Instrumental Texture Parameters as Freshness Indicators in Five Farmed Brazilian Freshwater Fish Species

The aim of this study was to assess the chemical quality and instrumental texture parameters, as well as their relationships, of five Brazilian freshwater fish species stored at 4 °C for 6 days. In general, ammonia, TCA-soluble peptides, and biogenic amine values increased with storage time, attributed to the advance of the deterioration process. Ammonia and TCA-soluble peptide concentrations correlated positively with the increase of putrescine, spermine, and histamine. Putrescine production began during the first days of storage, while cadaverine was produced later. Spermine and spermidine showed variable behavior, increasing and decreasing, respectively. With regard to the instrumental texture parameters, firmness, hardness, and chewiness decreased at the beginning of the storage period, whereas an increase was observed in springiness. All instrumental texture parameters demonstrated high correlations with ammonia and TCA-soluble peptides. The increase in certain biogenic amines (putrescine, cadaverine, and spermine) seems to correlate well with decreases observed in firmness, hardness, and chewiness. In addition, a strong relationship was observed between the initial days of storage and instrumental texture parameters, while a significant correlation between the end of the storage and the chemical quality analyses was verified. Firmness, hardness, chewiness, and cohesiveness were considered parameters with high potential in the evaluation of fish freshness during the first days of storage, whereas the chemical quality analyses and springiness were considered important for later evaluation of fish quality. Therefore, instrumental texture parameters may be used as quality indicators in the evaluation of freshwater fish freshness.     

Characterization of Common Squid Using Several Freshness Indicators

Changes in several components and properties were examined to find appropriate indicators of freshness of common squid during storage at 0°C, 5°C and 10°C. Total viable counts of bacteria, pH and volatile basic nitrogen did not change significantly during 2 wk storage at 0°C. Unlike usual fish meat, K value in squid muscle changed very quickly, but Hx/AMP ratio was a better indicator. Agmatine increased before initial decomposition started but was not suitable as an early freshness indicator. Free basic amino acids, arginine and ornithine also changed rapidly. Basic amino acids such as arginine and ornithine appeared to be appropriate indicators of freshness of common squid.     

Biomarkers in fish from Prince William Sound and the Gulf of Alaska: 1999-2000

To test the hypothesis that biomarker levels in fish collected at Prince William Sound (PWS) sites impacted by the 1989 Exxon Valdez oil spill were higher than those collected at unimpacted sites, a 1999-2000 study collected five fish species and associated benthic sediments from 21 sites in PWS and the eastern Gulf of Alaska (GOA). PWS sites were divided in three oiling categories based upon 1989 shoreline assessments: nonspill path (NSP), spill path oiled (SPO), and spill path not oiled (SPNO). Rockfish (N = 177), rock sole (N = 30), and kelp greenling (N = 49) were collected at near-shore locations (approximately 50-500 m from shore); Pacific halibut (N = 131) and Pacific cod (N = 81) were collected further offshore (approximately 500-7000 m). Fish were assayed for bile fluorescent aromatic contaminants (FAC) and cytochrome P4501A (CYP1A) levels measured as liver ethoxyresorufin O-deethylase (EROD) activity and by immunohistochemistry (IHC) of various tissues. For all species studied at all sites, bile FAC concentrations and CYP1A levels were low and in the same range for fish collected at PWS SPO and SPNO sites relative to NSP sites in PWS and the GOA. Consequently, the hypothesis is rejected for the species studied. The bile FAC results further indicate a pervasive exposure of fish at all sites, including those in the GOA far removed from the effects of the spill, to low levels of polycyclic aromatic hydrocarbons. Analysis of the benthic sediments indicates that the probable sources of this exposure are petrogenic hydrocarbons derived from natural oil seeps and eroding sedimentary rocks in the eastern GOA.     

Nucleotide Catabolism: Influence on the Storage Life of Tropical Species of Fish from the North West Shelf of Australia

The storage life of four species of fish from the North West Shelf was examined by means of nucleotide catabolism and sensory evaluation. It was found that the shelf life was related to the rate of inosine monophosphate (IMP) breakdown rather than to bacterial spoilage, because the endemic mesophilic bacteria were unable to adapt to ice storage conditions. The results indicated that the IMP level was fundamentally related to both flavor intensity, and acceptability, and was not merely circumstantially related to time of storage.     

