ROUNDUPS

• Research progress on preservation technology of Scomber japonicus

  CUI Pengbo, LIANG Jianqin, CHENG Tianyu, Lü Fei, DING Yuting

  2024,48(7):079801-079801, DOI: 10.11964/jfc.20231214277

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  Scomber japonicus is an important fishery resource in China, with high nutritional value, developed endogenous enzymes in the body, and rich histidine in protein. However, it is prone to deterioration if not treated in time after capture, resulting in low processing availability. In order to solve the problem of quality deterioration of Scomber japonicus after capture and to better meet consumers' demand for high-quality S. japonicus products, domestic and foreign researchers have adopted low-temperature preservation technologies such as partial freezing, controlled freezing-point storage temperature storage, frozen storage, cold seawater and slurry ice, as well as low-temperature preservation auxiliary technologies such as adding preservative, coating preservation, electrolyzed water, applied electric field device, dielectric barrier discharge atmospheric cold plasma and high pressure treatment to control the quality of S. japonicus resources, and have studied the factors causing S. japonicus spoilage. The results showed that although the low-temperature preservation technology could achieve the purpose of controlling the deterioration of quality and extending the shelf life of S. japonicus products to a certain extent, the preservation effect of these technologies alone was not ideal. The addition of low-temperature preservation auxiliary technology could not only effectively extend the shelf life of S. japonicus products, but also maintained the flavor and sensory characteristics of products to a certain extent. However, S. japonicus is still affected by multiple factors such as endogenous enzymes, microorganisms, and oxidation in S. japonicus, which will lead to spoilage. The research shows that it is necessary to fully understand the causes of spoilage in S. japonicus and take targeted preservation measures to curb the occurrence of spoilage. In this paper, the research progress of low-temperature preservation technologies of S. japonicus and their auxiliary technologies are systematically reviewed, and the factors of spoilage of S. japonicus are summarized, providing a reference basis for effective quality control and high value utilization of S. japonicus resources.

• Current situation and countermeasures for quality and safety management of raw oysters from out of water to table

  LI Man, WANG Zhuolin, LIU Zepeng, ZHAO Hui, LU Hang, JIANG Yusheng, YUAN Chunhong, TIAN Yuanyong

  2024,48(7):079802-079802, DOI: 10.11964/jfc.20240214365

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  The safety and quality of raw oysters are key factors influencing their sales price. This study first reviewed the current status of safety and quality management of raw oysters in various countries, catigorizing them into three main perspectives of safety, vitality, and flavor quality. Subsequently, the impact of key links such as farming, fishing, cleaning, purification, transportation and sale on the quality of raw oysters were analyzed from the perspective of the distribution chain. As filter-feeding bivalves, oysters were susceptible to multiple safety hazards from farming to sale, mainly including shellfish toxins, heavy metals, harmful microorganisms, and viruses, which can impact their safety. These hazards can be eliminated through standardized farming practice and distribution management. From out of water to the dining table, oysters were exposed to a series of environmental stressors (such as dehydration, temperature, oxygen, density, etc.), leading to a severe decline in vitality and flavor quality, as well as significant economic losses. Due to differences in the mode, intensity, and duration of stress, the effects of the same or different stressors at different links are highly complex. The rapid and accurate assessment of vitality is the foundation of distribution quality management. This article presents a systematic analysis of the metabolism and vitality of oysters under multiple stressors, as well as the correlation between metabolites and flavor, and explores targeted quality control strategies, which could help achieve precise quality control. We look forward to providing a theoretical basis for establishing controllable operations and enhancing the quality and market value of oysters at the point of sale.

• Research progress of analysis and control strategy of geosmin affecting the quality of freshwater fish

