Antonio Moral

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.

Growth and metabolic activity of Shewanella putrefaciens maintained under different CO2 and O2 concentrations

Growth, trimethylamine (TMA), off-odour and biogenic amine production by a strain of Shewanella putrefaciens isolated from spoiled hake (Merlucius merluccius L.) and cultured in a model system, were tested under four different gas compositions (60% CO2/40% O2, 60% CO2/15% O2/25% N2, 40% CO2/60% O2, 40% CO2/40% O2/20% N2) and under air. After 3 weeks of incubation, the control (air) batch showed the highest microbial counts (> 9 log cfu/ml) and TMA concentrations (45 mg N-TMA/100 ml), and strong putrid off-odours were detected from day 15. High amounts of putrescine and cadaverine were produced in this batch, but histamine increased only slightly. Batches under controlled atmospheres showed reduced growth, TMA, off-odour and biogenic amine production. The 40% CO2/60% O2 mixture had the strongest inhibitory effect on bacterial growth, while the 60% CO2/15% O2/25% N2 mixture was less effective. Putrescine and histamine production was lowest in S. putrefaciens under the 40% CO2/60% O2 mixture. However, the level of histamine in S. putrefaciens was higher under 40% CO2/40% O2/20% N2 than when the bacteria was incubated in air. Under the gas mixtures, there was a similar decrease in the production of cadaverine and agmatine by S. putrefaciens, irrespective of the gas concentrations. The production of 2-phenylethylamine appeared to be inhibited under any atmospheric condition.

Chilled bulk storage of gutted hake (Merluccius merluccius L.) in CO2 and O2 enriched controlled atmospheres

Abstract This work compares hake gutted whole and placed in boxes in ice under controlled atmospheres (CA) with four different gas mixtures: M1 CO 2 /O 2 /N 2 (%) (60/15/25), M3 (40/40/20), M4 (60/40/0) and M5 (40/60/0) and hake in air for 33 days of storage. The storage chamber temperature was 0±1°C. Biochemical analyses [pH, total volatile basic nitrogen (TVB-N), trimethylamine nitrogen (TMA-N) and thiobarbituric acid (TBA index) and sensory analyses (inspection and tasting)] were carried out to study the quality of the hake. The hake, kept under controlled atmospheres, did not exceed the limits for acceptability of 35 mg/100 g and 12 mg/100 g of TVB-N and TMA-N, respectively, throughout the storage period, and the TBA values remained lower than the recommended limits of 14 mg of malonaldehyde/100 g. Chemical results accorded with the tasters who did not detect any off-odour in the samples, and the M4C lots stored under 60/40/0 (CO 2 /O 2 /N 2 %) was rated the best. However, this result did not accord with the inspection or pH by which all the lots were rejected at day 25 of storage. Despite this, the atmosphere system for preservation of chilled hake could be used safely and effectively on fishing boats to extend the shelf life of this species, and was better than conventional storage in ice.

The effect of frozen storage on the functional properties of the muscle of volador (Illex coindetii)

Abstract Functional properties of muscle proteins of volador (Illex coindetii) were evaluated during frozen storage and classified according to gender and anatomical part of the animal. Solubility of protein in 5% NaCl, in all lots, showed a significant increase in the initial months and then a decrease. This solubility was generally greater in the mantles than in the arms. The viscosity was initially very high and fell rapidly, and there were no significant differences between the lots. This initial viscosity was greater in the arm lots than in the mantle ones. Likewise, extracts of the muscle of the arms also had the greatest initial emulsifying capacity values (P⩽0.05). Soluble collagen, in an acid medium-exhibited a similar trend in all lots, throughout frozen storage. At the early stages of storage, soluble collagen remained stable or increased slightly, and then tended to become insoluble. The lowest solubilities were for the muscles of the arms. Myofibrillar protein and collagen solubilities, as well as emulsifying capacities were effective for detecting molecular changes in the proteins during frozen storage and results showed that, the volador mantles were more suited to frozen storage than the arms.

