Optimization of Antioxidant Activity and Phenolic Compound Extraction Conditions from Red Seaweed (Laurencia obtuse)

ABSTRACT

Response surface methodology was used to investigate the effect of ultrasound-assisted extraction conditions including solvent:seaweed ratio (10:1–30:1), extraction temperature (30–50°C), and extraction time (30–60 min) on the total phenolic compounds and antioxidant activity of red seaweed (Laurencia obtuse) extracts. The optimum extraction parameters for maximum phenolic content were as follows: solvent:seaweed ratio, 30:1; extraction temperature, 50°C; and extraction time, 42.8 min. The experiment results showed that the solvent:seaweed ratio was the most significant parameter for the extraction. The optimum extraction conditions for maximum antioxidant activity were as follows: solvent:seaweed ratio, 24.3:1; extraction temperature, 45.3°C; and extraction time, 58 min. Under the above-mentioned conditions, the experimental total phenolic content and antioxidant activity value were 26.23 ± 0.75 mg GAE/g seaweed and 120.89 ± 0.81 TEAC, respectively, of seaweed tested, which are well compatible with the predicted contents.     

Identifying other suitable and potential indigenous carrageenophytes for commercial cultivation in India

In India, Kappaphycus alvarezii is the only alga being cultivated commercially for kappa carrageenan production and also being utilized for the socioeconomic upliftment of coastal rural population in India in the form of their cultivation and marketing. The production has been substantially increased from 21 dry tonnes to 1490 dry tonnes with increasing market purchase value from US$ 0.061 to 0.469 kg dry wt^?1 during 2001–2013. In India, annual import for carrageenan is 1800–2000 M tons year^?1 and its demand is reported to be increased by 5–6% every year (Mantri et al. 2017). To date, Aquagri Pvt Ltd is the only company in India producing kappa carrageenan from cultivated Kappaphycus alvarezii (Mantri et al. 2017). However, few other marine phycocolloid processing factories are producing kappa carrageenan from Hypnea musciformis and Hypnea valentiae at cottage level. The total annual production of carrageenan in India ranges between 100 and 132 tons. There is tremendous demand for other carrageenan such as iota and lambda carrageenan in food, beverage, and consumer product manufacturing industries. In order to ascertain suitability of unexplored other indigenous carrageenophytes for commercial cultivation in India, several red algal species such as Agardhiella subulata, Ahnfeltiopsis pygmaea, Laurencia caraibica, and Solieria robusta were collected from wild habitats in Kanyakumari (N 08°08′10.36″; E 077°34′28.06″) Tamil Nadu, India, and were evaluated for their mariculture potential and the presence of carrageenan. Preliminary cultivation experiments were carried out by raft culture method (1?×?1 m) for 45 days at two harvest cycles at Thonithurai (N 09°16′53.45″; E 079°11′19.22″), Tamil Nadu, South eastern coast of India. Except Ahnfeltiopsis pygmaea, all other seaweeds investigated showed daily growth rate (DGR) in the range of 1.59 to 3.822% and confirmed its mariculture potential. Phycocolloid was extracted with yield 4.5 to 29.37% from dry seaweed residues obtained after extraction of lipids using both water and aqueous alkali [5% Ca (OH)₂ solution]. Water was found the better solvent in terms of higher yield of the Phycocolloid (29.37%) from Solieria robusta. FT-IR of the extracted phycocolloid indicated presence of characteristic bands for carrageenan in all the samples. However, from the band positions, the presence of iota carrageenan was ascertained in the Agardhiella subulata and Solieria robusta and hybrid iota/kappa carrageenan is expected to be present in Laurencia caraibica and Ahnfeltiopsis pygmaea.

     

镉在海藻中的化学形态

利用化学试剂逐步提取法研究了紫菜、海带、裙带菜和羊栖菜中镉的存在化学形态。研究结果表明:镉以多种化学形态存在于4种海藻中,1 mol/L氯化钠提取态镉和 2% 醋酸提取态的镉所占比例较大,两者约占总镉含量的76.3%～92.9%。0.6 mol/L盐酸提取态、去离子水提取态和80%乙醇提取态镉所占比例较小,其中乙醇提取态(离子态镉)约仅占总镉含量的0.4%～9.2%,且对于4种海藻,紫菜中的离子态镉所占比例最低(均小于1%)。实验进一步证实以海藻中总镉含量作为检测标准不能准确反映海藻及其制品的食用安全性,因此亟需建立海藻中针对毒性较强的离子态镉的检测标准限量和快速有效的检测方法,以保障我国海藻产业和出口创汇经济的顺利发展。     