Polycyclic aromatic hydrocarbon sources related to biomarker levels in fish from Prince William Sound and the Gulf of Alaska

Seafloor sediments in Prince William Sound (PWS) and the eastern Gulf of Alaska (GOA) have a substantial regional hydrocarbon background from natural sources including oil seeps and eroding sedimentary rocks along the eastern GOA coast. Polycyclic aromatic hydrocarbons (PAH) from that background appear to be bioavailable to fish. Fish collected from PWS and the GOA in a 1999--2000 biomarker study (bile fluorescent aromatic contaminants and liver ethoxyresorufin O-deethylase) show evidence of exposure to low levels of PAH at all categories of sites sampled. Seafloor sediments at fish sampling sites in the GOA east of PWS and at three PWS site categories (nonspill path, spill path oiled, and spill path not oiled) contain hydrocarbons from four principal sources: regional background, combustion products, residues from the 1989 Exxon Valdez oil spill (EVOS), and Monterey (CA) petroleum residues. GOA sediments between PWS and Yakutat Bay, approximately 350 km to the east, are dominated by regional petrogenic background hydrocarbons (total PAH (TPAH) range approximately 60-3400 ng/g) that are the probable cause of low biomarker levels measured in halibut from this area. PWS sediments contain varying proportions of regional background, combustion products, Monterey residues, and EVOS residues at some spill path sites. Rockfish caught in PWS embayments in 1999 have liver EROD activities that correlate positively with the pyrogenic PAH indicator ratio (FI+Py)/C24Ph. Although traces (<5-100 ng/g TPAH) of EVOS residues were detected in seafloor sediments at some nearshore spill path sites, biomarker levels in fish from those sites are not elevated relative to other sites in PWS.     

Adenosine Triphosphate Catabolites as Flavor Compounds and Freshness Indicators in Pacific Cod (Gadus macrocephalus) and Pollock (Theragra chalcogramma)

Postmortem formation of 5′-inosine monophosphate, inosine and hypoxanthine in Pacific cod and pollock fillets during chilled storage was monitored over a two week period. Accumulation of hypoxanthine in Pacific cod (Gadus macrocephalus) fillets proceeded more slowly than has been reported for Atlantic cod (Gadus morhua) but similar to North Sea cod (Gadus callarias L.). For both both cod and pollock, hypoxanthine was negatively correlated with flavor and desirability (p < 0.01), while both inosine and 5′-inosine monophosphate were positively correlated with overall desirability (p < 0.01).     

大米鲜度仪在大米新鲜度检测中的应用

选用RN-820大米鲜度仪,通过染色测定p H来判定大米新鲜度。该方法操作简单,能直观区分开新、陈大米。简要介绍了RN-820大米鲜度仪的检测原理、操作,并以不同储存条件下大米新鲜度变化监测和市售大米样品新鲜度检测为具体实例,对该方法的实际应用作了详细介绍,对方法的优点和不足作出了评价,并预测和展望了其发展前景。     

猪肉新鲜度评价指标、存在问题及应对措施

介绍了猪肉新鲜度的感官鉴定、肉表面细菌总数、挥发性盐基氮(TVB-N)、pH值、K值、聚胺类化合物及硫化氢(H2S)等几种评价指标,指出猪肉新鲜度评价存在的问题,并提出了相应的解决措施。     

Slightly weathered Exxon Valdez oil persists in Gulf of Alaska beach sediments after 16 years

Oil stranded by the 1989 Exxon Valdez spill has persisted in subsurface sediments of exposed shores for 16 years. With annualized loss rates declining from approximately 68% yr(-1) prior to 1992 to approximately 4% yr(-1) after 2001, weathering processes are retarded in both sediments and residual emulsified oil ("oil mousse"), and retention of toxic polycyclic aromatic hydrocarbons is prolonged. The n-alkanes, typically very readily oxidized by microbes, instead remain abundant in many stranded emulsified oil samplesfrom the Gulf of Alaska. They are less abundant in Prince William Sound samples, where stranded oil was less viscous. Our results indicate that, at some locations, remaining subsurface oil may persist for decades with little change.     

Reassessment of the hydrocarbons in Prince William Sound and the Gulf of Alaska: identifying the source using partial least-squares

There has been considerable exchange in the literature regarding the source of the background hydrocarbons in Prince William Sound and the Gulf of Alaska. Page and coworkers suggest oil-based sources while Short and coworkers suggest coal. The multivariate statistical methodology of partial least-squares (PLS) has been used to reassess the percentage contribution of coal, seep oil, shales, and rivers to the hydrocarbon loading in the Gulf of Alaska. Data have kindly been provided by Short (NOAA) and Page (Bowdoin College, for Exxon), and these have been analyzed using selected sites as sources in order to develop signatures. These signatures are based on 40 and 136 compounds, respectively, and include the PAH and terpane/sterane biomarkers in the case of the Exxon data. The principal components describing these sources are then fitted to the data for other sites around the Prince William Sound (PWS) and Gulf of Alaska (GoA) to determine the proportion of the variability described by each source. Using the Exxon data, a mixed source of coal, seep oil, eroding shales, and rivers (1 and 2) sources described approximately 13%, 18%, 24%, 26%, and 20%, respectively, of the variance in PWS and GoA data. The rivers 1 signature was very similar to that of coal, while rivers 2 was more similar to the eroding shales. New coal data (Short, unpublished work) also indicated considerable overlap with the Exxon seep oil. With the NOAA data, spatial plots of the explained variance indicate that the prespill background has a wide range of explained fits. There is considerable overlap in the signatures developed from the data, and Coomans' Plots identify those compounds which are the most diagnostic: for the Exxon seep oil signature, naphthalene and methyl- and dimethylnaphthalene are the best markers, whereas for the NOAA prespill background, Exxon coals and shales are best defined by the larger PAHs such as benzo[ghi]perylene. The evidence suggests mixed sources whose contributions vary significantly across the sampling area.     

