Expressible Moisture Research Articles

Effects of Heat Stress on the Muscle Meat Quality of Rainbow Trout

The effects of heat stress on aquatic animals are increasingly being discerned, but little is known about the effects of heat stress on muscle meat quality or the flavor of muscle. This study aimed to evaluate the effects of heat stress on the muscle antioxidant properties, structural and physical properties (e.g., pH, muscle color, shear force, and expressible moisture), chemical composition (e.g., nucleotides, organic acids, amino acids, and minerals), and volatile substances of rainbow trout. We observed that the antioxidant capacity of muscle decreased after stress experiments at 22.5 °C for 24 h. The content of inflammatory factors notably increased (p < 0.05), the pH value and red value of muscle decreased (p < 0.05), the interfiber space increased, and several muscle fibers were broken. Heat stress changed the contents of nucleotides, organic acids, minerals, and amino acids in muscle. The contents of IMP and AMP, which play an important role in the flavor of muscle, decreased (p < 0.05). The contents of two amino acids that provide a sweet taste decreased; those of five amino acids that provide a bitter taste increased (p < 0.05). Heat stress also affected the amount and type of volatile substances in muscle, which affected muscle odor. These results suggest that heat stress may exert adverse effects on the oxidative stability, structure, meat quality, and flavor of muscle, requiring attention and prevention.

Double Freezing Beef Strip Loin Steaks at Blast or Consumer Freezing Temperatures in Vacuum and Overwrapped Packaging

Our objective was to evaluate the combined effect of blast freezing vacuum packaged USDA Low Choice Longissimus lumborum beef steaks followed by consumer freezing of retail overwrapped steaks upon objective and subjective measures of beef palatability. The experimental design utilized a randomized complete block with a 3 × 3 treatment structure of targeted freezing treatments initially in vacuum and secondly in overwrap packaging (unfrozen = NOT; blast frozen at −34.4°C = BF; consumer-frozen at −17.8°C = CF) to accomplish 9 treatment combinations. Descriptive sensory attributes were evaluated by trained panelists on a 100-point line scale. Slice shear force and expressible moisture were assessed. Data were analyzed via PROC GLIMMIX using a randomized complete block design with a 3 × 3 treatment structure. Of descriptive panel attributes, overall juiciness was the only interaction observed (P = 0.006). Though similar to steaks initially CF in the vacuum package and followed by a second freeze (CF/BF or CF/CF) in the overwrap package, steaks singly frozen to simulate a CF (CF/NOT and NOT/CF) resulted in the overall driest ratings by panelists (P = 0.006). Only bloody/serumy differed (P = 0.002) within the initial freeze, where steaks not frozen (NOT) in the vacuum package were rated higher than those that were frozen (BF or CF). During the second freeze in the overwrap package after retail display, steaks BF rated higher for oxidized (P = 0.051) off-flavor than steaks CF and higher than both CF and NOT steaks for refrigerator-stale (P = 0.006) off-flavor; all other attributes did not differ (P ≥ 0.155). Although some freezing combinations that included CF were generally lower for overall juiciness, BF vacuum packaged steaks had no effect on palatability when compared to NOT steaks. The beef industry and consumers should feel confident using freezing as a means to extend shelf-life of beef steaks.

Karakteristik Gel Surimi Ikan Bulan-Bulan (Megalops Cyprinoides) Terhadap Frekuensi Pencucian

The washing of fish meat in the manufacture of surimi is carried out to remove water-soluble components in order to obtain myofibrillar protein concentrate which plays an important role in the formation of surimi gel. This study aims to determine the frequency of washing that is able to produce the best surimi gel characteristics in Indo-Pacific Tarpon fish (Megalops cyprinoides). This study used a completely randomized design (CRD) with 4 washing frequency treatments and 3 replications. Parameters observed were proximate composition, gel strength, whiteness, and expressible moisture content. The frequency of washing had an effect on the characteristics of the fish surimi gel (p0.05) with the highest surimi gel strength in the one-wash treatment which had a load max value of 68.36±0.74 kg/cm2. The frequency of washing affects the gelling ability of this surimi.

