Search

Numerous Pseudomonas species can infect aquatic animals, such as farmed rainbow trout, sea trout, sea bass, and sea bream, by causing disease or stress reactions. In aquaculture facilities, a number of Pseudomonas species have been isolated and identified as the main pathogens. The present study describes the characterization of 18 Pseudomonas strains, isolated from fish products using shotgun proteomics. The bacterial proteomes obtained were further analyzed to identify the main functional pathway proteins involved. In addition, this study revealed the presence of 1015 non-redundant peptides related to virulence factors. An additional 25 species-specific peptides were identified as putative Pseudomonas spp. biomarkers. The results constitute the largest dataset, described thus far for the rapid identification and characterization of Pseudomonas species present in edible fish; furthermore, these data can provide the basis for further research into the development of new therapies against these harmful pathogens

This article summarizes the characterization, by shotgun proteomics, of 11 bacterial strains identified as responsible for seafood spoilage. A total of 4455 peptide spectrum matches, corresponding to 4299 peptides and 3817 proteins were identified. Analyses of data determined the functional pathways they are involved in. The proteins identified were integrated into a protein-protein network that involves 371 nodes and 3016 edges. Those proteins are implicated in energy pathways, peptidoglycan biosynthesis, spermidine/putrescine metabolism. An additional 773 peptides were characterized as virulence factors, that participates in bacterial pathogenesis; while 14 peptides were defined as biomarkers, as they can be used to differentiate the bacterial species present. This report represents the most extensive proteomic repository available in the field of seafood spoilage bacteria; the data substantially advances the understanding of seafood decay, as well as provides fundamental bases for the recognition of the bacteria existent in seafood that cause spoilage during food processing/storage

Food authentication and food allergy profiling are relevant topics that must be carefully considered by authorities, food production and manufacturing industries, and customers. Precise, sensitive, and efficient detection procedures are crucial for authenticating food and identifying allergens. In this paper, we present a current review of advanced proteomic approaches for food authentication and allergen profiling. We discuss three proteomics strategies, namely, discovery proteomics, targeted proteomics, and proteomics-based systems biology, used to authenticate food and profile allergens. This review includes a selection of the most representative papers published in this field in the last few years. Furthermore, we discuss future directions and potential opportunities in this field

Lyophilized alga Fucus spiralis powder was incorporated into a gelatin-based film and employed as a packaging system for mackerel (Scomber scombrus) muscle portions throughout a 9-day refrigerated storage period at 4 °C. In global terms, a progressive loss of quality could be observed in fish muscle with increasing storage time. Comparisons between batches allowed us to conclude an inhibitory effect of F. spiralis-containing films on microbial activity (assessment of aerobes, psychrotrophs, and proteolytic bacteria) and on lipid hydrolysis (as determined by free fatty acid formation) in mackerel muscle. The presence of the lyophilized macroalga in the packaging film also led to a higher retention of primary (peroxides) and secondary (thiobarbituric acid reactive substances) lipid oxidation compounds, while the formation of fluorescent compounds (interaction compounds between lipid oxidation compounds and nucleophilic molecules present in the fish muscle) decreased. Both antimicrobial and antioxidant effects were more intense when the concentration of alga in the packaging film was increased. The preservative effect resulting from the presence of F. spiralis in gelatin-based films demonstrates the potential employment of such bioactive films to improve the retention of fish quality and enhance its commercial value