The Influence of Seaweed Composite Flour on the Physicochemical Properties of Muffin

Seaweed has a great potential to be used as an important ingredient in food processing, as it contains a significant content of soluble polysaccharides and has a potential function as a dietary fiber. In this study, seaweed powder (Kappaphycus alvarezii) was incorporated (2–10%) with wheat flour for the production of muffins. The effect of seaweed composite flour on the quality of muffins was investigated using various techniques, such as texture profile and proximate analyses, as well as sensory evaluation. Modification of the muffin formulation to include seaweed powder improved the composition of ash, crude fiber, and moisture content, while the protein and carbohydrate levels decreased, compared to the control sample. An increase in the seaweed component reduced the muffin height, volume, and specific volume. According to the experimental texture profile analysis data, the seaweed affected the textural characteristics of the muffins, increasing the hardness and decreasing the springiness. Sensory evaluation revealed that seaweed powder could be used in the muffin formulation up to 6%, without significantly impacting the color, aroma, and taste attributes relative to the control sample. For overall acceptability, however, the panelists preferred muffins without seaweed powder.     

The effect of seaweed extracts,as a supplement or alternative culture medium,on the growth rate and biochemical composition of the microalga,Isochrysis galbana (Park 1949)

Aqueous extracts of green [Ulva lactuca Linnaeus and Enteromorpha intestinalis (Linnaeus) Nees] and red [Gracilaria corticata (J. Agardh) J. Agardh] seaweeds from the Persian Gulf of Iran were examined for their potential usefulness as components of microalga Isochrysis galbana culture medium against conventional f/2 medium. Isochrysis galbana was successfully cultured using the tested seaweed extracts (SWE) and exhibited higher or similar cell density and biomass when SWE were used as a supplement or an alternative medium respectively. When the SWE were used as an alternative medium, microalgal protein, lipid and ash content were similar but carbohydrate increased compared with control. Total saturated fatty acids decreased with a corresponding increase in total mono‐ and polyunsaturated fatty acids following supplementation of f/2 medium with SWE. Eicosapentaenoic acid (EPA) was not affected by SWE treatments but docosahexaenoic acid (DHA) tended to decrease, except for I. galbana cultured with U. lactuca extract. With the exception of potassium, SWE did not significantly impact the mineral content of cultured I. galbana. The study points to the potential usefulness of specific SWE in the production of microalgae as a food source in aquaculture.     

The Economics of Kappaphycus Seaweed Cultivation in Developing Countries: A Comparative Analysis of Farming Systems

The farming of the red seaweed Kappaphycus alvarezii and related species as raw material for the hydrocolloid carrageenan rapidly spread from the Philippines in the late 1960s to Indonesia, Tanzania, and other tropical countries around the world. Although numerous studies have documented positive socioeconomic impacts for seaweed farming, factors such as diseases and distance to export markets have led to an uneven development of the industry. Using standard budgeting techniques, this study adapted production and market data from a FAO-led global review of seaweed farming to develop comparative enterprise budgets for eight farming systems in six countries (Indonesia, the Philippines, Tanzania, India, Solomon Islands, and Mexico). Although the basic technology package is the same across countries, the study revealed large differences in the economic performance of systems due to wide variations in farm prices and the scale of operations. Although seaweed farming is a suitable activity for small-scale producers, a minimum of 2,000 m of cultures lines are still necessary to ensure adequate economic returns. Greater farming plots may be needed if farm prices are well below the average farm prices paid in Indonesia and the Philippines. Policy recommendations are made to improve the economic potential of underperforming systems.     