Effect of pretreatment temperature and time on fat bonding and fat reduction in deep-fried surimi

Deep frying (DF) is a popular cooking technique resulting in desirable sensory quality. However, DF also results in negative perception related to increased fat uptake and thus poor nutritional quality. In this study, a development of a novel strategy for fat reduction in DF surimi without additives and coatings was attempted. Novel pre-baking and pre-roasting were applied to surimi prior to DF. This novel pre-treatment strategy for DF surimi has not been reported in literature. Total, free, and bonded fat contents and corresponding fat reductions in DF surimi were determined. Cook and moisture losses as well as water holding capacity, expressible moisture, in addition to color and texture were also investigated. Fat uptake during DF of surimi was reduced (P < 0.05) by ≥ 25 % with pre-baking. Pre-baking improved (P < 0.05) or did not (P > 0.05) affect cook and moisture losses, water holding capacity, expressible moisture, color, and texture. However, pre-roasting increased (P < 0.05) fat content and adversely affected most quality parameters. Pre-baking of surimi at lower-temperature (116 °C) for longer-time (12–15 min) followed by DF at lower-temperature (170 °C) for longer-time (4 min) was most optimal for fat reduction, cook and moisture losses, water holding capacity, expressible moisture, color, and texture of surimi.

Effect of Faba Bean Isolate and Microbial Transglutaminase on Rheological Properties of Pork Myofibrillar Protein Gel and Physicochemical and Textural Properties of Reduced-Salt, Low-Fat Pork Model Sausages.

The study was performed to determine the effect of faba bean protein isolate (FBPI) alone or in combination with microbial transglutaminase (MTG) on the rheological properties of pork myofibrillar protein gel (MPG), and physiochemical and textural properties of reduced-salt, low-fat pork model sausages (LFMSs). The cooking yields of MPGs with MTG or FBPI alone decreased and increased, respectively. However, the combination of FBPI and MTG was similar to the control (CTL) without FBPI or MTG. Gel strength values of MPG added with both FBPI and MTG were higher than treatments with FBPI or MTG alone. The hydrophobicity values of CTL were lower than those of MPG with FBPI alone, whereas the addition of MTG decreased the hydrophobicity of MPGs. The incorporation of FBPI alone or in combination with MTG decreased sulfhydryl groups (p<0.05). Shear stress values of MPGs with MTG tended to be higher than those of non-MTG treatments at all shear rates, and the addition of FBPI into MPGs increased shear stress values. Reduced-salt (1.0%) LFMSs with FBPI alone or combined with MTG had both lower cooking loss and expressible moisture values than those of CTL and similar values to the reference sample (REF, 1.5% salt). Textural properties of reduced-salt LFMSs with FBPI or MTG were similar to those of REF. These results demonstrated that the combination of FBPI and MTG could improve the water binding capacity and textural properties of pork MPGs and LFMSs and might be suitable for application in the development of healthier meat products.

Effects of faba bean protein isolate on rheological properties of pork myofibrillar protein gels and quality characteristics of pork low-fat model sausages.

This study aimed to assess the effect of faba bean (Vicia faba L.) protein isolate (FBPI) on the rheological properties of pork myofibrillar protein gels (MPGs) and the quality characteristics of pork low-fat model sausages (LFMSs). Pork MPGs with 5 or 10 g kg-1 FBPI had higher cooking yield, gel strength, and viscosity than controls. The addition of FBPI to MPGs increased the protein surface hydrophobicity and decreased sulfhydryl groups. Adding FBPI to MPGs changed the protein profile and microstructure. The cooking loss and expressible moisture of LFMSs with 5, 10, or 15 g kg-1 FBPI were lower than those of controls and showed similar results to those with 15 g kg-1 soy protein isolate (SPI). Hardness values of LFMSs with FBPI and SPI were no different, and were higher than those of controls. The addition of FBPI potentially improves rheological properties of MPGs and the functional properties of LFMSs, including water-holding capacity and textural properties. © 2024 Society of Chemical Industry.

