Scallop Adductor Research Articles

Preparation of gelatin/gelatin-dextran/gelatin-based three-layer films with cinnamaldehyde and α-tocopherol for scallop (Patinopecten yessoensis) adductor muscle preservation

Preparation of gelatin/gelatin-dextran/gelatin-based three-layer films with cinnamaldehyde and α-tocopherol for scallop (Patinopecten yessoensis) adductor muscle preservation

Controlling the quality of Patinopecten yessoensis from the perspective of the ultrasound and ferulic acid influences.

In this study, the effects of ultrasound combined with ferulic acid (FA) on the quality of the Yesso scallop (Patinopecten yessoensis) adductor muscles (SAM) during refrigerated storage were investigated. The results demonstrated that the combined treatment with 350W ultrasound and FA (UFA) significantly delayed enzyme activities and microbial growth in SAM tissues compared to FA treatment alone. After 6 days of cold storage, samples treated with UFA exhibited higher hardness (2850g), lower thiobarbituric acid reactive substances (TBARS=9.35 MDA mg/g SAM), and lower total volatile basic nitrogen (TVB-N=19.75mg/100g SAM) values compared to control and FA-treated samples. Consequently, UFA treatment prolonged the shelf life of SAM by 3 days during storage at 4°C. Based on scanning electron microscopy and low-field nuclear magnetic resonance data, these findings are attributed to UFA treatment not only reducing the degradation of SAM tissue network structure but also minimizing water loss. PRACTICAL APPLICATION: Scallop adductor muscle (SAM) is commonly considered a delicacy owing to its unique mouthfeel and delicious taste. However, owing to its high moisture content and high levels of various nutrients, SAM has a short shelf life. In this work, a combination of ultrasound with ferulic acid (UFA) has been found to have effective preservation effects on SAM during refrigerated storage. Our study findings pave the way for a potential approach to maintain scallop quality during processing and storage. Moreover, our study also provides some theoretical basis for using and promoting these technologies in aquatic products.

Behavioral Characteristics and Related Physiological and Ecological Indexes of Cultured Scallops (Mizuhopecten yessoensis) in Response to Predation by the Crab Charybdis japonica

To investigate the effects of predation by the paddle crab Charybdis japonica on the culture and survival of scallops (Mizuhopecten yessoensis) during bottom culture, we investigated the behavioral characteristics of three sizes (small, medium, and large) of scallops in response to exposure to crabs. We found that scallops escaped from crab predation by continuous shell closure or movement. Shell closure force increased with scallop size, and scallops of the same size that were stimulated by the presence of crabs closed their shell more frequently than control scallops. We also measured the activities of superoxide dismutase, catalase, arginine kinase, and octopine dehydrogenase in the gill, adductor muscle, and mantle of scallops before and after exposure to predation. Tissues that showed significant differences between control and test specimens were selected for deep sequencing of the transcriptome to identify and validate the key genes that were sensitive to predation. We found that when M. yessoensis is stimulated by the presence of predators, its behavioral characteristics and related physiological and ecological indexes undergo significant changes. The results are relevant for developing specifications for M. yessoensis seedling casting during bottom culture.

Preparation of trilayer film with slow-release, antioxidant, and antibacterial activities and its effects on scallop preservation

Scallops are renowned for their delicious taste and rich nutritional profile, including high contents of eicosapentaenoic acid and docosahexaenoic acid. However, they are highly susceptible to spoilage caused by lipid oxidation and microorganism proliferation. Therefore, in this study, trilayer films based on gelatin/gelatin-dextran/gelatin with different concentrations (0%, 0.3%, 0.6%, 0.9%, and 1.2%, w/w) of active fillers (citronellal and α-tocopherol) were developed to preserve scallop adductor muscle during cold storage. Scanning electron microscopy images showed that each layer was well-bonded with no gaps, indicating the successful preparation of the trilayer films. The addition of citronellal and α-tocopherol resulted in a porous cross-section with a slightly rough surface and increased hydrophobicity of the trilayer films. With increase in concentrations of citronellal and α-tocopherol, the thickness, opacity, antioxidant capability, and antibacterial activity of the trilayer films increased, while water vapor permeability and mechanical properties decreased. Both citronellal and α-tocopherol showed controlled release properties in four food simulants, with the longest release times in 95% (v/v) ethanol solution. Furthermore, the incorporation of 1.2% (w/w) of active fillers into the trilayer film significantly enhanced the chemical and microbiological stabilities of the scallop adductor muscles, thereby prolonging their shelf life by six days during cold storage. The developed trilayer films showed excellent controlled release, antibacterial properties, and antioxidant capabilities, indicating their potential for effective preservation of aquatic food products.