  ZHAO Yong, WANG Tianyi, LI Kang, PAN Yingjie, LIU Haiquan

  2024,48(7):079803-079803, DOI: 10.11964/jfc.20221013729

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  Aquatic products are delicious and nutritious, and are an important source of food protein for human intake. However, the distinct odor represented by the fishy smell in freshwater aquaculture often occurs, which not only affects the flavor of aquatic products, but also reduces the consumer's willingness to consume them and restricts the stable development of the aquaculture industry. The scientific control and prevention of earthy odor in aquatic products is an important means to ensure the quality of aquatic products, which is important for meeting the needs of the industry and still needs to be studied in depth. This paper reviews the special odor in aquatic products with earthy odor as a typical representative, and discusses the mechanism of odor substances in aquatic products causing odors like the earth odor. It is now generally accepted that water quality conditions in the aquaculture environment indirectly affect the formation of odor substances, and various water quality indicators have a significant impact on the fishy odor of aquatic products. Most removal methods affect meat quality, destroy the protein of aquatic products, and cause changes in flavor and color. By improving the culture environment and reducing 2-Methylisoborneol (MIB) and geosmin (GSM) in aquatic products, the production of earth odor can be reduced at the source, which is one of the main methods to control earth odor in aquatic products, but this method is often costly. Therefore, in order to improve the economic efficiency of aquatic products, to solve the problem of fishy smell in freshwater farmed aquatic products, it is necessary to address the characteristics of various aspects of aquatic products breeding, distribution and processing, and make comprehensive use of various deodorization methods to achieve the deodorization effect.

PAPERS

• Effects of ATP content and exogenous enzyme addition on thephosphorylation level of myofibrillar protein in tilapia

  YU Ye, WEI Ya, CHEN Shengjun, HUANG Hui, CEN Jianwei, PAN Chuang, LI Chunsheng, WANG Di, WANG Yueqi, FENG Yang, ZHAO Yongqiang

  2024,48(7):079804-079804, DOI: 10.11964/jfc.20240514515

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  Protein phosphorylation modification can affect muscle quality. In order to investigate the effect of exogenous enzyme addition on the protein phosphorylation level of tilapia myofibrillar protein, tilapia myofibrillar protein solution was incubated in vitro by adding protein kinase A (PKA) and alkaline phosphatase (AP), respectively, and changes in phosphorylation level were determined by dodecyl sodium sulfate-polyacrylamide gel electrophoresis and fluorescence staining at different time intervals. In addition, the effect of adenosine triphosphate (ATP) on tilapia muscle was investigated by immersing the muscle in different concentrations of ATP solution to determine the level of myofibrillar fibrillar protein phosphorylation. The results showed that from 0 to 72 h, the phosphorylation level of PKA group was significantly higher than that of control group and AP group, and the overall phosphorylation level of PKA group increased from 0.35±0.01 at 0 h to 0.37±0.01 at 12 h, and then decreased to 0.29±0.01 at 72 h, with a general trend of increasing and then decreasing. In addition, the phosphorylation level of myosin heavy chain and actin phosphorylation level decreased from 0.73±0.01 and 0.86±0.01 at 0 h to 0.58±0.02 and 0.68±0.01 at 72 h, respectively (P<0.05). Phosphorylation levels were significantly different in all three groups when incubation time was 0, 4, 24 and 48 h. After addition of 0.3 mol/L exogenous ATP, the results showed that the overall phosphorylation level of myofibrillar proteins (0.46±0.001) was significantly higher than that of the control group (0.42±0.01). PKA promotes phosphorylation modification of myofibrillar proteins in tilapia, while alkaline phosphatase dephosphorylates them. It was shown that ATP content, PKA and AP activity levels in the muscle of slaughtered tilapia were key factors affecting the level of protein phosphorylation. This study may provide a theoretical basis for exploring the mechanism of quality change and regulatory strategies in tilapia.

• Correlation analysis between the thermal denaturation of myofibrillar proteins and adductor muscle shelling in Ruditapes philippinarum

  ZHI Huimin, LI Yang, WANG Wei, DONG Hanyu, LU Hang, ZHAO Hui, JIANG Yusheng, TIAN Yuanyong

