside A) [7], carotenoids (astaxanthin and canthaxanthin) [8], phenolics (phenolic acids and flavonoids) [9,10], and minerals [11]. These components demonstrate a wide spectrum of biological activities, such as anticoagulant, antithrombotic, anticancer, anti-inflammatory, anti-hypertension, antioxidant, anti-hyperglycemic, and antimicrobial activities, among others [12,13]. ...
... The production of protein hydrolysates using enzymatic methods is an efficient way to recover bioactive peptides, which exhibit the potential for disease risk reduction and health promotion [2]. Enzymatic hydrolysis could improve functional properties, such as water/oil-holding capacity, solubility, and emulsifying and foaming properties, through influencing the hydrophobicity, molecular size, and polar groups of peptides [5]. Apart from functional properties, protein hydrolysates are involved in numerous biological functions, including antihypertension, antithrombotic, immunomodulatory, anticancer, antioxidant, and antimicrobial activities [6]; for example, protein hydrolysates derived from sea cucumber have shown antioxidant, angiotensin-converting enzyme (ACE) inhibitory, immunomodulatory, and anti-inflammatory properties, among others, which are closely related to the structural properties of hydrolysates/peptides [7][8][9][10][11]. ...
Atlantic sea cucumber is a benthic marine echinoderm found in Northwest Atlantic waters and is harvested mainly for its body wall. The body wall, along with internal organs and aqua-phyrangeal bulb/flower, is a rich source of proteins, where the latter parts are often considered as processing discards. The objective of this research was to produce protein hydrolysates from sea cucumber tissues (body wall, flower, and internal organs) with bioactive properties associated with antioxidants, DNA and LDL cholesterol oxidation inhibition, and angiotensin-I-converting enzyme (ACE) inhibitory effects. The protein hydrolysates were prepared using food-grade commercial enzymes, namely Alcalase, Corolase, and Flavourzyme, individually and in combination, and found that the combination of enzymes exhibited stronger antioxidant potential than the individual enzymes, as well as their untreated counterparts. Similar trends were also observed for the DNA and LDL cholesterol oxidation inhibition and ACE-inhibitory properties of sea cucumber protein hydrolysates, mainly those that were prepared from the flower. Thus, the findings of this study revealed potential applications of sea cucumber-derived protein hydrolysates in functional foods, nutraceuticals, and dietary supplements, as well as natural therapeutics.
... Traditionally, protein hydrolysates are prepared using several chemical extraction methods. However, techniques such as enzyme hydrolysis, microwave-assisted extraction, ultrasound-assisted extraction, high-pressure processing-assisted extraction, supercritical fluid extraction, pressurized solvent extraction, pulsed electric field-assisted extraction, and fermentation are preferred (Cheung et al. 2015;Senadheera et al. 2023). Protein hydrolysates obtained from these processes are used in the food industry as milk replacers, protein supplements, stabilizers in beverages, and flavor enhancers, among others. ...
Salmon aquaculture generates 80% of the total revenue of finfish aquaculture across Canada. Salmon farming is carried out in a multilevel process, and at least 60% of the total production is considered as by-products, including skin, head, viscera, trimming, frames, bones, and roes. These by-products are an excellent source of protein, which can be converted to protein hydrolysates through enzymatic hydrolysis and non-enzymatic processes such as chemical hydrolysis (acid and alkaline) and salt extraction. Several studies have reported that peptides from salmon protein hydrolysates possess bioactivities, including antihypertensive, antioxidant, anticancer, antimicrobial, antidiabetic, anti-allergic, and cholesterol-lowering effects. Incorporating in-silico computational methods is gaining more attention to identify potential peptides from source protein. The in-silico methods can be used to predict the properties of the peptides and thereby predetermine the processing, isolation, and purification steps that can be used for the peptides of interest. Therefore, it is essential to implement robust, standardized, and cost-effective processing techniques that can easily be transferrable and scale up for industrial applications. This contribution summarizes the latest research information on Atlantic salmon, production statistics, growth lifecycle, processing, protein production techniques, nutritional and functional properties, peptide production and purification processes, as well as potential health benefits as a nutraceutical product.
Fish is a nutritious food that has been linked to human health, with bioactive peptides (BPs) playing an important role in this. Fish-derived BPs possess various functional properties, including antioxidant, antihypertensive, anti-diabetic, and antimicrobial activities. The mechanisms underlying these functional properties depend on the structural characteristics, such as amino acid composition, terminal amino acid type, hydrophobicity, molecular weight, and net charge of the BPs. To date, the production and identification of fish-derived BPs has been based primarily on conventional approaches. However, these methods are characterized by lengthy and time-consuming steps making BPs application expensive. To address these limitations, bioinformatics approaches based on biological data and computational modeling are emerging as a promising way to improve efficiency and reduce costs in the discovery and development of BPs. In recent years, several reports have demonstrated that bioinformatics approaches, either singular or in combination, can more rapidly and efficiently identify potential bioactivities, characteristics, and sequences of new fish-derived BPs. Quantitative structure-activity relationship and molecular docking studies provide basic structural information on the active site and reveal the mechanism underlying of BPs bioactivity. In light of the above discussion, this review discusses current research on the potential bioactivity of fish-derived BPs, structural characteristics, and methods of BPs production and identification, including both conventional and bioinformatics-driven approaches. This review highlights the role of bioinformatics in the identification of fish-derived BPs, using techniques such as database and proteolytic simulation, molecular docking and molecular dynamics. In addition, the review addresses existing challenges and outlines future perspectives for the use of fish-derived BPs and their bioinformatic analysis in advancing biomedical research
The structurally diverse bioactive compounds found in marine organisms represent valuable resources for the food and pharmaceutical industries. The marine ecosystem encompasses over half of the world’s biota, providing an extensive range of bioactive compounds that can be extracted from various marine life forms, including marine microorganisms (such as bacteria, cyanobacteria, and actinobacteria), algae (both macroalgae and microalgae), invertebrates (including sponges, mollusks, echinoderms, and crustaceans), and, most importantly, fish. Many of these organisms thrive in extreme marine environments, leading to the production of complex molecules with unique biological functions. Consequently, marine biomolecules, such as lipids (especially polyunsaturated fatty acids), proteins/peptides, polysaccharides, carotenoids, phenolics, and saponins, exhibit a wide range of biological properties and can serve as valuable components in nutraceuticals and functional foods. Nevertheless, most of these biomolecules are susceptible to oxidation and degradation; encapsulation-based technologies tend to preserve them and increase their bioavailability and functions. These biological compounds demonstrate diverse activities, including antioxidant, anticancer, antithrombotic, anticoagulant, anti-inflammatory, antiproliferative, antidiabetic, antimicrobial, and cardioprotective effects, making them promising candidates for applications in the food industry. Despite their numerous health benefits, marine bioactive compounds have remained underutilized, not only in the food industry but also in the pharmaceutical and nutraceutical sectors. Therefore, this review aims to provide an overview of the various sources of marine bioactive compounds and their potential contributions to the food industry.