Single nucleotide polymorphisms found in the red alga Furcellaria lumbricalis (Gigartinales): new markers for population and conservation genetic analyses

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Biochemical comparison of lectins among three different color strains of the red alga Kappaphycus?alvarezii

The red alga Kappaphycus alvarezii is economically important as an edible species and as a source of carrageenan, and has been extensively cultivated in many tropical countries. For this species, different color strains, which differ from each another in growth rate and carrageenan content, have been reported for decades. In this study, lectins from brown, red, and green strains of K. alvarezii cultivated in Vietnam were isolated and characterized for evaluation of their biochemical properties and contents. The results showed that each color strain contained in common the three lectins, named KAA-1, KAA-2, and KAA-3, which shared the hapten-inhibition profile of hemagglutination, 20 N-terminal amino acid sequence, and equivalent molecular mass within a range of 28,016 ± 1.2 to 28,021 ± 1.8 Da, but differed in their yields, with the highest yield of KAA-2. These properties of the three isolectins were also comparable among the three different color strains. However, the sum of the yields of the three isolectins decreased in the order: red (21.4 mg) to green (15.9 mg) to brown strains (15.1 mg), from 500 g fresh alga. Thus, this algal species can be a good source of useful lectins, irrespective of color strain.     

Amino acids composition difference and nutritive evaluation of the muscle of five species of marine fish, Pseudosciaena crocea (large yellow croaker), Lateolabrax japonicus (common sea perch), Pagrosomus major (red seabream), Seriola dumerili (Dumeril's amberjack) and Hapalogenys nitens (black grunt) from Xiamen Bay of China

A study was conducted to investigate the muscle amino acid profiles of five species of marine fish, Pseudosciaena crocea (large yellow), Lateolabrax japonicus (common sea perch), Pagrosomus major (red seabream), Seriola dumerili (Dumeril's amberjack) and Hapalogenys nitens (black grunt). These carnivorous fishes, all of which belong to the Perciforms, were sampled from Xiamen Bay. Chemical analysis shows significant difference (P < 0.01) among the five species in the muscle total amino acids (TAA). Lateolabrax japonicus has the highest level of TAA in muscle tissues. Significant difference in muscle total essential amino acid (TEAA) and total non‐essential amino acid (TNEAA) were also found among the five species. Lateolabrax japonicus has the highest TEAA level, and H. nitens has the highest level of TNEAA level. Significant difference (P < 0.01) existed in specific EAA except for lysine (P > 0.05). The significant difference (P < 0.05) of the A/E ratios [(each essential amino acid content/total essential amino acid content including cystine and tyrosine) ×1000] based on the essential amino acid composition of muscle tissue from the five species were found in lysine, histidine, methionine, cystine, valine, leucine, isoleucine, and arginine, except for threonine, phenylalanine and tyrosine. These differences indicate that the amino acids profile is species specific for the five species and their essential amino acid requirements are greatly different although they were fed similar feed. In contrast to the reference amino acid profile recommended by FAO/WHO, muscle proteins of each fish were all rich in lysine, the S‐containing amino acids and threonine, but histidine, valine, leucine, isoleucine, phenylalanine and tyrosine were deficient for children's diets. The first limiting amino acid was histidine for P. crocea and L. japonicus, valine for P. major and H. nitens, leucine for S. dumerili. The amino acid score was 66.8, 76.7, 78.4, 84.0 and 95.7 for P. crocea, L. japonicus, P. major, H. nitens and S. dumerili, respectively. In the adult human diet the muscle protein of the five species of marine fish can almost fulfil the requirements of all essential amino acids except for the histidine of P. crocea and L. japonicus and thus can serve as supplemental source of protein in cereal‐based adults diets if we reinforce the histidine correspondingly. Therefore, increasing the proportion of marine fish in the diet of the people in the area where paddy rice and wheat are the main protein sources is an effective way to enhance the nutrition value of food and improve the nutrition status of the developing countries. Moreover, all of five marine fish species contained a comparatively high content of glutamic acid and arginine, which are beneficial to the patients under such conditions as trauma, burn injury, massive small‐bowel resection and renal failure.     

Nutrient removal efficiency of Hydropuntia cornea in an integrated closed recirculation system with pink shrimp Farfantepenaeus brasiliensis