Texture improvement and in vitro digestion modulation of plant-based fish cake analogue by incorporating hydrocolloid blends

Hydrocolloids have proven effective in improving the texture of surimi gels, yet their application in plant-based seafood analogues remains underexplored. This study aimed to develop a hydrocolloid blend comprising methylcellulose (MC), curdlan gum (CG), and high-acyl gellan gum (GG) to achieve a surimi-like texture in plant-based fish cakes (PBFC) made from brown rice and pea protein isolates. The research showcased that higher MC concentration boosted protein powder's heated oil holding capacity, while CG concentration increments lowered it. However, heated water holding capacity remained stable despite changes in MC and GG levels. Incorporating hydrocolloids elevated PBFC moisture content, decreasing expressible moisture and oil amounts with rising MC, CG and GG concentrations. PBFC hardness increased with higher hydrocolloid levels and was influenced by temperature, while springiness remained unaffected. GG helped maintain storage modulus (G′) during PBFC cooling at higher concentrations, whereas the opposite effect was observed for MC. Analytically, higher MC concentrations reduced protein digestibility, while increased GG concentrations appeared to enhance it. Microstructural analysis corroborated these findings, with more protein aggregates in PBFC containing 3.8% MC and fewer in PBFCs with 6% CG and 3% GG. Consumer evaluations indicated that PBFC formulated with 1% MC, 3% CG, and 1.5% GG matched the springiness of commercial surimi-tofu fish cake, though it received slightly lower overall liking scores. In conclusion, the combined use of these three hydrocolloids demonstrated the potential to enhance the physical properties of PBFC and modify protein digestibility, offering insights into the development of innovative plant-based seafood analogues.

Gelling characteristics of fish surimi gel added with calcium hydroxyapatite (HAp)

Surimi is widely used as the main ingredient for various innovative seafood products (ISP), e.g., imitation crab meat, fish balls, fish sausage, kamaboko, fish sticks, and paupiette. Sodium chloride (NaCl), a primary ingredient of surimi, plays an important role in gelling and flavor. A reduced-NaCl product is preferred by consumers due to health-related reasons. This study focuses on evaluating the gelling characteristics of fish surimi gel formulated with different levels (0.5, 1, and 1.5%) of calcium hydroxyapatite (HAp). Surimi gel added with HAp showed a good gel-forming ability (p<0.05). The texture profile analysis indicated an acceptable value. As for the water-holding capacity (76.88%), the highest value (p<0.05) was recorded for 1% of HAp addition. On the contrary, the cooking loss (21.09%), expressible moisture content (23.48%), and whiteness index (70.20) for samples with 1% HAp were the lowest compared to other samples. This preliminary finding suggests that the addition of calcium HAp at 0.5 to 1% could be an alternative ingredient to NaCl for maintaining gelling characteristics of surimi. It also adds nutritional value to the product. This finding could be a reference to the industry in improving the processing of surimi-based products.

Nutrification and fat reduction of deep-fried protein isolates

Deep-fried (DF) foods are considered nutritionally-inferior due to increased fat content, although they are popular with consumers due to desirable sensory characteristics. This study attempted to reduce fat of DF surimi, DF fish-protein-isolate (FPI), and DF chicken-protein-isolate (CPI) by pre-baking or pre-roasting. Surimi, FPI, and CPI were also nutrified with ω-3-rich oil, fiber, and KCl-based salt substitute. Pre-baking decreased (p < 0.05) fat content, while pre-roasting increased (p < 0.05) it. Pre-baking resulted in less (p < 0.05) changes to cook loss, moisture loss, expressible moisture, water-holding-capacity, whiteness, and texture when compared to pre-roasting. Pre-baking also better maintained ω-3 PUFAs concentration than pre-roasting, resulting in higher (p < 0.05) concentration of α-linolenic (ALA, 18:3ω3), eicosapentaenoic (EPA, 20:5ω3), and docosahexaenoic (DHA, 22:6ω3) FAs as well as unsaturated FAs and total ω-3 FAs in DF surimi, DF FPI, and DF CPI. Pre-baking in combination with nutrification using ω-3 PUFAs improved nutritional value of DF foods, while causing minimal quality changes.