The first goal of this work was to enhance the quality of chilled fish by applying a preliminary dipping treatment containing a bioactive extract from the alga Fucus spiralis. Megrim (Lepidorhombus whiffiagonis) specimens were dipped in aqueous solutions containing two different concentrations of the alga extract (0.50% and 0.10% alga/dipping solution, w/v; HAC and LAC batches, respectively). In addition, two control batches were considered (water dipping control and no dipping control). Microbial, chemical and sensory qualities were assessed in fish specimens after 0, 2, 6, 9 and 13 days of chilled storage. An antimicrobial effect at advanced stages of storage (9–13-day period) was observed as determined by the comparative evolution of aerobes, psychrotrophs and Enterobacteriaceae counts in megrim muscle. Likewise, a protective effect against specific lipolytic and proteolytic spoilage bacteria was also achieved at that storage period, as well as a decrease of free fatty acids formation. However, alga extract in the dipping medium had no effect (p > 0.05) on the increase of lipid oxidation in fish muscle throughout chilled storage. Interestingly, average scores revealed improved sensory quality in megrim corresponding to the HAC batch for the 9–13-day chilled period. Consequently, the proposed novel dipping treatment can be considered of interest for both on-board and in-land fish storage, due to the simple methodology employed and the resulting protective effects on fish quality.

Active antimicrobial films based on biodegradable materials are now widely used for food packaging applications. In the present study, an extrusion process was used to prepare biodegradable films based on polylactic acid PLA and supplemented with sorbic acid and seaweeds (PLA + 0.5% sorbic acid; PLA + 0.5% sorbic acid + 8% seaweed). The kinetics of sorbic acid migration from the films into two food simulants (10% ethanol [v/v] and 95% ethanol [v/v]) were analysed at 5, 20 and 40 °C. The sorbic acid content in the food simulants was determined by reversed-phase high-performance liquid chromatography (detection wavelength, 260 nm). Separation was performed on a reversed-phase C18 column, at 30 °C. The diffusion coefficients were calculated using a mathematical model based on Fick's Second Law. The values obtained ranged between 4.11 × 10−9 and 1.00 × 10−13 cm2 s−1. The developed active films could be of great interest for food industry, since they could be useful for protecting packed food.

The present study provides a first approach on the employment of an icing medium including Fucus spiralis, an alga exhibiting antimicrobial and antioxidant activities, for the preservation of fish quality during chilled storage. For it, two different concentrations of a F. spiralis extract (0.67 and 2.50 g lyophilized alga L−1 aqueous solution; F-1 and F-2 batches, respectively) were tested as icing medium for the chilled storage of megrim (Lepidorhombus whiffiagonis) for 14 days. The effects of the alga were compared with a counterpart batch stored in traditional ice prepared only from water (F-0 batch). A significant (p < 0.05) inhibition of microbial activity (aerobes, psychrotrophs, proteolytic bacteria, lipolytic bacteria; pH and trimethylamine formation) in F-1 batch and, especially in F-2 batch, was concluded. Concerning lipid oxidation development, a significantly (p < 0.05) lower formation of interaction compounds (fluorescence assessment) in samples corresponding to the F-2 batch was also observed, proving the inhibitory effect of F. spiralis on the formation of tertiary lipid oxidation compounds in chilled megrim. The icing medium proposed in this study may open the way to the development of a natural biopreservation strategy for chilled seafood based on algae

During the industrial processing of jumbo squid (Dosidicus gigas), large amounts of by-products containing biological active compounds are generated. In this study, aqueous solutions including acetic acid-ethanol extracts of jumbo squid skin (JSS) were tested at three different concentrations as icing media. The effects of the JSS extracts on the quality evolution of chilled mackerel (Scomber scombrus) were monitored. A significant inhibition (p < 0.05) of microbial activity was determined in the fish batch corresponding to the icing condition including the highest JSS concentration. Additionally, fish specimens corresponding to batches including any of the JSS concentrations tested showed lower (p < 0.05) proteolytic counts and pH values than control mackerel. Sensory analysis revealed a marked shelf life extension in chilled mackerel stored in ice including the highest JSS concentration; specimens from such batch were found to be still acceptable after 13 days of storage, while all other mackerel batches were rejectable. The marked microbial activity inhibition observed could be explained on the basis of the presence in ice of lipophilic compounds obtained by acetic acid-ethanol extraction of JSS