In this study, we have tested the effect of seaweed stocking density in an experimental seaweed biofilter using the economically important red seaweed Hydropuntia cornea integrated with the cultivation of the pink shrimp Farfantepenaeus brasiliensis. Nutrient removal efficiency was evaluated in relation to seaweed stocking density (2.5, 4, 6 and 8 g fw L^?1). Total ammonia nitrogen (TAN) was the main nitrogen source excreted by F. brasiliensis, with concentrations ranging from 41.6 to 65 μM of NH₄⁺‐N. H. cornea specific growth rates ranged from 0.8 ± 0.2 to 1.4 ± 0.5% day^?1 with lowest growth rates at higher seaweed stocking density (8 g fw L^?1). Nutrient removal was positively correlated with the cultivation densities in the system. TAN removal efficiency increased from 61 to 88.5% with increasing seaweed stocking density. Changes in the chemical composition of the seaweed were analysed and correlated with nutrient enrichment from shrimp effluent. The red seaweed H. cornea can be cultured and used to remove nutrients from shrimp effluents in an integrated multi‐trophic aquaculture system applied to a closed recirculation system. Recirculation through seaweed biofilters in land‐based intensive aquaculture farms can also be a tool to increase recirculation practices and establish full recirculation aquaculture systems (RAS) with all their known associated benefits.     

Prebiotic effect of glycerol galactoside isolated from color-faded nori in rats

Glycerol galactoside (GG; floridoside: 2-O-glycerol-α-d-galactopyranoside, and isofloridoside: 1-O-glycerol-α-d-galactopyranoside) is known to be a component of edible red seaweed nori. Recently, we have found that low-quality nori (color-faded nori), which has a low protein content, contains a large quantity of GG. From further studies, we have also found that GG has prebiotic characteristics in vitro. In this study, we evaluated the in vivo prebiotic activity of GG in rats. Dietary GG selectively increased the cecal Bifidobacterium count in rats. Other indices of prebiotics, such as pH of cecal content, organic acid concentrations, and fecal weight, also supported the existence of prebiotic activity of GG. The present data will also contribute to the development of a new method of utilizing color-faded nori as a health-promoting foodstuff.     

Growth parameters of whiteleg shrimp Litopenaeus vannamei and red seaweed Gracilaria corticata in integrated culturing method under zero water exchange system

Growth parameters of whiteleg shrimp Litopenaeus vannamei and red seaweed Gracilaria corticata were measured using integrated culturing method under zero‐water exchange system in a 45‐day period. A 2 × 3 factorial design was used with two levels of shrimp stocking densities and three levels of seaweed weight densities. G. corticata was cultured on a net tied to a round polyethylene frame. Culture tanks were filled with 750‐L filtered seawater. A 40‐W compact fluorescent lamp was hung over each tank to provide adequate and sufficient light for seaweed growth. Growth parameters of shrimp and seaweed such as specific growth rate (SGR), weight gained (WG) and average daily growth (ADG) were computed based on the initial and final weight of shrimp and seaweed. The maximum and minimum SGR of L. vannamei (1.97 and 1.69%/day) were observed in treatment S₁A₃ (25 shrimp/m² and 400 g seaweed/m²) and S₂A₁ (50 shrimp/m² without seaweed) respectively. The best survival rate (94.67 ± 1.33%), WG (129.9 ± 2.9%) and feed conversion ratio (1.67 ± 0.04) were also observed in treatment S₁A₃. The SGR of G.corticata in the treatment S₁A₃ (1.97 ± 0.00%/day) was significantly higher, compared to others. Strong positive correlations were obtained between the density of G. corticata and the growth parameters of L. vannamei. The red seaweed G. corticata could boost the growth parameters, survival rate and total production of L. vannamei under zero‐water exchange system.     

Effects of supplementation of coated crystalline amino acids on growth performance and body composition of juvenile kuruma shrimp Marsupenaeus japonicus

Supplementation of crystalline amino acids (CAA) in shrimp diets is unsuccessful in most cases. In the present study, various pre‐coated CAA were developed to minimize the leaching losses from diets in water and assessed using kuruma shrimp Marsupenaeus japonicus juveniles. Experimental diets were supplemented with coated CAA or non‐coated CAA to simulate the dietary amino acid profile to that found in the whole body protein of shrimp. The four diets contained CAA coated with either carboxymethyl cellulose (CMC) (diet 1), zein (diet 2), k‐carrageenan (diet 3) or agar (diet 4), respectively. Another four diets contained CMC‐coated CAA with the addition of either zein (diet 5), casein‐gelatin (diet 6), zein and k‐carrageenan (diet 7), or casein‐gelatin and k‐carrageenan (diet 8), respectively. The 8 weeks feeding trial demonstrated that the diets containing coated CAA gave significantly higher weight gains than diets containing non‐coated CAA, with the highest value for the diet 6. The diets containing coated CAA also yielded higher feed conversion efficiency, protein efficiency ratio, and specific growth rate than diets containing non‐coated CAA. Leaching trials suggested that shrimp growth performance was improved partly due to the retardation or reduction of CAA leaching by coating them with specific binders.     

