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Four DNA extraction methods from canned tuna in diVerent liquid media were compared. Wizard DNA Clean Up system with proteinase K previous digestion, Nucleospin (Clontech), GenomicPrep (Amersham Pharmacia Biotech) and the CTAB precipitation method were employed. DNA was extracted from four diVerent canned tuna of the same tuna species, light tuna (Thunnus albacares): light tuna in brine, oil, vinegar and with a tomato sauce. Three samples of each type of product were analysed with the diVerent methods. Quantity and quality of DNA extracted was evaluated using the ratio A260/A280. Also, quality was evaluated by using a set of designed primers amplifying fragments of cytochrome b of increasing size ranging from 100 bp to 300 bp. Results show that DNA extraction from canned tuna preserved in diVerent liquid media could be optimized employing a speciWc DNA extraction method in each case. Best results were obtained with CTAB method for canned tuna in oil and for canned tuna in vinegar, with Wizard method for canned tuna in brine and with Genomic Prep method for canned tuna with tomato sauce.

Present production of wild fish resources is around 85 million tonnes per year, and the maximum long-term potential of marine capture fisheries of some areas and fisheries has been reached. However, not all that is obtained from the sea is adequately used and three clearly differentiated factors can be taken into account to explain this fact: discards, wastage on board and byproducts and wastage ashore. Although some efforts have been made to change this situation, a more efficient and intelligent use is needed of the natural resources extracted from sea and wasted. In this article, the present utilization of discards and fishery wastage and also the futuretrends and the expected future of fishery industry are presented.

The polymerase chain reaction (PCR) technique was employed to obtain a 464 bp amplicon from the mitochondrial cytochrome b gene from gadoid species to study its ability to differentiate them. The sequences of this fragment from 16 species were analysed using a genetic distance method, and polymorphic sites were determined. The fragment was shown to be moderately polymorphic (151 sites), and this permitted the differentiation of most of the species. A phylogenetic tree construction using Tamura-Nei distances was employed to allow the identification of Gadidae species, each species resulted in a well-differentiated clade, with the exception of Gadus ogac and Gadus macrocephalus, which could not be differentiated. Based on the sequences obtained, three restriction enzymes, Dde I, Hinc II and Nla III, were selected to provide specific restriction profiles, which allowed the differentiation of 15 species of gadoids in a faster and less expensive way than sequencing. The PCR-restriction fragment length polymorphism methodology was also tested using commercial samples.

Identification of commercial species is a relevant issue to assure the correct labeling of seafood products. In this work two different molecular techniques, FINS (Forensically Informative Nucleotide Sequencing) and PCR-RFLP (Polymerase Chain Reaction-Restriction Fragment Length Polymorphism) were developed to identify 8 cephalopod species (families Loliginidae and Ommastrephidae) employing a fragment of the cytochrome b gene. DNA amplification for all of the species was carried out with a new set of specific primers designed in this study for cephalopods. FINS is a technique based on DNA sequencing, while PCR-RFLP allows direct species identification by comparing specific DNA restriction patterns. Both techniques are useful for cephalopod species identification. 17 food products (mainly “squid rings”) were analyzed and the species employed for their manufacture identified by FINS.

An identification technique of commercially important cephalopods based on 16s RNA analysis was developed. A set of primers was designed to amplify a fragment of approximately 200 bp that presents enough variability for reliable species identification. Sequences from this fragment of 9 different authentic species were studied, genetic distances were measured, and a phylogenetic tree was constructed, with individuals of the same species grouped within the same cluster. Eight different types of commercial seafood products, mainly labelled as “squid rings”, were analyzed and sequences were employed for species identification showing that FINS is a suitable technique for identification of processed cephalopods.

Trimethylamine N-oxide demethylase (TMAOase) activity of several internal organs of hake were studied for 2 consecutive y. The correlation between enzymatic activity and season of year, sex, weight, and length were analyzed. While kidney and spleen showed the highest activities, liver, heart, bile, and gall bladder activities were much lower, and in some cases they were below the detection limit. A correlation between TMAOase activity of kidney and season was found. During winter and spring (February to May), the months matching the spawning peak, high activities were detected, while in summer months the activity level was lower. TMAOase activity in the rest of the organs did not seem to have a seasonal influence.

