Quality retention during the chilled distribution of farmed turbot (Psetta maxima): effect of a primary slurry ice treatment

The quality and shelf‐life of chilled farmed turbot (Psetta maxima) was evaluated by sensory, microbiological and biochemical procedures after being subjected to a two‐step refrigeration storage in slurry ice and flake ice, respectively. Turbot specimens were stored for 10 or 17 days in slurry ice, and then were transferred to flake ice for 1–3 days to simulate the sale conditions in the market. The results were compared with control batches stored only in flake ice and processed in parallel. Storage of turbot in the two‐step strategy resulted in a better maintenance of sensory quality, especially with regard to its mucus production and gill odour development, better control of microbial activity, especially of aerobes, and the slowing down of some biochemical degradation mechanisms such as the nucleotide degradation pathway and trimethylamine production. As a consequence, the shelf‐life was extended significantly. From these results it can be concluded that the refrigerated transport of farmed turbot in slurry ice enhances its shelf‐life, before its transfer into flake ice in the retail market.     

Effect of dietary lipid sources on odour‐active compounds in muscle of turbot (Psetta maxima)

Odour‐active compounds in muscle of turbot (Psetta maxima) fed experimental diets containing fish oil (FO), soybean oil (SO) or linseed oil (LO) were investigated by a gas chromatography/olfactometry technique. Thirty‐one areas associated with odours were detected in muscle extracts. Among the compounds responsible for these odours, 23 were formed by oxidation of unsaturated fatty acids. Independently of diet, (E)‐2‐penten‐1‐ol and (E)‐3‐hexen‐1‐ol contribute strongly to the odour of turbot. (E,Z)‐2,6‐Nonadienal, (E)‐2‐pentenal and (E,E)‐1,3‐(Z)‐5‐octatriene seem to contribute strongly to the odour of turbot fed diets containing high levels of n‐3 PUFA (FO and LO groups). Hexanal and decanal show a high detection frequency in turbot fed diets containing vegetable oils. Odorous compounds which are not formed by lipid oxidation (methional, 1‐acetyl pyrazine, 4‐ethyl benzaldehyde and 2‐acetyl‐2‐thiazoline) were not affected by dietary lipid sources. © 2001 Society of Chemical Industry     

Biochemical changes and quality loss during chilled storage of farmed turbot (Psetta maxima)

Changes in three of the major biochemical components – nucleotides, lipids and proteins – related to quality loss in farmed turbot, were determined during 29 days of iced storage; results were complemented with sensory analysis. Nucleotide degradation, as estimated by the K value, underwent a gradual increase until day 19, in agreement with the loss of freshness observed for the sensory scores (high quality: days 0–2; good quality: days 3–14; fair quality: days 15–19). After day 19, the fish was judged unacceptable and the K value did not show differences until the end of storage. Lipid hydrolysis and oxidation occurred at slow rates, free fatty acid contents and the peroxide value being below 20.0 g kg⁻¹ lipids and 4.00 meq active oxygen kg⁻¹ lipids, respectively, during the whole storage. The content of fluorescent compounds did not increase significantly until day 19, when a sharp increase was detected. The electrophoretic protein profiles of turbot muscle did not point to any major protein degradation event or any significant change in protein during storage. However, a new band, corresponding to 22 kDa, could be observed at day 2 in the low-ionic strength buffer extract, whose concentration seemed to increase at days 9 and 14 and was present until the end of the chilled storage. The results obtained in this work indicate slow and gradual biochemical changes and long shelf life and good quality times (19 and 14 days, respectively) for iced turbot; these long times would be very profitable when turbot commercialisation is carried out in places distant from production farms.     

Dietary uptake of dioxins (PCDD/PCDFs) and dioxin-like PCBs in Spanish aquacultured turbot (Psetta maxima)