Purine Content in Grass Shrimp during Storage as Related to Freshness

In grass shrimp ( Penaeus monodon ), the combined total content of the uricogenic bases adenine (Ade) and hypoxanthine (Hyp) decreased gradually during storage. Whether stored at 5°C or at room temperature (22°C), a negative regression of log Ade and a positive regression of the Kp value (Hyp/Ade) were observed. Volatile basic nitrogen (VBN) increased during storage at 5°C and 22°C. Correlations between the content of log Ade and VBN at 5°C and 22°C were –0.9248 (p<0.01) and –0.8139 (p<0.05, while those between the Kp value and VBN were 0.9557 (p<0.001) and 0.8197 (p<0.05), respectively. At the point where the shrimp would remain acceptable, the upper limits of Kp were 1.42 and 1.29 for storage at 5°C and 22°C, respectively; the corresponding lower limits of Ade were 18.72 and 20.42 μmole/g dry wt.     

Suitability of Volatile Amines as Freshness Indexes for Iced Mediterranean Hake

Batches of gutted Mediterranean hake (Merluccius merluccius var. Mediterraneus) were stored, in different seasons of the year, for up to 20 d in ice. Changes in trimethylamine (TMA‐N), total volatile bases (TVB‐N), P‐ratio and trimethylamine oxide (TMAO) were measured; sensory evaluation of raw and cooked hake samples was also carried out. Similar profiles were observed between the different trials for all the parameters studied. TVB‐N was not correlated with the time of ice storage, and proved to be better as a spoilage index than a freshness one. In contrast, TMA‐N appears to be a good index of hake quality, and the value of 5 mg/100g offish seems an appropriate limit of acceptability. P‐ratio was a poorer index of freshness than was TMA‐N.     

Patterns of adenosine triphosphate catabolism as freshness indicators in fish species from the baltic sea

The breakdown products of adenosine triphosphate (ATP) were determined in order to evaluate the freshness of six Finnish fish species. The degradation of ATP was faster in white bream, in flounder and especially in pike than in other species.     

离水花蛤鲜度和组织形态及Bax蛋白的表达变化

为了解日常生活中花蛤离水放置后的生存状态及细胞凋亡在此过程中的作用及其机制。在4℃和25℃条件下将离水花蛤分别放置2、6、12、24h和2、4、6h,利用挥发性盐基氮测定、HE染色和免疫组化SABC法研究花蛤鲜度、形态学及促凋亡蛋白Bax的表达变化,探讨细胞凋亡在保鲜保活花蛤中的作用。结果表明,随着离水时间的延长,花蛤组织细胞趋于松散,肌纤维断裂,颗粒化程度加深。4℃和25℃下Bax的表达呈相似的变化趋势,但25℃下的变化进程明显快于4℃下。因此,放置温度及离水时间对花蛤组织形态及促凋亡蛋白Bax表达均有相似趋势的影响。     

清香香型参照香料的选择

对清香香型参照香料的水蒸气蒸馏、分子蒸馏等制备技术进行了研究,并综合运用GC-MS和香味轮廓法对相应产品进行验证和鉴定;结果表明:通过水蒸气蒸馏法制得的Y-01产品清香香型/香韵特征凸出,可作为清香香型的参照香料样品。     

电子鼻技术研究臭氧水处理对罗非鱼鱼片的新鲜度的影响

采用电子鼻PEN3系统对经不同臭氧水处理的罗非鱼肉进行检测。对传感器进行相关性分析与Loadings分析,由W1C、W5S、W1S、W1W、W2S、W2W和W3S组成新的传感器阵列。对优化后的传感器阵列进行主成分分析,结合挥发性盐基氮（total volatile basic nitrogen,TVB-N）值、硫代巴比妥酸反应物（thiobarbituric acid reactivesubstances,TBARS）值综合评价臭氧水处理对罗非鱼鱼片的新鲜度的影响。结果表明,利用电子鼻技术得到罗非鱼鱼片的贮藏品质区分结果与TVB-N值、TBARS值0级动力学分析结果基本一致;1 mg/L臭氧水处理5 min不能明显地减缓罗非鱼鱼片在贮藏期新鲜度下降,5 mg/L臭氧水处理10 min能明显地减缓罗非鱼鱼片在贮藏期新鲜度下降。     

鱼肉鲜度测定方法研究进展

综述了用于鱼肉鲜度测定的几类不同方法 ,包括感官评价方法、微生物学方法、物理和化学方法和生物传感器方法等 ,并比较了不同测定方法的特点 ,阐明了鱼肉鲜度测定方法的未来发展趋势。