The Effect of Fermented Grains (koji) on Physicochemical and Sensory Characteristics of Chicken Breasts.

This study investigated the tenderizing and flavor-enhancing effects of koji, a fermented grain cultured with a single microorganism, on chicken breasts during curing. Chicken breasts were cured with different ingredients, including 4% (w/w) curing agent (GC), 5% (w/w) Aspergillus oryzae with rice (FR), A. oryzae with soybean (FS), and Bacillus subtilis with soybean (BS) for 4 h at 4 °C prior to cooking. After the superheated steam procedure, all samples were cooked in a convection oven, and their physicochemical properties were analyzed. Koji-treated samples exhibited significantly higher expressible moisture due to the degradation of the protein matrix (p < 0.05). Texture profile analysis showed that the tenderness of koji-treated samples was significantly higher than that of GC (p < 0.05). Furthermore, koji-treated samples were regarded as tenderer, and they were preferred over GC (p < 0.05) in the sensory evaluation. Principal attributes analysis revealed that the overall preference for koji-treated samples was highly correlated with umami, juiciness, and tenderness (p < 0.05). Overall, this study provides insights into applying koji as a potential curing treatment to improve the eating quality of chicken breasts. Koji can be used as a novel technology in the food industry to improve taste and tenderness simultaneously.

Incorporation of microalgae (Nannochloropsis oceanica) into plant-based fishcake analogue: Physical property characterisation and in vitro digestion analysis

This study examined how incorporating microalgae into plant-based fishcake (PFC) analogue affected its physical properties and in vitro digestive profiles. PFCs were prepared using pea protein isolate blended with varying amounts of defatted Nannochloropsis oceanica biomass. Increasing the concentration of N. oceanica (up to 30%) progressively influenced the texture and rheological properties of PFC: the hardness and gel strength of PFC significantly increased, while springiness, expressible moisture and oil content decreased, making PFC more similar to the surimi-based fishcake. In vitro protein digestibility of PFCs varied with the concentration of N. oceanica: from 59.8% in the control PFC (without N. oceanica) increased to 74.9% with 10% N. oceanica, but only to 70.1% with 30% N. oceanica, which highlighted the role of microalgae concentration on the PFC's digestive profile. Furthermore, the release of metabolites in the PFC samples after in vitro digestion was evaluated using nuclear magnetic resonance (NMR) spectroscopy. The results showed that the digesta of PFC with 30% N. oceanica had reduced levels of most amino acids and linoleic acid, which might have ripple effects on the associated amino acid and fatty acid metabolisms in the human body upon consumption. Overall, the combination of pea proteins and N. oceanica biomass had the potential to contribute to the development of innovative plant-based seafood alternatives with modified physical properties and unique digestive characteristics. This study also provided valuable insights into the bioavailability of nutrients from N. oceanica-incorporated PFC, laying the foundation for their further launch on the market.

Effect of sea tangle extract on the quality characteristics of reduced-salt, low-fat sausages using pre-rigor muscle during refrigerated storage.

