Isabel Fernández-Segovia

Evaluation of sea bream (Sparus aurata) shelf life using an optoelectronic nose.

A new optoelectronic nose for the shelf-life assessment of fresh sea bream in cold storage has been developed. The chromogenic array used eight sensing materials (based on aluminium oxide and silica gel) containing pH indicators, Lewis acids and an oxidation-reduction indicator. The colour changes of the sensor array were characteristic of sea bream spoilage. Colour modulations were measured on day 0 and for the samples held in cold storage for 2, 4, 7, 9 and 11 days. Determination of moisture content, pH, total volatile basic nitrogen (TVB-N), drip loss, ATP-related compounds and K(1)-value and microbial (mesophilic bacteria and Enterobacteriaceae) analyses were carried out on the same days. The changes in the chromogenic arrays data were processed by statistical analysis (PCA). Moreover, PLS statistical studies allowed the creation of models to correlate the chromogenic data with concentrations of mesophilic and Enterobacteriaceae. The results suggest the feasibility of this system to help develop optoelectronic noses for fish freshness monitoring.

Development of a colorimetric sensor array for squid spoilage assessment

The aim of this work was to develop and evaluate a rapid, easy-to-use optoelectronic system for the shelf-life assessment of squid in cold storage. For this purpose, an optoelectronic nose was designed, which consisted of an array containing six sensing materials prepared by combining different dyes and two inorganic supports (aluminium oxide and silica gel). Samples were packaged with the colorimetric array and kept in cold storage for 12 days. Squid spoilage was monitored simultaneously by the colorimetric array and by the physico-chemical and microbial analyses during storage. Samples exceeded the acceptability limits for microbial counts on the third day. PCA analysis carried out with CIELab showed that the colorimetric array was able to discriminate between fresh squid fit for consumption and spoiled squid. The statistical models obtained by PLS, with the optoelectronic nose, successfully predicted CO2 and O2 content in the headspace as well as microbial growth.

Effect of partial sodium replacement on physicochemical parameters of smoked sea bass during storage

The objective of this work was to study the effect of partial sodium replacement by potassium and packaging conditions on the physicochemical properties of smoked sea bass during cold storage. Sea bass fillets were salted with 100% NaCl (Na samples) or with 50% NaCl–50% KCl (Na:K samples), smoked, packaged under three different conditions (air, vacuum and modified atmosphere) and stored at 4 °C for 42 days. Physicochemical parameters, color and texture were periodically determined in the raw material and in smoked samples during cold storage. The smoking process led to a reduction in moisture, pH and aw values, and an increase in water holding capacity, ash and mineral contents. Smoked fish exhibited significant differences in color and texture as compared to fresh fish. The type of packaging had an effect on the pH, water holding capacity and texture. Samples in air exhibited the highest pH values and water holding capacity in these samples gradually decreased during storage. Textural parameters decreased during storage in samples packaged in vacuum and modified atmosphere. The pH of Na samples was initially higher than in Na:K samples, and this difference remained over the rest of the study. The type of salt did not affect the texture or other physicochemical parameters.

Influence of the Presence of Skin on the Salting Kinetics of European Sea Bass

The objective of this work was to study the influence of the presence of skin, as well as the effect of size, thickness, initial weight and salting time on the dry salting kinetics of European sea bass, in order to characterise the salting process to obtain a lightly salted product. Fillets salted by the skin side showed lower salt gain and water and weight losses, which would indicate the barrier effect of skin on mass transfer. Processing time, contact area, initial weight and volume had significant effect on weight loss. Meanwhile, only processing time and initial weight were significant variables for water and NaCl weight changes, however thickness, contact area and volume were not significant due to the high effect of initial weight. However, it could be considered that thickness, contact area and volume had an indirect effect on mass transfer because initial weight was directly related to these variables. Salt diffusivity value in samples salted on the flesh side (7.54 × 10-11 m 2/s) was similar to that reported in other studies.