PCR-based methods have been developed to differentiate four species of commercially important eels (Anguilla anguilla, A. rostrata, A. japonica, A. australis). By means of universal primers a 464 base pair (bp) section of the cytochrome b gene was amplified. The amplicon was sequenced and restriction enzymes were selected for RFLP analysis; a short part (123 bp) of the 464 bp section was amplified by another set of primers and used for SSCP analysis. The suitability of RFLP and SSCP for differentiating hot-smoked eel was verified by a collaborative study

Folleto conmemorativo del 50 aniversario del Instituto de Investigaciones Marinas de Vigo

Analysis of restriction fragment length polymorphism (RFLP) profiles of a 464 bp amplicon obtained from the mitochondrial cytochrome b gene was used to differentiate between several different fish species. The method was tested by a collaborative study in which 12 European laboratories participated to ascertain whether the method was reproducible. Each laboratory was required to identify 10 unknown samples by comparison with RFLP profiles from authentic species. From a total of 120 tests performed, unknown samples were correctly identified in 96% of cases. Further work attempting to use the method to analyze mixed and processed fish samples was also performed. In all cases the species contained within mixed samples were correctly identified, indicating the efficacy of the method for detecting fraudulent substitution of fish species in food products

The use of DNA-based methodologies in identification of hake species belonging to the Merluccius genus was shown to be successful. A short fragment of the left hypervariable domain of the mitochondrial control region was amplified, sequenced, and digested from 11 hake species. The hake-specific PCR product, due to its limited size, was obtained in a variety of tissue samples with different levels of DNA concentration and degradation, including sterilized food products. On the basis of this phylogenetically informative 156-bp sequence were selected four restriction enzymes (ApoI, DdeI, DraIII, and MboII) that allow the hake species discrimination. Species identification by phylogenetic analysis of sequences or by PCR−RFLP methodologies is useful in a variety of scenarios including authentication of thermally processed food, detection of food components, and species determination of individuals whose morphological characters are removed.

Identification of flatfish species using a DNA-based methodology was studied. The polymerase chain reaction was employed to obtain a 464 bp amplicon from mitochondrial cytochrome b gene. The sequences from this fragment belonging to 24 species were analyzed using a genetic distance method, and polymorphic sites were determined. The fragment was found to be highly polymorphic (231 sites), and this permitted the differentiation of most of the species. Phylogenetic tree construction was employed to allow the identification of flatfish species. As a result, each species was grouped in a well-differentiated clade, except for two pairs: Limanda ferruginea and L. limanda, and Solea impar and S. lascaris, which could not be differentiated. On the basis of the sequences obtained, restriction enzymes were selected to provide specific restriction profiles, which allow the differentiation of 21 species of flatfish in a faster and less expensive manner than sequencing. This polymerase chain reaction−restriction fragment length polymorphism methodology (PCR−RFLP) was tested using commercial samples.

The use of a PCR-RFLP based method for the identification of salmon species in food products was investigated. The reliability and practicality of the method was tested by a collaborative study in which five European laboratories participated. Two unknown samples (a commercial product of known species composition and a mix of two salmon species) required identification by comparison with authentic reference species. From a total of 50 cases, 100% of authentic species were correctly assigned, with all unknown samples also correctly identified. A larger scale analysis of UK commercial products was also performed spanning the whole range of salmon products available. In almost all cases the salmon species declared was confirmed, although, a trout species was detected in one product declaring only the presence of salmon. The investigation confirms the reproducibility of the method in different laboratories, and its applicability for commercial product analysis.

A collaborative study on the use of sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), urea-isoelectric focusing (urea-IEF) and native isoelectric focusing for the identi®cation of species of smoked salmonids, gravad salmonids and smoked eels was carried out by eight laboratories. With SDS-PAGE, minor changes took place in the pro®les of the processed salmonid species making it impossible or very di cult to identify closely related species. With urea-IEF, there were fewer changes in the pro®les due to processing and the system generally had greater species-discriminating power for the processed salmonids than SDS-PAGE. The pro®les of the eel species as obtained on SDS-PAGE or urea-IEF were not a ected by smoking. Urea-IEF had greater species-discriminating power than SDS-PAGE for the eel species. Native IEF was useful in providing supplementary iden- ti®cation on species di cult to identify by SDS-PAGE or by urea-IEF in the case of cold smoked products.

