Abstract
Aquaculture produces today more than half of the fish consumed in the world. The objective of the present doctoral thesis is to study the application of different technologies to increase and to diversify products coming from aquaculture. Specifically, technologies of vacuum frying and cooking, restructured products and biopreservation have been analyzed from sea bream (Sparus aurata). Three chapters approach the study of these technologies to obtain alternative products from sea bream that allows the diversification of this sector. The first chapter is focused in the study of the process of vacuum frying and cooking of sea bream fillets to evaluate aspects related to its quality like oil uptake, water loss, colour changes, etc. with a goal to establish the optimal times of product processing. In the second chapter the development of restructured products is studied. The effect of different formulations (with or without fiber addition) on the, physico-chemical, sensorial and microbiological characteristics of products obtained (with or without cooking) is analyzed. Finally, in the third chapter the application of biopreservation techniques is analyzed to determine the conditions of biopreservant agent preparation, the process of application and the effect on sea bream fillets shelf life. The obtained results show that the treatment of vacuum frying at 110 ºC and 25 kPa with a time between three and five minutes contributes to reduce the oil content with appropriate losses of moisture, weight and shrinkage. These conditions could be adequate for the application of this treatment. The vacuum cooking treatments studied showed that they do not affect the total fish content of proteins and fats, but this technique can be interesting for the preservation of monounsaturated fatty acids since they maintain higher values of moisture and present a smaller shrinkage. The vacuum cooking at 70 ºC with cooking times higher than six minutes, could be appropriate to obtain juicy products and with a suitable lipidic profile. Related to the development of restructured products, the function of microbial transglutaminase (MTGasa) has been studied and analyzed and salt level (NaCl) in the characteristics of a product formulated with sea bream (Sparus aurata). The effect of the addition of different hidrocolloyds: konjac glucomannan (KGM), sodium carboxymethylcellulose (CMC) and xanthan gum, on the fish protein matrix gel has been analyzed. The obtained result shows that it is possible to develop precooked restructured products as fiber source from sea bream with suitable sensorial, physico-chemical and microbiological characteristics. As far as the use of biopreservants, Lactococcus lactis and nisin were selected and incorporated by means vacuum impregnation technique, with the purpose to increase the shelf life of sea bream fillets packaged and stored in refrigeration. The vacuum impregnation of fillets with nisin and L. lactis showed to be a suitable technique of biopreservation to increase the sea bream fillet shelf life preserved under refrigeration conditions.