Bioinformatic tools are widely used in predicting potent bioactive peptides from food derived materials. This study was focused on utilizing sea cucumber processing by-products for generating antioxidant and ACE inhibitory peptides by application of a range of in silico techniques. Identified peptides using LC−MS/MS were virtually screened by PepRank technique followed by in silico proteolysis simulation with representative digestive enzymes using BIOPEP-UWM TM data base tool. The resultant peptides after simulated digestion were evaluated for their toxicity using ToxinPred software. All digestive resistance peptides were found to be non-toxic and displayed favorable functional properties indicating their potential for use in a wide range of food applications, including hydrophobic and hydrophilic systems. Identified peptides were further assessed for their medicinal characteristics by employing SwissADME web-based application. Our findings provide an insight on potential use of undervalued sea cucumber processing discards for functional food product development and natural pharmaceutical ingredients attributed to the oral drug discovery process.
Sea cucumbers are considered a luxury food item and used locally in traditional medication due to their impressive nutritional profile and curative effects. Sea cucumbers contain a wide range of bioactive compounds, namely phenolics, polysaccharides, proteins (collagen and peptides), carotenoids, and saponins, demonstrating strong antioxidant and other activities. In particular, phe-nolic compounds, mainly phenolic acids and flavonoids, are abundant in this marine invertebrate and exhibit antioxidant activity. Protein hydrolysates and peptides obtained from sea cucumbers exhibit antioxidant potential, mainly dependent on the amino acid compositions and sequences as well as molecular weight, displayed for those of ≤20 kDa. Moreover, the antioxidant activity of sea cucumber polysaccharides, including fucosylated chondroitin sulfate and fucan, is a combination of numerous factors and is mostly associated with molecular weight, degree of sulfation, and type of major sugars. However, the activity of these bioactive compounds typically depends on the sea cucumber species, harvesting location, food habit, body part, and processing methods employed. This review summarizes the antioxidant activity of bioactive compounds obtained from sea cucumbers and their by-products for the first time. The mechanism of actions, chemical structures, and factors affecting the antioxidant activity are also discussed, along with the associated health benefits.
Sea cucumber processing discards, which include mainly internal organs, represent up to 50% of the sea cucumber biomass, and are a rich source of bioactive compounds, including phenolics. This work aimed to extract free, esterified, and insoluble-bound phenolics from the internal organs of the Atlantic sea cucumber (C. frondosa) using high-pressure processing (HPP) pre-treatment. The sea cucumber internal organs were subjected to HPP (6000 bar for 10 min), followed by the extraction and characterization of phenolics. Samples were evaluated for their total contents of phenolics and flavonoids, as well as several in vitro methods of antioxidant activities, namely, free radical scavenging and metal chelation activities. Moreover, anti-tyrosinase and antiglycation properties, as well as inhibitory activities against LDL cholesterol oxidation and DNA damage, were examined. The results demonstrated that HPP pre-treatment had a significant effect on the extraction of phenolics, antioxidant properties, and other bioactivities. The phenolics in sea cucumber internal organs existed mainly in the free form, followed by the insoluble-bound and esterified fractions. Additionally, UHPLC-QTOF-MS/MS analysis identified and quantified 23 phenolic compounds from HPP-treated samples, mostly phenolic acids and flavonoids. Hence, this investigation provides fundamental information that helps to design the full utilization of the Atlantic sea cucumber species and the production of a multitude of value-added products.
Cucumaria frondosa is the main sea cucumber species harvested from Newfoundland waters. During processing, the viscera of sea cucumber are usually discarded as waste. As a matter of fact, sea cucumber viscera are abundant in various nutrients and promising for valorization. In the present study, sea cucumber viscera were pretreated by air drying and freeze drying, and the nutritional compositions of the dried products were investigated, including proximate composition, lipid class, fatty acid profile, and amino acid composition. The dried viscera had similar levels of ash, lipids, and proteins compared to fresh viscera. Both air- and freeze-dried viscera had total fatty acid composition similar to fresh viscera, with high levels of omega-3 polyunsaturated fatty acids (PUFAs) (30–31%), especially eicosapentaenoic acid (27–28%), and low levels of omega-6 PUFAs (~1%). The dried samples were abundant in essential amino acids (46–51%). Compared to air-dried viscera, freeze-dried viscera contained a lower content of moisture and free fatty acids, and higher content of glycine and omega-3 PUFAs in phospholipid fraction. The high content of nutritious components in dried viscera of Cucumaria frondosa indicates their great potential for valorization into high-value products.
Sea urchin Mesocentrotus nudus, Glyptocidaris crenularis, and Strongylocentrotus intermedius gonad protein isolates (mnGPIs, gcGPIs, and siGPIs) were extracted by isoelectric solubilization/precipitation (ISP) from the defatted gonads, and their functional properties were compared. Sodium dodecyl sulfate polyacrylamide gel electrophoresis results showed the similar protein pattern between each protein isolate and defatted gonad, indicating the high efficiency of ISP processing for protein recovery. Amino acid profileconfirmed that the mnGPIs and siGPIs could be potential sources of essential amino acid in nature. As regard to functional properties, mnGPIs showed higher water‐ and oil‐ holding capacities followed bysiGPIs and gcGPIs and all protein isolates presented great foaming property. As for emulsifying activity index (EAI), mnGPIs, gcGPIs, and siGPIs showed the minimum solubility and EAI at pH 5, 3, and 4, respectively, and behaved a pH‐dependent manner. The gcGPIs revealed the highest EAI from pH 6 to 8 among the samples. In addition, circular dichroism showed increased content of β‐sheet at the expense of α‐helix and β‐turn, suggesting the structure denaturation of the protein isolates. Indeed, no statistical difference was observed between secondary structure of mnGPIs and siGPIs. Moreover, ISP processing increased free sulfhydryl content of sea urchin protein isolates, but no difference was observed among the samples. Furthermore, siGPIs revealed the highest amount of total sulfhydryl and disulfide bonds, whereas both defatted gonads and protein isolates from G. crenularis presented the maximum surface hydrophobicity. These results suggest that gonad protein isolates from three species of sea urchin possess various functionalities and therefore can be potentially applied in food system.
Practical Application
Sea urchin M. nudus, G. crenularis, and S. intermedius gonads are edible, whereas the functional properties of protein isolates from sea urchin gonad remain unknown. In this case, the extraction and comparison of three species of sea urchin gonad protein isolates will not only confirm functional properties but also screen food ingredients with suitable functions. In this study, functionalities of protein isolates derived from M. nudus, G. crenularis, and S. intermedius gonads would provide potential application in bakery food and meat products or as emulsifier candidates in food system.
Collagen is the major fibrillar protein in most living organisms. Among the different types of collagen, type I collagen is the most abundant one in tissues of marine invertebrates. Due to the health-related risk factors and religious constraints, use of mammalian derived collagen has been limited. This triggers the search for alternative sources of collagen for both food and non-food applications. In this regard, numerous studies have been conducted on maximizing the utilization of seafood processing by-products and address the need for collagen. However, less attention has been given to marine invertebrates and their by-products. The present review has focused on identifying sea cucumber as a potential source of collagen and discusses the general scope of collagen extraction, isolation, characterization, and physicochemical properties along with opportunities and challenges for utilizing marine-derived collagen.