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

An isoelectric point (pI) calibration kit containing fish muscle parvalbumins was prepared and tested for its suitability for isoelectric focusing (IEF) in the presence of 8 M urea. The pattern obtained by urea CleanGel IEF consisted of nine bands covering the pI range 4.96—5.64. This range is relevant for species identification of heated fish by urea IEF. The kit may also be used for native IEF in the low pH range, as demonstrated by running an extract made from the kit together with water-soluble fish muscle proteins on Servalyt Precotes 3—6.

A collaborative study, to validate the use of SDS−PAGE and urea IEF, for the identification of fish species after cooking has been performed by nine laboratories. By following optimized standard operation procedures, 10 commercially important species (Atlantic salmon, sea trout, rainbow trout, turbot, Alaska pollock, pollack, pink salmon, Arctic char, chum salmon, and New Zealand hake) had to be identified by comparison with 22 reference samples. Some differences in the recoveries of proteins from cooked fish flesh were noted between the urea and the SDS extraction procedures used. Generally, the urea extraction procedure appears to be less efficient than the SDS extraction for protein solubilization. Except for some species belonging to the Salmonidae family (Salmo, Oncorhynchus), both of the analytical techniques tested (urea IEF, SDS−PAGE) enabled identification of the species of the samples to be established. With urea IEF, two laboratories could not differentiate Salmo salar from Salmo trutta. The same difficulties were noted for differentiation between Oncorhynchus gorbuscha and Oncorhynchus keta samples. With SDS−PAGE, three laboratories had some difficulties in identifying the S. trutta samples. However, in the contrast with the previous technique, SDS−PAGE allows the characterization of most of the Oncorhynchus species tested. Only Oncorhynchus mykiss was not clearly recognized by one laboratory. Therefore, SDS−PAGE (Excel gel homogeneous 15%) appears to be better for the identification, after cooking, of fish such as the tuna and salmon species which are characterized by neutral and basic protein bands, and urea IEF (CleanGel) is better for the gadoid species, which are characterized by acid protein bands (parvalbumins). Nevertheless, in contentious cases it is preferable to use both analytical methods

Identification of 10 salmon species using DNA-based methodology was investigated. Amplification of DNA was carried out using a primer set which amplified a region of the mitochondrial cytochrome b gene. Sequences of PCR-amplified DNA from the salmon species were used to select six restriction enzymes allowing species to be uniquely classified. RFLP patterns generated following analysis with each enzyme were resolved using polyacrylamide gel electrophoresis and visualized by silver staining. Results indicate that it is possible to differentiate between all 10 salmon species and that the technique could be easily adopted by the food industry for analysis of processed salmon products.

The identification of fish species becomes a problem when the usual identifying characteristics are removed on processing and only a portion of flesh is available. When the flesh is raw or cooked under normal conditions, the species is readily established by electrophoresis of the muscle proteins. The procedure cannot be used for heat-sterilised canned fish as the proteins are severely denatured. DNA is also degraded but techniques are now available for targeting and amplifying species-specific fragments. The amplified products can then be analysed by a range of techniques some of which are suitable for food control laboratories.

Analysis of single strand conformation polymorphism (SSCP) of an amplicon (123 bp) obtained by polymerase chain reaction (PCR) of the mitochondrial cytochrome b gene was used to identify the ®sh species in canned tuna. Single-stranded DNA (ssDNA) was separated by polyacrylamide gel electrophoresis, and visualised by silver staining. The reliability of the method was tested by a collaborative study in which eight European laboratories participated. Seven unknown samples (®ve from individual species and two mixtures of two tuna species) of canned tuna had to be identi®ed by comparison with reference material. From a total of 72 cases, 65 (90.3%) were assigned correctly. Intra-species variability of SSCIP patterns was found in the case of Katsuwonus pelamis and Sarda sarda. As specimens from various ®shing grounds gave two or three di erent patterns of ssDNA, the possibility of some variability of the DNA patterns has to be considered in SSCP analysis of these species

Two fragments of the mitochondrial cytochrome b gene were analysed by PCR-SSCP to differentiate sturgeon caviar. Amplicons of 116, respectively 123, nucleotides were transformed into single strand DNA, separated by native polyacrylamide gel electrophoresis, and visualised by silver staining. Several combinations of gel and buffer types were tested. Species specific patterns of single strand DNA were obtained for beluga-, osietra-, and sevruga-caviar.

