Seaweed extract effect on the quality of meat products

Resumo

This Docthoral Thesis tried to contribute knowledge in the field of natural antioxidants applied to meat products. Three brown macro-algae, Ascophyllum nodosum, Fucus vesiculosus and Bifurcaria bifurcata and two micro-algae, Chlorella vulgaris and Spirulina platensis were selected to carry out the experiments of this research work, whose aims were, on the one hand, the study of the antioxidant potential of the previous algae extracts and the evaluation of the inhbitory effect of the macro-algae extracts in an oily food matrix, such as the canola oil and in a meat product such as the pork liver paté, and on the other hand, the study of the efficiency of several extraction conditions to provide extracts with good antioxidant properties, in order to select one of the extracts, from the macro or micro algae chosen for this thesis, to prove its efficacy in delaying oxidation reactions in pork patties. The macro-algae were analysed for their nutritional contribution before experimenting with their extracts. They showed a good nutritional profile, with high amount of PUFAs and proteins with a remarkable biological value. Then, the antioxidant potential of the aqueous extracts of the macro-algae was assessed and their phenolic compounds tentatively identified, higligting the F. vesiculosus extract, which showed the highest antioxidant activity, and the presence of phlorotannins as major phenolic compounds in the three extracts analysed. The aqueous extracts showed to be efficient in delaying both primary and secondary oxidation of lipids when they were applied in canola oil under accelerated storage conditions. Nevertheless, this antioxidant power could not be seen in pork liver pâtés. This unexpected result could be caused by the absence of contact among the product and the oxygen. The low amounts of phenolic compounds found in the aqueous extracts of the macro-algae led to make the decision to analyse several extraction conditions to improve the antioxidant properties of the extracts. The UAE along with water/ethanol (50:50 v/v) was found the one that provided the best results. Once tested in both the macro and micro-algae, it was decided to select the extract from the alga F. vesiculosus to be applied in pork patties, since its antioxidant activity per amout of extract was the highest of the extracts tested. The addition of 1000 ppm of the F. vesiculosus extract to the pork patties protected them against oxidative phenomena. However, this protection was limited, thus the use of this extract in commercial meat or meat products is unviable. The most relevant results extracted from this thesis are that aqueous extracts of macro-algae successfully protected canola oil from lipid oxidation, and that the UAE along with water/ethanol (50:50 v/v) provided an extract capable of delaying oxidation reactions in pork patties, although in a limited way.