The oil from thraustochytrids, unicellular heterotrophic marine protists, is increasingly used in the food and biotechnological industries as it is rich in omega-3 fatty acids, squalene and a broad spectrum of carotenoids. This study showed that the oilcake, a by-product of oil extraction, is equally valuable as it contained 38% protein/dry mass, and thraustochytrid protein isolate can be obtained with 92% protein content and recovered with 70% efficiency. The highest and lowest solubilities of proteins were observed at pH 12.0 and 4.0, respectively, the latter being its isoelectric point. Aspartic acid, glutamic acid, histidine, and arginine were the most abundant amino acids in proteins. The arginine-to-lysine ratio was higher than one, which is desired in heart-healthy foods. The denaturation temperature of proteins ranged from 167.8–174.5 °C, indicating its high thermal stability. Proteins also showed high emulsion activity (784.1 m2/g) and emulsion stability (209.9 min) indices. The extracted omega-3-rich oil melted in the range of 30–34.6 °C and remained stable up to 163–213 °C. This study shows that thraustochytrids are not only a valuable source of omega 3-, squalene- and carotenoid-containing oils, but are also rich in high-value protein with characteristics similar to those from oilseeds.
Sea cucumber (Cucumaria frondosa) is the most abundant and widely distributed species in the cold waters of North Atlantic Ocean. C. frondosa contains a wide range of bioactive compounds, mainly collagen, cerebrosides, glycosaminoglycan, chondroitin sulfate, saponins, phenols, and mucopolysaccharides, which demonstrate unique biological and pharmacological properties. In particular, the body wall of this marine invertebrate is the major edible part and contains most of the active constituents, mainly polysaccharides and collagen, which exhibit numerous biological activities, including anticancer, anti-hypertensive, anti-angiogenic, anti-inflammatory, antidiabetic, anti-coagulation, antimicrobial, antioxidation, and anti- osteoclastogenic properties. In particular, triterpene glycosides (frondoside A and other) are the most researched group of compounds due to their potential anticancer activity. This review summarizes the latest information on C. frondosa, mainly geographical distribution, landings specific to Canadian coastlines, processing, commercial products, trade market, bioactive compounds, and potential health benefits in the context of functional foods and nutraceuticals.
Four roe protein isolates (RPIs) from skipjack tuna were prepared using isoelectric solubilization (pH 11 and 12) and precipitation (pH 4.5 and 5.5) (ISP) at different pH points to evaluate their physicochemical and functional properties and in vitro bioactivities. Moisture (<6.3%) and protein (71%–77%) content were maintained. Sulfur, sodium, phosphorus, and potassium were the major elements, and glutamic acid and
leucine were the prevalent amino acids (12.2–12.8 and 9.6–9.8 g/100 g protein, respectively) in RPIs. RPI-1 showed the highest buffering capacity at pH 7–12. RPIs and casein showed similar water-holding capacities. At pH 12, RPI-1(pH 11/4.5) showed the highest solubility, followed by RPI-3(pH 12/4.5), RPI-2(pH 11/5.5), and RPI-4(pH 12/5.5) (p < .05). Oil-in-water emulsifying activity indices of RPI-1 and RPI-3 significantly differed. At pH 2 and 7–12, pH-shift treatment improved the food functionality of RPIs, which was superior to positive controls (casein and hemoglobin). RPI-1 showed ABTS+ radical scavenging (102.7 μg/ml) and angiotensin-converting enzyme inhibitory activities (44.0%).
Protein isolates were recovered from scallop (Patinopecten yessoensis) gonads to develop a novel functional matrix by investigating their physiochemical and functional properties. Scallop gonad protein isolates (SGPIs) were prepared from degreased scallop gonads (DSGs) by an alkali extraction and isoelectric solubilization/precipitation (ISP) process. The protein compositions of the SGPIs were mainly vitellogenin and beta‐actin with molecular weights of 266 and 42 kDa, respectively, as determined using Nano‐liquid chromatography‐mass/mass (Nano‐LC‐MS/MS). After the ISP process, the protein solubility of the SGPIs was significantly improved, and the surface hydrophobicity of SGPIs intensely increased by 1.1‐fold, which were attributed to the exposure of aromatic residues such as phenylalanine, tyrosine, and tryptophan. However, the content of total/reactive sulfhydryl in SGPIs was decreased compared with that of DSGs. Meanwhile, the ISP process caused partial protein unfolding, as indicated by circular dichroism analysis, which exhibited a remarkable rise in the β‐sheet content with a parallel decline in the α‐helix and random coil contents (P < 0.05). SGPIs exhibited a better oil absorption capacity and foaming property than both DSGs and soybean protein isolates (SPIs). Moreover, the emulsifying capacity of SGPIs was greatly enhanced by the ISP process, which was superior to the effect of commercial SPIs and was ascribed to its favorable solubility as well as surface characteristics.
Practical Application
During the processing of scallop (Patinopecten yessoensis) adductors, scallop gonad, a high‐protein part, is usually discarded as processing by‐products despite its edibility. In recent years, scallop gonads are regarded as good sources to develop protein matrices due to their high protein content and numerous nutrients. In this study, scallop gonad protein isolates (SGPIs) were isolated by isoelectric solubilization/precipitation (ISP) process. The preferable solubility, foaming property coupled with high emulsifying property of SGPIs indicated that the SGPIs could be potentially utilized as a good protein emulsifier and additives in production of kamaboko gels, hamburger patties, sausages, and pet foods.
Protein isolate of sea cucumber guts (SCGPI) was extracted from defatted power of sea cucumber guts (SCGs) by alkaline extraction and acid precipitation method. The physicochemical and functional properties of SCGPI were evaluated in comparison with those of SCGs. It was found that the SCGPI showed higher whiteness, and contained 39.5% of the essential amino acids with higher protein efficiency ratio. The functionalities of SCGPI, including solubility, water/oil holding capacity (WHC/OHC), foaming capacity (FC), and emulsifying abilities (EAI), were significantly higher than those of SCGs. SCGPI exhibited higher total sulfhydryl group, disulfide bond, β‐turns, and random coil, while less surface hydrophobicity and α‐helix than SCGs. The thermal denaturation temperature of SCGPI was 46.55°C and the microstructure of SCGPI was flaky. Moreover, OHC, FC, and EAI of SCGPI were significantly better than those of SPI. These results suggest SCGPI can be used as functional bases in the food industry.
Practical applications
Sea cucumber (Stichopus japonicus) guts are the main byproducts in the sea cucumber processing, which are rich in protein. In this study, we prepared protein isolate from sea cucumber guts (SCGPI) by alkaline extraction and acid precipitation method. The results showed that SCGPI exhibited great solubility, water/oil holding capacity, foaming capacity, and emulsifying abilities. The present study demonstrates that SCGPI can be used as a functional base in the food industry.
Isoelectric solubilization/precipitation (ISP) processing allows selective, pH-induced water solubility of proteinswith concurrent separation of lipids and removal of materials not intended for human consumption such asbone, scales, skin, etc. Recovered proteins retain functional properties and nutritional value. Four roe proteinisolates (RPIs) from yellowfin tuna roe were prepared under different solubilization and precipitation condition(pH 11/4.5, pH 11/5.5, pH 12/4.5 and pH 12/5.5). RPIs contained 2.3–5.0 % moisture, 79.1–87.8 % protein, 5.6–7.4%lipidand3.0–3.8 % ash. Protein content of RPI-1 and RPI-2 precipitated at pH 4.5 and 5.5 after alkalinesolubilization at pH 11, was higher than those of RPI-3 and RPI-4 after alkaline solubilization at pH 12 (P< 0.05).Lipid content (5.6–7.4 %) of RPIs was lower than that of freeze-dried concentrate (10.6 %). And leucine and lysineof RPIs were the most abundant amino acids (8.8–9.4 and 8.5–8.9 g/100 g protein, respectively). S, Na, P, K asminerals were the major elements in RPIs. SDS-PAGE of RPIs showed bands at 100, 45, 25 and 15 K. Moisture andprotein contents of process water as a 2’nd byproduct were 98.9–99.0 and 1.3–1.8 %, respectively. Therefore,yellowfin tuna roe isolate could be a promising source of valuable nutrients for human food and animal feeds.