The aim of this study was to investigate quality characteristics of reduced-salt, low-fat pork sausage (PS) using pre-rigor muscle and sea tangle extract (STE) to reduce salt level of sausages during refrigerated storage. Pork ham was prepared with pre-rigor and post-rigor muscle from the local market. Sausages using post-rigor muscle were manufactured with the 1.5% of salt content, and samples with pre-rigor muscle were processed by different salt concentrations (0.8%). Accordingly, PSs were prepared in 4 treatments (REF, PS with 1.5% of salt using post-rigor muscle; CTL, PS with 0.8% of salt using pre-rigor muscle; TRT1, PS with 0.8% of salt and 5% of STE using pre-rigor muscle; TRT2, PS with 0.8% of salt and 10% of STE using pre-rigor muscle). For the evaluation of quality characteristics and shelf-life of reduced-salt PS, pH and color values, cooking loss (%), expressible moisture (%), textural properties, lipid oxidation (thiobarbituric reactive substances), protein denaturation (volatile basic nitrogen), and microbiological analysis (total plate counts and Enterobacteriaceae counts) were determined. The pH and temperature of pre-rigor raw pork ham were higher than those of post-rigor pork ham. Hardness of TRT2 was higher than that of REF or CTL. TRT2 had higher gumminess and chewiness than CTL. TRT1 and TRT2 had lower volatile basic nitrogen than CTL. Total plate counts of TRT2 were lower than those of CTL. Expressible moisture values of TRT1 and TRT2 were similar to those of REF. The addition of STE into PS improved functional properties and shelf-life of PS. Reduced-salt PS containing pre-rigor muscle and STE had similar functional properties to those of regular-salt ones, while containing approximately 47% less salt compared to regular-salt level.

The Effects of Okara Ratio and Particle Size on the Physical Properties and Consumer Acceptance of Tofu.

Okara, the solid byproduct of soymilk production, poses a sustainability concern, despite being rich in fiber and other healthful compounds. In this study, the physical properties of tofu made from soymilk fortified with differing levels of okara-either whole or fine (<180 µm)-and made with the traditional coagulant nigari were examined. The yield increased linearly with the okara concentration with values of 18.2-29.5% compared to 14.5% for the control. The initial moisture in the fortified samples was higher than the control (79.69-82.78% versus 76.78%), and both the expressible moisture and total moisture after compression were also greater in the fortified samples. With a few exceptions, the texture parameters did not differ between samples. Dynamic rheology showed that all samples had G' > G″. The storage moduli increased at different rates during each gelling step, with G' before and after gelling increasing with the fortification level, and was greater for the samples with fine particles than with whole particles. Consumer sensory panels using the hedonic scale showed traditional tofu had a slightly higher acceptability, but the panelists indicated they would be more willing to purchase okara-fortified tofu because of the health and sustainability benefits it might have. Thus, tofu could be produced with added okara with predictable but not profound changes in its physical properties.

Textural and Consumer-Aided Characterisation and Acceptability of a Hybrid Meat and Plant-Based Burger Patty.

The hamburger has been targeted for substitution by numerous plant-based alternatives. However, many consumers find the taste of these alternatives lacking, and thus we proposed a hybrid meat and plant-based burger as a more acceptable alternative for these consumers. The burger was made from 50% meat (beef and pork, 4:1) and 50% plant-based ingredients, including texturised legume protein. Texture and sensory properties were evaluated instrumentally and through a consumer survey (n = 381) using the check-all-that-apply (CATA) method. Expressible moisture measurements indicated a significantly juicier eating experience for the hybrid compared to a beef burger (33.5% vs. 22.3%), which was supported by the CATA survey where "juicy" was used more to describe the hybrid than the beef burger (53% vs. 12%). Texture profile analysis showed the hybrid burger was significantly softer (Young's modulus: 332 ± 34 vs. 679 ± 80 kPa) and less cohesive than a beef burger (Ratio 0.48 ± 0.02 vs. 0.58 ± 0.01). Despite having different textural and CATA profiles, overall liking of the hybrid burger and a beef burger were not significantly different. Penalty analysis indicated that "meat flavour", "juiciness", "spiciness" and "saltiness" were the most important attributes for a burger. In conclusion, the hybrid burger had different attributes and was described with different CATA terms than a beef burger but had the same overall acceptability.