Behavioral characteristics and transcriptome analysis of Mizuhopecten yessoensis in response to Neptunea arthritica cumingii predation during laboratory bottom-sowing culture

In this study, we investigated the effects of predation by the whelk Neptunea arthritica cumingii on the culture and survival of scallops (Mizuhopecten yessoensis) during bottom culture. The behavioral characteristics of three sizes (small, medium, and large) of scallops were assessed in response to exposure to N. cumingii. We also measured the activities of superoxide dismutase, catalase, arginine kinase, and octopine dehydrogenase in the gill, adductor muscle, and mantle tissues of scallops before and after exposure to predation. We found that scallops escaped from N. cumingii predation by continuous shell closure or movement. The shell closure force increased with the scallop size, and scallops of the same size that were stimulated by the presence of N. cumingii closed their shells more frequently than control scallops. The shell closure ability of scallops of all sizes decreased as the duration of the experiment continued. The enzyme activities in the three scallop tissues changed significantly after continuous stimulation, and the trend was particularly obvious for the enzyme activities in the adductor muscles of medium-sized scallops. Transcriptome analysis of the adductor muscles from medium-sized scallops detected 405 differentially expressed genes (172 upregulated and 233 downregulated), where the expression levels of RYK, APC, BAMBI, WNT16, CACYBP, and RUVBL1 changed after stimulation by N. cumingii. The sequencing results were verified by quantitative real-time PCR. We hypothesize these genes may be related to muscle movement and regulation in M. yessoensis after stimulation.

Gelatin/dextran active films incorporated with cinnamaldehyde and α-tocopherol for scallop (Patinopecten yessoensis) adductor muscle preservation.

Scallops are rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid but perishable due to their microbial growth and lipid oxidation. In this study, gelatin/dextran films containing cinnamaldehyde and α-tocopherol (0%+0%, 0.3%+0.3%, 0.6%+0.6%, 0.9%+0.9%, and 1.2%+1.2%, w/w) as active fillers were developed by solution casting method, and their preservation effects on scallop adductor muscle refrigerated at 4°C for 0, 3, 6, 9, and 12 days were evaluated. Inclusion of the two active fillers did not influence the thermal stability of the films but created heterogenous and discontinuous film microstructure and increased the film hydrophobicity. Increase in the concentrations of active fillers lowered the mechanical properties and water vapor permeability of the films but increased their crystallinity, thickness, water contact angle, opacity, antibacterial property, and antioxidant property. The longest release times for both cinnamaldehyde and α-tocopherol were found in 95% (v/v) ethanol solution. The gelatin/dextran films containing 1.2% (w/w) of active fillers (Gelatin [Ge]/Dextran [Dx]/1.2 film) improved the chemical stability of refrigerated scallop adductor muscle. The total viable count (TVC) of the unpackaged scallop adductor muscle exceeded the recommended limit of 7lgCFU/g on day 6 (7.07±0.50lgCFU/g), whereas the TVC of the Ge/Dx/1.2 film-packaged scallop adductor muscle was still below the limit on day 9 (5.60±0.50lgCFU/g). Thus, the Ge/Dx/1.2 film can extend the shelf life of refrigerated scallop adductor muscle by at least 3 days. Overall, the developed gelatin/dextran active packaging films are promising for the preservation of aquatic food products.

