Seasonal variation in the chemical composition and microbiological condition of Mediterranean horse mackerel (Trachurus mediterraneus) muscle from the North Aegean Sea (Greece)

The aim of this work was to determine the chemical composition and microbiological quality of Mediterranean horse mackerel (Trachurus mediterraneus) muscle during the year and the consequent advantages or disadvantages in processing the raw material. A total of 180 samples were examined (15 samples per month) during two years (November 2001–November 2003). Fish were caught in the coastal waters of Chalkidiki peninsula (Northern Greece). Proximate composition of the muscle during the year resulted in: water 76.8 ± 1.39%, proteins 20.3 ± 0.68%, fat 1.3 ± 1.08% and ash 1.5 ± 0.08%. In March, April and May an increase in fat content of the muscle (2.5%, 2.8% and 2.1%, respectively) and a decrease in water content of the muscle (below 75.9%) were observed. On the contrary, fat content showed a decrease in September and October (0.4% and 0.6%, respectively), while water content of the muscle increased during these months (78.2% and 77.6%, respectively). The protein content of the muscle remained at high values, while the ash content was almost constant during the year. The mean value of muscle pH was 6.38 ± 0.16; extreme values (<6 or >7) of muscle pH were not observed. Total Viable Bacteria, Shewanella putrefaciens and Pseudomonas spp. were used as microbial indices to evaluate the microbiological quality of the muscle. Mean counts of Total Viable Bacteria, S. putrefaciens and Pseudomonas spp. during the year were: 4.01 ± 0.38 log₁₀ cfu/g, 2.37 ± 0.43 log₁₀ cfu/g and 3.34 ± 0.27 log₁₀ cfu/g, respectively. The variations of the values within seasons are minimal and significant homogeneity in the chemical composition and microbiological quality of Mediterranean horse mackerel muscle is observed. This is an important advantage in processing of the raw material.     

The influence of superchilling storage methods on the location/distribution of ice crystals during storage of Atlantic salmon (Salmo salar)

The objective of this work was to study the influence of superchilling storage methods, shell freezing and non-shell freezing on the location/distribution of ice crystals during the superchilled storage of salmon. Physical measurements, water holding capacity and drip loss were also studied. Non-shell frozen samples resulted in extracellular ice crystals. Shell frozen samples showed both intracellular and extracellular ice crystals with a uniform distribution. Liquid loss (LL) decreased with storage time in both superchilling storage methods. There was no significant difference (p > 0.05) in LL between shell and non-shell frozen samples. There was significant difference (p < 0.05) in the drip loss between shell frozen samples (1.62% as maximum) and non-shell frozen samples (1.4% as maximum). The information on the characteristics of ice crystals (location/distribution), which has a strong influence on the quality of the final superchilled food, is a factor key for the manufacturing of products with desired quality and shelf life.     

Sensory analysis to assess the freshness of Mediterranean anchovies (Engraulis encrasicholus) stored in ice

A quality index method and a sensory scheme were developed to assess raw and cooked Mediterranean anchovies (Engraulis encrasicholus), respectively. Fresh anchovies were stored in ice for 7 days in three trials. The changes in sensory punctuations showed satisfactory correlations with time of storage. Enterobacteria were the first microorganisms that exceeded the maximum allowable limit for marketable fish according to the Spanish regulations, reaching more than 10³ colony former units/g after 5 days of storage. Receiver operating characteristic curves of the sensory scores of raw and cooked anchovy against Enterobacteria counts were used to corroborate the suitability of the schemes. Areas under the curves were satisfactory and the estimated rejection values ranged from 0.43 to 0.51 and from 6.6 to 7.1 for raw and cooked anchovies, respectively.     

