Multisensor for fish quality determination

The European fish industry is still reluctant to implement methods other than sensory to monitor freshness and quality of fish products, although general concensus exists about the importance of various quality attributes and the need for methods to monitor quality. The objective of the project FAIR CT98-4076 (MUSTEC) was to evaluate several physico-chemical techniques and to integrate their outputs into a more robust estimate of the freshness quality of fish. The techniques used for this multisensor approach were based on visible light spectroscopy, electrical properties, image analysis, colour, electronic noses and texture. Combining the outputs of the instrumental techniques and calibrating them with sensory scores of Quality Index Method (QIM) for attributes like appearance, smell and texture, gives an Artificial Quality Index (AQI) that can be as accurate and precise as the QIM sensory score. The outcome provides a basis for the construction and industrial exploitation of multi-sensor-devices for defining the quality of fish.     

Development of a Quality Index Method for Frozen Hake (M. capensis and M. paradoxus)

A quality index method (QIM) consisting of 9 parameters with a total of 17 sensory points was developed for frozen hake (M. capensis and M. paradoxus). The score sheet was divided into 2 parts. The 1st, including 7 parameters with up to 13 sensory points, was directly related to loss of quality during storage at ?20 °C. Multivariate analysis confirmed the relevance of these parameters for prediction of storage time. The 2nd part contained 2 additional parameters scoring up to 4 sensory points. These parameters are commercially important but not directly linked to storage time.     

USE OF SEMITRAINED PANEL MEMBERS IN THE SENSORY EVALUATION OF HAKE (MERLUCCIUS MERLUCCIUS, L) ANALYZED STATISTICALLY

Abstract The main objective of this study was to evaluate the responses of semitrained sensory assessors to parameters traditionally used in the sensory analysis of hake and to compare their performance with that of trained inspectors. Appropriate statistical methods were used to validate this objective.
The study was carried out with whole gutted hake stored for 7 and 12 days in a controlled atmosphere consisting of 60%/15%/25% (CO₂/O₂/N₂), followed by conventional storage in ice. The hake stored under the CA conditions were preserved better than the control hake at 7 days and at 12 days the difference was even more in favor of the CA storage. Ten parameters evaluated in the sensory tests could be reduced to five with no loss in essential information. The evaluations of the semitrained assessors largely correlated with those of trained inspectors. A model using five parameters and semitrained assessors could be routinely used to evaluate the quality of cooked hake previously stored in ice.     

Effects of previous frozen storage on chemical, microbiological and sensory changes during chilled storage of Mediterranean hake (Merluccius merluccius) after thawing

The present work aimed to investigate the influence of freezing (−20 °C for 6 months) on the susceptibility of hake to chemical, microbiological and sensory spoilage once thawed and stored in ice. Thus, volatile and biogenic amines, counts of psychrotrophic and mesophilic bacteria, enterobacteria, pseudomonads and Shewanella together with sensory evaluation (of raw and cooked samples) were monitored during 14 days of iced storage in both fresh and frozen-thawed hake (Merluccius merluccius). At the beginning of ice storage, freshness parameters were equivalent in both batches (fresh and frozen-thawed hake), but different behaviour was observed during the iced storage. Overall, levels of volatile and biogenic amines increased much later and then decreased to lower values in frozen-thawed hake in accordance with the delay of microbial development in comparison with fresh hake. On the contrary, sensory spoilage occurred earlier in frozen-thawed hake. Therefore, the usual accepted or regulated limits of acceptability of chemical and microbiological parameters would not be suitable for freshness assessment of frozen-thawed hake.     

Suitability of Volatile Amines as Freshness Indexes for Iced Mediterranean Hake

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

TIME- TEMPERATURE TOLERANCE AND PHYSICAL-CHEMICAL QUALITY TESTS FOR FROZEN RED HAKE

Frozen storage life of red hake fillet blocks was estimated by sensory evaluation to be 150 weeks at —20°F, 71 weeks at —5°F, 25 weeks at +5° F, 7.5 weeks at +10°F and 2.7 weeks at +20°F. Shelf life was limited by the development of a tough, fibrous texture and the reaction proceeded at a faster rate at temperatures above +5°F. Dimethylamine content, formaldehyde content and shear force measurement correlated very well with sensory texture score and thus, these objective tests could be useful for predicting textural quality. For product stored at temperatures above —5° F there was good correlation between extractable protein nitrogen and sensory texture score, but this correlation decreased with lower storage tempratures. Trimethylamine oxide content and pH diminished during the early phase of storage and then progressively increased during continued storage. Centrifuged drip as an objective quality test did not appear to be sufficiently sensitive or reliable for assessing textural quality.     