The human population is exposed to dioxins (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) mainly through diet; bioaccumulation and biomagnification in aquatic environment results in fishery products and by-products being an important vector to humans. The determination of PCDD/Fs and dl-PCBs in fillets of young turbots (Psetta maxima) (0-2 years) from aquaculture plant (Galicia, Spain) (N = 21) and in feeding stuffs were carried out, and dietary accumulation values and lipid-normalized biomagnification factors (BMF) relating concentration in fish and in feed were calculated. Levels found in feeding stuffs (0.5 pg TEQ-PCDD/F/g and 1.6 pg TEQ-dl-PCB/g), and turbots (0.13-0.27 pg TEQ-PCDD/F/g fresh weight and 0.35-1.2 pg TEQ-dl-PCB/g fresh weight) were below maximum permitted levels set by EC. Levels of toxic compounds in feeding stuff are reflected in fish fillets; predominant isomers are 2,3,7,8-TCDF, OCDD, 1,2,3,7,8-PeCDF, 2,3,4,7,8-PeCDF and 1,2,3,4,6,7,8-HpCDD, and PCBs 118, 105, 156 and 167. Relevant compounds accounting for total toxicity are the same congeners in feeding stuff and turbots: 2,3,4,7,8- PeCDF; 2,3,7,8-TCDF; 2,3,7,8-TCDD and 1,2,3,7,8-PeCDD, and PCB 126. Higher accumulation efficiency values were obtained for dl-PCBs (30-46%); tetra- and penta-chloro substituted PCDD/Fs showed the highest values (27-34%) of the PCDD/F group. Biomagnification was shown for these compounds (BMF around 1.5).     

Characterisation of histamine-producing bacteria from farmed blackspot seabream (Pagellus bogaraveo) and turbot (Psetta maxima)

Turbot (Psetta maxima) and blackspot seabream (Pagellus bogaraveo) represent two of the most important emerging farmed fish species in European countries. However, no information of the presence and development of histamine-producing bacteria on them has been reported so far. Accordingly, the aim of this study was to isolate and identify the main histamine-producing bacteria in farmed turbot and blackspot seabream. For this study, 24 isolates (12 from turbot and 12 from blackspot seabream) were preliminarily selected on Niven medium. Two of these isolates were confirmed as prolific histamine producers by HPLC. Thus, Pseudomonas fragi (isolated from turbot) and Pseudomonas syringae (isolated from blackspot seabream) were able to produce 272 ± 69 ppm and 173 ± 45 ppm of histamine in vitro, respectively, after incubation at 30 °C/24 h. While turbot fillets proved to be quite resistant to histamine formation at temperatures below 10 °C, blackspot seabream fillets inoculated with P. syringae and the prolific histamine former Morganella morganii accumulated 696 ± 84 and 760 ± 59 ppm histamine, respectively, under such conditions. Genetic identification based on 16S rRNA sequencing was performed in parallel with the investigation of characteristic mass spectral profiles of the isolates by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). The MALDI-TOF MS analyses provided species-specific fingerprints, which allow rapid identification and classification of the isolates. Six genus-specific mass peaks in the range of 2218-4434 m/z were shared by both strains. Bacterial identification was achieved by the identification of six species-specific mass peaks in the ranges of 2534-7183 m/z and 2536-9113 m/z for P. fragi and P. syringae, respectively.     

Assessment of protein changes in farmed giant catfish (Pangasianodon gigas) muscles during refrigerated storage

Farmed giant catfish (Pangasianodon gigas) muscles (dorsal and ventral sites) were stored in a refrigerator (at 4 °C) for 14 days to determine the effect of refrigerated storage on biochemical and physical changes. The analyses were carried out at 0, 2, 4, 7, 10 and 14 days of storage. At day 14, Ca²⁺ ‐ATPase activity markedly decreased when compared to its value at day 1 (>90%), while a small decrease was observed for surface hydrophobicity and reactive sulfhydryls content. Total volatile basic nitrogen and trichloroacetic‐soluble peptide content gradually increased when the storage period was extended. The myosin heavy chain decreased slightly on SDS‐PAGE for both meat cuts with increased storage time. Expressible drip and cooking loss were highest during the first day of storage and slightly decreased with storage time. Instrumental hardness was significantly higher in the ventral compared to the dorsal muscle, while the toughness was the highest at the second day of storage. The muscle bundles with scanning electron microscopy were less attached, resulting in the observed big gaps over increasing storage time. Results indicated that changes of proteins have detrimental effects on the quality attributes of farmed giant catfish muscles during refrigerated storage, particularly physical and biochemical properties.     

Effects of different cooking methods on the mineral contents of wild and farmed sea bream (Sparus aurata)

The effects of different cooking methods (steaming, boiling, oven cooking, grilling, frying in olive oil, frying in soybean oil, frying in corn oil and frying in sunflower oil) on mineral contents (Ca, Mg, K, Na, Fe, Zn, Cu and Mn) of wild and farmed sea bream (Sparus aurata) were determined. The moisture rate decreased significantly (P < 0.05) after boiling, grilling, oven cooking and frying but remains stable after steaming. The fat content increased with different frying treatments. The Ca, Mg, Na, K and Zn contents of wild and farmed sea bream cooked by almost all methods significantly decreased (P < 0.05). The Cu content in grilled wild and farmed sea bream increased significantly (P < 0.05). Losses of mineral content in fried sea bream were higher than those of fish cooked by other methods. On comparing the raw and cooked fish, the results indicated that cooking had considerable effect on the mineral contents.     