Quality predictive models of grass carp (Ctenopharyngodon idellus) at different temperatures during storage

To study quality changes in cold chain circulation, kinetic models were developed to predict the freshness changes of grass carp at different temperatures during storage. Sensory assessment, total aerobic count (TAC), K value, total volatile basic nitrogen (TVB-N) and 2-Thiobarbituric acid (TBA) at ?3, 0, 3, 9 and 15 °C were accessed to investigate the relation between the freshness changes and temperature. The kinetic models of sensory assessment, TAC, K value, TVB-N and TBA with respect to storage time and temperature were developed based on Arrhenius equation. The high regression coefficients (R² > 0.9) indicated the acceptability of the first-order reaction and Arrhenius model for predicting the quality changes of grass carp. Activation energies (E_A) of sensory assessment, TAC, K value, TVB-N and TBA are 114.38, 75.88, 57.11, 111.55, 63.09 kJ mol^?1, and corresponding rate constants (k₀) are 2.97 × 10²⁰, 1.12 × 10¹³, 8.30 × 10⁹, 8.34 × 10¹⁹, 9.06 × 10¹⁰ respectively. Relative errors between predicted and observed freshness indictors values of TAC, K value and TVB-N are all within ±10%. Therefore the quality changes of grass carp can be predicted based on the prediction model of TAC, K value and TVB-N within ?3–15 °C.     

储存过程中油品的质量变化及对策

介绍了油品在储存过程中造成质量变化的原因,其主要有油品的蒸发、氧化、水分和杂质。要保证油品质量,延缓油品质量变化应采取减少储存温差,减少油罐内的气体空间及定期清洗油罐和设备,定期化验,及时掌握库存油品质量情况等措施。     

Anisakis sp. and Hysterothylacium sp. larvae in anchovies (Engraulis encrasicolus) and chub mackerel (Scomber colias) in the Mediterranean Sea: Molecular identification and risk factors

Larval ascaridoids in fish destined to human consumption represent an important public health issue, besides to be an economical problem. Indeed, marine ascaridoids are the etiological agents of the fish-borne zoonosis anisakidosis. Due to an increase of new cases reported worldwide, a continuous monitoring of infection in fish is mandatory. The study was aimed to evaluate the risk of infection by larval ascaridoids in fishes from Mediterranean Sea. Two species of fishes among those representing a major potential threat for human health were selected. Epidemiological and molecular study was carried out. At Milan Fish Market, Italy, 179 anchovies (Engraulis encrasicolus) and 84 chub mackerels (Scomber colias) caught in different fishing areas in the Mediterranean Sea were sampled and inspected for the presence of larvae. For each fish, larvae were counted and morphologically identified. Predictors of infections were investigated through general linear models. A subsample of 100 larvae was molecular characterized with PCR–RFLP targeting the nuclear ribosomal internal transcribed spacer (ITS) region. Moreover, 26 Hysterothylacium spp. larvae were analyzed by sequencing of both nuclear ITS and mitochondrial ribosomal rrnS regions.Overall, 1080 anisakids larvae were collected from 103 anchovies (P = 57.5%) and 53 chub mackerels (P = 63.09%). Larvae were morphologically identified as Anisakis Type I larvae (P = 6.14% in anchovies and P = 55.95% in chub mackerels) and as Hysterothylacium spp. (P = 54.18% in anchovies and P = 13.09% in chub mackerels). Fishing area and fish weight resulted predictors of both Anisakis Type I land Hysterothylacium spp. infections in anchovies; in chub mackerels, only fishing areas resulted to be associated to both infections. Molecular analysis on ITS region identified Anisakis pegreffii, heterozygote genotype between A. pegreffii and A. simplex sensu stricto, and Hysterothylacium aduncum. Sequences analysis on Hysterothylacium specimens revealed a great homogeneity in rrnS marker, with eight variable nucleotides and an average evolutionary divergence over all sequence of 0.3%.     