  2024,48(7):079805-079805, DOI: 10.11964/jfc.20240314417

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  Frozen-cooked product is a common product form of Ruditapes philippinarum, with heating shelwith being a key processing technique.The basic principle of heating shelling relies on thermal contraction of the adductor muscle to separate the meat from the shell. Temperature is one of the crucial factors significantly affecting the protein in the adductor muscles of R. philippinarum. To inivestigate the correlation between adductor muscles decalcification and thermal denaturation of myofibrillar proteins in R. philippinarum following heat treatment, the thermal denaturation behavior of adductor muscle protein was initially investigated using a differential scanning calorimeter (DSC). Subsequently, the impact of heating on the microstructure of adductor muscles was observed using optical and electron microscopy.additionally, the thermal denaturation pattern of myofibrillar proteins was examined using Ca²⁺-ATPase activity, salt solubility, and SDS-PAGE as indicators. The results showed that the DSC analysis of fresh adductor muscle revealed three absorption peaks at temperatures of 50, 60 and 78 °C. After heating for 5 minutes, the absorption peaks at 50 °C and 80 °C were no longer detectable, suggesting they likely correspond to the thermal denaturation of myosin and actin, respectively. Following boiling treatment, the adductor muscle fibers in R. philippinarum demonstrated lateral aggregation and longitudinal contraction. This morphological change resulted in varying degrees of separation between the muscle and shell due to differential contraction rates. A specific heating regimen for myofibrillar proteins (0.5 mol/L NaCl at 45 °C for 5 min) led to a marked decrease in Ca²⁺-ATPase activity and salt solubility, indicating myosin thermal denaturation. Additionally, actin played a significant protective role over myosin before denaturation. The simultaneous denaturation of myosin, actin, and tropomyosin, which contributed to the facilitation of shelling. This study provided a scientific basis and data support for futher developing processing techniques for R. philippinarum.

• Effect of microwave-assisted drying on the quality of abalone muscle cured with Agaricus bisporus extract

  LIAO Yuqin, SHI Linfan, REN Zhongyang, WENG Wuyin, HUANG Wenmei

  2024,48(7):079806-079806, DOI: 10.11964/jfc.20230113863

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  In order to explore the effect of microwave-assisted drying on the quality of abalone muscle, the effect of microwave treatment on the physicochemical properties and volatile flavor of abalone muscle marinated by 30% NaCl and 5% Agaricus bisporus extract solution during the drying process were studied. The physicochemical properties including browning intensity, fluorescence intensity, sugar reduction, amino acid composition, and glycoproteins were determined. The result shows that the fluorescence and browning intensity values of abalone muscle gradually increased with increasing drying time irrespective of undergoing microwave treatment (MT) and without it (WMT), and reached the maximum at 105 dafter being dried. The sugar content reduction in the WMT abalone muscle decreased from 7.24 mg/g to 5.58 mg/g after drying for 120 d, while that in the MT sample increased from 7.24 to 14.05 mg/g. The total amino acid content in the WMT and MT abalone muscle increased from 39.69 g/100 g to 44.06 and 41.54 g/100 g, respectively. The formed macromolecular compounds and glycoproteins were observed in the electrophoretic profile of abalone muscle after drying for 30 d. Compared to the WMT abalone muscle, not only did the wave number of amide A band in the FT-IR spectra of MT abalone muscle decrease more significantly, but also the absorption peak intensities of amide I and II bands were stronger. Irrespective of MT or WMT, the sensor response values of W2W (aromatic components, organic sulphides) and W2S (aldehydes, alcohols and ketones) in the electronic noses of abalone muscles dried for 90 d were higher than those of the untreated samples. Based on the results determined by gas chromatography mass spectrometry, it was found that the content of nonanal and 1-octen-3-ol in abalone muscle decreased significantly after being dried for 90 d, while the content of linalool increased significantly. At the same drying time, the linalool content in the MT abalone muscle was higher than that of WMT abalone muscle. The results of this study suggested that microwave treatment can promote the Maillard reaction of abalone muscle during the drying process, thereby generating a good volatile odor. This result can provide a theoretical reference for improving the preparation process of dried abalone using microwave assistance.

• Effects of temperature and vibration stress on tissue damage and biochemical indices in sea bass (Lateolabrax japonicus) during the process of keeping-alive