This work focused on the on-board chilled storage of European hake (Merluccius merluccius) and megrim (Lepidorhombus whiffiagonis). To enhance fish quality, an aqueous solution including citric (1.25 g l−1) and lactic (0.50 g l−1) acids was prepared, frozen, ground and employed as icing medium. Its effect on sensory, microbiological and chemical changes was monitored after 9, 12 and 15 days of on-board storage. Lower (p < 0.05) bacterial growth was detected according to microbiological (aerobe, anaerobe, psychrotrophe, proteolytic, and Enterobacteriaceae counts) and chemical (trimethylamine content) assessments. An inhibitory effect (p < 0.05) on autolysis development (K value assessment) in hake was also detected. Finally, an enhancement of sensory scores (eyes, external odour and gills) in both species was obtained. Results described allow to conclude that on-board employment of such acid-mixture icing system can provide a profitable strategy to obtain higher quality and safe products while unloading

Three combinations of two natural organic acids, citric acid (CA) and lactic acid (LA), in the form of novel flake icing systems were evaluated for the preservation of European hake (Merluccius merluccius), one of the most commercialised gadoid fish species in Europe. The flake icing systems were prepared with fresh water and 0.075%/0.050% (C-75 batch), 0.125%/0.050% (C-125 batch) and 0.175%/0.050% (C-175 batch) CA/LA, respectively. Aerobic mesophiles, psychrotrophs, proteolytic bacteria, anaerobes, Enterobacteriaceae, trimethylamine, lipid hydrolysis, primary, secondary and tertiary lipid oxidation events, and pH levels were evaluated in hake muscle in all batches during 13 d of chilled storage and the results were compared with sensory analyses. Significantly (p < 0.05) lower microbial counts were found in the C-175 batch for all five microbial groups investigated when compared with the control batch, with differences between batches of greater than 2 log CFU/g in the case of aerobes and anaerobes. The presence of organic acids in the icing systems also inhibited (p < 0.05) the increase in trimethylamine-nitrogen (TMA-N) content, with greater inhibition as the CA concentration in the ice increased. An inhibitory effect (p < 0.05) on fluorescent compound formation due to the presence of organic acids in the icing systems, which is indicative of tertiary lipid oxidation, was also observed at advanced storage times. These results correlated well with sensory analysis, which revealed that the shelf lives of the C-125 and C-175 batches were extended. The melting of the ice crystals containing the natural organic acid solutions, especially in the C-175 batch, exerted an antimicrobial washing effect that may explain the better protection of hake quality when stored in the proposed flake icing system.

Streptococcus parauberis is known as an etiological agent of mastitis in cows and for producing streptococcosis in farmed fish, although its presence in foods has seldom been reported. In this work, two bacterial isolates were recovered from a spoiled vacuum-packaged refrigerated seafood product. Both isolates were identified by 16S rRNA gene sequencing, exhibiting 99% homology with respect to S. parauberis. Both isolates were also characterized by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS). Genetic analysis revealed the clonal homogeneity of the isolates and their grouping together with other S. parauberis strains in a different cluster with respect to Streptococcus uberis strains. Proteomic analysis by MALDI-TOF MS allowed for the identification of five mass peaks in the range of 2200–6000 m/z that resulted to be specific to the species S. parauberis and allowed its rapid and direct identification with respect to other pathogenic and spoilage bacteria potentially present in seafood and other food products. This study represents, to our knowledge, the first report of S. parauberis in seafood in general and in vacuum-packed food products in particular. Moreover, it provides a rapid method based on MALDI-TOF MS for the identification of S. parauberis.