Quality differences of whole ungutted sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) while stored in ice

The aim of this study is to determine the quality changes in whole ungutted sea bass and sea bream while stored in ice. Changes in chemical quality were determined by using pH, total volatile basic nitrogen (TVB-N, mg N/100 g), trimethylamine (TMA-N, mg/100 g), thiobarbituric acid (TBA, mg malonaldehyde/kg), water activity (a_w), color measurement, and sensory analysis. Changes in microbiological quality were determined by using the analysis of total viable mesophilic and psychrophilic bacterial counts. Result of this study indicated that the shelf life of sea bass and sea bream stored in ice as determined by overall acceptability sensory scores and microbiological data was 15 days.     

Development of Quality Index Method (QIM) scheme for spiny lobster (Panulirus argus,Latreille, 1804) stored in ice

The objective of this study was to evaluate the freshness of spiny lobster (Panulirus argus) stored on ice up to 18 days. Changes during storage were observed with sensory evaluation (Quality Index Method – QIM), pH, total volatile basic nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), and microbiological analyses (total mesophilic and psychrotrophic count). The maximum shelf life of spiny lobster stored in flake ice at 1 ± 0.2 °C was determined with loss of freshness (sensorial, physico-chemical and microbiological evaluations). High correlation R² = 0.922 between Quality Index (QI) and storage time at 1 °C was verified. QI ranged from zero (maximum freshness) to 15 (total loss of freshness) and reached the acceptable limit for consumption (QI = 9.54), which corresponds to a period of 10 days. The microbiological results showed an increase of psychrotrophic count along the storage time. TVB-N ranged from 5.23 to 20.31 mg 100 g⁻¹, TMA-N from 1.07 to 5.72 mg 100⁻¹ and pH from 6.91 to 7.19 in the first and 18th day of storage, respectively. It is suggested that spiny lobster has to be fresh and acceptable for consumption by cooling up to 10 days.     

Quality of live packaged mussels during storage as a function of size and oxygen concentration

The commercialization of live mussels is limited by their capacity to resist the adverse conditions associated with their removal from the natural environment. Packaging under modified atmospheres has been proposed as an alternative method for the stabilization of mussels and shelf life extension. This study investigates how different concentrations of oxygen (20, 75 and 85%) influence the percentage mortality and quality of packaged Mediterranean mussels (Mytilus galloprovincialis) of different sizes (30 and 44 units/kg). In general, mussels packaged with oxygen-rich atmospheres had a higher organoleptic rating and lower percentage mortality. The decrease in pH of both the tissues and intervalval fluid was less pronounced in the larger mussels compared to the smaller mussels. Mussel size and packaging atmosphere also influenced the metabolic survival strategies. The smaller mussels produced more ammonium and volatile fatty acids, which decreased as initial oxygen increased. After 10 days of storage no consumption of glycogen was detected in any of the samples analyzed. The marketable period for the mussels, defined as a 20% mortality threshold, was reached earlier in the packages displaying a greater accumulation of acidic and basic metabolites.     

Changes in the microbiological and physicochemical quality of high-pressure-treated oysters (Crassostrea gigas) during chilled storage

Changes in the physicochemical and microbiological quality of oysters HP-treated at 260, 400 or 600 MPa for 5 min and stored at 2 °C on ice for 31 days were investigated. Microbial counts after HP treatment showed that the bacterial load was initially reduced at all pressures to levels below the detection limit. HP-treated oysters showed significantly increased pH and lightness (P < 0.05) relative to untreated oysters; during storage, pH changed little in the pressurised oysters but decreased slightly in untreated oysters. Little changes in colour were observed during storage at 2 °C on ice, compared to untreated oysters, which showed increased b-values (stronger yellow colour). From tests of mechanical properties, HP-treated oysters showed significantly increased cutting strength (P < 0.05) with increasing treatment pressure compared to controls throughout storage. However, HP increased lipid oxidation, the rate of which was dependent on the pressure applied. This study confirmed that HP processing can inactivate microorganisms and delay microbial growth in chilled stored oysters, but also affects their quality attributes.     

