Total Volatile Basic Nitrogen in Meat and Brine During Marinating of Herring

ABSTRACT

The content of total volatile basic nitrogen (TVB-N) is highly determined by the variety of raw material, freezing, salt, and acetic acid concentrations, and therefore the effect of these factors on marinated herring quality was determined in this study. A higher TVB-N content was determined in marinades from fillets than from carcasses and from frozen than fresh herrings. An increase in salt concentration from 5 to 15% reduced the content of TVB-N to a greater extent than the increase in acid concentration from 3 to 8%. However, the increase in salt concentration above 11–13% or of acid above 5% in brine did not result in any significant decrease of meat TVB-N value. The brine TVB-N content was significantly correlated with meat TVB-N and was higher than in meat. The best freshness indicators were NH₃-N and tyrosine in brine, which can be deemed more universal indicators of the freshness of marinated herring meat. The diffusion from meat to brine was found to significantly decrease the meat TVB-N value and potentially increase marinated meat quality. Therefore, the removal of TVB-N from fish, via changing the brine several times, may be a better option than increasing the concentration of salt/acetic acid in marinating brine.     

Proteolytic and Sensory Changes During Marination of Rainbow Trout (Oncorhynchus mykiss) Flesh in Pomegranate Juice

Suitability of pomegranate juice (PJ) alone or mixed with acetic acid versus acetic acid control solution, a traditional fish marinating media, was investigated in this research. With that purpose, rainbow trout fillets were marinated for 12 days at 4°C in one of three different marinating solutions: 100% acetic acid solution (AAS), 50% acetic acid/50% pomegranate juice solution (AAPJS), and 100% pomegranate juice solution (PJS). Moisture content and pH value of rainbow trout flesh decreased, whereas fat, protein, ash, and salt contents increased at the end of the marinating process for all treatments (p < 0.05). Fish flesh marinated in solution containing PJ had darker, more red and lower yellow color values due to migration of color components from the PJ (p < 0.01). Traditionally marinated fish flesh had the highest total free amino acid amount (p < 0.01) due to a higher level of proteolytic breakdown under the low pH condition, which could be seen on sodium dodecyl sulfate polyacrylamide gel electrophoresis image. This treatment also had higher sensory scores than those of fish marinated in solution containing 50% or 100% PJ. In addition, fish marinated in AAPJS and PJS solution had firmer texture and sweeter taste compared to that of marinated in AAS.     

Rapid Multiparameters Approach to Differentiate Fresh Skinless Sea Bass (Dicentrarchus labrax) Fillets from Frozen-Thawed Ones

Food authenticity is one of the major issues in the mind of today’s consumers. The sale of frozen-thawed fish fillets under the “fresh fillet” label is considered as a commercial fraud. However, their close sensory properties complicate the differentiation. This study focused on analyzing the composition of exudate (pressured flesh juice) in order to rapidly differentiate between fresh and frozen-thawed skinless fillets of sea bass (Dicentrarchus labrax). Protein concentration, α-D-glucosidase specific activity, nucleotides and related compounds (NRCs) concentration, and free calcium concentration were measured in exudates corresponding to fresh or frozen-thawed sea bass fillets. Significant increases of these four parameters were observed in exudates from frozen-thawed fillets, especially with a twofold increase in NRCs and free calcium concentrations. These results suggest that NRCs and free calcium concentrations can be promising indicators to rapidly detect mislabeling of fresh fillets.     