Scallop (Patinopecten yessoensis) female gonad hydrolysates (SFGHs) were obtained by using neutrase. The resulting hydrolysates possessed DPPH radical scavenging activity, ferrous ion-chelating ability, and reducing power with IC50 or AC0.5 values of 9.44, 0.94, and 5.88 mg/mL, respectively. SFGHs contained nearly 80 % of fractions with molecular weight around 250–5000 Da, and antioxidant-related amino acid residues in SFGHs reached to more than 30 %. Six fractions were separated from SFGHs on a Sephadex G-25 column, and one of the fractions with the highest DPPH radical scavenging activity was further analyzed by ESI-MS/MS, and a tetrapeptide His-Met-Ser-Tyr (536 Da) and a pentapeptide Pro-Glu-Ala-Ser-Tyr (565 Da) were identified. Both peptides showed hydroxyl radical scavenging activities with IC50 values of 3.6 and 16.8 mM, respectively, by electron spin resonance method. These results imply that peptides derived from scallop female gonads are potent antioxidants and may be utilized as functional ingredients in food systems.
Protein isolates of beach pea were prepared using sodium hydroxide (NaOH) and sodium hexametaphosphate (SHMP). Functional properties of the isolates so prepared were investigated and compared with those of other pea samples. Protein isolate of beach pea, prepared via NaOH extraction, had a protein content of 86.6%, while SHMP-extracted isolates contained 85.1% protein. Corresponding values for NaOH- and SHMP-extracted green pea and grass pea were 90.6, 89.9, 90.6 and 88.3%, respectively. Sulphur-containing amino acids were more prevalent in SHMP-extracted beach pea and green pea, while they were higher in NaOH-extracted grass pea. Tryptophan content was higher in NaOH-extracted than SHMP-extracted isolates. The predicted biological value and protein efficiency ratio of beach pea protein isolates indicated the high quality of products so prepared. Beach pea protein isolates exhibited a minimum solubility at pH 4.5. The pH and NaCl concentration effectively changed the functional properties of protein isolates. Beach pea protein isolates (NaOH- and SHMP-extracted) had in-vitro digestibility of 80.6 to 82.6% for pepsin-trypsin and 78.6 to 79.2% for pepsin-pancreatin.
The acid and alkaline solubilization processes for isolating muscle protein from ground fish raw materials are investigated
by scrutinizing the literature. Following an introduction to the processes, with some underlying chemistry, patents related
to the acid and alkaline solubilization process are described together with previously patented methods for processing of
protein isolates. Focus is then placed on comparing a range of factors important in fish muscle protein isolation between
the acid and alkaline solubilization processes, and classic washing-based surimi technology. The factors addressed were: protein
yield, gel quality, color, lipid reduction, lipid oxidation, microbial stability, and frozen storage stability. A long series
of studies made with different fish/shellfish species have been used for this purpose. Certain results are summarized in table
form (protein yields, gel strength, and whiteness), others only in text form. From this part of the review, it is obvious
that the acid process often has certain advantages (e.g., protein yield) and the alkaline process other ones (gel strength,
whiteness, lipid removal, lipid oxidation, and total microbial count). Thus, the choice of method depends on the application.
It is clear that most species respond differently to acid and alkaline solubilization, which is why the two methods are initially
compared. In a section about new processing attempts, the use of the acid and alkaline methodology for isolating proteins
from whole fish/shellfish and fish by-products is reviewed together with attempts to recover waste water proteins and attempts
to modify the process. Tentative uses of the new protein isolates, e.g., as coatings, protein brines, and emulsifiers are
finally described together with some conclusions and future opportunities for the acid and alkaline processes.
Protein isolates were prepared from wet heat processed (APIp) and unprocessed alfalfa seeds (APIc) and characterized for composition and functionality at different pH. APIc and APIp exhibited high content of all the essential amino acids. Antinutrient content of APIp was lower in comparison to APIc and marked reduction in the trypsin inhibitor (85.97 %) and lectin activity (100 %) was observed. Processing did not cause much reduction of bioactive constituents and antioxidant activity of APIp. Alfalfa protein isolates exhibited complex polypeptide banding ranging from molecular weight of 11-75 kDa. APIp exhibited change in the conformation of protein discerned as alteration in interrelated nuances of ATR-FTIR spectra, XRD-pattern, morphology, charge on proteins and reduced solubility in comparison to APIc due to processing. APIp exhibited marked improvement in the functional properties in comparison to APIc discerned as improved hydration, surface active and gelation properties. Highest hydration and surface active properties were exhibited at pH 9.0, even though APIp at pH 7.0 showed fairly similar functional properties as APIc and APIp at pH 9.0. APIp exhibited reduced least gelation concentration in comparison to APIc at pH 7.0 and also engendered gelation at pH 4.0 and 9.0 contrary to APIc.
In the present study, the soybean protein isolate (SPI) was treated by pH shifting process, as the protein was incubated in low pH solutions (pH 1.5–3.5) for 12 h, following neutralized to pH 7.0 and held for 4 h, which resulted in a conformation unfolding/refolding confirmed by the fluorescence spectra and a substantial increase in α-helix content revealed by circular dichroism (CD) spectra, along with the increased exposure of hydrophobic and sulfhydryl groups. In addition, the heat-induced gelation process and enhanced gel strength of pH 3.0 and 3.5 shifted SPIs were observed. Maillard reaction was then applied and the glycosylated SPI was further applied to the sub-micron gel particles formation. Results showed that low-pH shifting obviously improve the glycosylation ability of SPI as the conjugation degree and browning degree were enhanced. The sub-micron gel particles with core–shell structure and the average sizes of 100–250 nm were formed via heating self-assembly reaction and confirmed through Z-average of particle size, meanwhile, the increasing stability of gel particles in the solution was determined by Zeta potential analysis, suggesting that the improvement of hydrophobicity and glycosylated ability of SPI could promote gelling properties. Hence, the protein modification stage of pH shifting process would provide a great potential application in the formation of nano- or microscale gel particles.
The objective of this study was to simultaneously obtain protein isolates and lipids from the dried powder of large yellow croaker (Pseudosciaena crocea) roes (pcRs) to achieve high-value utilization. Protein isolates and lipids were extracted simultaneously from pcRs by saline and acidic solutions. The purity of the protein isolates from the pcRs (pcRPIs) was greater than 70%, with vitellogenin, vitellogenin B and vitellogenin C as the main proteins. The lipids from pcRs (pcRLs) were mainly composed of triglycerides with high levels of EPA and DHA. The pcRPIs exhibited a higher surface hydrophobicity, water/oil holding capacity and emulsifying ability than those of the pcRs. Moreover, pcRPIs had a better oil holding capacity and emulsifying ability than soy protein isolate. These results suggest that protein isolates and lipids can be simultaneously extracted by saline and acidic solutions, and pcRPIs and pcRLs can be used as functional materials in the food industry.