Genomic and proteomic techniques for species identification of meat and seafood products are being widely used. In this study, a genomic approach was used to differentiate Pandalus borealis (the Northern shrimp), which belongs to the superfamily Pandaloidea, from 30 crustaceans consisting of 19 commercially relevant prawns/shrimps species that belong to the superfamily Penaeoidea, which include the families Penaeidae and Solenoceridae, and 11 other crustacean species, including prawns, shrimps, lobsters, and crabs. For this purpose, a polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) method was designed based on the amplification of the 16S rRNA/tRNAVal/12S rRNA mitochondrial regions using the primers 16S-CruF and 16S-CruR. The 966-bp PCR products were produced and cleaved with the restriction enzymes AluI, TaqI, and HinfI, which provided species-specific restriction patterns. In addition, a proteomic approach, based on matrix-assisted laser desorption/ionization time-of-flight (MALDI–TOF) and electrospray ionization–ion trap (ESI–IT) mass spectrometry, was used to identify and characterize new P. borealis-specific peptides that could be useful as potential markers of this species in protein-based detection methods. To our knowledge, this is the first time a molecular method has been successfully applied to identify a wide range of prawn and shrimp species, including P. borealis, for either whole individuals or processed products. However, validation of the methods proposed here is required by applying them to a larger sample of individuals from different populations and geographic origins in order to avoid mainly false-negative results

Natural preservative organic acids (ascorbic, citric and lactic acids) were used to prepare a novel organic acid-flake icing system for the chilled preservation of hake (Merluccius merluccius), megrim (Lepidorhombus whiffiagonis) and angler (Lophius piscatorius). The icing system was prepared with two different concentrations of a commercial acid mixture-formula containing the three organic acids at 800 mg/kg and 400 mg/kg (C-800 and C-400 batches, respectively). Aerobic mesophiles, psychrotrophs, proteolytic bacteria, trimethylamine and pH were evaluated and the results compared with sensory analyses. Significantly (P < 0.05) lower counts of mesophiles were found for hake and megrim in the C-800 and C-400 batches compared with the control batch. In the case of angler, significantly (P < 0.05) lower counts of mesophiles, psychrotrophs and proteolytic microorganisms (P < 0.05) were found for fish stored in the C-800 icing conditions. Both C-400 and C-800 megrim batches exhibited significantly (P < 0.05) lower pH values than the control batch, and this result was also observed in the C-800 angler batch. Sensory analysis confirmed that the shelf lives of the three fish species in the C-800 batch were extended. According to the parameters assessed, storage of hake, megrim and angler in the proposed ice system better protects their microbial and sensory qualities.

Polymerase chain reaction-based methodologies have been developed for the identification of three commercially- relevant penaeid shrimp species, these were: Litopenaeus vannamei, Penaeus monodon and Fenneropenaeus indicus in food products. Such three species represent more than 80% of the whole farmed shrimp production worldwide and may be fraudulently replaced by species exhibiting lower value such as Litopenaeus stylirostris, Penaeus semisulcatus and Fenneropenaeus merguiensis, respectively. For it, preliminary sequencing of a mitochondrial sequence of ca. 530 bp in the 16S rRNA/tRNAVal mitochondrial region was performed in nearly 20 penaeid shrimp species of commercial relevance. Careful analysis of such sequences allowed the design of primers PNVF/PNVR, which allowed the combined identification of P. monodon and L. vannamei, and PNIF/PNIR, which allowed the specific identification of F. indicus. In addition, P. monodon and L. vannamei could be easily differentiated by either restriction with TspE1 or by amplification with novel primers MPNF/MPNR, specific for P. monodon. The proposed specific methods improve current general identification methods of these species based on more general RFLP analyses. In addition, these methods can be easily completed in less than 8 h.

Native isoelectric focusing (IEF) of water-soluble sarcoplasmic proteins was applied to the identification of 14 shrimp species of food interest belonging to the order Decapoda. These species have different commercial values, but due to their phenotypic similarities and carapace removal in their industrial processing, incorrect food labelling and deliberate or inadvertent adulteration can occur. Each of the 14 tested species showed species-specific protein band profiles and intra-specific polymorphism was low, not preventing the correct identification of the species. Therefore, IEF of water-soluble sarcoplasmic proteins allowed the differentiation of the 14 species considered. In addition, sarcoplasmic calcium-binding proteins (SCPs) were identified by tandem mass spectrometry (MS/MS) as the major species-specific proteins in these species, opening the way to further studies focusing on their potential use as specific biomarkers