Comparison of the fillet yield, protein content and amino acid profile of Clarias gariepinus and the Clarias gariepinus 5 Heterobranchus longifilis hybrid

The fillet yield, total protein content and amino acid profile of the African sharptooth catfish Clarias gariepinus (Burchell) was compared with that of its hybrid with the African catfish Heterobranchus longifilis Valenciennes. The flesh of the C. gariepinus × H. longifilis hybrid had a protein content of 18.3%, compared with 18.6% for C. gariepinus. The amino acid profiles were similar for the two groups. The fillet yield of the C. gariepinus females was significantly lower than that of the male and female hybrids and C. gariepinus males. The difference in fillet yield was attributed to the high gonadosomatic index (GSI) of the C. gariepinus females, compared with the other groups. The overall fillet yield was 38.9% for C. gariepinus and 43.8% for the hybrid, which has important implications for African catfish production.     

Assessment of rocky reef fish assemblages close to seaweed farming

The seaweed Kappaphycus alvarezii (Doty) Doty ex P. C. Silva, a red algal species, is the main global source of Kappa carrageenan. The introduction of such exotic species in regions outside their original locale can change the community structure of the areas into which they are introduced. The possible influence of seaweed farming on the rocky reef fish assemblage was assessed in Paraty, Brazil. The reef fish assemblage in the seaweed farming area was compared before and after the commencement of farming with two undisturbed control areas. Among the ten species ranked as the most frequently occurring in each area, eight were the same. The fish community structure close to the seaweed farming area did not change from that of the control areas, over the months of the study. Neither the fish diversity and richness indices, nor the total average abundance among areas was significantly altered. The average abundance of the different trophic groups varied over time in both the farm and control areas, revealing similar patterns. These results suggest that K. alvarezii can be cultivated up to at least 50 m from a rocky coast without altering the fish community structure of the surrounding waters.     

Nutrients removed by Kappaphycus alvarezii (Rhodophyta, Solieriaceae) in integrated cultivation with fishes in re-circulating water

The potential of the red alga Kappaphycus alvarezii to remove nutrients was tested to treat effluents of Trachinotus carolinus fish cultivation, and the production of carrageenan in this condition was analyzed. Experiments were conducted in four tanks of 8000 L with approximately 1200 fishes of 30 g each integrated with three tanks of 100 L with 700 g of K. alvarezii, as initial biomass per tank. Seawater was re-circulated between tanks with seaweed and with fish. As a control, three tanks with seawater circulating in an open system were utilized. Seawater samples were collected daily for 10 days and concentrations of nitrate, nitrite, ammonium and phosphate were determined in the inflow and outflow water of the tanks. Significant differences between both collecting points were considered as nutrient removal by the seaweed. Growth rates and carrageenan yields were also analyzed in seaweed cultivated in seawater and in effluents. Growth rates of seaweed cultivated in tanks were lower than those obtained in open sea and in laboratory cultivation. Effluents had concentrations of nitrate and nitrite ca. 100 times higher than in the control. Maximum values of nutrient removal on effluents were: nitrate = 18.2%; nitrite = 50.8%; ammonium = 70.5% and phosphate = 26.8%. All plants survived throughout the experimental period, but some developed “ice–ice”, a disease associated with physiological stress. After the experimental period, some plants selected and cultivated in open sea presented higher growth rates in 40 days, indicating nutrient storage. No significant differences between carrageenan yields of K. alvarezii cultivated in seawater and in the effluents were observed. Our results show that K. alvarezii can be utilized as a biofilter for fish cultivation effluents, reducing the eutrophication process and can also be processed for carrageenan production, which provides an additional benefit to the fisheries.     