A comprehensive evaluation was conducted to compare the generation of antioxidative peptides produced by alcalase versus trypsin from Atlantic sea cucumber. The in vitro antioxidative peptides were sequenced by de novo sequencing using LC-MS/MS. Key constituent antioxidative amino acids (KCAAA), i.e., Cys, His, Met, Trp and Tyr in the peptides and the molecular interactions between peptides and myeloperoxidase (MPO, a mediator and marker of in vivo oxidative stress), were analyzed by in silico methods. Alcalase-produced protein hydrolysates showed 5-35% higher in vitro antioxidant activity than the trypsin-produced ones. UPLC analysis revealed the total amino acid composition in peptide fractions <2 kDa. Alcalase produced 35.4% of peptides with both KCAAA and potential MPO inhibitory activity, compared with only 30.3% for trypsin. A representative peptide sequence TEFHLL generated by alcalase had intense molecular interactions with MPO active site, predicting a capacity to inhibit in vivo oxidative stress.
Over the past 2 decades, the number of scientific papers on properties of fish proteins recovered from various aquatic resources, including the rest raw materials obtained from seafood processing have grown dramatically. Whereas the fish protein isolate (FPI) is a new source of animal protein that can be used to develop value-added food products as well as animal feed enrichment. But to date, very few practical studies have been done on the application of FPI in food and feed systems, and it may have caused the lack of commercial development of this product. Therefore, in order to optimal utilization of aquatic and raw materials in addition to the fight against malnutrition and protein deficiency in poor countries more attention to this technology will be caused this product commercialized. However, for realizing this potential in FPI, several challenges have to be solved. Therefore, this article explores in depth the researches into the use of FPI in food systems and discusses the challenges that this protein source is faced in developing food products. The authors believe that in order to overcome the current challenges in commercial applications of protein isolates in food systems, the following issues should be paying attention and further researches being carried out based on them: industrial process scale-up, production costs, choosing the optimum pH for protein extraction, solubility of proteins, lipid and protein oxidation, the ratio of FPI in food systems, storage stability, sensory defects of FPI, marketing, and economic aspects and future trends of the use of FPI.
Three microalgae proteins (MPs) were isolated from Chlorella pyrenoidosa (CPP), Arthospira platensis (APP) and Nannochloropsis oceanica (NOP), and their physicochemical properties and the effect of pH on their functional properties were investigated. It was found that the molecular weight distribution of CPP, APP and NOP were 109–151,790 Da, 99–128,110 Da and 99–341,662 Da, respectively. The structural conformations vary from microalga to microalga to some extent based on the results of UV and FTIR spectra analysis. Intrinsic fluorescence intensity and thermal properties analysis revealed poor structural conformations of NOP, while CPP and APP displayed highly ordered protein structure and less denatured structures. Consistent with the structural data, CPP and APP showed higher solubility, oil absorption capacity, foaming capacity and foam stability than NOP, especially for APP. The minimum protein solubility (PS), foam capacity, foam stability and emulsifying activity of CPP and APP were observed near isoelectric point, which increased when the pH was lower or higher than the isoelectric point. In conclusion, functional properties of MPs are dependent on their physicochemical characteristics and these MPs, especially APP can be used in the formulation of food products under appropriate conditions.
Chinese quince seed protein isolate (CPI) was extracted using aqueous extraction and the isoelectric precipitation method, and its physicochemical and functional properties were investigated. Results showed that CPI contained all essential amino acids with exception of methionine which met the minimum recommendations for adults (World Health Organization/Food and Agriculture Organization). The electrophoresis analysis of sodium dodecyl sulphate polyacrylamide gel indicated that the molecular weights of protein fractions were approximately 15–60 kDa. Differential scanning calorimetry analysis was conducted, and the denaturation temperature of CPI was 103.4 °C. The surface hydrophobicity of CPI was found to be 932.80. The experiments showed that CPI had high emulsifying capacity, foaming stability, water holding capacity and oil adsorption capacity. Moreover, CPI also had outstanding gel formation capacity since its least gelation concentration of CPI was only 8%. All these results implied that CPI could be a nutritional protein resource and functional ingredient in the food industry.
Structural changes and emulsion properties of proteins extracted by acid processes (ACP, pH 2.0, 2.5 and 3.0) and alkaline processes (ALP, pH 11.0, 11.5 and 12.0) were evaluated, with non-treated goose-liver (GL) paste set as the control. Increasing contents of either reactive-sulfhydryl or surface hydrophobic groups were observed in isoelectric solubilisation/precipitation-recovered proteins (P < 0.05). The ACP-proteins showed higher surface hydrophobicity but lower reactive-sulfhydryl content than that of ALP-proteins (P < 0.05). Compared to the control, ACP-proteins had lower α-helix and β-sheet contents (P < 0.05); meanwhile, ALP-proteins exhibited a lower α-helix content but higher β-sheet content (P < 0.05). Tentative application of these recovered proteins as emulsifiers exhibited that proteins underwent treatment at pH 11.0 had a higher emulsifying activity index (3.2 mg/m²), emulsifying stability index (17.2%) and emulsifying viscosity (62 Pa s) than that of the control (P < 0.05), along with smaller and spherical droplets uniformly distributed in the emulsion. However, ACP-protein emulsions exhibited adverse trends. Different secondary structures of the proteins in ACP-/ALP-cream layers explained these divergences in part, where the lower β-sheet content of ACP-samples could impair protein interactions, leading to inferior emulsion properties. In contrast, the increased β-sheet fraction of alkali treatment favoured a more stable emulsion. Potential of ALP-proteins as an emulsifier was verified.
This study investigated the functional properties of three species of edible insects: Gryllodes sigillatus, Schistocerca gregaria, and Tenebrio molitor. The water and oil holding capacity, solubility, and foaming and emulsion properties were evaluated. The protein solubility showed minimum values at pH 5. The highest water and oil holding capacity was noticeable for the T. molitor protein preparation (3.95 g/g) and for the G. sigilltus protein preparation (3.33 g/g), respectively. The G. sigillatus protein preparation also showed the highest foaming capacity, foam stability, and emulsion activity (99.0%, 92.0%, and 72.62%, respectively), while the protein preparation from S. gregaria exhibited the highest emulsion stability (51.31%). This study has shown that whole insects and protein preparations thereof can be suitable for development of new food formulations.
Proteins from pangas (Pangasius pangasius) fillet frame were recovered using alkaline solubilization method. Effect of process variables like pH, time, weight of paste to extractant volume ratio, temperature, centrifugation speed and stirring frequency on concentration and recoveries were studied. pH, weight of paste to extractant volume ratio, temperature and centrifugation speed were found to have significant effect (p < 0.05) on protein solubility as well as on recoveries. The optimum extraction conditions found were pH-13.0, extraction time – 60 min, temperature – 50 °C, weight of paste to extractant volume ratio-1:6, centrifugation speed – 8000 rpm and continuous stirring, with a total recovery of 68.52%. During alkaline processing lipids, myoglobin and pigment contents were reduced by 90.33, 97.65 and 58.27%, respectively. Despite of improving the color of the isolates and gel, alkaline processing could cause some denaturation resulting in low gel strength and water holding capacity of gels. Alkaline processing did not affect the amino acid profiling substantially, resulting in maximum recovery of all the amino acids. Glutamic acid (GLU), aspartic acid (ASP), leucine (LEU) and lysine (LYS) were found to be the major amino acids in isolates. Alkaline processing could cause enrichment of the essential amino acids in isolates.