Establishment of quality predictive models for bighead carp (Aristichthys nobilis) fillets during storage at different temperatures

Quality predictive models were developed to predict the freshness of bighead carp (Aristichthys nobilis) fillets during storage at different temperatures. Quality indices [sensory score, total volatile base nitrogen (TVB‐N), total aerobic counts (TAC) and K value] at ?3, 0, 3, 9 and 15 °C were estimated and kinetically modelled by the Arrhenius equation. The activation energy (E_A) of sensory score, TVB‐N, TAC and K value was 78.17, 75.93, 106.53 and 76.21 kJ mol^?1, and the corresponding rate constants (k₀) were 1.16 × 10¹⁵, 2.60 × 10¹⁴, 4.05 × 10¹⁹ and 1.36 × 10¹⁵. The high regression coefficients (R² > 0.87) indicated the acceptability of the zero‐order reaction for sensory score, TVB‐N, TAC and K value. Relative errors between predicted and observed freshness indicators values of sensory score, TVB‐N, TAC and K value were all below 10% except the values at 6th day of K value, 3rd day and 9th day of TVB‐N. These results indicated that the models based on sensory score, TVB‐N, TAC and K value could effectively predict the freshness indicators of bighead carp fillets at the range of ?3 to 15 °C.     

Effect of modified atmosphere packaging on Quality Index Method (QIM) scores of farmed gilthead seabream (Sparus aurata L.) at low and abused temperatures

A Quality Index Method (QIM) scheme was developed for modified atmosphere packaging (MAP) packed gilthead seabream, and the effect of MAP gas mixtures (60% CO2 and 40% N2; 60% CO2, 30% O2, and 10% N2), temperature (2, 4, and 8 °C), and time of storage on QI scores was assessed. QI scores were crossed with sensory evaluation of cooked fish according to a modified Torry scheme to establish the rejection point. In order to reduce redundant parameters, a principal component analysis was applied on preliminary QIM parameters scores coming from the best performing MAP among those tested. The final QIM scheme consists of 13 parameters and a maximum demerit score of 25. The maximum storage time was found to be 13 d at 4 °C for MAP 60% CO2 and 40% N2. Storage at 2 °C do not substantially improved sensory parameters scores, while storage under temperature abuse (8 °C) accelerated drastically the rate of increase of QI scores and reduced the maximum storage time to 6 d.     

Development of an indirect α-actinin-based immunoassay for the evaluation of protein breakdown and quality loss in fish species subjected to different chilling methods

α‐Actinin release from the myofibrillar protein fraction to the sarcoplasm can be considered as an accurate proteolysis index in seafood muscle. The main objective of the present study was to develop a specific enzyme‐linked immunosorbent assay (ELISA), based on the use of a monoclonal antibody against α‐actinin to evaluate the degree of proteolysis in two different chilled fish species – European hake (Merluccius merluccius) and turbot (Psetta maxima) – kept under two different storage systems: flake ice and slurry ice. Comparison with sensory assessment, K‐value and sarcoplasmic protein profiles was carried out. A different degree of proteolysis could be observed in both fish species; thus, the immunoassay was shown to be useful in monitoring the protein degradation events in hake muscle especially under flake ice storage. In the case of turbot, as very low proteolysis development could be obtained, the assay was not suitable for assessing quality changes. A different break point of immunoassay values for each fish species is suggested.     

Total,non-volatile free fatty acids as a freshness index for hake (Merluccius hubbsi) stored in ice

Total, non-volatile free fatty acids (FFA) content was determined in hake muscle during fish storage in ice. FFA increased linearly in every season according to freshness loss as determined by sensory scoring. FFA determination is proposed as a valuable alternative to sensory scoring in determining fish deterioration in ice.     