Eight gadoid fishesfive hakes (Merluccius spp.), cod (Gadus morhua), pollack (Pollachius pollachius), and blue whiting (Micromesistius poutassou)were characterized in their water-soluble protein profiles by two-dimensional (2D) electrophoresis both by nondenaturing isoelectric focusing (IEF) in the 4−6.5 pH range and gradient SDS−PAGE in the 12−14% range. Species-specific parvalbumin patterns (MW < 13 kDa, pI < 4.6) were observed in most of the species. 2D analysis of mixed extracts revealed that M. merluccius had one parvalbumin (10.4 kDa, pI 3.9) in common with M. australis and M. hubbsi, and two parvalbumins (10.3 kDa, pI 4.1; 10.4 kDa, pI 3.9) in common with M. capensis, respectively. 2D electrophoresis allowed detailed characterization of both the isoelectric points and molecular weights of the major water-soluble proteins and proved to be a valuable tool for the differential characterization among closely related Merluccius spp.

Identification of six canned tuna species using DNA-based methodology was studied. DNA was degraded during the canning process of fish muscle: DNA fragment sizes that ranged from <100 up to 200 bp were obtained from canned tuna muscle, whereas DNA sizes for frozen tuna muscle ranged from <100 up to 20 000 bp. Amplification of DNA from canned tuna muscle was carried out using primers flanking a region of cytochrome b gene of 126 bp. Sequences from PCR-amplified DNA of six tuna species were studied for polymorphic sites; seven diagnostic positions were identified in this fragment for the species studied. The suitability of a genetic distance measurement with phylogenetic tree construction method for the identification of canned tuna species using two cytochrome b sequences (299 and 126 bp) was studied. PCR-amplified DNA from canned tuna was also analyzed by using three restriction endonucleases, BsiYI, MboI, and MnlI. The restriction fragments allowed for the identification of the six tuna species studied.

This contribution addresses the control problem associated with tracking temperature profiles in batch sterilization processes. Dynamic variability of the plant and the unsteady state heat transfer to the product are shown to cause a significant performance degradation when simple PID-type controllers are employed to control the operation. This is especially true when operating at high temperature and low energy consumption. To improve performance, several adaptive control techniques such as selftuning regulator, stable adaptive control and adaptive IMC are compared on a simulation background, and their advantages and drawbacks discussed. In particular, it is shown that performance degradation often occurs at the early stages of recursive estimation, resulting in product overprocessing. To overcome such control degradation, a priori information derived from conservation principles of mass and energy, is incorporated into the control structure and combined with classical recursive identification techniques. This will avoid the appearance of high parameter uncertainty that otherwise would cause degradation of the closed loop response and/or instability. The complete scheme will be included into the IMC framework and their efficiency demonstrated on tracking sets of constant as well as variable (optimum) set point profiles for batch thermal processing

By using single-strand conformation polymorphism (SSCP) analysis of three amplicons of the cytochrome b gene obtained by the polymerase chain reaction (PCR) it was possible to differentiate between various species of tunas and bonitos processed as canned fish. Four different techniques were used to produce single-strand DNA (ssDNA): (i) Denaturation of double-strand DNA (dsDNA) by formamide and alkali, (ii) two-step asymmetrical PCR, (iii) one-step asymmetrical PCR, and (iv) exonuclease digestion of the phosphorylated strand of dsDNA. The technique rendering optimal results depended on the type of amplicon (i.e. the sequence).

A simple and rapid method to identify raw or frozen gadoid fish species is described. The methodology is based on the HPLC separation of water-soluble proteins and monitoring at 230 nm. Chromatographic profiles were reproducible between individuals belonging to the same species; lower variations in the relative retention time than in peak area percentage were observed. Results obtained from an ANOVA test allowed the distinction of characteristic peaks. Profiles were independent of fish quality: fish refrigerated for 10 days showed the same HPLC protein profile as those that were fresh. The ability of the identification procedure was checked by analysis of a set of frozen commercial samples.

Multivariate statistical analyses have been applied to different parameters regarding phospholipid classes with the aim of differentiating between three species of canned Atlantic tuna: albacore (Thunnus alalunga), bonito (Sarda sarda), and big eye tuna (Thunnus obesus). Using forward discriminant function analysis to generate classification functions, 14 variables were chosen, showing the content of the 20:4n−6 fatty acid in the phospholipid fraction, the highest value of Wilk's lambda. An excellent percentage of right classification in the three species groupings was obtained. The efficiency of the generated functions was tested using a set of canned tuna samples. Commercial albacore and bonito samples, samples caught during different years, and overprocessed samples were successfully identified employing this technique.