Protein hydrolysates were prepared from shrimp discards, using various enzymes, which were subsequently analyzed for their antioxidant potential and biological activities. Raw shrimp shell discards hydrolysates (RSH) and isolated shrimp shell protein hydrolysates (SPH) exhibited radical scavenging activities (ABTS, DPPH and hydroxyl), reducing power and ferrous ion chelating ability. In addition, RSH and SPH inhibited beta-carotene bleaching in an oil-in-water emulsion, cupric ion induced LDL cholesterol peroxidation as well as peroxyl and hydroxyl radical induced DNA strand scission effectively. In-vitro determination of ACE inhibitory activity by RSH and SPH showed that these hydrolysates could be used in supplements, foods or in the purified form as potential pharmaceuticals for blood pressure control. Moreover, shrimp shell discard protein hydrolysate fractions with highest ACE inhibitory activity were further subjected to gel filtration, mass spectrometry and peptide sequencing. Three potential ACE inhibitory bioactive peptides were identified form shrimp shell discard for the first time.
Mass balance analysis was conducted for isoelectric solubilization/precipitation (ISP) processing of carp, chicken, menhaden, and krill based on proximate composition of input materials and recovered fractions (i.e., protein, lipid, insoluble, and process water). Protein recovery yield and lipid reduction were also determined. Thin layer chromatography (TLC) and SDS-PAGE electrophoresis allowed determination of lipid classes and protein electrophoretic patterns. ISP concentrated crude protein (72–90 g/100 g, dry basis) and reduced total lipid (3–16 g/100 g, dry basis) in the protein fraction recovered with ISP when compared to the input materials (48–68 g of crude protein and 15–45 g of total lipid per 100 g, dry basis). Protein recovery yield and lipid reduction were 45–66 and 79–98 g/100 g, respectively. However, lipid fraction did not form when menhaden and krill were processed with ISP. Krill and menhaden lipids were distributed in the process water in addition to the protein and insoluble fractions. TLC showed that krill and menhaden lipids had high phospholipid (PL), but low triglyceride (TAG) content, contributing to emulsification and preventing formation of lipid fraction. SDS-PAGE confirmed presence of myosin and actin in protein fraction recovered from carp and chicken as well as proteolysis in menhaden and severe protein degradation in krill.
This study aimed to evaluate how blending pH-shift produced protein isolates from gutted kilka (Clupeonella cultriventris) and silver carp (Hypophthalmichthys molitrix) affected dynamic rheological and chemical properties of the proteins as well as microstructural and physico-mechanical properties of produced gels. Studied variables were protein solubilization pH (acid vs. alkaline) and blending step (before or after protein precipitation). Comparisons were made with conventionally washed minces from kilka and silver carp fillets; either alone or after blending. Rheological studies revealed that blending alkali-produced protein isolates before precipitation resulted in rapid increase of G' reflecting the formation of intermolecular protein-protein interactions with higher rate. Furthemore, blending of alkali-produced protein isolates and washed minces, respectively, of kilka and silver carp improved physico-mechanical properties of the resultant gels compared to pure kilka proteins. However, the pH-shift method showed higher efficacy in development of blend surimi at the same blending ratio compared to the conventional washing.
A main challenge preventing optimal use of protein isolated from unconventional raw materials (e.g., small pelagic fish and fish by-products) using the pH-shift method is the difficulty to remove enough heme-pigments. Here, the distribution of hemoglobin (Hb) in the different fractions formed during pH-shift processing was studied using Hb-fortified cod mince. Process modifications, additives and prewashing were then investigated to further facilitate Hb-removal. The alkaline pH-shift process version could remove considerably more Hb (77%) compared to the acidic version (37%) when proteins were precipitated at pH 5.5; most Hb was removed during dewatering. Protein precipitation at pH 6.5 improved total Hb removal up to 91% and 74% during alkaline and acid processing, respectively. Adding phytic acid to the first supernatant of the alkaline process version yielded 93% Hb removal. Combining one prewash with phytic acid at pH 5.5 followed by alkaline/acid pH-shift processing increased Hb removal up to 96/92%.
The functional properties of pH-shifted protein isolates from bigeye snapper head were evaluated. Alkaline isolate showed a superior salt-solubility and gel forming ability to acid counterpart as indicated by a regular gel structure (i.e. imaged by scanning electron microscope) with higher gel strength and lower expressible drip (p<0.05). Acid isolate exhibited higher surface hydrophobicity (p<0.05) and thereby improved interfacial properties. Emulsifying activity index of acid isolate was lower than commercial whey protein and egg white (p<0.05) but its emulsion stability was better (p<0.05). Both protein isolates had lower foamability than commercial proteins but their foam stability was not different (p>0.05).
It is possible to recover muscle protein isolates from food processing by-products and under-utilized or difficult to process sources that otherwise would be discarded or diverted from direct human consumption by using isoelectric solubilization/precipitation (ISP). ISP selectively induces water solubility of muscle proteins by changing pH. When muscle proteins are dissolved, they are separated from lipids and other insoluble fractions such as skin, bones, scales, etc. Following separation, the dissolved proteins are subjected to subsequent pH change that causes protein precipitation and yields protein isolate. ISP processing efficiently recovers protein isolates of high quality from both nutritional and technological stand point. However, attempts at commercializing food products developed from the ISP-recovered protein isolates have been very limited. Results from laboratory-scale product development research demonstrate the potential for the use of ISP-recovered protein isolates as a base and functional ingredient for prototypes of nutraceutical foods with specific health benefits. This article reviews ISP as an innovative means to recover functional protein isolates from low-value sources. It also covers recent attempts to develop prototypes of nutraceutical food products using the ISP-recovered protein isolates targeting diet-driven cardiovascular disease.
To exploit a new collagen resource from the body wall of tropical sea cucumber, pepsin-solubilized collagen of Stichopus monotuberculatus (PSC-Sm) was isolated and characterized with UV-vis spectra, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), amino acid composition, enzyme-digested peptide maps, Fourier transform infrared spectroscopy (FTIR), maximum transition temperature (Tm ), and solubilities. The maximum absorbance of PSC-Sm was exhibited at 218 nm in UV-vis spectra. The triple helical structure and activity of PSC-Sm could be indicated by FTIR. SDS-PAGE showed that the triple helix of PSC-Sm was formed as (α1 )3 by 3 α1 chain homologous with molecular weight of 137 kDa. The Tm of PSC-Sm and calf skin collagen (CSC) were 30.2 and 35.0 ºC, respectively, which consistent with the result of FTIR that CSC contained more stable triple-helix than PSC-Sm. Peptide maps were different between PSC-Sm and CSC, indicating the differences in their amino acid compositions and sequences. The maximum and minimum solubilities of PSC-Sm were observed at pH 2.0 and 4.0, respectively. A sharp decrease in solubility appeared when NaCl concentration was between 3% and 5%. These results showed that collagen from S. monotuberculatus had the type I collagen characteristics and good thermal stability, and therefore, it could be used as an alternative resource of collagen.
© 2015 Institute of Food Technologists®
The consumption of aquatic food has globally increased in recent decades, as a result of better understanding of their health benefits and the good image of seafood among consumers. Due to the wide range of their living environments, marine organisms have developed unique properties and bioactive compounds compared to terrestrial sources. The importance of functional food ingredients has been well recognized in connection with health promotion, disease risk reduction and reduction in health care costs. These include omega-3 fatty acids from fish, marine mammals and algal/fungal sources, chitosan, chitosan oligosaccharides and glucosamine, carotenoids, enzymes and protein hydrolysates as well as algal phenolics, and carbohydrates. This contribution summarizes novel functional ingredients from marine resources.