Autodigestion and Peptidase Activity in Low Quality Baltic Sprat (Sprattus sprattus balticus Schneider, 1908)

This study was conducted on fresh and frozen-thawed sprat of the lowest utility, which is not used for consumption. The peptidase activity was measured (i) against acid- and base-hemoglobin (GPA) and as (ii) autodigestion with an effect of NaCl concentration in the range of 5–30% and a pH effect in the range of 3.5–8.0. The activity has been shown to be divided into endo and exopeptidases. The optimum endopeptidase activity in whole fresh fish was observed at pH 8.0, whereas for exopeptidases it was observed at 5.0. Under acidic conditions, the activity of endopeptidases from intestines was the same as that from carcasses, but under basic conditions, it was over 130 times higher. After freezing the sprat, the GPA was higher than in fresh spat. The increase in GPA was significant especially for endopeptidases. Freezing also affected the activity of endo and exopeptidases. The addition of 5% salt to the whole fresh sprat caused an increase in endopeptidase activity, but higher NaCl concentrations decreased it. At 20% concentration, the endopeptidase activity was almost 20 times lower than that at 5% salt. The salt concentration did not significantly affect the sprat exopeptidase activity. Sprat with the lowest utility has high peptidase activity and can produce hydrolysates used in food technology.     

水溶性壳聚糖对鱼糜制品保鲜效果的影响

研究了添加不同质量分数的水溶性壳聚糖对鱼糜制品冷藏保鲜效果的影响。以感官评分、菌落总数、挥发性盐基氮（TVB-N）、硫代巴比妥酸（TBA）和pH为指标,考察鱼糜制品在4℃冷藏过程中的品质变化。结果表明,水溶性壳聚糖能够明显抑制细菌的生长与繁殖,阻止感官品质的下降,延缓TVB-N和TBA的上升。其中,添加2.0%的水溶性壳聚糖保鲜效果最佳,与空白组相比,能将鱼糜制品的冷藏保鲜期从9 d延长至13～14 d。     

Impact of marination,pre‐harvest salt acclimation and sodium chloride concentration on the sensory acceptability of freshwater prawn,Macrobrachium rosenbergii

This study was conducted to evaluate the consumer acceptability of post‐harvest freshwater prawns marinated in salt solutions (0.5%, 1%, 1.5% and 2% NaCl in the cooked product), and to compare the sensory acceptability of these treatments against prawns that had been salt acclimated pre‐harvest while still alive. The salt‐acclimated prawns were transferred to 250‐L tanks containing 10 ppt solar salt (NaCl with small concentrations of CaCl₂ and KCl). Salts were increased by 5 ppt in 2 h increments until 30 ppt was reached. After 18 h of salt acclimation, prawns were chill killed. Prawns that were used for post‐mortem marination treatments were transferred to 250 L tanks with freshwater for 18 h prior to harvest and post‐mortem marination. Two consumer‐based sensory tests were conducted (n = 102). Results indicate that flavour, texture and overall acceptability of prawns increased (P < 0.05) as the salt concentration increased from 0.5% to 1.5% in marinated prawns. In addition, marinated prawns that contained 1% sodium chloride after cooking did not differ (P > 0.05) in acceptability when compared to salt acclimated prawns which contained 0.5% sodium chloride in the cooked product. The salt‐acclimated product was preferred (P < 0.05) over the 0.5% salt marination treatment, although they did not differ in final salt concentration. This indicates that salt acclimation enhanced product acceptability through increased salt concentration as well as due to the salt acclimation process, thus lowering the amount of sodium chloride that was necessary to enhance product acceptability.     

Effects of Feeding High Monounsaturated Sunflower Oil Diets on Sensory Attributes of Salmonid Fillets

The purpose of this study was to determine if substituting high oleic acid sunflower oil for herring oil in formulated salmonid diets affected sensory attributes of fillets from coho salmon (Oncorhynchus kisutch) and rainbow trout (Oncorhynchus mykiss). Two feeding trials were conducted in which coho salmon and rainbow trout were fed diets containing either high oleic acid sunflower oil or herring oil as the supplemental lipid source (12.4% of the diet by weight) for 6-8 weeks. In standard directional triangle tests on previously frozen rainbow trout and coho salmon fillets stored at 5¦C for up to 10 days, a significant number of panelists were able to differentiate between fillets from the two dietary treatments based on aroma, and determined that the herring oil fillets had a ôfishierö aroma than the sunflower oil fillets. The panelists tended to prefer rainbow trout fillets from the sunflower oil treatment to fillets from the herring oil dietary treatment. These results suggest that increasing the monounsaturated fatty acid level in fish by feeding a high monounsaturated fatty acid finishing diet could potentially decrease oxidative rancidity, a major cause of quality deterioration in aquatic food products, and thereby improve the shelf life and sensory characteristics of the fillets.     