  GUO Meijie, MEI Jun, XIE Jing

  2024,48(7):079807-079807, DOI: 10.11964/jfc.20221113783

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  In order to explore the effects of combined stress of temperature and vibration intensity on tissue damage and biochemical indexes of sea bass (Lateolabrax japonicus) during in-water keep-alive transportation, six experimental groups were designed with transportation temperature of 20 °C and 12 °C and vibration intensity of 0, 20 and 50 r/min as variables. After simulated transportation for 48 h, the effects of temperature and vibration stress on L. japonicus during simulated transportation were studied by analyzing oxidative stress, tissue damage and immune indexes. The results show that: ① The vibration intensity of different temperature ratios has great influence on the survival rate of L. japonicus. After 24 h transportation, the survival rates of the transportation group at 20 °C at 0, 20 and 50 r/min were 72.70, 62.50 and 18.2% respectively. However, the survival rate of all transport groups at 12 °C is 100%. ② The change trend of each index is different at different temperatures. Under the transport conditions of 20 °C, catalase (CAT), glutathione-S-transferase (GST), malondialdehyde (MDA), glutamic acid transaminase (ALT), aspartate transaminase (AST), acid phosphatase (ACP), alkaline phosphatase (AKP), and lysozyme (LZM) increased with the increase of transport time, and superoxide dismutase (SOD), immunoglobulin ( IgM) showed a tendency to increase and then decrease with increasing transport time, and blood glucose (GLU) showed a tendency to decrease with increasing transport time. Among them, low temperature treatment can reduce the oxidative stress, tissue damage and immune system damage of L. japonicus. At the transportation temperature of 12 °C, the activities of CAT, MDA, ALT, AST and LZM increased first and then decreased, while the activities of SOD, GST, GLU and IgM decreased first and then increased. The highest value of SOD was 0.64 U/mgprot in the transportation groups at 20 °C and 50 r/min, but only 0.37 U/mgprot in the transportation group at 12 °C and 50 r/min. The research shows that the L. japonicus should be transported at low temperature, the temperature should be kept at 12 °C, and the flat transportation road should be chosen to reduce vibration frequency during transportation. This study explored the effects of combined stress of temperature and vibration intensity on marine fish. The results can provide reference for short-distance transportation of L. japonicus and improve the survival rate of live fish during transportation.

• Changes in survival rate and muscle quality of Megalobrama amblycephala in fish bags during the process of keeping-alive

  YANG Han, ZHANG Tonghao, YONGSAWADIGUL Jirawat, YIN Tao, YOU Juan, LIU Ru

  2024,48(7):079808-079808, DOI: 10.11964/jfc.20240314427

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  With the development of aquatic logistics industry, China has now formed a live fish transportation system mainly based on high-density live transportation, supplemented by single fish transportation through plastic fish bag filled with oxygenated water. Although keeping-alive with fish bags has the advantages of shortening the transportation intermediate link, improving the survival rate of fish, and promoting the sales of local specialty fish, there is relatively little research on stress response and muscle quality changes in live fish transported with fish bags, which greatly limits the development of this transportation method. In order to promote the development of live fish transportation industry, this study adopts the fish bag to preserve the survival of the blunt snout bream (Megalobrama amblycephala). Firstly, the influence of survival conditions (temperature, fish-water ratio, and water source) on the survival rate was studied, and the optimal survival conditions were determined; then, the changes in blood stress indicators and muscle quality of fish during the keeping-alive process were studied under the optimal conditions. The results showed that when the transportation environment temperature was 10 ^oC, the fish to water mass ratio was 1:3, and the water source was aerated tap water, the fish survival rate was the highest. The survival rates were 90% and 70% at 36 and 48 hours of keeping-alive process, respectively. During the keeping-alive process, the stress indicators in the blood of the bream showed a fluctuating trend. However, overall, the content of cortisol (COR), urea (URA), and malondialdehyde (MDA) increased first and then decreased; the content of lactate dehydrogenase (LDH) first decreased and then increased; the content of superoxide dismutase (SOD) gradually decreased; the content of catalase (CAT), aspartate transferase (AST), and creatinine (CR) gradually increased. In terms of muscle quality, physical indicators such as whiteness value, shear force, and drip loss show an overall trend of first increasing and then decreasing, which was consistent with the formation of pale, soft and exudative (PSE) meat after stress. Compared with 0 hour, the crude protein, lactate, and glycogen content decreased by 19.0%, 27.2%, and 50.0% respectively after 72 hours of keeping-alive process; The nucleotide compounds of freshness (ADP, AMP, IMP) and bitterness (HxR, Hx), as well as the freshness value K, showed an overall increasing trend; the gap between muscle fibers gradually increased with the prolongation of survival time. This study has shown that during the keeping-alive process, fish are subjected to sustained stress, and the intensity of single stress may gradually weaken. The main reason for the deterioration of fish muscle quality may be related to physiological processes such as energy metabolism disorders. This study can provide a theoretical basis for the e-commerce logistics of fish by fish bags. However, further research is needed on how to effectively alleviate the stress response of fish during the transportation, thereby improving survival rate and muscle quality.