Characterisation of non-protein nitrogen in the cephalopods volador (Illex coindetii), pota (Todaropsis eblanae) and octopus (Eledone cirrhosa)

Abstract A characterisation of non-protein nitrogen (NPN) was carried out in the muscle of three species of cephalopods: volador (Illex coindetii), pota (Todaropsis eblanae) and octopus (Eledone cirrhosa). These species were classified according to sex, sexual development (immature, mature) and anatomical zone (mantle, arms). There were no major differences in the NPN contents of the three species studied. The anatomical zone clearly marks the difference in NPN content, with the content being greater in the mantle than in the arms for all the species. The trimethylamine oxide–nitrogen levels in volador were greater in the mantle than in the arms and these differences were not observed in the other two species. In pota and octopus, however, it is the stage of sexual development that exhibited differences, with a greater quantity of trimethylamine oxide–nitrogen in the immature specimens than the mature ones. The trimethlyl and total volatile basic nitrogen behaviour had no clear trend, the TVB-N levels were probably so low that these differences were not important. The same thing occurred with the pH, where the lowest values were recorded in octopus and the highest in pota. The free amino acid (FAA) compositions varied to a great extent, depending on the species and, to a less extent, depending on the sex, stage of sexual development and anatomical zone. The total FAA content was virtually the same in volador and pota, while it was about 75% lower in octopus. The highest concentrations of FAA in the three species were for proline, arginine and alanine, but in different proportions.

Changes in fatty acid composition of fresh and frozen sardine (Sardina pilchardus W.) during smoking

Abstract Changes in fatty acid composition in both fresh and frozen sardine during mixed smoking (2h at 30°C and 45 min at 75°C) were studied. After extraction, the lipids from unsmoked and smoked sardine were separated into the three main fractions (triglycerides, phospholipids, and free fatty acids) by thin-layer chromatography; the fatty acids were then analyzed using gas chromatography. Oxidation during smoking brought about losses in the proportion of the long-chain n -3C 20 and C 22 fatty acids, as determined by increases in the peroxide value and in the 2-thiobarbituric acid index. On the other hand, the above polyunsaturated long-chain fatty acids in some conditions increased in frozen sardine, because of extraction-related effects caused by weakening of the protein-lipid linkages.

Formation of biogenic amines in bulk-stored chilled hake (Merluccius merluccius L.) packed under atmospheres.

The production of biogenic amines in the lots of whole hake stored bulk under a controlled or modified atmosphere for 12 days with the gas mixture 40% CO2:40% O2:20% N2 and after packing in trays under a modified atmosphere in the same mixture of gases or with air was studied. Results indicated a close relation between the development of trimethylamine nitrogen (TMA-N) and the sensory parameters gill appearance and odor but not with the general appearance of the skin and eyes. These results were related to changes observed in the concentration of gases (CO2 and O2) during storage containers and trays. The lot of bulk-stored whole hake in controlled atmospheres for 12 days with the gas mixture 40% CO2:40% O2:20% N2 and then packed in trays with the same atmosphere exhibited TMA-N levels below the 12.5 mg/100 g limit designated by the legislation in force (Directive 91/143/EU) on day 31 of storage when the sensory parameters general appearance and skin and gill color were not rejected. Histamine and tyramine levels were less than 1 mg/kg, putrescine levels were approximately 7 mg/kg, and cadaverine and agmatine levels were 33.91 and 20.33 mg/100 g, respectively.

Frozen storage behaviour of squid (Loligo vulgaris)

Abstract Samples of squid were subjected to five different methods of preparation and were then kept at −20°C for 408 days. The texture, as measured by sensory, instrumental and chemical methods, was maintained for all samples and no rancid flavour or odour was found. No melanosis was detected, but if thawed material was held at a chill temperature for three days melanosis then appeared in all batches which were not skinned.