Effects of Chitosan Coatings Enriched with Different Antioxidants on Preservation of Grass Carp (Ctenopharyngodon idellus) During Cold Storage

To investigate the effects of chitosan composite coatings for maintaining the quality of grass carp portions, indictors of microbiology (total bacteria count, TBC), chemistry (pH; total volatile basic nitrogen, TVB-N; 2-thiobarbituric acid, TBA; K-value), and sensory characteristics were analyzed periodically. The results showed that chitosan (1.5%, w/v) + acetic acid (1.0%, v/v) + tea polyphenol (TP, 0.5%, w/v) coating significantly (p ≤ 0.05) reduced growth of microorganisms as reflected in TBC, lipid oxidation as displayed in TBA, chemical spoilage as reflected in pH, TVB-N, K-value, and sensory characteristic scores compared to the control samples. The effect of chitosan (1.5%, w/v) + acetic acid (1.0%, v/v) + vitamin C (VC, 0.5%, w/v) coating was better than chitosan (1.5%, w/v) + acetic acid (1.0%, v/v) coating. Chitosan together with acetic acid and TP can be used as a type of preservative coating for grass carp portions under chilled storage.     

罗非鱼碎肉酶法制备蛋白胨的工艺研究

为探讨罗非鱼碎鱼肉酶法制备蛋白胨的加工工艺,采用正交试验的方法,分别研究了木瓜蛋白酶、AS.1398中性蛋白酶、复合蛋白酶水解罗非鱼碎肉制备蛋白胨的工艺条件。结果表明:木瓜蛋白酶的最佳水解工艺条件为pH6.5,温度65℃,水解时间4h,加酶量1250 U/g,蛋白胨得率达12.63%;AS.1398中性蛋白酶最佳水解工艺条件为pH 7.5,温度55℃,水解时间4 h,加酶量750 U/g,蛋白胨得率达13.25%;复合蛋白酶的最佳水解工艺条件为pH 7.0,温度50℃,水解时间4.5 h,加酶量850 U/g,蛋白胨得率达11.43%。     

Opportunities for the Herring Industry to Optimize Operations Through Information Recording,Effective Traceability Systems,and Use of Advanced Data Analysis

ABSTRACT

Two case studies of the herring industry reveal that insufficient data on processes and traceability are currently recorded onboard fishing vessels, at primary processing into marinated herring fillets and at secondary processing into small jars as pickled herring products. This means that the traceable unit of a batch of herring is at the level of a whole fishing trip, and that there is a disconnection in traceability along the chain. Data on process and product parameters are insufficient and precludes the use of modern data analysis to examine where improvements and greater efficiencies can be obtained. Suggestions and procedures to overcome these deficiencies are outlined and discussed.     

Production of Fish Sauce and Acceleration of Sauce Fermentation Using Proteolytic Enzymes