Functional, physicochemical and nutritional properties of protein from whole Klunzinger's ponyfish (Equulites klunzingeri) extracted by pH shifting methods were evaluated. The alkaline protein isolate (AlPI) had higher protein content (88.69 %) than the acid protein isolate (AcPI, 86.13%). AlPI had generally higher content of essential amino acid than AcPI, except methionine. The ratio of total essential amino acid/total amino acid in AlPI and AcPI of Klunzinger's ponyfish was found to be 47.5 and 44.9%, respectively. According to differential scanning calorimetry analysis, the Tmax values of raw Klunzinger's ponyfish (R), AlPI and AcPI were determined to be 40.4, 71.2 and 70.44C, respectively. The initial thiobarbituric acid reactive substance value was higher in AcPI (1.99) than that in AlPI (1.19). AlPI was also found to be lighter and whiter than AcPI (L*: 66.56, whiteness: 59.50 and L*: 60.76, whiteness: 56.41, respectively). The results of “emulsion capacity,” “water- and oil-holding capacity” and “foam capacity and stability” of AlPI and AcPI indicated that satisfactory functional properties are needed in food processing.Practical ApplicationsKlunzinger's ponyfish is a discard fish that exists in large amount in Mediterranean Sea. Even if it has a potential as high quality protein source, it is not being used for human food products as functional ingredients. This study investigates the functional, physicochemical and nutritional properties of protein from whole Klunzinger's ponyfish extracted by pH shifting methods. According to the obtained data in this study, the nutritional, functional and physicochemical properties of protein isolates of Klunzinger's ponyfish were suitable for supplementing as an ingredient for human consumption. Protein as an ingredient developed from an inexpensive source is important to the industry.
Date seed protein hydrolysates were evaluated for antioxidant activity in food and biological model systems as well as solubility and water holding capacity. Date seed protein hydrolysates as well as carnosine exhibited more than 80% of solubility over a pH range of 2-12. The hydrolysates and carnosine at 0.5%(w/w) were also found to be effective in enhancing water-holding capacity and cooking yield in a fish model system, which was nearly similar to sodium tripolyphosphate (STPP; 0.3%,w/w). Incorporation of hydrolysates (200ppm) in fish model systems resulted the highest inhibition (30%) of oxidation in comparison to butylated hydroxytoluene (BHT; 9%). In addition, hydrolysates and carnosine inhibited β-carotene oxidation by 75%. The hydrolysates (0.1 mg/mL) inhibited LDL cholesterol oxidation by 60%, while carnosine inhibited oxidation by 80% after 12 hours of incubation. Additionally, hydrolysates and carnosine effectively inhibited hydroxyl (6 mg/mL) and peroxyl (0.1 mg/mL) radical-induced DNA scission. Therefore, date seed protein hydrolysates could be used as a potential functional food ingredient for health promotion.
: Channel catfish muscle was subjected to 2 novel protein extraction and precipitation techniques using acid (pH 2.5) or alkaline (pH 11) pH and compared with surimi processing (3 wash cycles). Solubility of catfish proteins was found to be highest at pH 2.5 and 11, and at these pH levels, viscosity was found to be low enough to cause separation of proteins from insoluble materials via centrifugation. Both the acid-aided and alkali-aided processes led to higher recoveries (P < 0.05) of protein and larger reduction (P < 0.05) in lipids compared with surimi processing. The protein recovery could be increased even more with a modified version of the acid-aided and alkali-aided processes. There was no hydrolytic breakdown detected during low and high pH. The acid-aided process recovered more protein types than the alkali-aided process during isolelectric precipitation (pH 5.5), which indicated that it led to more protein denaturation and thus more aggregation at pH 5.5. The alkali-aided process had more soluble proteins (including heme proteins) at isoelectric precipitation than the acid-aided process, and the soluble proteins were of the same type as the soluble proteins for non-pH-treated catfish muscle at pH 5.5. This suggested the alkali-aided process led to less denaturation than the acid-aided process. Both acid-aided and alkali-aided processes recovered proteins of higher (P < 0.05) whiteness scores than surimi. The alkali-aided process recovered proteins of higher whiteness (P < 0.05) than the acid-aided process. The acid-aided process led to higher yellowness (P < 0.05) than the other 2 processes. All processes led to minimal levels of lipid oxidation as assessed by secondary oxidation products.
In the present study proteins isolated from herring brine, which is a by-product of marinated herring production were evaluated for their functional properties and antioxidant activity. Herring brine was collected from the local herring industry and proteins were precipitated by adjusting the pH to 4.5 and the obtained supernatant was further fractionated by using ultrafiltration membranes with molecular weight cut offs of 50, 10 and 1kDa. The obtained >50kDa, 50-10kDa, 10-1kDa fractions and pH precipitated fraction were studied for their functional properties and antioxidant activity. Functional properties revealed that >50kDa polypeptides showed good emulsion activity index when compared to the other fractions. However all fractions had low emulsion stability index. The pH precipitated fraction showed the highest foaming capacity and stability at pH 10. The 50-10kDa and 10-1kDa peptide fractions showed good radical scavenging activity and reducing power at a concentration of 0.5mg protein/ml. All the fractions demonstrated low iron chelating activity and did not inhibit oxidation in a soybean phosphatidylcholine liposome model system. However all the fractions were to some extent able to delay iron catalyzed lipid oxidation in 5% fish oil in water emulsions and the 10-50kDa fraction was the best. These results show the potential of proteins and peptide fractions recovered from waste water from the herring industry as source of natural antioxidants for use in food products.
Isoelectric solubilization/precipitation (ISP) allows efficient recovery of fish protein isolate (FPI) that
could be used in functional foods. There is an increasing interest in incorporating u-3 polyunsaturated
fatty acids (PUFAs) oils in food with a simultaneous sodium reduction. FPI was recovered from whole
gutted trout using ISP. FPI was used as a main ingredient in heat-set gels made with u-3 PUFAs oils
(flaxseed, algae, fish, krill, and blend) and KCl-based salt substitute. The objectives were to determine (1)
protein gelation, (2) color and texture, and (3) sodium and potassium content of the developed functional
food (i.e., heat-set gels). Color properties were improved except when krill or algae oil was added.
Texture profile analysis showed that u-3 PUFAs generally did not affect texture of trout protein gels. The
addition of u-3 PUFAs oil improved heat-induced protein gelation as demonstrated by dynamic rheology.
Elastic modulus increased when u-3 PUFAs oil was added except krill oil. Salt substitute resulted in
reduced sodium and increased potassium content in the heat-set gels. The functional food products
developed from FRI were nutritionally enhanced with u-3 PUFAs, had reduced sodium and increased
potassium; while the color and texture properties were good and gelation properties were improved.
The effect of time-temperature variations during heat processing on changes in sulfhydryl groups and disulfide bonds in seal meat was investigated. The content of free SH groups in raw meat was about 63-mu-mol/g of protein, and after 40 min of heating at 99-degrees-C, it decreased by about 50%. The total content of sulfhydryl groups after reduction of disulfide bonds was 84.7-mu-mol/g of protein in the raw sample and did not change significantly in the cooked meat. The correlation coefficients between the amount of disulfide bond formation in heated seal meat and their solubility in 0.035 M sodium dodecyl sulfate solution or the degree of thermal coagulation of the proteins were -0.982 and +0.897, respectively.