In this study, we infer the phylogenetic relationships within commercial shrimp using sequence data from a novel mitochondrial marker consisting of an approximately 530-bp region of the 16S ribosomal RNA (rRNA)/transfer RNA (tRNA)Val genes compared with two other mitochondrial genes: 16S rRNA and cytochrome c oxidase I (COI). All three mitochondrial markers were considerably AT rich, exhibiting values up to 78.2% for the species Penaeus monodon in the 16S rRNA/tRNAVal genes, notably higher than the average among other Malacostracan mitochondrial genomes. Unlike the 16S rRNA and COI genes, the 16S rRNA/tRNAVal marker evidenced that Parapenaeus is more closely related to Metapenaeus than to Solenocera, a result that seems to be more in agreement with the taxonomic status of these genera. To our knowledge, our study using the 16S rRNA/tRNAVal gene as a marker for phylogenetic analysis offers the first genetic evidence to confirm that Pleoticus muelleri and Solenocera agassizi constitute a separate group and that they are more related to each other than to genera belonging to the family Penaeidae. The 16S rRNA/tRNAVal region was also found to contain more variable sites (56%) than the other two regions studied (33.4% for the 16S rRNA region and 42.7% for the COI region). The presence of more variable sites in the 16S rRNA/tRNAVal marker allowed the interspecific differentiation of all 19 species examined. This is especially useful at the commercial level for the identification of a large number of shrimp species, particularly when the lack of morphological characteristics prevents their differentiation.

The resistance rates of intestinal Escherichia coli populations from poultry were determined during treatment and withdrawal period with 3 antimicrobial agents commonly used as therapeutics in poultry medicine. A total of 108 chickens were considered: 18 were treated orally with enrofloxacin, 18 with doxycycline, and 18 with sulfonamides, whereas another 18 chickens were maintained as controls for each antimicrobial group. Fecal samples were taken during the treatment and after the withdrawal period, and E. coli were isolated through Fluorocult media plating. A total of 648 E. coli strains (216 per antimicrobial tested) were isolated and identified though biochemical methods. Minimal inhibitory concentrations to the antimicrobials used were also determined using a broth microdilution method. The resistance rates of intestinal E. coli to all of the antimicrobials tested significantly increased during the course of the therapeutic treatment. In addition, significant differences (P = 0.0136) in resistance rates persisted between the intestinal E. coli of the enrofloxacin-treated and control batches until the end of the withdrawal period, but this difference was not observed for the cases of doxycycline or sulfonamides treatments. Antimicrobial use in poultry medicine seems to select for antimicrobial-resistant strains of pathogenic bacterial species such as E. coli. In some cases, the higher frequencies of resistant strains may persist in the avian intestinal tract until the end of the withdrawal period, when it is legal to use these animals for human consumption

A novel PCR-RFLP method was evaluated as a tool to assess the incidence of incorrect labelling of prawns and shrimps in commercial food products. The whole method can be performed in less than 8 h in only one day of work. PCR amplification with primers 16Scru4/16Scru3, targeted to the amplification of a ca. 530 bp region of 16S rRNA and tRNAVal mitochondrial genes, was coupled to restriction analysis with AluI, TaqI or HinfI. Forty-one commercial food products were considered. The molecular method considered allowed the identification of up to 17 different prawn and shrimp species in all the processed products considered. Seven (28%) of the 25 food products declaring one or more species in their labels were incorrectly labelled. Authentication was successfully assessed in commercial peeled products subjected to industrial processing, in which none of the products displayed labelling at species level. Overall, incorrect labelling was detected in 10 (24.4%) of the 41 commercial products tested, while another 16 samples (39%) exhibited incomplete labelling. The molecular method evaluated in this study proved to be a rapid and easy-to-perform two-step analytical approach to achieve species identification of commercial whole specimens of frozen prawns and shrimps and in peeled processed products where such raw materials are included as added-value ingredients.