The effect of addition of trypsin and chymotrypsin (0.3%, w/w) at various proportions (100:0, 50:50, and -0:100) was investigated to accelerate fish sauce fermentation using herring as raw material. Results showed that supplementations with trypsin and chymotrypsin significantly increased protein hydrolysis (P<0.05). Fish sauce prepared form herring with enzyme supplementation contained significantly more total nitrogen, soluble protein, free amino acid content and total amino acid content compared to fish sauce with no added enzyme (P<0.05). Supplementation with tryspin and/or chrymotrypsin mixture *ratios 50:50 and 0:100) enzyme produced the most favorable results in term of protein hydrolysis, while there was no difference among enzyme treated sauce in term of free amino acid composition. With the exception of the amino acid profile, and microbiological composition compared to Nampla, a first grade commercially produced Thai fish sauce. Sensory analysis of products for color, flavor and aroma indicated that panelist preferred the lighter colored fish sauce prepared with enzyme supplementation compared to the darker colored commercially produced Nampla. However, There was no significant preference (p<0.05) for aroma and flavor of the enzyme supplemented sauce or Nampla. The results of this stuffy indicate that an acceptable fish sauce product can be produced form herring and the addition of enzymes has the potential to reduce the fermentation time to --2 months without compromising product quality.     

Does Ralstonia eutropha,rich in poly‐β hydroxybutyrate (PHB), protect blue mussel larvae against pathogenic vibrios?

The natural amorphous polymer poly‐β‐hydroxybutyrate (PHB‐A: lyophilized Ralstonia eutropha containing 75% PHB) was used as a biological agent to control bacterial pathogens of blue mussel (Mytilus edulis) larvae. The larvae were supplied with PHB‐A at a concentration of 1 or 10 mg/L for 6 or 24 hr, followed by exposure to either the rifampicin‐resistant pathogen Vibrio splendidus or Vibrio coralliilyticus at a concentration of 10⁵ CFU/ml. Larvae pretreated 6 hr with PHB‐A (1 mg/L) survived a Vibrio challenge better relative to 24 hr pretreatment. After 96 hr of pathogen exposure, the survival of PHB‐A‐treated mussel larvae was 1.41‐ and 1.76‐fold higher than the non‐treated larvae when challenged with V. splendidus and V. coralliilyticus, respectively. Growth inhibition of the two pathogens at four concentrations of the monomer β‐HB (1, 5, 25 and 125 mM) was tested in vitro in LB₃₅ medium, buffered at two different pH values (pH 7 and pH 8). The highest concentration of 125 mM significantly inhibited the pathogen growth in comparison to the lower levels. The effect of β‐HB on the production of virulence factors in the tested pathogenic Vibrios revealed a variable pattern of responses.     

化学冰保鲜非鲫的研究

以纯水冰作对比，研究了分别含有０．１％山梨酸钾和０．５％低分子壳聚糖的冰对非鲫的保鲜效果，感官评定，以及细菌总数，ＴＶＢ－Ｎ和Ｋ值的定量分析结果表明：山梨酸钾冰和ＬＭＷ－Ｃ冰的保鲜效果明显优于纯水冰，其保鲜期比纯水冲中保鲜的非鲫延长６天以上。但是，采用Ｋ值和ＴＶＢ－Ｎ值作鲜度指标所得出的结果有明显差异。     

Production of High Quality Fish Oil by Thermal Treatment and Enzymatic Protein Hydrolysis from Fresh Norwegian Spring Spawning Herring By-Products

There is an increasing demand for omega-3 containing fish oils. By-products from fish fillet production can be utilized for the production of fish oils and be a valuable source of omega-3 for human consumption. The aim of this work was to evaluate industrial processes for production of quality oil for human consumption made from Norwegian spring spawning herring by-products. A mobile production plant was used to compare two industrial processes, thermal treatment (wet rendering) and enzymatic protein hydrolysis, for production of oil from herring by-products immediately after filleting. Results show that high quality herring oil can be produced from fresh by-products. The use of by-products immediately after filleting resulted in a low amount of free fatty acids for all the produced oils (below 0.4%). Thermal treatment at 70°C resulted in an oil with lower oxidation status and higher stability compared to the oils produced by enzymatic protein hydrolysis. Nevertheless, both processing methods gave a crude oil of high quality compared to crude oils on the market.     