Biogenic amine index for freshness evaluation in iced Mediterranean hake (Merluccius merluccius)

Biogenic amine accumulation was studied during the ice storage of Mediterranean hake. Sensory analysis and counts of Shewanella, Pseudomonas, enterobacteria, psychrotrophic, and mesophilic bacteria provided complementary information on hake spoilage. Putrescine and cadaverine were the main amines accumulated, whereas histamine and tyramine were minor amines but had qualitative interest from the hygienic point of view. Although all biogenic amines were less abundant than in pelagic fish, they may also be used as indicators of freshness and/or spoilage in hake. Cadaverine was the amine best correlated with Shewanella, which was the specific spoilage organism. Therefore, cadaverine may be regarded as the specific spoilage biogenic amine for hake stored at chilling temperatures. However, the biogenic amine index, which considers cadaverine, putrescine, histamine, and tyramine, has several advantages as an indicator of hake quality. Taking into account sensory data, an acceptability limit of the biogenic amine index could be established in 15 to 20 microg/g.     

Correlation between biochemical and sensory quality indices in hake stored in ice

Whole gutted hake was stored for 25 days in ice. Changes in pH, trimethylamine nitrogen (TMA-N), total volatile basic nitrogen (TVB-N), and lipid deterioration [2-thiobarbituric acid (TBA) index] was studied, and correlated with sensory analysis (inspection and tasting). There was a very high correlation between TMA-N and TVB-N indices. TBA levels remained very low throughout the assay and were correlated with the results found in the tasting analysis, where the tasters did not detect any rancidity. However, the TBA results had a very low correlation with the inspection analysis and the TMA-N and TVB-N analyses. The pH, TMA-N and TVB-N indices had a very high correlation with the sensory analyses, which means these parameters are more suitable as indices for spoilage of hake.     

Stress-relaxation test to evaluate textural quality of frozen stored Cape hake (M. capensis and M. paradoxus)

A stress-relaxation test was developed for frozen stored Cape hake (M. capensis and M. paradoxus) to be used as a quality assessment tool. Fish was compressed by 5% and deformation was kept constant for 60 s. The resulting relaxation curves were fitted to different multiexponential regression models. A three-term exponential fit without a residual term was chosen as the best model. Relaxation parameters from this test correlated well with sensory texture attributes derived from the quality index method (QIM). The high degree of correlation (0.90) suggests that these relaxation parameters could be used as markers for evaluating textural quality of frozen Cape hake, replacing sensory assessment. The regression model was: STA = 0.117 + 0.967 RP (where STA = PC1 from sensory texture attributes and RP = PC1 from relaxation parameters), with P < 0.001.     

Residual effect of CO2 on hake (Merluccius merluccius L) as a function of the period of time in controlled atmosphere storage

Whole gutted hake kept in a controlled atmosphere (60% CO₂/15% O₂/25% N₂) for 7 and 12 days in containers in the hold of the fishing vessel and then stored conventionally in ice was compared with hake stored in ice and treated in the traditional way. The residual effect of the atmosphere containing CO₂ prolonged the shelf‐life of chilled hake by 2–5 days compared with that of hake stored in ice. This residual effect of CO₂ was dependent on the period of time in the controlled atmosphere; 12 days in this atmosphere was the optimum to obtain the maximum residual effect of CO₂. On day 25 the legal limit of total volatile basic nitrogen (TVBN) was reached in hake previously kept under the controlled atmosphere for 12 days (CA12), and the hake was also rejected in the inspection and pH analyses. However, this lot did not reach the legal limit of trimethylamine nitrogen (TMA‐N) during the 25 days of storage. Similar results were found by a sensory panel, who rated the hake kept in controlled atmosphere storage (CA12) well. Copyright © 2002 Society of Chemical Industry     

Effects of Vacuum Packaging, Glazing, and Erythorbic Acid on the Shelf-Life of Frozen White Hake and Mackerel

The quality changes during frozen storage of two underutilized species of fish: mackerel (Scomber scombrus), a fatty species, and white hake (Urophycis tenuis) a nonfatty, gadoid species, with or without a bag, vacuum, and/or erythorbic acid, were measured using the dimethy-lamine (DMA) test for hake and the thiobarbituric acid (TBA) test for mackerel, and by Instron deformation, expressible moisture, thaw drip, cook loss, and sensory evaluation for both species. Texture deterioration and lipid oxidation limited the shelf-life of hake and mackerel, respectively. Air (oxygen) prolonged the shelf-life of hake but lessened that of mackerel. Erythorbic acid accelerated the rate of texture deterioration in hake but inhibited the rate of lipid oxidation in mackerel.     