野生与池养刀鲚肌肉品质特性及抗氧化性的比较分析

比较研究了野生和池养刀鲚（Coilia nasus）肌肉营养成分组成、质构特性和抗氧化特性。结果显示,野生刀鲚肌肉中水分、羟脯氨酸、胶原蛋白含量以及胶原蛋白/总蛋白比值均显著低于池养型,而脂肪含量则显著提高;两者的蛋白质含量、pH均无显著性差异;池养刀鲚肌肉弹性、硬度、咀嚼度、胶着性相较于野生型呈上升趋势,但无统计学差异。野生刀鲚肌肉中SOD、CAT、T-AOC、MDA、GSH-PX、iNOS、GSH/GSSG均显著高于池养型。表明野生和池养刀鲚营养品质存在差异,建议在人工养殖刀鲚中应该注意饵料的种类和丰度,其养殖模式有待进一步改善。     

野生食用菌中矿物质和重金属研究概况

食用菌(Edible mushroom)由于其独特的风味和鲜嫩的肉质,在很多国家都被誉为佳肴。野生食用菌富含多糖、维生素和矿物质等,具有抗肿瘤和调节免疫等多种功能,是世界公认的不可多得的高营养兼药膳的\     

电子鼻结合气质联用法分析大菱鲆冷藏过程中挥发性成分变化

通过测定大菱鲆在4℃冷藏过程中的感官品质、菌落总数和TVB-N值等指标的变化,确定贮藏20d时已达腐败阶段。利用电子鼻检测新鲜及腐败鱼肉的气味差异,并对所获数据进行主成分分析,同时结合顶空固相微萃取(HS-SPME)和气质联用技术(GC-MS)对新鲜及腐败鱼肉的挥发性成分进行分析鉴定。结果表明:电子鼻对新鲜及腐败鱼肉整体风味的区分快速、灵敏,其分析结果与常规新鲜度评价指标的变化致;采用GC-MS法在新鲜及腐败鱼肉中分别检测出27及28种挥发性物质,主要为醛类、酮类、醇类、酯类、烃类和胺类化合物等,其中醛类、酮类和醇类物质在新鲜鱼肉中的含量较高,而胺类物质在腐败鱼肉中含量较高。     

Water-holding capacity of wild and farmed cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) muscle during ice storage

The aim of this study was to investigate how the presence of normal spoilage bacteria influenced the water-holding capacity (WHC) of wild cod, farmed cod and haddock during chilled storage. Bacterial growth was inhibited by soaking the fillets in 3 mmol/l NaN₃ prior to storage. The results clearly showed that the three groups were different with respect to WHC and pH. Muscle pH was highest in haddock, lower in wild cod and lowest in the farmed cod. Significant differences in WHC between the NaN₃-treated and nontreated groups of wild cod and haddock were found on the last sampling day. However, there was an inconsistency with respect to the relationship between pH and percentage liquid loss (LL%). The microflora of farmed cod is obviously altered from what is normal for wild cod. The results showed that bacterial growth may influence the WHC of the muscle. However, the relationship is inconsistent and may be temporal and not causative.     

Evaluation of Sensory and Microbiological Changes and Identification of Proteolytic Bacteria during the Iced Storage of Farmed Turbot (Psetta maxima)

ABSTRACT Sensory and quantitative microbiological analyses were performed in farmed turbot ( Psetta maxima ) during iced storage. Sensory analyses revealed a shelf life of 19 d for farmed turbot. The production of total volatile base nitrogen (TVB-N) and trimethylamine-nitrogen (TMA-N) was low and reached levels close to 40 mg TVB-N/ 100 g muscle and 3.5 mg /TMA-N/100 g muscle, even after 40 d of refrigerated storage. The pH value of turbot muscle increased from an initial value of 6.3 to close to 7.0 after 29 d of iced storage. Microbial growth was slow in iced turbot: total aerobic counts reached levels below 7 log colony forming units/g units even after 40 d of storage. Lactic acid bacteria—mainly Lactobacillus delbrueckii subsp. delbrueckii and Lactococcus lactis subsp. lactis strains—were predominant among the proteolytic strains isolated from iced turbot. Proteolytic strains of L. lactis subsp. lactis, Brochothrix thermosphacta, Plesiomonas shigelloides, Proteus vulgaris , and Pantoea species were also isolated from temperature-abused turbot, such proteolytic strains being predominant with respect to nonpro-teolytic microorganisms, suggesting a preferential role of such proteolytic bacteria in the spoilage of turbot. The slow bacterial growth, together with the relative predominance of lactic acid bacteria over Gram-negative microorganisms, may be related to the extraordinary maintenance of the quality and extended shelf life of farmed turbot.     