Histamine levels in samples of Þsh and marine products were determined by capillary zone electrophoresis using phosphate bu¤er at pH 2.44 and UV detection at 214 nm. A plot of the area of the peaks versus histamine concentration was linear over the range of 1Ð100 ppm with a correlation coe¦cient of 0.9996. Calibration using the height of the peak also gave good correlation, with a correlation coe¦cient of 0.9969, at concentrations between 1 ppm and 20 ppm. The recovery of added histamine in di¤erent samples of Þsh and Þsh products was, on average, 99.65%. The method described in this work was used for the quantitation of histamine in Þsh and Þsh products.

In this paper, we present the development and experimental validation of a dynamic model, based on first principles, for the thermal processing of bioproducts in steam retorts. The dynamic variability exhibited in the experiments is explained on the basis of nonlinear flow relations in the input and output streams and its coupling. The performance of the model in simulating several experimental situations proved its validity over a wide range of operating conditions. The utility of the model must be understood in the context of testing and designing efficient control structures. Two examples will illustrate this fact: first, the model is employed to tune PID-type controllers by IMC techniques to control pressure and temperature in the sterilization cycle. The performance of the control configuration will be discussed and their limitations analysed on the basis of the dynamic model. In the second example, the model will be employed to design multivariable nonlinear model-based controllers for the control of pressure and level during the cooling stage. Its performance and robustness will be tested on simulation.

[ES] Durante 16 días se almacenaron sardinas en hielo. A lo largo de este tiempo se estudió la formación de compuestos fluorescentes a distintos máximos de longitud de onda de excitación/emisión con el fin de seguir las posibles variaciones de estos compuestos producidas al aumentar el tiempo de almacenamiento; las medidas de fluorescencia se realizaron sobre las fases acuosa y orgánica (lipídica) resultantes de la extracción de lípidos. Asimismo, estos análisis se compararon con medidas tradicionales de hidrólisis (contenido en ácidos grasos libres, AGL) y oxidación (contenido en dienos conjugados, índice de ácido tiobarbitúrico, TBA) lipídicas. Los índices clásicos de alteración lipídica no proporcionaron una buena medida del estado de alteración en el caso de encontrarse ésta en estado avanzado. Así, el contenido en dienos reflejó un valor creciente hasta el noveno día, produciéndose después un descenso paulatino. Por su parte, las medidas de AGL e índice de TBA mostraron su valor máximo el decimotercer día de almacenamiento, produciéndose posteriormente un ligero descenso. Se observó que a medida que aumentaba el tiempo de almacenamiento se producía un incremento en la fluorescencia de la mayoría de los máximos considerados (393/463 nm, 446/490 nm y 479/516 nm), mientras que otros tenían tendencia a disminuir (327/415 nm, especialmente); como resultado global se producía un incremento relativo de la fluorescencia de los máximos de mayor longitud de onda frente a los de menor longitud de onda. La relación entre dos de los máximos de fluorescencia estudiados (393/463 y 327/415) experimentó un incremento progresivo respecto al tiempo de almacenamiento de la muestra de sardina; el estudio de esta relación en la fase acuosa reflejó una mejor correlación (r= 0,8533) que en el caso de la fase orgánica (r= 0,7457). Con los resultados del presente trabajo se concluye que la medida de compuestos de interacción a través de sus propiedades fluorescentes resulta útil como me, [EN] Sardine was stored at 0°C on ice during 16 days. During this time the fluorescent compounds formation was studied at different wavelength maxima in order to assert quality changes; fluorescence analyses were undergone on the aqueous and organic (lipids) phases resulting from the lipid extraction. Quality measures of lipid hydrolysis (free fatty acids content, FFA) and oxidation (conjugated diene formation and thiobarbituric acid, TBA, test) were also carried out. Traditional indexes of lipid damage did not assert deterioration in the case of advanced damage. Diene content reflected and increasing value till the day 9 of storage, and then a continuous decrease. Further, FFA content and TBA test showed the highest values on the day 13 of storage, followed by a slight decrease. An increase in fluorescence content was observed in most of the excitation/emission maxima studied (393/463 nm, 446/490 nm and 479/516 nm), at the time that others decreased (327/415 nm, specially); as an overall result, a relative increase in the maxima of higher wavelength was observed in comparison with the lower ones. The ratio between two of the fluorescence maxima analyzed (393/463 nm and 327/415 nm) exhibited an overall increase respect to the time of chilled storage. The study of this ratio in the aqueous extract showed a better correlation (r= 0,8533) than in the case of the organic one (r= 0,7457). From the present results, it is concluded that the interaction compounds determination by mean of their fluorescent properties is useful as a damage measure during the chilled storage.