• Evaluation of the nutritional composition and quality ofthree pelagic squid species

  WU Junjie, TANG Fenghua, GUO Quanyou, SONG Xiaoyan, ZHANG Xiaohui, YANG Xu, ZHENG Yao

  2024,48(7):079809-079809, DOI: 10.11964/jfc.20220713617

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  In order to investigate the differences in the nutritional composition and quality of muscle and skin of Illex argentines, Dosidicus gigas and Ommastrephes bartrami, fatty acid composition and amino acid composition of their muscle and skin were determined and analyzed using the national standard method, and the texture and moisture distribution of their muscle and skin were analyzed using a mass spectrometer and low-field nuclear magnetic resonance instrument. The results showed that the crude lipid content of I. argentines muscle was 1.23%, which was significantly higher than that of the other two species (P<0.05). In addition to moisture content, the crude protein content, crude lipid content and ash content of the muscle were significantly higher than those of the skin (P<0.05). The unsaturated fatty acid content of both muscle and skin was higher than 61%, and the total unsaturated fatty acid (ΣUFA) of I. argentines muscle was 66.51%, which was significantly higher than those of the other two species (P<0.05). 17 amino acids were detected in different parts of the muscle. The total amount of essential amino acids in the Il. argentines muscle was 5.54, 6.68 and 5.97 g/100 g, which accounted for more than 40% of the total amino acids. The content of non-fluid water in the muscle was significantly higher than that in the skin(P<0.05), and the percentage of immobile water (96.92%) in the I. argentines muscle was the highest. The hardness and springiness of I. argentines were significantly higher than those of the other two species (P<0.05), and the gumminess and adhesiveness of skinned squid muscle were significantly higher than those of unskinned squid muscle (P<0.05). Compared to the other two species of squid, I. argentines muscle had highest unsaturated fatty acid content, best textural properties, and highest water retention capacity. There was no significant difference in hardness, cohesiveness and chewiness between skinned and unskinned squid muscle (P>0.05), and although the nutritional value of squid skin was slightly lower than that of muscle, squid skin still had high processing and utilization prospects.

• Novel modified QuEChERS combined with UPLC-MS/MS technology for the detection of antibiotic residues in several common kinds of aquaculture products

  XU Xuejiao, HUANG Cheng, YANG Jiacheng, DAI Zhiyuan, ZHENG Zhenxiao

  2024,48(7):079810-079810, DOI: 10.11964/jfc.20240114333

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  Aquatic products play an important role in human diet. Compared with other livestock and poultry products, aquatic products are featured with low fat content, high protein content, and easy digestion. Therefore, aquatic products are deeply loved by consumers. Generally speaking, aquatic products can be divided into two categories: naturally caught aquatic products and aquaculture aquatic products. In recent years, with the decline of marine resources and the increase of marine pollution, aquaculture is booming. In order to improve the efficiency of aquaculture, antibiotics are usually used, which brings risk to human health. Therefore, the monitoring of antibiotic residues in aquaculture products has been an important part in the field of food safety. To supervise antibiotic residues in aquaculture products, a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) combined with UPLC-MS/MS for the simultaneous determination of 28 antibiotic residues in aquaculture products was established, with nano grapheme oxide/multi walled carbon nanotubes (n-GO/MWCNTs) composite as the adsorbent. Moreover, parameters such as the ratio of acetonitrile and methanol in extractant, the amount of the n-GO/MWCNTs, were optimized through the recovery of 28 antibiotics. Besides, the adsorbent action of n-GO/MWCNTs was also compared with PSA, C18, MWCNTs, and graphene. Finally, method validation was accomplished according to Codex guideline (CAC/GL-71) with the following performance characteristics: the linearity, limit of detection and quantification, matrix effects, recovery, intra-day and inter-day precision. The results showed that the absorption effect of n-GO/MWCNTs was the best with acetonitrile: methanol (75∶25, V/V) and 10 mg of n-GO/MWCNTs. Good linearity (R²>0.99) was observed for all tested antibiotics with the limit of detection and quantification were 0.06-1.42 μg/kg and 0.20-4.72 μg/kg. Low matrix effects (<10%) was observed for most tested drugs (except for SIA, SQX, DAN and LOM). The average recovery of this protocol was 80.1%-100.4% in the spiked levels of 5-100 μg/kg. The intra-day precision was lower than 10.3%, while the inter-day precision below 13.4%. Method applications authenticated that the established method had favorable repeatability and high sensitivity, which could be applied to the regulatory routine analysis. We hope this work could provide technical support for the monitoring of antibiotic residues in aquaculture products and be helpful to the quality and safety control of aquaculture products.