Potential of Cellulase From Bacillus megaterium for Hydrolysis of Sargassum

Bacterial cellulase can be a promising biotechnological approach in seaweed degradation to facilitate extraction of bioactive molecules. In the present study, bacterial cultures were isolated from marine and terrestrial samples and screened for cellulase production. The selected cultures were grouped by random amplification of polymorphic DNA (RAPD) profiling, and the cultures showing a distinct banding pattern were identified by 16S rDNA sequence analysis. Cellulase from Bacillus megaterium (CB-sw1-I), a native isolate, was purified by ion-exchange chromatography with a purification fold of 6.91 and specific activity of 1.66 U. The purified enzyme with molecular weight of 43 kDa was optimally active at pH 6.0 and temperature of 60°C. The potentiality of enzyme in degradation of Sargassum thallus was evident with an increase in reducing sugar. Morphology of the thallus after 10 days digestion observed by scanning electron microscope also provided additional evidence for degrading ability of the enzyme. This enzyme could subsequently be used in hydrolysis of seaweed for extraction of bioactive molecules.     

Comparison of amino acid profiles of feeds and fish as a quick method for selection of feed ingredients: a case study for Colossoma macropomum (Cuvier)

The amino acid profile of Colossoma macropomum was determined. Indispensable amino acid levels were similar to those reported in other fish species. Suitability of local, Costa Rican, ingredients as protein sources for C. macropomum was evaluated based on their protein content and indispensable amino acid profile. It was calculated that, in a standard diet (40% protein. 25% fish meal), blood meal, soya meal, poultry byproducts, meat and bone meal, and meat meal can substitute more than 80% of the fish meal. More than 40% of the fish meal can be substituted by shrimp meal, pigeon pea, cotton meal, peanut oil cake, cow pea, corn gluten and water hyacinth. As differences between amino acid profiles between fish species seem to be small, promising alternative ingredients for C. macropomum might be equally interesting for formulation of feeds for other species. Soya meal is the currently used ingredient with the highest potential to substitute fish meal completely. Further research is needed to determine if the use of alternative ingredients is limited by constraints such as decreased feed digestibility, presence of anti-nutritional factors, additional production and processing costs.     

Nutrient composition and sensory evaluation of fillets from wild-type Nile tilapia (Oreochromis niloticus, Linnaeus) and a red hybrid (Florida red tilapia × red O. niloticus)

A comparison of composition and sensory evaluation were performed on fillets of Oreochromis niloticus (wild type) and red hybrid tilapia (RHT) (Florida red tilapia ♂× red O. niloticus♀). Fifty male tilapia, 25 O. niloticus (initial weight 159.3 g) and 25 red hybrid (initial weight 132.4 g), were placed in each of three 2.0 m³ volume tanks. The fish were fed a commercial feed containing 35.9% crude protein during the 120‐day experimental period and then killed in cold water (3°C). All the fish were filleted. Twelve fillets from each treatment were used for proximate analyses, five fillets from each treatment were used for fatty acids analyses and the remaining fillets were used for sensory evaluation. The compositional analyses showed similar moisture, true protein and ash content in both genetic groups, but a lower crude fat content was measured in the red hybrid fillets (0.70%) compared with that of O. niloticus fillets (0.97%). No differences between O. niloticus and the red hybrid were observed in their fillet profile of fatty acids. In the sensory evaluation test, a difference in fillet flavour between both genetic groups was perceived. Of the 112 consumers in the preference test, 81.2% perceived a difference in fillet flavour between the two tilapias, with a general preference for the red hybrid over the wild‐type O. niloticus. The benefits of cultivating a RHT with a low lipid content are discussed.     

Development of an in vitro model to assess protein bioavailability in diets for common octopus (Octopus vulgaris)

An in vitro model designed to assess protein bioavailability in diets for growing Octopus was developed. The model required a previous assessment of some functional features of protein digestion in this species like the main producing organs, optimum pH for activity and total production per g tissue. The main producing organs identified were the salivary glands and the hepatopancreas (HP), being optimum pH for protease activity quite different in both organs (mostly alkaline in the posterior salivary glands and acid in the HP). In spite of the high‐specific protease activity measured in the salivary glands, a major role of the HP in protein hydrolysis is suggested due to the much bigger size of this viscera. All this information was used as a basis to develop an in vitro two‐step hydrolysis process, which simulated protein hydrolysis performed by these two organs using the Octopus enzymes. The assay was used to evaluate differences in amino acid bioavailability from several protein sources (casein, gelatin, fish meal, squid meal and krill meal) that could be used as feed ingredients for this species. As significant differences were detected both in total amount and in rate of release of the amino acids from such proteins, the model is proposed as a complementary tool in the selection and nutritional evaluation of protein ingredients to be used in diets for Octopus.