The Grand Sole North Atlantic fishing bank is exploited by several European countries, although time lapsed between catch and destiny arrival can attain 15 days. In the present work, the use of slurry ice (SI) system was investigated for the on-board storage of chilled fish and carried out in parallel to traditional flake icing (FI). Three species (hake, Merluccius merluccius; angler, Lophius piscatorius; ray, Raja clavata) widely present in the mentioned bank were studied. A lower (p < 0.05) microbial (aerobes, psychrotrophes, proteolytics) development was observed in fishes subjected to SI system than in their counterpart specimens stored under FI. This correlated with lower (p < 0.05) productions of trimethylamine (hake and angler) and total volatile bases (ray) and extended shelf-life for fish species kept under SI conditions. In summary, on-board employment of SI can provide higher quality and safety products to consumer and allow increased commercial values while unloading and sale.

The application of slurry ice, a biphasic system formed by small spherical ice crystals surrounded by seawater at sub-zero temperature, was evaluated as a new storage method for ray (Raja clavata), the elasmobranch fish species that exhibits highest commercial value in the European food markets. This advanced technique was used to compare with a control batch stored 10 days in flake ice. The results obtained in the sensory analysis indicated a significant extension of the overall quality (A class fish) from 3 days (flake ice) to 6 days (slurry ice). The development of ammonia external odour was the limiting parameter in both batches and was correlated with the activity of the endogenous mechanisms involved in the degradation of proteins and non-protein-nitrogen (NPN) rather than with the activity of proteolytic microorganisms. Storage of ray in slurry ice significantly (P<0.05) slowed down both biochemical (as estimated by the follow-up of the pH, TVB-N and K-value evolution) and microbial degradation mechanisms (estimated by the development of psychrotrophes and mesophiles counts) in chilled ray muscle. According to the parameters evaluated, storage of ray in slurry ice extends the shelf-life of this elasmobranch fish species due to a better maintenance of sensory, biochemical and microbiological quality, thus facilitating its commercialization

The slurryice technology has shown profitable advantages when employed instead of traditional flake ice for the manufacture of chilled aquatic species. The present work is aimed at evaluating the effect of slurryice as a preliminarytreatment prior to frozen storage. For it, specimens of a small pelagic fatty fish species (sardine; Sardina pilchardus) were stored in slurryice for 2, 5 and 9 days, then subjected to freezing (–80 °C; 24 h) and finally kept frozen (−20 °C) during 1, 2 and 4 months. At such times, ranciditydevelopment in frozen sardine was measured by sensory (odour, skin, colour and flesh appearance) and biochemical (lipid hydrolysis and oxidation) analyses and compared to a control batch previously chilled in flake ice. Sensory analysis indicated an extended shelf-life time for frozen sardine that was preliminary stored under slurryice for 2, 5 or 9 days, as compared to their counterparts subjected to flake icing. Sensory results were corroborated (P<0.05) by biochemical lipid oxidation indices (thiobarbituric acid reactive substances and the fluorescence formation). The present work opens the way to the use of slurryice instead of flake ice as preliminarytreatment of fish material prior to the frozen storage.