The reliability of isoelectric focusing (IEF) of sarcoplasmic proteins for fish species identification was evaluated by a collaborative study among eight European laboratories. Each laboratory used its own method of IEF to identify 10 unknown samples of raw muscle by means of reference material. In 93% of cases the assignment between sample and reference was correct. In a second study, the influence of extractant (water, low ionic strength buffer, or detergent) and the position of sample application on the protein pattern was examined. Working with light muscle of rainbow trout (Oncorhynchus mykiss), it was found that the type of extractant did not influence the protein pattern. Comparison of the patterns of samples, which had been applied near the anode, in the middle, or near the cathode, revealed differences in the number and nosition of the nrotein bands under the experimental conditions applied by most laboratories. T-his effect was not observed with the Phast System.

A comparative study of the phospholipids of white muscle of six of the comercially utilized tuna species, including quantitative analyses of phospholipid classes and studies of the acyl composition of the major components. Plasmalogen compounds also were identified and quantified. Choline and ethanolamine glycerophospholipids were the most abundant classes in all the samples, as well as the only molecules containing plasmalogens (16∶0, 18∶0, and 18∶1 alkenyl ether chains). The patterns of fatty acid distribution within each of the phospholipid classes showed general similarities in the species analyzed. However, ratios between certain saturated and polyunsaturated fatty acids in different phospholipid classes showed remarkable diffences. The high content of n−3 polyunsaturated fatty acids in the principal phospholipids, such as the plasmalogens, and taking into account the fatty acids possible importance in human nutrition, indicates that the white muscle of tuna species may be a potentially important dietary item.

Changes in total volatile bases (TVB), dimethylamine (DMA), formaldehyde (FA), trimethylamine (TMA) and trimethylamine oxide (TMAO) of whole hake (Merluccius merluccius L.) were evaluated at different temperatures of storage: -5, -12 and -20°C. Significant changes in TVB, DMA, TMA, TMAO nitrogen and FA were observed at -5°C. Only TMAO changed significantly at -12°C and -20°C. TMAO decrease was not, therefore, followed by DMA an&or TMA production at those temperatures.

A capillary zone electrophoresis (CZE) method is described for the analysis of fish sarcoplasmic proteins at low pH. Aqueous extracts of eight flatfish species, containing the sarcoplasmic proteins, were subjected to the action of an electric field in a capillary electrophoresis apparatus; the separated proteins were detected by means of an W detector after less than 35 min. Acceptable resolution and reproducibility were obtained using low protein concentration (0.1 mg/mL) in the extracts analyzed. The CZE protein profiles that resulted were specific for each species and could be employed for differentiation and identification purposes.

[EN] The damage to tuna fish lipids induced by cooking was investigated in theThunnus obesus andTh. thynnus varieties, using conventional and fluorescence detection methods, and the results were compared. As a consequence of thermal processing, the peaks at longer wavelengths increased, which correlated with other conventional indices of lipid damage (i.e. carbonyl compound formation, browning and increases in the free fatty acid content). A special significance was given to the fluorescence ratio between the maxima of the excitation emission data at 393/460 nm and 327/415 nm; increases in this ratio as a result of cooking were less dependent on the samples than were other conventional methods of measuring lipid damage., [DE] Lipidschäden während des Abkochens von zwei Thunfisch-Arten (Thunnus obesus undTh. thynnus) wurden untersucht. Fluorescenzmeßungen in verschiedenen Wellenlängenbereichen wurden mit anderen Methoden verglichen, die zur Bestimmung von Lipidschäden gebraucht werden. Als Ergebnis der Wärmebehandlung wurde eine Fluorescenzverschiebung zu höheren Wellenlängenmaxima offenbar; gleichzeitig zeigten die Qualitätskriterien eine verstärkte Lipidschädigung (Carbonylbildung und Bräunungsentwicklung sowie Zunahme von freien Fettsäuren). Die Fluorescenzverhältnisse zwischen 393/460 nm und 327/415 nm (Maxima) zeigten weniger Abhängigkeit von den Proben als andere Lipidschädenmessungen.