Effects of air frying on protein digestive properties in scallop (Patinopecten yessoensis) adductor muscles and the mechanisms involved

The effects of air frying at different temperatures (140 °C, 160 °C, 180 °C, and 200 °C) on the simulated digestive properties of proteins in scallop adductor muscle (SAM) and the mechanisms involved were investigated. The results of the simulated gastrointestinal digestion showed that the 160 °C-treated SAM group had significantly higher protein digestibility than the fresh SAM group, which was reflected in higher degree of hydrolysis, more low molecular weight (<0.5 kDa) protein digestive products, and less insoluble residues, while the 140 °C-, 180 °C- and 200 °C-treated SAM groups all had opposite results. Moreover, air frying altered the solubility, secondary structure percentage and surface hydrophobicity of SAM proteins, as well as the microstructure of insoluble residues in simulated gastric juice. Correlation analysis showed that the protein digestive level of the air fried SAMs was positively correlated with the ratio of soluble proteins before digestion and the surface hydrophobicity of insoluble residues, but negatively correlated with the content of α-helix of soluble proteins dissolved in simulated gastric juice. Therefore, the highest digestibility of the 160 °C-treated SAM group can be attributed to the lowest α-helix content of soluble proteins, as well as the highest surface hydrophobicity and the largest pores size of insoluble residues. The present study provides a good basis for understanding the effects of air frying temperature on the digestive properties of aquatic muscle foods and the mechanisms involved, which contributes to establish precise air frying method for aquatic muscle foods.

Effects of Protein Structure Changes on Texture of Scallop Adductor Muscles under Ultra-High Pressure

In order to investigate the effect of protein structure changes on the texture of scallop adductor muscles under ultra-high pressure, the protein structure, hardness, elasticity, cohesion, and chewing properties of untreated scallops maintained at 200 MPa for 60 s, 120 s, and 180 s were measured and compared. At the same time, sensory indicators were evaluated to verify the effect of ultra-high pressure treatment on the quality of scallop adductor muscles. The results indicated that the mass fraction of the α-helix was decreased by 13.70% and the mass fraction of β–folding was 2.72 times higher in the adductor muscle of scallops compared to the fresh adducts without ultra-high pressure treatment, maintained for 180 s at an ultra-high pressure of 200 MPa. At the same time, the value of I850/I830 of protein tyrosine residues was 1.094, which weakened the water retention ability of the protein, the elasticity of the scallop adduct was reduced from the original 7.16 N to 6.17 N, the cohesion was reduced by 3.76%, and the hardness was increased by 17.45%. This improved the cooking quality of scallops, which was consistent with the sensory evaluation results. Therefore, under ultra-high pressure treatment, changes in the protein structure of the adductor muscle of scallops had a certain impact on their texture, which was able to provide support for in-depth research on the mechanism of ultra-high pressure action.

Heat-induced gelation of SAM myofibrillar proteins as affected by ionic strength, heating time and temperature: With emphasis on protein denaturation and conformational changes

There is a growing consumption of scallop adductor muscle (SAM) based food due to its great nutritional value and high digestibility. SAM gelation has a key effect on final products, however, the gelling properties of SAM, particularly the denaturation and conformational changes of proteins, are far less known. Thus, the present study aimed to improve our understanding on the gelation of SAM as affected by different heating temperatures, time, and ionic strength at low salt concentration ranges. Protein denaturation is the primary reason for the physicochemical changes of minced SAM during thermal gelling. Both gel strength and storage modulus showed positive correlations with heating temperature and time. However, the water holding capacity decreased gradually from 60 to 90 °C due to the shrinkage of myofibril proteins induced by protein denaturation, resulting in the transformation of immobilized water into free water, as proved by LF-NMR results. DSC and FTIR results indicated that heating at 90 °C led to complete degeneration of myosin and actin, and partial conversion of α-helices to β-sheets and random coil, resulting in a more rigid gel. It was further discovered that rapid heating (90 °C-10min) of low salt SAM at 1.5% NaCl concentration during gelation contributed to a superior gel strength and the reinforcement of fine-stranded three-dimension gel matrix as revealed by SEM. The investigation of heat-induced SAM provides a practical value for the processing of low-salt minced SAM products for the food industry.