• Preparation and physicochemical properties of Aristichthys nobilis bone collagen polypeptide

  YANG Qinzi, CHEN Lili, ZHANG Zhaosen, WU Siyu, WANG Bingtao, ZHAO Li

  2024,48(7):079811-079811, DOI: 10.11964/jfc.20240114319

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  Collagen is an important biomass resource, which has the characteristics of low antigenicity, hypoallergenicity, biodegradability, excellent biocompatibility and promoting cell proliferation and differentiation. Collagen peptides are generally composed of short sequences of 2 to 20 amino acid residues with a relative molecular mass of less than 10 ku. Through hydrolysis of macromolecule collagen, small molecule peptides are generated, which not only contain all amino acids of collagen, but also have better absorbability and processing characteristics than collagen, and are easier to be absorbed and utilized by the human body. In recent years, a variety of bioactive peptides have been isolated and identified from collagen peptides, such as antioxidant peptides, antihypertensive peptides, antibacterial peptides and so on. China is not only rich in aquatic resources, but also a big consumer of aquatic products. According to statistics, in 2022, the output of large-scale freshwater fish aquaculture in China is about 20.26 million tons, accounting for 62% of the total freshwater aquaculture in the country, of which the output of bighead fish aquaculture is firmly in the top three, reaching 3.27 million tons, and shows an overall growing trend, while the processing by-products of aquatic products are also increasing. In order to improve the high value utilization of Aristichthys nobilis bone, the best hydrolysis protease was selected with the A. nobilis head bone meal as raw material and the yield of collagen polypeptide as index, and the process of A. nobilis head bone collagen polypeptide was optimized. The amino acid composition, relative molecular weight, particle size, potential and microstructure of A. nobilis head bone collagen polypeptide were analyzed. The results showed that trypsin was the best hydrolysis enzyme for A. nobilis head bone meal, and the optimal hydrolysis process of bone collagen polypeptide was as follows: initial pH 8, enzyme dosage 2.5%, enzymolysis time 5 h, enzymolysis temperature 50 °C, solid-liquid ratio 1∶10 (g/mL). At this time, the yield of bone collagen polypeptide was 52.19%. The hydrolyzed polypeptide of A. nobilis head bone collagen contained 17 kinds of amino acids, among which the contents of glycine, proline, glutamic acid and alanine were (18.68±0.22), (10.06±0.09), (8.94±0.13) and (8.01±0.12) g/100 g, respectively. In line with the typical composition characteristics of collagen amino acids, the acidic amino acid content was 14.15 g/100 g, which had a high content and strong calcium binding ability. The relative molecular weight of A. nobilis head head collagen polypeptide was < 180 u, 500-180 u, 1 000-500 u, 2 000-1 000 u, 3 000-2 000 u and 5 000-3 000 u. The proportion of u was 2.26%, 21.04%, 44.40%, 22.02%, 4.86% and 3.23%, respectively, and the proportion of peptides below 5 000 u was as high as 97.81%, indicating that the products of enzymatic hydrolysis were mainly small molecular peptides with high absorption rate and high affinity for stomach and intestines. The average Z-particle size of A. nobilis head bone collagen polypeptide was (399.90±2.70) nm, and the polydispersion index (PDI) was 0.40±0.01, which was between monodisperse system and medium disperse system (0.30-0.50), indicating that the substance distribution was uniform, and the intercept was close to 1, indicating that the particle size distribution curve was well fitted. The surface of A. nobilis head bone collagen polypeptide particles was negatively charged. The A. nobilis head bone collagen polypeptide is loose in structure, porous and uneven in size, and has a lamellar structure. Studies have shown that A. nobilis head bone collagen polypeptide is rich in nutrients, its small molecule peptide is easy to be absorbed by the human body, and its loose porous structure is also conducive to the preparation of peptide calcium chelates. This study not only provides theoretical basis for the intensive processing of A. nobilis bone products, but also provides excellent raw materials for the preparation of new calcium preparations.