The use of slurry ice is gaining increasing importance as an advanced method for the hygienic and efficient chilling and sub-zero storage of aquatic food products. In this work, this technology was applied as a novel technique for the chilling and storage of Norway lobster (Nephrops norvegicus) – a crustacean species of high-commercial value – under refrigeration conditions at 1.5 C. In addition, the effects of a preliminary treatment with 0.5% Na HSO3 on surface browning were evaluated and compared with the results obtained in control batches not subjected to such treatment. The processing of lobster in slurry ice significantly (p < 0.05) slowed down microbial spoilage, as determined by the counts of aerobes, psychrotrophs, proteolytic bacteria, and lactose-fermenting Enterobacteriaceae, and by the formation of volatile amines. Likewise, the autolytic breakdown mechanisms – as determined by the K value – were also significantly (p < 0.05) inhibited in the slurry ice batch. Remarkably, preliminary treatment with 0.5% sodium metabisulphite permitted better maintenance of the parameters involved in sensory quality – especially as regards the aspect of the carapace – as compared with nontreated batches, and allowed a shelf life of 9 days without surpassing the 150 mg/kg legal limit established for this food additive. On contrast, the non-treated batch stored in slurry ice exhibited a shelf life of 5 days. The combination of technological treatments proposed in this work – preliminary antimelanosic treatment and storage in slurry ice – may be successfully applied to other fresh and frozen shellfish species with a view to extending shelf life and to avoiding the legal and toxicological problems derived from current abuse of such antimelanosic agents to prevent shellfish browning.

The use of ozonised slurry ice was investigated as a new refrigeration system for the storage of farmed turbot (Psetta maxima). With this purpose in mind, an ozone generator device was coupled to a slurry ice system working subzero at 1.5 C. The ozone concentration was adjusted to a redox potential of 700 mV, and the slurry ice biphasic mixture was prepared at a 40% ice/60% water ratio and 3.3% salinity. Certain biochemical parameters indicative of fish freshness, such as the rate of nucleotide degradation or TMA-N formation, were not significantly affected by the presence of ozone in the slurry ice mixture. However, storage in ozonised slurry ice significantly slowed down the mechanisms responsible for lipid hydrolysis and lipid oxidation in farmed turbot. Storage in ozonised slurry ice also led to significantly (p < 0.05) lower counts of both total aerobes and psychrotrophic bacteria in both turbot muscle and skin, as compared with the control batch stored without ozone. Sensory analyses confirmed an extended shelf life of turbot specimens stored in ozonised slurry ice; these maintaining ‘‘A’’ sensory quality up to day 14, while the counterpart batch stored in slurry ice kept this quality only up to day 7. The combination of ozone and slurry ice may be recommended for the chilling and storage of farmed turbot with a view to extending its shelf-life.

The application of slurry ice, a binary mixture of small spherical ice crystals surrounded by seawater at subzero temperature, is a potentially new preservation method for farmed turbot (Psetta maxima), a flat fish species of increasing commercial interest. Comparative biochemical, microbiological and sensory analyses were carried on turbot specimens stored in either slurry or flake ice for up to 40 days. The results obtained in the sensory analysis correlated well with the observed chemical and microbial changes. Storage of turbot in slurry ice resulted in a slowing-down of the nucleotide degradation pathway and lipid oxidation mechanisms. A good stabilisation of the high molecular weight protein fraction of turbot muscle was also achieved as a consequence of storage in slurry ice. A slower production of both trimethylamine and total volatile bases was also observed. Likewise, low levels of total aerobes, anaerobes, coliforms, and proteolytic bacteria were attained. The application of slurry ice to farmed is advisable to achieve better quality maintenance during storage and distribution.

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.

The use of slurry ice, both alone and in combination with ozone, as compared with traditional flake ice was investigated as a new refrigeration system for the storage of sardine (Sardina pilchardus). Microbiological, chemical and sensory analyses were carried out throughout a storage period of 22 days. According to sensory analyses, sardine specimens stored in ozonised slurry ice had a shelf life of 19 days, while counterpart batches stored in slurry ice or flake ice had shelf lives of 15 and 8 days, respectively. Storage in ozonised slurry ice led to significantly lower counts of aerobic mesophiles, psychrotrophic bacteria, anaerobes, coliforms, and both lipolytic and proteolytic microorganisms in sardine muscle, and of surface counts of mesophiles and psychrotrophic bacteria in sardine skin as compared with the slurry ice and the flake ice batches. In all cases, the slurry ice batch also exhibited significantly lower microbial counts, both in muscle and skin, than the flake ice batch. Chemical parameters revealed that the use of slurry ice slowed down the formation of TVB-N and TMA-N to a significant extent in comparison with storage in flake ice. A combination of slurry ice with ozone also allowed a better control of pH and TMA-N formation as compared with slurry ice alone. This work demonstrates that the combined use of slurry ice and ozone for the storage of sardine can be recommended to improve the quality and extend the shelf life of this fish species.