Examination of the effects of dry storage stress on mitochondrial energy synthesis in the scallop Mizuhopecten yessoensis

Postharvest dry storage was simulated by storing scallops at 4 °C for different durations. The quantification of 40 energy metabolites related to the glycolysis, tricarboxylic acid (TCA) cycle and oxidative phosphorylation pathways in the scallop adductor muscle was performed by LC–MS/MS. The results showed that during the early stage (0–6 h), 6-phosphofructokinase-2 (PFK-2) in glycolysis was inhibited, and the TCA cycle was maintained at a low level. Concurrently, the aspartate pathway and opine pathway were initiated, and alanine and opines were the early metabolites found during this stage. During the middle and late stages (6–12 h) of dry storage, muscle pH decreased. Phosphoenolpyruvate carboxy kinase (PEPCK) was activated, leading to the competitive inhibition of pyruvate synthesis by PEPCK. Phosphoenolpyruvate enters the reverse TCA cycle via the phosphoenolpyruvate → malate pathway to produce succinate. The increase in succinate further induced the succinyl-CoA → propionate pathway, and the end products were acetate and propionate. Alteration of the metabolic pathway was observed, leading to a change in the NADH level. Subsequently, a fluctuating mitochondrial membrane potential was observed. Reimmersion after 6 h of dry storage promoted the recovery of the muscle TCA cycle. Nevertheless, after long-term dry storage (24 h), reimmersion storage did not restore the succinate → oxaloacetate metabolism in the TCA cycle. High-intensity air exposure had a long-term and irreversible effect on mitochondrial energy metabolism. Therefore, it is concluded that the dynamics of mitochondrial metabolism may be sensitive to dry exposure during postharvest operations.

Effect of boiling on texture of scallop adductor muscles and its mechanism based on label-free quantitative proteomic technique

The mechanism behind textural changes in scallop adductor muscle during boiling was investigated through proteomic analysis, determination of water holding capacity (WHC) and oxidative indices, as well as observation with scanning electron microscopy and multiphoton nonlinear optical microscopy. The hardness and shear force showed the trend of first rising and then falling in 45 min-boiling time. The results suggested that short-time boiling caused the oxidation, denaturation and aggregation of proteins, resulting in the transverse contraction of myofibers and lateral cross-linked aggregation of muscle fibers and a rise in WHC, which led to the increase in hardness and shear force. While long-time boiling caused the progressive degradation of structural proteins such as fibrillin-1, collagen alpha-2(I) chain, myosin heavy chain, basement membrane-specific heparan sulfate proteoglycan core protein, and paramyosin, resulting in a loose myofibril network and the decrease in WHC, which led to the decrease in hardness and shear force.

Structural Changes of the Interface Material of Scallop Adductor under Ultra-High Pressure

Because of their high nutritional value, the demand for scallops is increasing year by year. In the process of improving people’s living standards, the ready-to-eat characteristics and dry sales characteristics of this product make its shelling process particularly important in the production process. However, the mechanism of ultra-high pressure shelling has not yet been clarified. Therefore, in-depth study of the structural change of the scallop connection interface is of vital importance to explore the mechanism of ultra-high pressure shelling and the development of intelligent equipment from the mechanical point of view. The obturator muscle fibers and the inner surface materials of the shell at the obturator muscle scar of the scallop at 100, 200 and 300 MPa were obtained for Raman spectrum, Fourier-transform infrared spectrum and scanning electron microscopy analysis. The results showed that under the pressure of 200 MPa, the degree of protein denaturation of scallop adductor muscle increased, the elasticity disappeared, and the fiber was stretched; The deformation of the organic plasma membrane connected by the inorganic–organic interface weakens the binding force of the interface material and increases the possibility of the composite interface failure. To sum up, ultra-high pressure can effectively weaken the interface adhesion of scallop organic-inorganic composite materials, and is one of the effective ways of shelling. The research results can provide a basis for the in-depth analysis of ultra-high pressure mechanisms and the development of intelligent equipment, and provide technical support for the realization of ultra-high-pressure industrial production.