Characterization of Mediterranean mussels (Mytilus galloprovincialis) harvested in Adriatic Sea (Italy)

The aim of this work was to analyse some quality parameters of Mytilus galloprovicialis harvested monthly in the period ranging from April 2002 and February 2003 in a longline off-shore mussel farm, located in the Adriatic Sea, near Cattolica (Emilia Romagna Region, Italy). After harvesting, the samples were analysed in order to determine the counts of fecal coliforms (FC) and Escherichia coli, the presence of Salmonella, as prescribed by Italian and European Community regulations, and other pathogens (Vibrio parahaemolyticus, Listeria monocytogenes), as well as the meat yield and its proximate composition, its Fe, Cr, Cd, Zn, Pb and Cu content, the total lipids of the meat and their specific composition. The results obtained evidenced that many of the parameters studied, i.e. the meat proximate composition, the lipid fatty acid composition and the microbiological indices, were subjected to seasonal fluctuations. In particular, the microbiological data showed that 4 mussel samples (June, December, January and February) out of 12 did not match the limit imposed by Italian law and Emilia Romagna protocol concerning the FC and E. coli counts. While L. monocytogenes and Salmonella spp. were never detected in all the samples analysed, three samples (April, January and February) were positive for the presence of V. parahaemolyticus. No seasonal fluctuations were evidenced for Fe, Cr, Cd, Zn, Pb and Cu contents, always under the limits imposed by Italian law.     

Effect of tea polyphenols on the physical and chemical characteristics of dried-seasoned squid (Dosidicus gigas) during storage

The effects of tea polyphenols (TP) dip treatment on the physical and chemical characteristics of dried-seasoned squid (Dosidicus gigas) during storage at 25 °C were assessed. After the storage, the b* value increased significantly, while the free amino acids (FAA) including Ser, Gly, Arg, Tyr and Lys, and the dominant reducing sugar (RS), lactose, decreased remarkably, which revealed the occurrence of browning reaction in dried-seasoned squid. The progressive conversion of trimethylamine oxide (TMAO) and production of thiobarbituric acid (TBA) and total volatile basic nitrogen (TVB-N) were found during the entire period of storage. Furthermore, the advantages of reducing moisture loss, inhibiting oxidation of lipids, depressing TMAO breakdown and TVB-N accumulation were observed, while the browning reaction exhibited no significant decrease for the TP samples. These results indicated that the addition of TP could maintain quality of dried-seasoned squid.     

NAS系统的工作原理和系统的救援

网络附加存储NAS指的是一种将分布、独立的数据,整合为大型、集中化的管理数据中心,以方便对不同主机和应用服务器进行访问的技术。就是因为NAS的这种特点,非常适合428地震勘探仪这种以网络技术搭建起来的地震勘探系统的数据存储。本文介绍了通用NAS系统的原理,并以428地震勘探系统常用的NAS Start 800为列,结合在生产过程中可能出现的问题,阐述了NAS Start 800的基本组成和系统救援。     

Single- and multi-cycle high hydrostatic pressure treatment on microbiological quality of mud snail (Bullacta exarata) during refrigerated storage

High hydrostatic pressure (HHP) processing is an industrial technology used for preservation of a wide range of food products, and vacumm-packed mud snails (Bullacta exarata) were HHP processed to ensure food safety and shelf-life stability. The effects of single- and multi-cycle HHP treatment, especially the combination of different intensities, on the microbial behavior and shelf-life extension of B. exarata during subsequent storage were investigated. Total microbial count, psychrophilic microorganisms, Clostridium bacteria, total Enterobacteriaceae and H₂S-producing bacteria were enumerated during subsequent refrigerated storage, and Gompertz model was chosen to predict the shelf-life, growth rate, lag time and generation time. The results showed that the initial microbial load was obviously reduced as the pressure increased. Total Enterobacteriaceae and H₂S-producing bacteria were not detected in multi-cycle HHP processing during refrigerated storage. Moreover, multi-cycle HHP method (B + F) could improve the shelf-life of B. exarata for more than 38 days. The model indicated that the lag time for Clostridium bacteria processed with multi-cycle HHP (B + F) was extended to 24.65 days. Our findings will be of aid for the establishment of general process guidelines, and demonstrated that multi-cycle HHP technology has potential for application in mud snail preservation and processing.     