Process optimization and evaluation of the effects of different time-temperature sous vide cooking on physicochemical, textural, and sensory characteristics of whiteleg shrimp (Litopenaeusvannamei)

The objective of the current study was to optimize the cook-chill conditions of high-value whiteleg shrimp (Litopenaeus vannamei) processed using the sous vide (SV) technique and to assess the effects of various time-temperature combinations on the physicochemical, textural, and sensory qualities. For optimization, a Response Surface Methodology (RSM) approach utilizing a Central Composite Design (CCD) was adopted. Optimum SV cooking conditions to acquire minimum texture (hardness) of 7235 g was 13.48 min and 81.87 °C, expressible moisture of 18.48% was 14.5 min and 84.5 °C, and cook loss of 5.58% was 5 min and 75 °C. Texture (hardness) and expressible moisture decreased while cooking loss increased with increasing time-temperature treatment. Redness and yellowness values increased (p < 0.05) with increasing SV cooking time-temperature, but lightness values were nearly consistent in all treatments. With increasing time and temperature, TBARs and total carotenoid content increased (p < 0.05). However, the TBARs values were within accepted limits and ranged from 0.05 to 0.08 mg malonaldehyde/kg. Sensory evaluation indicated that all SV cooked samples were well accepted, with overall scores ≥7. These results suggest that the SV cooking temperature and time had a substantial impact on the textural, physicochemical, and sensory characteristics of shrimp. In addition, increasing time-temperature increased cooking and moisture loss, but decreased hardness and higher sensory scores made the product more acceptable to consumers.

Evaluation of salt level and rigor status on the physicochemical and textural properties of low-fat pork sausages added with sea tangle extract using rapidly chilled pre-rigor pork ham.

This study was performed to evaluate the quality characteristics of pork sausage (PS) with sea tangle extract (STE) and rapid chilled pre-rigor muscle (RCPM) for the development of reduced-salt low-fat sausage. Pre- and post-rigor pork ham muscles were prepared to process PSs. Positive control (reference, REF) using post-rigor muscle were manufactured at a regular-salt level of 1.5%. Fresh and rapid-chilled pre-rigor muscle (FPM and RCPM) were used to manufacture reduced-salt sausages with 0.8% salt. Reduced-salt PSs were prepared with four treatments: FT1 (FPM alone), FT2 (FPM with 5% STE), RT1 (RCPM alone), and RT2 (RCPM with 5% STE). The physicochemical and textural properties of the sausages with reduced-salt levels and RCPM combination were measured to determine if the characteristics of RCPM were similar to those with FPM. The pH values of PS with FPM and RCPM were higher than those of REF with post-rigor muscle. Color values (L*, a*, b*) were not affected by different rigor-states and salt addition level. Textural properties of reduced-salt PSs were similar to those of REF due to the improved functionalities of pre-rigor muscle. RT2 had lower expressible moisture (%) than other treatments with post-rigor muscle and RCPM except for RT1. The addition of STE and RCPM to reduced-salt PS increased the waterholding capacity, which was lower than those of PS with STE using RCPM but similar to those of regular-salt sausage.

Gelation properties of silver carp (Hypophthalmichthys molitrix) surimi as affected by phenolic compounds in lotus root knot extract

ABSTRACT The objective of this study was to investigate the effects of aqueous extract of lotus root knot (AELRK) on the gel characteristics of silver carp surimi. Gel strength, storage modulus, and disulfide bond of surimi gels were significantly increased with the addition of the AELRK (p < 0.05), especially at 10% AELRK (p < 0.05), where gel strength and disulfide bond were enhanced by 14.7% and 41.6%, respectively, but decreased in expressible moisture content, ionic bond, hydrogen bond and hydrophobic interaction. Adding 10% AELRK could enhance cross-linking degree surimi gels with the denser and smoother microstructure. There was the reduction in myosin heavy chain but not significant change in actin. More addition of the AELRK significantly decreased in L* and whiteness of surimi gels (p < 0.05) but increased in a * . Therefore, there would be a potential to utilize the phenolic compounds from lotus root to improve the quality of silver carp surimi.