Keeping quality of vacuum-packed smoked sardine fillets: Microbiological aspects

ZusammenfassungDer Einfluß eines modifizierten Räucherverfahrens (2 h bei 30 °C und 45 min bei 75 °C) auf die Haltbarkeit von mageren und fetten Sardinenfilets aus im Mittelmeer gefangenen Fischen, wurde untersucht. Das Rohmaterial für die Räucherversuche umfaßte sowohl frische aus auch tiefgefrorene Sardinenfilets. Mikrobiologische und sensorische Analysen wurden während der gesamten Lagerzeit (120 Tage bei 0 °C ± 1 °C) durchgeführt. Räuchern reduzierte die Werte der mikrobiellen Flora von 3 bis 5 × 104 cfu/g auf Werte von 2 × 102 cfu/g. Die antimikrobielle Wirkung des Räucherns hatte zusammen mit dem Einfluß der Vakuumverpackung den Effekt, daß eine grampositive Flora selektiert wurde, die hauptsächlich aus Milchsäurebakterien bestand. Als praktische Konsequenz hieraus konnte eine Verlängerung der Haltbarkeit der geräucherten Sardinen auf 4 Monate erreicht werden. Eine Gefrierlagerung bei −18 °C der Proben für 6 Monate vor dem Räuchern beeinflußte das Verhalten der mikrobiellen Flora während der Kaltlagerung bei 0 °C für 3 Monate insoweit, daß die anfängliche Bakterienzahl abnahm und das mikrobielle Wachstum verzögert wurde. Am Ende der Lagerzeit war die Zahl der Bakterien in den Proben von tiefgefrorenen fetten Sardinen höher als in denen von tiefgefrorenen mageren Sardinen. Sulfit reduzierende Chlostridien wurden während der Lagerzeit nicht gefunden.SummaryThe effect of mixed smoking (2 h at 30 °C and 45 min at 75°C was studied on the keeping quality of lean and fatty sardine fillets from fish caught in the Mediterranean Sea in March and June, respectively. Raw material for smoking included both fresh and frozen sardine fillets. Microbiological and sensory analyses were performed over the storage period, which lasted for 120 days at 0 ± 1 °C. Smoking reduced the viable microbial flora values from 3–5 x 104 cfu/g to 2 × 102 cfu/g. The antimicrobial action of smoking, combined with that of vacuum packaging, had the effect of producing a gram-positive flora made up mainly of lactic acid bacteria. A practical consequence of this was to extend the shelf life of the smoked sardines for a period of 4 months. Frozen storage of samples at −18 °C for 6 months prior to smoking affected the behaviour of the microbial flora during cold storage at 0 °C, but did not affect the behaviour of the flora over a period of 3 months frozen storage, since the initial numbers of bacteria decreased and microbial growth was retarded. Furthermore, at the end of the storage period, the number of bacteria in the samples of frozen fatty sardines were higher than in the samples of frozen lean sardine. Physical conditions, therefore appear to exert an influence on bacterial growth. Sulphite-reducingClostridia were not detected during the storage period.

Preservation of shelf life of pota and octopus in chilled storage under controlled atmospheres.

Whole ungutted pota and octopus were stored in bulk in stainless steel refrigerated containers under controlled atmospheres. In order to evaluate the effectiveness of this treatment, physicochemical tests (pH, trimethylamine nitrogen, total volatile basic nitrogen, 2-thiobarbituric acid) and sensory assessments (inspection) were done. For both pota and octopus, the control lot had the highest physicochemical values and the lowest sensory values, and of the two assayed atmospheres, the 60/15/25% atmosphere (CO2/O2/N2) had the best physicochemical results. pH, trimethylamine nitrogen, and total volatile basic nitrogen levels were lower (P < or = 0.05) in octopus than in pota, and the inspection results were significantly (P < or = 0.05) higher. However, the octopus had a higher 2-thiobarbituric acid index than the pota. Therefore, the application of controlled atmospheres on these cephalopods during chilled bulk storage considerably increases their shelf life.