Effect of air frying and baking on physicochemical properties and digestive properties of scallop (Patinopecten yessoensis) adductor muscle

In this study, the effects of dry heat treatments including air frying and baking on the physicochemical and digestive properties of proteins in scallop adductor muscle (SAM) were evaluated. After heat treatments, the proteins in SAM exhibited different degrees of oxidation, aggregation and degradation. For both heat treatments, the increase of carbonyl and dityrosine contents and the decrease of free sulfhydryl groups and surface hydrophobicity of proteins in SAM were observed along with increasing heat temperature. Meanwhile, with increasing heat temperature, there was a progressive transition from α-helix to β-sheet in protein secondary structure. However, the protein solubility first increased and then decreased with increasing temperature. Among which, the solubility of 160°C-treated samples was the highest, which were 21.02% and 20.32% for air frying and baking. The protein digestive properties which reflected by the degree of hydrolysis (DH), soluble amino groups and soluble peptides showed a trend of increasing first and then decreasing with increasing temperature. After gastrointestinal digestion, the DH, soluble amino groups and soluble peptides of 160°C-treated SAMs cooking by air frying were 69.96%, 61.14% and 39.33%, respectively, which were significantly higher than all other samples including the fresh ones. Correlation analysis showed that the protein digestive indexes were positively correlated with solubility, free sulfhydryl content and surface hydrophobicity, and negatively correlated with protein carbonyl content, dityrosine content and protein aggregation degree. These results provide evidence for knowing more about the effects of dry heat treatments on physicochemical and digestive properties of aquatic muscle food.

Effects of flash-boil shucking on biochemical, sensorial and ultrastructural properties of Yesso Scallop (Mizuhopecten yessoensis) adductor muscle during refrigeration

Abstract Scallop adductor muscle has great popularity for raw consumption in Japan, but conventionally shucking live scallops with high vitality by knife requires skill and is time-consuming. Flash-boil shucking is a convenient shucking method in sushi restaurants for live scallops. However, the effects of this treatment on the quality of its main edible part, the adductor muscle, are not clear. This study was conducted to investigate the impact of flash-boil shucking on the quality of raw-edible scallop adductor muscle, focusing on flavor-enhancing components and ultrastructure. Thermal treatment could contribute to the formation of flavor-enhancing nucleotides in the external layer of the adductor muscle. Adenosine monophosphate content increased with the boiling time, which significantly increased to 1.47±0.42 µmol/g in the 30 s-boiled group compared with 0.38±0.13 µmol/g in the control group (p&amp;lt;0.05). The rapid adenosine monophosphate accumulation after boiling resulted in a faster accumulation of inosine and hypoxanthine during subsequent refrigeration, which could bring bitterness to aquatic products. Flash-boil shucking had no discernible effect on the proportion of free amino acids relevant to the flavor of scallop adductor muscle, despite the possibility of a reduction in total free amino acids. The external layer of the scallop adductor muscle could be hardened after flash-boil shucking. At the ultrastructural level, muscle fibers tend to aggregate transversely and contract longitudinally depending on the heating time. Flash-boil shucking is ideal for consuming the raw-edible scallop adductor muscle promptly. Flash-boil shucking treatment is recommended for households, restaurants, and small factories for treating scallops with high vitality.