Determination of the shelf life of cluster of the red king crab (Paralithodes camtschaticus) during chilled storage

Red king crab (Paralithodes camtschaticus) presents a commercial and economical important species that is mainly consumed in high-end markets in Japan and USA. The product is either sold live, cooked and refrigerated or frozen. The meat in the legs and in the shoulder is utilized. In this study, shelf life of cooked king crab clusters (shoulder plus three legs) during chilled storage was studied. We utilized sensory, chemical and microbiological methods to describe spoilage during storage of the clusters, and to estimate its shelf life. The results revealed that a cluster is a heterogeneous product, where the shelf life of the leg and shoulder meat is 8 and 5 days, respectively, during chilled storage. As it is impractical to operate with two different shelf lives for the same product, the overall recommended shelf life is 5 days for cooked and chilled clusters. Corresponding maximum level of TVC and Pseudomonas spp. in leg meat stored for 5 days was log 4.6 and 3.7 CFU/g, respectively. A correlation between odour of the shoulder joint and flavour of the leg meat was revealed. By using, exponential regression, the flavour of the leg meat could be predicted based on the odour of the shoulder joint.     

气藏型地下储气库的库存量曲线特征与达容规律

中国石油天然气集团公司2010年启动的第二批地下储气库正在陆续建成投产,地下储气库开始进入达容阶段,需要提前了解和掌握地下储气库库容量的达容规律和达容特征。为此,论述了气库达容物质平衡原理、气库达容库存量曲线特征和气库达容的普遍性规律,以气藏物质平衡理论为基础,阐述了地下储气库的库容参数与压力的对应逻辑关系,建立了库容量计算方程,定义了库容参数,以国内第一批地下储气库即大港储气库群的扩容达容生产实践为依据,建立了地下储气库逐步扩容达容的库存量曲线的基本模式,从技术上论述了库存量曲线的物理意义、曲线特征、关键点参数,并介绍了应用地下储气库生产动态资料绘制库存量曲线的方法,以气库物质平衡理论结合地下储气库扩容达容的库存量曲线特征,系统总结了地下储气库由开始扩容到多周期达容的普遍规律,为指导和掌握地下储气库的扩容达容规律提供了理论知识与技术方法。     

Inhibitory effects of high-hydrostatic-pressure treatments on histamine production in mackerel (Scomber japonicus) muscle inoculated with Morganella morganii and Photobacterium phosphoreum

Histamine or scombroid fish poisoning is caused by ingestion of histamine in spoiled fish, which arises because of the activity of bacterial histidine decarboxylase (HDC), resulting in allergy-like symptoms. To investigate the inhibitory effects of HHP on the activity of HDC, crude HDC extracts were prepared from Morganella morganii and Photobacterium phosphoreum, and subjected to HHP (100–400 MPa) or were left untreated (controls). Pressure levels of up to 200 MPa did not significantly affect the activity of crude HDC in M. morganii (<5%); however, HHP treatments of 300 and 400 MPa showed inhibitory activity at 19.4% and 23.2%, respectively. HHP treatments of 100, 200, 300, and 400 MPa considerably inhibited the crude HDC activities of P. phosphoreum at 46.1, 57.0, 63.3, and 84.5%, respectively. HHP treatment was then applied to mackerel muscle inoculated with M. morganii and P. phosphoreum in situ. We observed that HHP significantly delayed the overall microbial growth in mackerel muscle, regardless of the inoculated species. Moreover, histamine production in mackerel muscle inoculated with M. morganii was strongly inhibited by both 200 and 300 MPa (but not 100 MPa). Furthermore, in the sample inoculated with P. phosphoreum, all of the HHP treatment conditions at 100–400 MPa strongly inhibited histamine production. Taken together, the findings of this study might be helpful to enhance the safety of mackerel consumption.     