• Effects of potato-based emulsions on the quality of surimi gels

  LU Huimin, ZHAO Ruixuan, ZHANG Liang, LIU Wei, LIU Qiannan, LIU Shucheng, HU Honghai

  2024,48(7):079812-079812, DOI: 10.11964/jfc.20240314418

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  To investigate effects of potato-based emulsion (PE) on the quality of surimi gels, corn oil (CO) or PE was mixed with surimi at different additive levels (0%-14%), and the effects of PE as a fat replacer on the quality and mechanism of surimi gels were investigated by texture, moisture, color, intermolecular interactions, rheological properties, and microstructure of the surimi gels. At the same oil addition level, PE could avoid the degrading effect of oil droplets on the textural properties and water-holding capacity of surimi gels compared with CO, so that the samples added with PE exhibited higher elastic modulus and viscosity; in addition, the results of transverse relaxation time showed that PE inhibited the transition from immobile to free water, so that more immobile water was bound, which might enhance the diffuse reflection of light, thus resulting in the higher whiteness of the PE-added samples. The results of microstructure and intermolecular force measurements showed that the oil droplets in PE samples were more uniformly distributed, the hydrogen bonding, hydrophobic interactions and disulfide cross-linking were stronger, and the gel network was denser due to the filling effect of starch granules; the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the neutralization of oil droplets in the PE group intervened less in the cross-linking of surimi proteins. These results indicate that PE can be used as a fat substitute to improve the quality of surimi gels, and this study provides a theoretical basis for the development of starch-based fat substitutes and their application in surimi gelatine products

• Process and mechanism of softing fish bones of Ctenopharyngodon idella by ultrasound-acetic acid treatment

  ZHANG Yihan, MA Huawei, LUO Yongkang, TAN Yuqing, HONG Hui

  2024,48(7):079813-079813, DOI: 10.11964/jfc.20240414448

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  In 2022, the total freshwater fish production in China reached 2 800.31 million t, accounting for 77.04% of the total domestic fish production. In recent years, against the background of the rapid growth of the ready-to-eat leisure food market in China, a variety of categories of ready-to-eat freshwater fish products have been developed, among which vacuum-packed seasoned fish pieces are one of the mainstream types. However, the processing technology of vacuum-packed seasoned fish pieces still has key technical difficulties, which hinder the development of the industry. The hard fish bones may puncture the packaging bag due to compression during transportation, leading to oil leakage and spoilage, which is the main reason for the high product wastage rate. The presence of large and hard fish bones in the products poses serious food safety hazards, including puncture of the esophagus and damage to organs. The problem of fish bone softening in freshwater fish products needs to be addressed urgently, both from the perspective of production, storage, and transport of the product and from the perspective of food safety. To solve the problem of fish bone softening in ready-to-eat freshwater fish products, the study designed a fish bone softening rate measuring method for ready-to-eat freshwater fish products and then developed the ultrasound-cetic acid (U-CA) fish bone softening technique. The optimal fish bone softening conditions were screened according to the fish bone softening rate and the quality indexes of the fish pieces, and the mechanism of fish bone softening was investigated subsequently. Ctenopharyngodon idella pieces were prepared by ultrasonic combined with acetic acid treatment, marination, deep-frying, vacuum packaging, and autoclaving to obtain soft bone fish pieces, whose quality was evaluated by sensory characteristics, pH value, color value, and muscle structure. The fish bone softening rate measuring method was established according to the sensory evaluation and TPA analysis of the standard fish bone samples. The optimal process conditions of U-CA treatment were obtained by evaluating the bone softening rate. Finally, SEM and FTIR were used to analyze the mechanism of fish bone softening of U-CA treatment. The results showed that the fishbone softening rate measuring method we designed can easily and objectively evaluate the degree of fish bone softening in ready-to-eat fish products. After the evaluation of the bone softening rate, sensory evaluation, and other quality indexes, the optimal U-CA treatment conditions were: acetic acid concentration at 1.2% (V/V), ultrasonic power at 120 W, and processing time of 45 min. The fish pieces obtained under these conditions had better bone softening rate, color, texture, and taste. The results of SEM and FTIR showed that U-CA treatment under the optimal process conditions could weaken the bind between collagen and hydroxyapatite, and contribute to the escape of hydroxyapatite. Heat treatment may also disrupt the triple-helical structure of collagen and reduce the hardness and toughness of fish bones. It was shown that U-CA treatment under appropriate conditions could disrupt the original structure of fish bones and effectively soften the fish bones in C. idella pieces without affecting the quality of the product. This study provides ideas for the development of freshwater fish bone softening technology and theoretical support for the development of ready-to-eat fish.