Many processes in the food and bioproducts industry are of the batch type. The increased public awareness about product quality and environmental impact has stressed the need to improve this processes. This can be achieved using computer-aided optimal control methods. The selection of an appropriate algorithm is therefore critical. The advantages of alternative discretized decision methods over the traditional maximum principle have been indicated in the literature. Following these ideas, we have developed a computer package, ICRS/DS (Integrated Controlled Random Search for Dynamic Systems) for the optimization (optimal control) of batch processes, including distributed parameter systems. In a first step, the original optimal control problem is transformed in a constrained nonlinear optimization problem using an adequate parameterization of the control function(s). Finite differences/finite elements methods are used for the solution of PDE's. In a second step, the constrained NLP problem is solved using a stochastic optimization algorithm. This procedure assures convergence with reasonable computation times. Two important operations were optimized using this algorithm: thermal processing of canned foods and air dehydration of bioproducts. Different objective functions (overall nutrient retention, quality factor retention, process time, energy efficiency, etc.), control functions and constraints were considered, resulting in several complex optimal control problems. In all cases, ICRS/DS proved to be a reliable and easy-to-use computational tool. In many cases, the calculated optimal control policies have significant advantages over the present operation conditions.

Protein solubility of whole and minced muscle of hake (Merluccius merluccius L.) was evaluated at different temperatures of storage: -5 °, -12 ° and -20°C. Proteins soluble in 1% NaCI did not show any change at any of the temperatures of storage, while the 5% NaCl-soluble proteins decreased significantly when whole hake was stored at -5 ° and -12°C (p < 0.01). A correlation was found between the decrease of solubility and the production of formaldehyde at -5 ° and -12°C (p < 0.001 and p < 0.01, respectively). Bound formaldehyde (formaldehyde not extractable) increased with storage time at -5 ° (p < 0-001). The addition of formaldehyde to the minced muscle brought about a decrease in both the 1% and the 5% NaCl-soluble proteins. The decrease was dependent upon the temperature, the amount of formaldehyde added and the time of storage. The role of formaldehyde in the denaturation of sarcoplasmic proteins was confirmed by measuring trimethylamino oxide demethylase activity during the experiment.

The opening up of international load markets has resulted in the establishment of new regulations that affect different aspects of labeis, including ingredients lists. Many fish species sold around the world, especially those caught far away from the countries in which they are consumed, need to be processed on board ship, which may result in the subsequent removal of characteristics used for their classification (head, fins, internal organs). ]'he biochemical characterization of fish species could be achieved using proteins or DNA sequences as species-specific markers. Since different seafood products undergo different processes, the method of analysis has to be chosen according to the modifications undergone by fish constituents during processing. As DNA molecules are more stable than proteins to various processes, including thermal treatment, DNA analysis appears to be a promising method for fish species identification.

Thermal processing of conduction-heated canned foods is modelled using three approaches: (A) homogeneous isotropic, (B) homogeneous anisotropic and (C) non-homogeneous anisotropic systems. Based on these models, numerical simulations are performed, using finite differences and finite elements methods. The simulation results are validated with experimental data obtained from the sterilization of canned tuna, a rather complex system. The last approach is found to be the most appropriate, though the second can be used for practical purposes.

The recently developed Q-PI approach for quality control of linear continuous systems is extended to non-linear batch systems. The new control law contains proportional and integral terms with which the operators are intimately familiar. It is shown that control quality may be improved or costs reduced, constktent with the process specifications, by adjusting the tuning constants of the controller. The performance of the control law is demonstrated on a simulated batch retort, and the results indicate the excellent capability of the proposed approach for quality control of (nonlinear) batch processes.

The qualitative and quantitative compositions of 1-0-alk-1-enylglycerolipidosf albacore tuna (Thunnus alalunga) were studied along the canning process. Ether-linked lipids were found as 1-0-alk-1-enyl- 2-acylglycerophospholipids(p lasmalogens). They were studied by means of their dimethyl acetal (DMA) derivatives resulting from the transmethylation of lipid samples. DMA and fatty acid methyl esters could be simultaneously analyzed by gas chromatography using a polar fused silica capillary column (SP-2330). Three major 1-0-alk-1-enyl ether chains (16:0”, 180”, and 18:l”) were identified in albacore lipids using their mass spectra. Phosphatidylethanolamine showed the highest level in plasmalogen content (54.73 5% 1. The acyl composition of plasmalogens and diacylphospholipids was studied. During canning, the plasmalogen content showed a great decrease along the different steps of processing (raw, cooked, and sterilized). However, polyunsaturated fatty acids (PUFAs) from the polar fraction did not show any difference. These results suggest that alkenyl ethers are more susceptible to heat damage than PUFA and should be taken into account when damage in the lipid fraction during thermal processing is considered.