Evolution of Volatile Fraction and ATP Related Compounds During Storage of Desalted Cod (Gadus morhua)

The objective of this work was to study the evolution of the volatile fraction, and ATP and its breakdown products, in desalted cod thermally treated (water blanching, steam blanching and microwave heating), stored at 4 °C. All analyses were carried out at 0, 7, 14, 21, and 28 days of storage, as in the treated samples as in the control samples (desalted cod without thermal pre-treatment). The study of the volatile fraction revealed a similar behavior of the water blanched and steam blanched samples, by one hand, and of the control samples and those treated with microwave, on the other hand. This fact would imply a lower effectiveness of the microwave treatment on the preservation of the initial odor of desalted cod. The initial K1-values were lower in control and microwave samples than in water and steam blanched samples. However, the higher increase of K1-values throughout the storage in control and microwave samples would indicate a higher spoilage for these samples during the studied period. According to these results, the two blanching treatments were more effective than microwave heating in the preservation of desalted cod.

Characterization of Spanish powdered seaweeds: Composition, antioxidant capacity and technological properties

This work aimed to characterise four seaweed species: nori (Phorphyra), kombu (Laminaria), wakame (Undaria) and sea spaghetti (Himanthalia elongata). Their nutritional composition, total phenolic compounds (TPC), antioxidant capacity, oil and water holding capacity (OHC and WHC), and swelling capacity (SC) were determined. Wakame and nori exhibited the highest proteins contents, rich in essential amino acids and in those related to umami flavour. All the samples had a low lipid content and high ash content values. High fibre levels were observed, especially in kombu. The TPC content and antioxidant capacity of sea spaghetti was significantly higher than in the other samples. The OHC, WHC and SC of the seaweeds demonstrated their potential influence on texture of food products. The incorporation of these seaweeds into different foodstuffs could entail an improvement of the nutritional quality and texture properties, and could also reduce the use of Na and synthetic additives.

Development of a novel smoke-flavoured salmon product by sodium replacement using water vapour permeable bags

BACKGROUND Food manufacturers need to reduce sodium content to meet consumer and public health demands. In the present study, the use of sodium-free (SF) salt and KCl to develop a novel smoke-flavoured salmon product with reduced sodium content was evaluated. Fifty percent of NaCl was replaced with 50% of SF salt or 50% KCl in the salmon smoke-flavouring process, which was carried out using water vapour permeable bags. RESULTS Triangle tests showed that samples with either SF salt or KCl were statistically similar to the control samples (100% NaCl). Because no sensorial advantage in using SF salt was found compared to KCl and given the lower price of KCl, the KCl-NaCl samples were selected for the next phase. The changes of physicochemical and microbial parameters in smoke-flavoured salmon during 42 days showed that partial replacement of NaCl with KCl did not significantly affect the quality and shelf-life of smoke-flavoured salmon, which was over 42 days. CONCLUSION Smoke-flavoured salmon with 37% sodium reduction was developed without affecting the sensory features and shelf-life. This is an interesting option for reducing the sodium content in such products to help meet the needs set by both health authorities and consumers.

Effect of thyme and oregano essential oils on the shelf life of salmon and seaweed burgers

The effect of different essential oils on the quality and shelf life of fish and seaweed burgers during storage was evaluated. For this purpose, thyme and oregano essential oils were selected at a concentration of 0.05% (v/w). Three types of salmon and seaweed burgers were prepared: without essential oil, burgers with red thyme essential oil (0.05% (v/w)) and burgers with oregano essential oil (0.05% (v/w)), which were vacuum packaged and stored at 4 ℃ for 17 days. Physicochemical and microbiological analyses were carried out periodically throughout storage. The addition of both essential oils did not have any effect on the evolution of the pH, the moisture content or texture parameters. Only the thyme essential oil managed to slightly slow down the increase of total volatile basic nitrogen and trimethylamine nitrogen. The samples with oregano essential oil and especially those with thyme essential oil showed minor oxidation. The salmon and seaweed burgers without essential oils and those which contained oregano essential oil showed a faster increase of mesophilic counts than those which had thyme essential oil, but no noticeable improvement was observed in the shelf life of the burgers with thyme essential oil. To improve the shelf life of the fish and seaweed burgers, it would be necessary to increase the concentration of both essential oils.