Effect of nutmeg (Myristica fragrans) essential oil on the oxidative and microbial stability of cooked sausage during refrigerated storage

This paper examines the oxidative and microbial stability of cooked sausages, produced with the addition of 10 ppm (NO1) and 20 ppm (NO2) nutmeg (Myristica fragrans) essential oil. Instrumental parameters of color (CIE L*, CIE a* and CIE b*), Thiobarbituric acid-reactive substance (TBARS) values, microbial profile and sensory properties of aroma have been determined on the 1st, 30th, 45th, and 60th day of storage. Addition of the nutmeg essential oil had no effect on the color of cooked sausages. At the end of the storage, NO2 sausages had the best oxidative and microbial stability. TBARS values of NO1 and NO2 sausages were 1.21 mg MDA/kg and 0.95 mg MDA/kg, respectively, and were significantly lower (P < 0.05) compared to control (1.53 mg MDA/kg). Total number of aerobic mesophilic bacteria was lowest in NO2 sausages (78.3 cfu/g) and highest in control (185 cfu/g). After 45 and 60 days of storage, sensory properties of aroma of NO1 (4.21; 3.92) and NO2 sausages (4.39, 4.28) were better compared to those in control (4.07, 3.25). Hence, the addition of nutmeg essential oil in amount of 20 ppm can be successfully applied in order to extend the shelf life of cooked sausages.     

Occurrence and infection dynamics of anisakid larvae in Scomber scombrus,Trachurus trachurus,Sardina pilchardus,and Engraulis encrasicolus from Tarragona (NE Spain)

Between February 1996 and January 2000, parasitological examination of Scomber scombrus (n = 447), Trachurus trachurus (n = 175), Sardina pilchardus (n = 160) and Engraulis encrasicolus (n = 153) from the fishing-ground of Tarragona (NE Spain) were made for anisakids. Three anisakid species (Anisakis larva type I sensu Berland, 1961, Contracaecum sp. and Hysterothylacium aduncum) were morphologically identified. The prevalence of Anisakis larva type I sensu Berland (1961) ranged from 11.0% (S. scombrus) and 2.6% (T. trachurus) to 0.0% (S. pilchardus and E. encrasicolus). The prevalence of H. aduncum in S. scombrus was 1.1%. The prevalence of Contracaecum sp. was 2.0% in S. scombrus, and 0.7% in T. trachurus respectively. There was a positive and significant correlation between the host length and the number of Anisakis larva type I sensu Berland, 1961 found in S. scombrus.     

Antimicrobial effects of cinnamon bark oil on microbial composition and quality of grass carp (Ctenopharyngodon idellus) fillets during chilled storage

In this study, 11 essential oils were initially screened for antimicrobial activity against Aeromonas veronii, Acinetobacter johnsonii, Shewanella putrefaciens, and Pseudomonas jessenii. Cinnamon bark oil exhibited the highest antimicrobial activity and was used as a natural preservative in grass carp fillets stored at 4 ± 1 °C. Sensory assessment, total volatile basic nitrogen (TVB-N), color, biogenic amines, adenosine triphosphate (ATP)-related compounds, K-value, and presence of microbiota were analyzed during storage. Cinnamon bark oil treatment was found to be effective in enhancing organoleptic quality, inhibiting microbial growth, and delaying the increase of TVB-N, putrescine, cadaverine and K-value. Based on sensory analysis, shelf-life of grass carp fillets was 8 days for the control and 12 days for the treatment group. According to high-throughput sequencing, Aeromonas and Pseudomonas were the predominant microbiota in fresh grass carp. As storage time progressed, the microbial composition of both control and treatment samples became less diverse. Pseudomonas followed by Aeromonas were dominant in spoiled control samples. However, there were significant differences in microbial composition between control and treatment samples at the end of storage. Cinnamon bark oil treatment inhibited the growth of Aeromonas and Shewanella, and Pseudomonas was the only predominant microbiota found in spoiled treatment samples.