[ES] The kinetics of thermal degradation of thiamine and surface colour (lightness measured as Hunter L-value) in canned white tuna were determined using an unsteady-state experimental procedure. Kinetic parameters were calculated by weighted non-linear regression considering a first-order kinetic model with a dependence of the kinetic coefficient (D) with temperature of the Thermal Death Time (TDT) type. Mass-average retentions of thiamine were calculated using a mathematical model which takes into account the non-uniform and unsteady distribution of temperature inside the container during thermal processing. The high correlation obtained between the predicted and the observed retention values and the small confidence intervals found for the kinetic parameters indicate a high statistical reliability. The kinetic model thus determined permits the simulation and optimization of the process resulting in a better quality of the final product., [DE] Die Kriterien der Wärmedegradation von Thiamin und der Oberflächenfarbe (Messung der Helligkeit mit dem Hunter-Wert L) in Konserven mit weißem Thunfisch werden mittels eines experimentellen Vorgehens von nicht-stationärem Typ bestimmt. Die kinetischen Parameter werden mit nicht-linearer, beschwerter Regression kalkuliert, wobei man einen kinetischen Koeffizienten D mit der Temperatur des Typs TDT bedenken muß. Für die Berechnung der durchschnittlichen Massenerhaltung von Thiamin benutzt man ein mathematisches Modell, das die nicht-uniforme und nichtbeständige Verteilung der Temperatur im Behälter während des Prozesses berücksichtigt. Die erhaltene starke Wechselbeziehung zwischen den vorhergesagten und den beobachteten Werten und zwischen den geringen Konfidenz-Intervallen, die für die kinetischen Parameter gefunden wurden, belegt eine hohe statistische Zuverlässigkeit. Das so bestimmte kinetische Modell erlaubt es, den Prozeß zu simulieren und zu optimieren, mit dem Ziel, die endgültige Qualität des Produktes zu verbessern.

Changes in available lysine and protein digestibility which take place during thermal processing of canned white tuna with olive oil were evaluated using a steady-state procedure. Kinetic parameters were then calculated by means of weighted nonlinear regression and the jac!+ procedures. Good agreement was found between predicted and observed values. The resulting kinetic equations can be used to evaluate, design and optimize thermal processing of tuna in oil.

The role of acetaldehyde (AcH) in producing fluorescent compounds as a result of interaction with food constituents was studied. A model system consisting of albacore (Thunnus alalunga) muscle and AcH in 0.1 M phosphate buffer (pH 7.0) was used. Fish muscle was submitted to three different temperatures (5, 15, and 30 OC) and four different concentrations of AcH (0, 1, 2, and 5% ) during 1 month. Resulting fluorescent compounds were analyzed in the aqueous and organic extracts at three different excitationlemission maxima wavelengths: 3271415,3931463, and 4791516 nm. Brown color formation was also measured in organic extracts at 420 nm. A strong relationship between fluorescence formation as a function of AcH concentration, time, and temperature of reaction was evident. An augmentation in all three variables produced a significant shift of fluorescence to higher excitationlemission maxima wavelengths which was accompanied by a marked increase in browning.

[EN] Lipid damage during albacore processing was investigated by following fluorescence formation at four different excitation/emission wavelength maxima and brown colour development. Analyses were made on aqueous and organic extracts, as well as in dipping oil samples. A fluorescence shift to higher wavelength maxima was observed as a result of processing. At the same time a marked increase in browning was obtained. The most energic sterilization treatment showed the highest damage and fluorescence shift to higher wavelength maxima., [DE] Lipidschäden während der Verarbeitung von Albacore (Thunnus alalunga) wurden durch die Entwicklung von Fluorescenz (Maximum vier verschiedener Wellenlängen) und Bräunung untersucht. Analysen wurden mit wäßrigen und organischen Extrakten sowie Ölmustern durchgeführt. Als Ergebnis des thermischen Prozesses wurde eine Fluorescenzverschiebung zu höheren Wellenlängenmaxima offenbar. Gleichzeitig nahm die Bräunung zu. Daher zeigte die höchste Sterilisationstemperatur die größten Schäden und Fluorescenzverschiebungen zu höheren Wellenlängenmaxima.