Antioxidative activities of protein hydrolysates from yellow stripe trevally (Selaroides leptolepis) prepared using Alcalase 2.4 L (HA) and Flavourzyme 500 L (HF) with the degree of hydrolysis of 15% by pH-stat method were determined. Both protein hydrolysates exhibited the antioxidative activity in a concentration dependent manner. HF generally showed the greater antioxidative activity than HA (P < 0.05) as indicated by the higher 2,2-diphenyl-1-picryhydrazyl (DPPH) radical scavenging activity, reducing power and metal chelating activity. Antioxidative activity of both hydrolysates was stable when heated at 90 °C for 10 and 30 min and subjected to a wide pH range (2–12). Nevertheless, metal chelating activity decreased in very alkaline and acidic pH ranges. HA and HF at 200 ppm retarded the formation of conjugated diene and thiobarbituric acid reactive substances (TBARS) in lecithin liposome system. HF possessed the stronger antioxidative activity than HA (P < 0.05). However, -tocopherol at 200 ppm showed the higher antioxidative activity in the system.
Extraction and recovery of fish muscle proteins with the pH-shift process was investigated for Atlantic croaker and compared to a laboratory scale surimi process. The acid-aided process led to higher recoveries (P < 0.05) than the alkali-aided process, which in turn led to higher recoveries (P < 0.05) than surimi processing. Lipid reductions were highest (P < 0.05) for the alkali-aided process, followed by the acid-aided process, with surimi giving the least reduction. No major differences in recovered proteins could be seen for the three processes, except both pH-shift processes had a protein band (∼150 KDa) possibly representing partial hydrolysis of myosin. Oscillatory rheology on protein pastes during heating and cooling showed the highest storage moduli for the alkali-aided isolate, followed by the acid aided isolates and surimi. Torsion testing on protein gels demonstrated significantly higher strain and stress values for gels made from frozen isolates with added cryoprotectants compared to fresh gels without added cryoprotectants. Gel stress was significantly higher (P < 0.05) for the frozen gels with added cryoprotectants made from the isolates, compared to surimi. Although isolate pastes had higher (P < 0.05) lightness values than surimi pastes, surimi gels had higher (P < 0.05) lightness than isolate gels. The acid-aided gels had higher levels of yellowness than the other treatments. Both surimi and alkali-aided isolates had significantly (P < 0.05) lower oxidation levels compared to the ground raw material. The acid isolate had poor oxidative stability and gave higher oxidation values than the raw material. Surimi and alkali-aided pastes and gels also had higher oxidative stability than acid-aided gels.
Concentrations of “reactive” and total sulfhydryl groups and disulfide bonds were determined in raw and ultra-high-temperature sterilized skim milk and compared to values for conventional laboratory heat treatments with lower temperatures and longer times. The method of analysis, which represents a modification of previously reported methods, gave results agreeing with theoretical values calculated from the protein composition of milk. Analyses for total half-cystine, which included that protein deposited on the heating surfaces, indicated that 6 to 15% of this amino acid was lost during a heat treatment of 100 C for 30 min, presumably by volatilization. A smaller fraction was lost during ultra-high-temperature processing. Comparison of our data for direct heating with that previously reported for indirect heating suggests that less whey protein is “denatured” by the direct heating method. Studies of sterilized skim milk stored at refrigeration or room temperature suggested that the “reactive” sulfhydryl groups oxidized more rapidly and also that a larger fraction was oxidized during storage at room temperature. These concentrations of “reactive” sulfhydryl groups in sterilized milk have been correlated with undesirable “cooked” flavor and possibly could contribute to instability of milk protein through disulfide interchange reactions.
Protein hydrolysates from grass carp skin were obtained by enzymatic hydrolysis using Alcalase®. Hydrolysis was performed using the pH-stat method. The hydrolysis reaction was terminated by heating the mixture to 95 °C for 15 min. At 5.02%, 10.4%, and 14.9% degree of hydrolysis (DH), the hydrolysates were analyzed for functional properties. The protein hydrolysates had desirable essential amino acid profiles. Results demonstrated that the hydrolysates had better oil holding and emulsifying capacity at low DH. The water holding capacity increased with increased levels of hydrolysis. Enzymatic modification was responsible for the changes in protein functionality. These results suggest that grass carp fish skin hydrolysates could find potential use as functional food ingredients as emulsifiers and binder agents.
Composition, functional properties and antioxidative activity of a protein hydrolysate prepared from defatted round scad (Decapterus maruadsi) mince, using Flavourzyme, with a degree of hydrolysis (DH) of 60%, were determined. The protein hydrolysate had a high protein content (48.0%) and a high ash content (24.56%). It was brownish yellow in colour (L∗ = 58.00, a∗ = 8.38, b∗ = 28.32). The protein hydrolysate contained a high amount of essential amino acids (48.04%) and had arginine and lysine as the dominant amino acids. Na+ was the predominant mineral in the hydrolysate. The protein hydrolysate had an excellent solubility (99%) and possessed interfacial properties, which were governed by their concentrations. The emulsifying activity index of the protein hydrolysate decreased with increasing concentration (p < 0.05). Conversely, the foaming abilities increased as the hydrolysate concentrations increased (p < 0.05). During storage at 25 °C and 4 °C for 6 weeks, the antioxidative activities and the solubility of round scad protein hydrolysate slightly decreased (p < 0.05). Yellowness (b∗-value) of the protein hydrolysate became more intense as the storage time increased but the rate of increase was more pronounced at 25 °C than at 4 °C.
Several fisheries are over-exploited and may collapse; yet the amounts of fish processing by-products containing muscle proteins and ω-3-rich oil are staggering. The by-products are land-filled, ground and discarded or otherwise diverted from human consumption. Due to the lack of technology to recover proteins and lipids from by-products or low-value species, this tremendous resource is unavailable for human consumption. Isoelectric solubilisation/precipitation (ISP) allows efficient recovery of fish proteins and oil which retain functionality and nutritional value of food products. Isoelectric point (pI) is a pH where protein maintains zero electrostatic charge. At pI, protein–protein hydrophobic attraction overcomes protein–water electrostatic attraction resulting in isoelectric precipitation. Conversely, isoelectric solubilisation occurs at a pH different from pI, whereby protein–water attraction and protein–protein electrostatic repulsion are favoured. Therefore, protein solubility/insolubility is induced by ISP, respectively. Consequently, ISP allows selective protein recovery. Lipids are also recovered during ISP processing. This article reviews recent ISP developments to recover proteins and lipids from by-products and low-value marine species.
Protein hydrolysates were prepared from male and spent capelin (Mallotus villosus) using commercially available Alcalase, Neutrase and papain. Short-time autolysis of proteins by endogenous enzymes in fish viscera was also investigated and compared to procedures of accelerated enzymatic hydrolysis. While protein recovery varied from 51.6 to 70.6% for commercial enzymes, a yield of 22.9% was obtained for autolyzed products. All methods of preparation afforded products containing about 71–78% proteins after dehydration. Alcalase served best for preparation of capelin protein hydrolysates (CPH). Thus, products of Alcalase-assisted hydrolysis of capelin proteins were further assessed for their nutritional and functional characteristics. The amino acid composition of CPH was similar to that of the starting capelin, except for methionine and tryptophan which were present in smaller amounts. The products had excellent solubility (≥84%) over a pH range of 2–11. Incorporation of CPH (up to 3%) in meat model systems resulted in an increase of 4% in cooking yield and inhibition of oxidation (determined by the 2-thiobarbituric acid test) by 17.7–60.4%.