Molecular characterization of myosin heavy chain and its involvement in muscle growth and development in the Yesso scallop Patinopecten yessoensis

Myosin found in scallop adductor muscles is a regulatory protein that is responsible for muscle contraction. Myosin heavy chains (MyHCs) form the core component of myosin and play important roles in myofibril assembly and maintenance. In the present study, we obtained the full-length cDNA sequences encoding MyHC from the Yesso scallop Patinopecten yessoensis and investigated its expression patterns as well as regulatory functioning in muscle growth and development. Py-MyHC was 6054 bp in length and was comprised of a 5′-untranslated region (51 bp), a 3′-untranslated region (180 bp), and an open reading frame (5823 bp) encoding 1940 amino acids. Analysis of the MyHC sequences in bivalves revealed that they were closely homologous to each other, with identities ranging from 74.48% to 95.16%. qPCR analysis and immunohistochemistry staining revealed the existence of tissue-specific expression patterns for Py-MyHC with maximal expression occurring in the striated adductor muscles. Whole-mount in situ hybridization showed that during larval development, Py-MyHC mRNA was mainly expressed in the velum retractor muscles, and in the anterior and posterior adductor muscles. Furthermore, noticeable defects in myofibril structure were found in the striated adductor muscles following the application of RNA interference. Based on the above, it is considered that MyHCs play a crucial role in myofibril assembly and maintenance in both larvae and adults. These findings are considered to provide useful information with regard to the functional basis of muscle growth and muscle production with potential implications for actual aquaculture production.

Effects of Ultrasound-Assisted Immersion Freezing on the Protein Structure, Physicochemical Properties and Muscle Quality of the Bay Scallop (Argopecten irradians) during Frozen Storage.

In this study, the comparison effects of ultrasound-assisted immersion freezing (UIF) at different ultrasonic power, immersion freezing (IF), and air freezing (AF) on the protein thermal stability, protein structure, and physicochemical properties of adductor muscle of scallop (Argopecten irradians) (AMS) during frozen storage were investigated. Principal component analysis and the Taylor diagram were used to comprehensively analyze all the indicators tested. The results showed that the UIF at 150 W (UIF-150) treatment was the most effective way to delay the quality deterioration of AMS during 90-day frozen storage. This was mainly because, compared to AF and IF treatments, UIF-150 treatment more effectively minimized the changes in the primary, secondary and tertiary structures of myofibrillar proteins, and it preserved the protein thermal stability of AMS by producing small and regular ice crystals in the AMS tissue during the freezing process. Moreover, the results of physicochemical properties indicated that UIF-150 treatment significantly inhibited the fat oxidation and microbiological activities of frozen AMS, and it finally maintained the microstructure and texture of AMS during frozen storage. Overall, UIF-150 has potential industrial application prospects in the rapid freezing and quality preservation of scallops.

Effects of Different Antioxidants of Bamboo Leaves Treatments on Lipid Oxidation of Scallop (Argopecten irradians) Adductor Muscle During Hot Air Drying

ABSTRACT The effect of different antioxidants of bamboo leaves (AOB) treatment on lipid oxidation of scallop (Argopecten irradians) adductor muscle during hot air drying was investigated. The results demonstrated that the marinated sample had the lowest peroxide value, thiobarbituric acid-reactive substances, polyunsaturated fatty acids loss, free radical level, and lipoxygenase activity during drying, indicating that the marination process maximized the antioxidant effects of AOB. The results indicate that this process could interfere with free radical chain reaction and inhibit lipoxygenase activity since AOB is correctly distributed on the site of lipid oxidation. After drying, eicosapentaenoic acid + docosahexaenoic acid content in control, unmarinated, and marinated samples decreased by 26.10%, 11.25%, and 7.29%, respectively, suggesting that the marination process maintained more efficiently its high nutritive value in terms of lipid content. Overall, the use of AOB provides a more effective strategy to control lipid oxidation in seafood, mainly scallops, during drying.

Marine Biotoxins in Whole and Processed Scallops from the Argentine Sea.