Deterioration of muscle quality caused by ammonia exposure in rainbow trout (Oncorhynchusmykiss)

In order to explore deterioration of muscle quality caused by ammonia exposure in rainbow trout (Oncorhynchus mykiss), and then preliminarily investigating the regulatory mechanism of muscle quality in O. mykiss after ammonia exposure based on the lipid metabolism, different concentrations of ammonia stress experiment were conducted, and the physicochemical properties of muscle, antioxidant system, products of energy and lipid metabolism were investigated at total ammonia concentration of 0 (control group), 10 mg/L (T1), 20 mg/L (T2), 30 mg/L (T3), 45 mg/L (T4) and 60 mg/L (T5). In comparison with the control group, the fillets after ammonia stress exhibited higher a* value, expressible moisture, essential amino acids (EAA), the bitter amino acid and mono-saturated fatty (MUFA), less the umami and sweet amino acids and polyunsaturated fatty acid (PUFA), worse flavor and taste. The lower ammonia exposure (lower than 30 mg/L) did not change the content of EPA and DHA while significant decreases were observed after higher ammonia exposure (higher than 30 mg/L). Meanwhile, the lower ammonia exposure activated the antioxidant system and higher ammonia exposure inactivated antioxidant enzymes to defend against reactive oxygen species (ROS). Moreover, the expression of d9D, FAS, LPL, PPARa, PPARy and SREBP were inhibited and the expression of CPT1 was promoted after ammonia stress, inhibiting lipid synthesis and promoting lipid oxidation. The results are important in establishing the relationship among muscle quality, lipid metabolism and the environmental adaptability of rainbow trout (O. mykiss).

Effects of hypoxia on meat qualities and muscle metabolism in rainbow trout (Oncorhynchus mykiss) during short-time transportation and its relief by reoxygenation

For rainbow trout, hypoxia usually occurs during transportation and leads to deterioration of meat qualities. Hence, the study aimed to investigate the impacts of hypoxia during short-time transportation on the muscle quality of rainbow trout and its relief attempt by reoxygenation. In comparison with the sample without hypoxia (CG), the fillets from sever hypoxic trout (SHG) exhibited lower shearing force (SF), a⁎, saturated fatty acid content and delicious amino acids, and higher expressible moisture, Metmyoglobin (MetMb) and essential amino acids content. After subjected to reoxygenation for 24 h, the muscle qualities of trout recovered to the level of CG, except for expressible moisture and tissue structure. Metabolomic analyses indicated that hypoxia led to the up-regulation of succinate, xanthine, adenine and down-regulation of 15(S)-HETE ((15S,5Z,8Z,11Z,13E)-15-Hydroxyeicosatetraenoic acid). And the reoxygenation promoted glycine and serine biosynthesis, thiamine and cysteine metabolism and inhibited succinate accumulation, thus relieved the hypoxia. This work suggested that reoxygenation for 24 h was an effective action to relief the quality deterioration of rainbow trout fillets induced by hypoxia.

Effect of Swamp Eel (Monopterus albus) Plasma on The Quality of Tilapia (Oreochromis mossambicus) Surimi

The effects of crude plasma and ethanol-extracted of swamp eel plasma at different concentrations (0, 0.25, 0.5, 0.75, 1, 1.5, 2 mg/g) as inhibitor protease in the quality of tilapia (Oreochromis mossambicus) surimi were investigated. The parameters analyzed were gel strength, expressible moisture, whiteness, microstructure, protein solubility, hydrolysis pattern of surimi by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, percent inhibition, and zymogram. The results showed that ethanol-extracted plasma could maintain gel strength, expressible moisture, microstructure, protein solubility, and percent inhibition in lysis of tilapia surimi from protease activity that caused formation of modori structure better than crude plasma. The whiteness decreased as the concentration of plasma used increased. SDS-PAGE for hydrolysis pattern analysis showed that the effectiveness of crude plasma as a protease inhibitor decreased as the concentration increased. There was an increase in the inhibition of protease in the ethanol-extracted plasma at a concentration of 1.5 mg/g. It suggested that the crude plasma contained an internal protease enzyme that might interfere with the reduced myosin intensity.