• Optimization and validation of spiral staged drying process for Euphausia superba meal

  OUYANG Jie, MA Jingsong, MA Tiantian, HUANG Tian, SHEN Jian

  2024,48(7):079814-079814, DOI: 10.11964/jfc.20240414494

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  Abstract:

  Antarctic krill (Euphausia superba) meal is one of the most important processed products of E. superba, and its quality iscritical to the quality of the subsequent shrimp oil and other deep processing products. However, in the yield and quality of E. superba meal processing, there is still a big gap between China and leading countries in the E. superba industry such as Norway. Spiral drying has the advantages of autonomously pushing material and reducing the accumulation of materials, suitable for E. superba drying; compared to constant temperature drying, staged drying process can consider the drying efficiency and energy consumption, and can effectively ensure the stability of product quality. In order to optimize the spiral drying process parameters of E. superba powder and obtain a high quality and efficient drying process of E. superba meal, the staged drying process of E. superba was studied by using spiral drying equipment, and the optimum experiment was designed on the basis of Box-Behnken experimental design principle based on single factor experiment. The effects of the first stage drying temperature, the switch node and the second stage drying temperature on the drying time, the content of fat and astaxanthin were studied. The results showed that the order of influence of different factors on drying time and astaxanthin content was first stage drying temperature (A) > second stage drying temperature (C) > stage switching moisture (B), and the order of influence on fat content was stage switching moisture (B) > first stage drying temperature (A) > second stage drying temperature (C). Response surface obtained the optimal process parameters for the first stage drying temperature at 105 °C, stage switching moisture of 50%, the second stage drying temperature of 88 °C. Under this condition, drying time, fat and astaxanthin content were 160 min, 16.83%, and 159.32 μg/g, respectively; the quality of the E. superba meal under the spiral staged drying were better than that of spiral constant temperature drying. The study shows that the use of an optimized spiral drying process can effectively improve the quality of shrimp meal while ensuring drying efficiency. This study can provide technical references for the high-quality production of E. superba and E. superba meal shipboard processing technology and the development of localization of key equipment.

• Expression and properties of an endo-1,3- fucoidanase in Lactobacillus

  LI Xinyu, CHEN Guangning, SHEN Jingjing, CHEN Huanhuan, XUE Changhu, CHANG Yaoguang

  2024,48(7):079815-079815, DOI: 10.11964/jfc.20240414496

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  Fucoidan is a marine polysaccharide with diverse physiological activities. Endo-1,3-fucoidanase is a favorable tool for the preparation of fucooligosaccharides. Nevertheless, the lack of food-grade fucoidanase with clear cleavage sites has hindered its application. This study aimed to obtain a food-grade endo-1,3-fucoidanase from GH174 family (Fun174Sb) and to investigate its cleavage site. The study demonstrated that the food-grade expression of Fun174Sb could be achieved through the Lactobacillus NICE system. Fun174Sb exhibits significant endo-acting hydrolysis activity towards fucoidan from Holothuria tubulosa (Ht-FUC), with an enzymatic activity of 1.90 U/mL. Fun174Sb showed significant activity within a temperature range of 35-50 °C and a pH range of 7.5-8.5, and it possessed good temperature and pH stability. Furthermore, the structure of the dominant oligosaccharide in the enzymatic product was analyzed using ultra performance size exclusion chromatography-mass spectrum (UPSEC-MS) and nuclear magnetic resonance (NMR). It could be inferred that Fun174Sb cleaves the α-1,3-glycosidic bond between Fucp2 (OSO₃^-) and Fucp2,4 (OSO₃^-) in Ht-FUC. The study showed that Fun174Sb expressed in Lactobacillus exhibited favorable biochemical properties and a clear mode of action. It laid the foundation for the application of food-grade fucoidanase.