Some comments on the usefulness of 2-thiobarbituric acid (TBA) test for the evaluation of rancidity in frozen fish

Rancidity of frozen fish (Baltic cod and herring, mackerel, horse mackerel and hake) was determined by means of TBA value, organoleptical scoring and peroxide value. The correlation between the rancid odour sensory assessment and TBA test results proved insignificant (r = 0.53). Model experiment was undertaken in which promine D with addition of papain was incubated at 50°C over 44 h. It was shown that as accumulation of protein hydrolysis products proceeded the increase of TBA value has taken place without development of rancid odour and with peroxide content below sensibility of sulphocyanide method. With regard to fish, therefore, it seems that the TBA test applied by means of techniques in which the reaction with TBA proceeds in the presence of interfering substances should be treated as a ?freshness test”? rather than a strictly rancidity one.     

Extra-Cold Storage of Hake and Mackerel Fillets and Mince

Extra-cold storage (?30 and ?40°C) of mackerel (Scomber scombras) mince and fillets showed lower free fatty acid formation. Extra-cold storage (-30°C) of white hake (Urophycti tenuis) fillets produced fish with better quality based on sensory and chemical indices. The colder the storage temperature, the less firm the hake mince and fillets. Ascorbic acid accelerated cohesiveness development of mackerel mince and fillets. Over time, the quality of the hake and mackerel decreased according to sensory and chemical indices. They became tougher and generally more cohesive.     

Restructuring Veal Steaks with Salt/Phosphate and Sodium Alginate/Calcium Lactate

Quality characteristics of restructured steaks formulated with veal trimmings or veal leg meat and Na-alginate/Ca-lactate or salt (NaCl)/phosphate were evaluated. Trimmings restructured with salt/phosphate had higher (P<0.05) bind scores (measured instrumentally and by sensory) than veal trimmings restructured with Na-alginate/Ca-lactate. Salt/phosphate (0.3–0.5%) reduced (P<0.05) purge and increased binding force and sensory score of bind in restructured veal trimmings and leg meat compared to control and Na- alginate/Ca-lactate treatments. The use of Na-alginate/Ca-lactate as a binder for veal leg meat increased (P<0.05) binding force and sensory score of bind and decreased cook loss when used at 0.4%.     

Sensory and flavor profiles as a means of assessing freshness of hake (Merluccius merluccius) during ice storage

Freshness of hake stored in ice was evaluated by sensory and instrumental means. The European Union scheme and the quality index method (QIM) were used to sensorially index freshness. Aroma extract dilution analysis (AEDA) and SPME-headspace determinations were applied to monitor important odorants of hake at different freshness stages. Based on AEDA, potent odorants of hake in the very fresh state were (Z)-1,5-octadien-3-one and 3 unknown volatiles. Attempts were made to relate overall odor changes to individual volatiles: after 2 days storage, the higher FD-factors found for trans-4,5-epoxy-(E)-2-decenal, (Z)-4-heptenal, methional, and 2-acetyl-1-pyrroline were associated with the “masking” of the seaweed character, whereas the higher concentrations of (Z)-1,5-octadien-3-one and (Z)-4-heptenal in hake that reached the B grade were likely responsible for the pungent odor. No highly volatile odorants were detected in hake using SPME-headspace analysis, but in contrast to AEDA, the odor intensity of some volatiles, e.g., (E,Z)-2,6-nonadienal and 3-methylnonane-2,4-dione indicated a higher contribution. The detection of two low boiling odorants associated with fresh fish flavor is reported for the first time.     

Effect of frozen storage on the quality of whole fish and fillets of horse mackerel (Trachurus trachurus) and mediterranean hake (Merluccius mediterraneus)

 Whole fish and fillets of horse mackerel (Trachurus trachurus) and mediterranean hake (Merluccius mediterraneus) were assessed for quality (physical, chemical and sensory attributes) changes throughout 12 months of frozen storage at −18 °C. The pH, expressible water (EXW), quantities of trimethylamine (TMA), dimethylamine (DMA), formaldehyde (FA), the total volatile base nitrogen (TVB-N) the thiobarbituric acid number (TBA), peroxide value (PV) and amount of free fatty acids (FFA) increased, while sensory attributes (odour, taste, texture) decreased during the frozen storage period. A comparison of quality scores between whole fish and fillets of horse mackerel and mediterranean hake showed that there were no significant differences (P>0.05) in attribute scores. There were, however, significant differences (P<0.05) in pH, EXW, TMA, DMA, FA, TVB-N, TBA, FFA and PV. Received: 19 April 1996/Revised version: 7 September 1996