Preliminary Results on the Fatty Acid Composition of Freshwater Crayfish, Astacus astacus and Pacifastacus leniusculus, Held in Captivity

The fatty acid compositions of the tail muscle and hepatopancreas of captive noble crayfish Astacus astactus and of signal crayfish pacfastacus leniusculus were investigated. The major fatty acids in the tail muscle of A. astacus were 16:0. 18:ln-7 + 9, 20:4n–6 and 20:5n–3 and the fatty acid composition of hepatopancreas was principally 16:0, 18:In-7 + 9 and 20: ln-9+ 11. These animals had been fed marine fish (sprat and herring) for 2 mo. They were kept in a flowthrough system with gravity-fed fresh water from a nearby lake with a high concentration of calcium and pH above 8. The major fatty acids in the tail muscle of P. leniusculus were 16:0. 18:ln-7+9, 18:2n–6 and 20:5n–3, and in the hepatopancreas 16:0, 18:1n–7 + 9 and 18:2n–6. These animals had been fed mainly plant material (green peas, maize and alder leaves) in a different laboratory for a period of about 2 yr and kept in a flow-through system with ambient water of pH around 7. In A. astacus the total fatty acid content was nearly 13 times higher in the hepatopancreas than in the tail muscle, however, three fatty acids 18:0, 20:4n–6 and 20:Sn-3 were, respectively, 289, 403, and 320% more concentrated in the fatty acids of tail muscle than in the hepatopancreas. Total fatty acids of the hepatopancreas of male P. Ieniusculus was 42 times higher than in the tail muscle and was three times greater than in the hepatopancreas of A. astacus .     

Aspartic acid racemization in fish meal as induced by thermal treatment

The effect of heat treatment during fish meal processing on amino acid racemization was studied. The hydrolysis-induced racemization rate (R) and the d -isomer content in the sample before hydrolysis (I) were differentiated by means of deuterium labelling and gas chromatography-mass spectrometry (GC-MS) analysis in selected ion monitoring mode. A preliminary experiment on laboratory-made herring meals cooked at 125°C for different time intervals showed aspartic acid (Asp) as the only amino acid with significant racemization before hydrolysis. Aspartic acid racemization rate appeared to be a nearly linear function of the duration of thermal treatment (R²= 0.93; P < 0.01). Analyses were carried out on several samples of commercial fish meals from different origin. Low-temperature-dried fish meals had a d -Asp content, expressed as I= 100 [d -isomer concentration before hydrolysis / (d - +l -isomer concentration before hydrolysis)], at less than 1%, while the d -isomer content of high-temperature dried fish meals exceeded 2%. Differences between the two commercial categories were statistically significant (P < 0.001). Further studies are required in order to evaluate the effects of d -Asp in protein of fish feeds and the role of the raw material and processing parameters in inducing amino acid racemization in protein of fish meals.     

不同加热条件下海螺足部质构的变化

研究了鲜活和不同加热条件下(5、20、60 min)海螺足部的组织构造及其流变学特性的变化,并进行了质地剖面分析(TPA)和感官评定试验,为海螺深加工制品的开发及加工工艺的优化提供理论基础和科学依据.组织构造变化采用Van Gieson染色法观察,流变学特性参数和TPA通过质构仪测定,同时比较了TPA和感官评定间的相关性.结果表明:不同的加热处理对海螺足部的组织结构和流变学特征参数有明显影响.流变学特性与组织结构的变化之间具有一定的关联性.流变学特征参数表明鲜活海螺足部的肌肉具有硬度大、弹力和粘着性小的质地特点,而加热样品则是硬度小、弹力和粘着性大.海螺足部的热加工应以加热20 min为宜,时间太短或过长都无法给人以最佳的口感.TPA和感官评定在硬度(R=0.969 2)、弹性(R=0.927 2)和咀嚼性(R=0.854 2)方面呈显著相关性,在粘着性(R:0.794 5)方面也有较好的相关性.     