Differences in muscle cellularity and flesh quality between wild and farmed Coilia nasus (Engraulidae)

BACKGROUND: Populations of Coilia nasus, an anadromous fish, have declined dramatically in the Yangtze River estuary and its associated lakes owing to excessive fishing and changes in aquatic ecology. Recently, the success of artificial breeding programmes and advanced methods of propagation have allowed great increases in production of this species. Thus, to gain a better understanding of the flesh quality of C. nasus, muscle cellularity and quality parameters of the flesh were studied in wild and farmed specimens. RESULTS: Muscle cellularity was different between wild and farmed fish. Muscle fibre density was significantly higher in farmed specimens, while muscle fibre diameter was higher in wild specimens. Farmed fish had higher moisture, hydroxyproline and collagen contents and a lower fat content compared with wild fish. No significant differences in textural parameters were found between the two groups. Saturated (SFA), polyunsaturated (PUFA) and total n‐6 fatty acid contents were significantly higher in farmed fish, but monounsaturated fatty acid (MUPA) content was higher in wild fish. CONCLUSION: The variation in the studied parameters determined significant differences in the flesh quality of wild and farmed C. nasus. Depending on muscle cellularity and fatty acid composition, farmed fish could be more suitable for human consumption than wild fish. Copyright © 2011 Society of Chemical Industry     

High resolution two-dimensional electrophoresis as a tool to differentiate wild from farmed cod (Gadus morhua) and to assess the protein composition of klipfish

Tris and CHAPS–urea extracts from wild and farmed cod muscle and from rehydrated cod klipfish fillets were analyzed by one (1DE) and two-dimensional electrophoresis (2DE). 2DE maps of tris extracts from farmed cod differed from the wild in a series of spots of Mw 35 and 45 kDa. The CHAPS–urea extracts from farmed cod had a several spots of Mw between 100 and 45 kDa, which were hardly detectable in wild cod and very prominent in klipfish. Klipfish was clearly different from the other samples: the myosin heavy chain was hardly detectable in these samples, and the tris extracts contained fewer, and the CHAPS–urea more spots than the corresponding extracts from the raw muscles. Further identification of these potentially diagnostic spots will make it easier the differentiation of farmed from wild cod and the evaluation of klipfish processing on the protein content of the product.     

Metals and other elements in tissues of wild fish from fish farms and comparison with farmed species in sites with oxic and anoxic sediments

Farmed fish and wild fish aggregating in the vicinity of four Mediterranean fish farms with different environmental conditions were sampled. Levels of metals (including As and Se) were measured in the muscle, liver, gills, bone and intestine. The wild fish from sites with anoxic substrata accumulate metals (including As and Se) from the ambient habitat in their gills whereas those from sites with oxic substrata concentrate these elements through their diet in their intestine. Tissues of wild fish aggregating around farm cages accumulate a greater number of these elements and with higher concentrations than farmed fish. Habitat, diet, ecological needs, fat content of fish, and protein expression may play an important role in these element differences between fish species. Fe in flathead grey mullet, As in surmullet, rainbow wrasse, grey gurnard and picarel and Hg in bogue may pose a risk for human health. Farmed and wild fish are good sources of P, K, Cr and Se while flathead grey mullet, picarel and comber are excellent sources of Ca and Se.     

Nutritional value and flavor of turbot (Scophthalmus maximus) muscle as affected by cooking methods

In this study, the effects of five cooking methods on nutritional value and flavor of turbot muscle were evaluated. Chemical compositions of samples were determined using AOAC methods, and the fatty-acid composition was determined by gas chromatography–mass spectrometry (GC–MS). Flavors of samples cooked using different methods were characterized by electronic nose. Volatile compounds were determined using solid-phase microextraction (SPME) followed by gas GC–MS. All the samples were investigated before/after cooking. The results showed that the fatty acids found in abundance in the raw sample were C22:6n-3, C16:0, C18:1n-7, and C20:5n-3. All of the fatty acids were detected in steamed samples, while some of the fatty acids were degraded in other cooking methods. Electronic nose can be used to distinguish samples cooked differently. 20, 17, 34, 20, and 23 compounds were detected in samples cooked by frying, baking, microwave heating, boiling in vacuum-sealed bag (BIVSB) and steaming, respectively. Aldehydes, ketones, alcohols, acids, and hydrocarbons were the main volatile components detected. In summary, steaming preserves water, protein, lipids and fatty acids the best in cooked samples while generates desirable flavor, it is recommended as the choice of cooking for turbot.     