Harmful algal blooms are an increasing worldwide threat to the seafood industry and human health as a consequence of the natural production of biotoxins that can accumulate in shellfish. In the Argentine Sea, this has been identified as an issue for the offshore fisheries of Patagonian scallops (Zygochlamys patagonica), leading to potentially harmful effects on consumers. Here we assess spatial and temporal patterns in marine biotoxin concentrations in Patagonian scallops harvested in Argentinian waters between 2012–2017, based on analyses for paralytic shellfish toxins, lipophilic toxins, and amnesic shellfish toxins. There was no evidence for concentrations of lipophilic or amnesic toxins above regulatory acceptance thresholds, with trace concentrations of pectenotoxin 2, azaspiracid 2 and okadaic acid group toxins confirmed. Conversely, paralytic shellfish toxins were quantified in some scallops. Gonyautoxins 1 and 2 dominated the unusual toxin profiles (91%) in terms of saxitoxin equivalents with maximum concentrations reaching 3985 µg STX eq/kg and with changes in profiles linked in part to seasonal changes. Total toxin concentrations were compared between samples of the adductor muscle and whole tissue, with results showing the absence of toxins in the adductor muscle confirming toxin accumulation in the digestive tracts of the scallops and the absence of a human health threat following the processing of scallop adductor meat. These findings highlight that paralytic shellfish toxins with an unusual toxin profile can occur in relatively high concentrations in whole Patagonian scallops in specific regions and during particular time periods, also showing that the processing of scallops on board factory ships to obtain frozen adductor muscle is an effective management process that minimizes the risk of poisonings from final products destined for human consumption.

Effect of ultra-high pressure on the relationship between endogenous proteases and protein degradation of Yesso scallop (Mizuhopecten yessoensis) adductor muscle during iced storage.

This study aimed to explore the effect of ultra-high pressure (UHP) treatment (100-500MPa, 5min, 15±1℃) on the relationship between endogenous proteases and protein degradation of Yesso scallop (Mizuhopecten yessoensis) adductor muscle during iced storage for 28days. Our findings showed that the UHP treatment kept the water holding capacity stable, increased the hardness and decreased the springiness of scallop adductor muscle during iced storage. 400 and 500MPa UHP treatments caused protein denaturation and oxidation significantly, decreased protein degradation rate and inhibited the activities of endogenous proteases. According to the correlation analysis, the activities of cathepsin B, D, H, L, calpain and serine protease were positively correlated with TCA-soluble peptides. The activities of endogenous proteases were significantly correlated with protein degradation. Therefore, the effect of UHP on endogenous protease caused the protein degradation rate to slow down and prevented the texture deterioration in scallops.

Distribution of vitamin B12 in bivalve tissues: Investigations of larval and adult lifestages

Shellfish, in particular bivalves, are an often-overlooked source of vitamin B12 (B12) in the human diet although they have significantly higher tissue levels of B12 than other animal meat or fish sources, including all vertebrates. However, the origins and key metabolic processes involving B12 in bivalves remain largely unknown. In this study, we examined the distribution of B12 in tissues of several adult Australian bivalve species and assessed hypotheses concerning their B12 utilisation and principal uptake, specifically whether it is derived from diet or gut microbiome. Pacific oysters, Crassostrea gigas, and Goolwa cockles, Plebidonax deltoides (‘pipis’), are both high in B12 (28.0–49.4 μg/100 g total per individual). Vitamin B12 tissue distribution, particularly in oysters, varied significantly, with higher amounts in the adductor muscle (44.0–96.7 μg/100 g), and other tissues, such as gonads, were relatively low (12.7–35.9 μg/100 g). In comparison, concentrations of B12 in the adductor muscle and roe of Southern Australian scallops, Pecten fumatus, were appreciably lower (3.4–10.8 μg/100 g). We also demonstrated that microalgal feed commonly grown in aquaculture can be supplemented directly with B12, resulting in an enriched feed. However, the B12-enriched diet did not transfer to a significant increase in oyster larval B12 concentrations, contradicting our theory that vitamin uptake through feed was a primary B12 source. Vitamin B12 concentrations across oyster larval life stages showed a significant decrease post metamorphosis, which indicates a higher utilisation of B12 during this life event. Our findings also provide insight into B12 uptake and tissue distribution in bivalve species, which can aid the aquaculture industry in promotion of bivalves as a valuable source of dietary B12 for human consumers, while also suggesting ways to optimise vitamin supplementation in bivalve hatchery production.