Antioxidant Assessment of Schizochytrium Meal Protein Enzymatic Hydrolysate and Its Potential Application

Schizochytrium meal protein (SMP) extracted from Schizochytrium meal was hydrolyzed by flavourzyme. Response surface methodology (RSM) was used to optimize the extraction conditions for the protein extraction yield from Schizochytrium meal. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (DRSA) was used to evaluate the antioxidant activity of hydrolysates. The orthogonal test was used to investigate the effects of three independent variables, namely protease dosage, hydrolysis time, and pH. The optimum conditions obtained were as follows: protease dosage of 7%, hydrolysis time of 1.5 h, pH of 6, under which, DRSA at the concentration of 2 mg/mL was 89.38%. Aspartic and glutamic acid constituted approximately 26.32% of the total amino acids, and glutamic acid was the most abundant amino acid of Schizochytrium meal protein hydrolysate (SMPH) by amino acid composition analysis, which may have contributed to the scavenging activity of SMPH. Moreover, SMPH was made into chewable tablets with suitable formula and high humidity stability. These findings indicate that Schizochytrium meal can be reused as a raw material for preparation of antioxidant peptides.     

Influence of type of raw material on fishmeal physicochemical properties,the extrusion process,starch gelatinization and physical quality of fish feed

The aim of this study was to investigate the impact of two types of fish raw material on fishmeal (FM) physicochemical properties, specific mechanical energy, starch gelatinization and physical feed quality. Eleven feed mixes based on six independent FMs from herring (FMH) and five from sand eel (FMSE) were extruded according to standardized conditions. Type of fish raw material influenced FM physicochemical properties and had significant impact on starch gelatinization and pellet hardness. Multivariate models were established based on partial least squares regression (R² = 0.637–0.999). Improved degree of starch gelatinization was associated with increased degree of protein hydrolysis (P = 0.011) and by replacement of FMH with FMSE in the feed mix (P = 0.012). A large span in pellet hardness was observed (4.9–94.1 N). Improved hardness was associated with decreased level of non‐soluble protein (P < 0.001) and by replacement of FMSE with FMH (P < 0.001). For FMSE, improved hardness was associated with decreased level of non‐soluble protein (P < 0.001) and increased degree of protein hydrolysis (P = 0.002), compressed bulk density (P = 0.039) and dust fraction (P = 0.001). The underlying physical and chemical mechanisms are discussed. The study documents differences in technical quality of FM produced from herring and sand eel with significant impact on fish feed extrusion and pellet quality.     

Evaluating the Effects of Dietary Prebiotic Mixture of Mannan Oligosaccharide and Poly‐β‐Hydroxybutyrate on the Growth Performance,Immunity, and Survival of Rainbow Trout,Oncorhynchus mykiss (Walbaum 1792), Fingerlings

This study investigated the effects of dietary poly‐β‐hydroxybutyrate (PHB) and mannan oligosaccharide (MOS) on the growth performance, digestive enzyme activities, and disease resistance of rainbow trout fingerlings. A total of 420 fingerlings, distributed equally into four different groups, each with three replicates, were fed a basal diet (control), 2% PHB (PHB), 0.2% MOS (MOS), or a diet supplemented with a mixture of 2% PHB and 0.2% MOS (PHB+MOS) for 60 d. Results showed that dietary PHB and/or MOS did not cause significant improvement in the growth performance of the fingerlings. The gut pH was markedly reduced; however, the activities of the digestive enzymes (except for pepsin and amylase by dietary PHB) were not significantly improved by the dietary supplements. Results also showed that dietary PHB and/or MOS markedly increased the resistance of the fingerlings toward Yersinia ruckeri infection, while the lowest total antibody was observed in fish fed control and MOS, indicating that MOS exerts its protective effects by modulating other mechanisms. Overall, this study provided a first screening effort to determine the effects of PHB and/or MOS as dietary supplements in rainbow trout fingerlings to develop an optimal prebiotic mix for improving the growth and health status of rainbow trout.