Preliminary characterization of bacteriocins from Lactococcus lactis,Enterococcus faecium and Enterococcus mundtii strains isolated from turbot (Psetta maxima)

The aim of this work was the characterization of new strains of lactic acid bacteria (LAB) from farmed fish and with potential application as biopreservatives against both Listeria monocytogenes and Staphylococcus aureus. Twenty-five strains of LAB isolated from the muscle of farmed turbot were investigated. Genetic identification of the bacteriocin-producing LAB strains was performed by means of a PCR method using novel BAL1/BAL2 16S ribosomal-RNA-targeted primers. Maximum bacteriocin production by Lactococcus lactis ssp. lactis USC-39, Enterococcus faecium USC-46 and Enterococcus mundtii USC-51 was detected in the stationary phase of growth. Both acidification and the production of hydrogen peroxide by LAB were ruled out as the source of the inhibition. In contrast, the antimicrobial activity of all three LAB strains was inactivated by the addition of proteinase K, thus confirming the proteinaceous nature of the inhibition. The activity against L. monocytogenes was maintained in the 3.5–5.5 or 3.5–6.5 pH range, depending on the LAB strain. Likewise, inhibition of S. aureus strains was observed in the 3.5–4.5 and in the 3.5–5.5 pH ranges, depending on the LAB strain and on the S. aureus strain tested. Bacteriocin activity was stable in all three strains after heating the cell-free extract for 60 min at 100 °C, or even for 15 min at 121 °C, in all the three LAB strains. The acidic and heat-resistant bacteriocins produced by the three LAB strains isolated from turbot, able to inhibit the growth of both L. monocytogenes and S. aureus may find application as biopreservatives in fermented and/or heated food products.     

Protein and mineral content of a novel collection of wild and weedy common bean (Phaseolus vulgaris L)

Protein and total calcium, iron, and zinc were determined in 70 accessions of wild and weedy common bean (Phaseolus vulgaris L) from different sites in two Mexican states (Jalisco and Durango). Protein digestibility, essential amino acid profiles, tannins, phytic acid and extractable iron were determined in selected accessions. The phytate/zinc and the phytate × (calcium/zinc) molar ratios were also determined as predictors of zinc bioavailability. For comparative purposes, two cultivated common beans were included. The wild and weedy beans contained more protein and similar protein digestibility compared with cultivated samples. The contents of sulfur amino acids were low in all samples; additionally, beans from Jalisco had higher contents of sulfur amino acids than cultivated ones. Beans from Durango showed higher leucine, valine and aromatic amino acids contents than cultivated beans. Some wild and weedy beans from Jalisco and Durango showed high contents of calcium (7470 mg kg⁻¹), iron (280 mg kg⁻¹), and zinc (33.1 mg kg⁻¹). The phytic acid × (calcium/zinc) molar ratios of some wild and weedy beans were similar to those of cultivated beans. Amounts of extractable iron were in the order of 26–74%. © 2000 Society of Chemical Industry     

Physicochemical Responses and Quality Changes of Turbot (Psetta maxima) During Refrigerated Storage

The sensory, physicochemical, microbiological, and volatiles changes of postmortem turbot during 20 days of chilled storage at 4°C were studied. No significant changes were found in pH value and whiteness during the storage, while total viable counts, total volatile base nitrogen, and K-values increased significantly with storage time. The textures profile, springiness and resilience, and sensory attributes changed significantly during storage. A total of 50 volatile compounds including aldehydes, ketones, esters, alcohols, alkenes, alkanes, aromatics, amines, and others were identified in turbot muscle during storage by the solid-phase microextraction and gas chromatography–mass spectrometry methods. Among these volatile components, the relative content of some decreased significantly with time, while others increased significantly. The results suggested that hardness, springiness, resilience, sensory attributes, total volatile base nitrogen, K-value, and total viable counts combined with some volatile compounds could more perfectly reflect the quality changes of turbot during storage. The study indicated that turbot fillets stored at 4°C maintain better quality for 16 days during storage.