Slurry ice is a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature. Its employment was evaluated in the present work as a new chilled storage method for whole horse mackerel (Trachurus trachurus) and compared with traditional flake icing. Different chemical analyses (nucleotide degradation, lipid hydrolysis and oxidation, interaction compounds formation and electrophoretic protein profiles) related to quality loss were checked and compared to sensory evaluation. An inhibitory effect on quality loss mechanisms was observed for the slurry ice treatment, according to the assessment of the K value, free fatty acid content, thiobarbituric acid index, fluorescent compounds formation and sarcoplasmic protein profiles. The sensory analysis showed a higher shelf-life time for fish treated under slurry icing than for flake iced fish (15 and 5 days, respectively). Results confirm the practical advantages of using slurry ice as a chilling storage method. According to the inhibition of lipid hydrolysis and oxidation obtained, the employment of slurry ice on relatively fat fish species is recommended to obtain safer and higher quality fish products.

The application of slurry ice systems—consisting of ice-water suspensions prepared from marine water and chilled at subzero temperatures—to the storage of aquatic food products is receiving increasing attention. Such binary systems—described in the scientific literature as flow ice, fluid ice, slush ice or liquid ice—afford two main advantages concerning the handling and storage of seafood: a faster chilling rate as compared with flake-ice or refrigerated seawater (RSW), deriving from its higher heat-exchange capacity, and the reduced physical damage caused to seafood products by its spherical microscopic particles as compared with conventional ice. Oxidation and dehydration mechanisms may also be limited by the overall coverage of the whole surface of the products. In this article we review the theoretical rationale of slurry ice systems, their main technical features, and current and future practical applications aimed at increasing the added value of aquatic food products

Slurry ice, a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature, was evaluated as a new chilled storage method for whole European hake (Merluccius merluccius), a gadoid fish species of remarkable commercial interest, and this method was compared with a control batch stored for 19 days in traditional flake ice. The results obtained in the sensory analysis indicated a significant extension of shelf-life – from 5 days (flake ice batch) to 12 days (slurry ice batch) – in the latter batch, mainly deriving from a better maintenance of both external and fresh odour, the appearance of the gills and consistency. The slurry ice batch exhibited a significantly lower increase in pH as compared to the flake ice batch, this indicating a better control of the former over alkalinising microflora. Thus, significantly lower counts of total aerobes and proteolytic bacteria were also attained in hake muscle stored in slurry ice, microbial numbers reaching average differences of 1 log unit before 12 days of storage and above 2 or 3 log units, respectively, when this period was extended up to 19 days. The formation of total volatile basenitrogen and trimethylamine were also significantly lower in the slurry ice batch after 12 days of storage. According to the parameters assessed, storage of European hake in slurry ice extends the shelf-life of this species and allows a better maintenance of sensory and microbiological quality.

The presence of specific enzymes in the sarcoplasmic protein fraction of eight gadoid fish species has been investigated following isoelectric focusing (IEF) in the 3.5–9.5 pH range. Lactate dehydrogenase (LDH) and glycerol-3-phosphate-dehydrogenase (G-3-PD) allowed the differentiation of most of the gadoids tested, even in the case of closely related species belonging to the genus Merluccius. Investigation of arginine kinase and creatine kinase afforded non-specific enzyme patterns in the species tested. Adenylate kinase and malate dehydrogenase did not give specific or reproducible enzyme patterns. Analysis of LDH and G-3-PD activities in commercial IEF gels was shown to be a reliable and reproducible technique for distinguishing closely related Merluccius spp. and other gadoid fish species