Use of high pressure and ultrasound as a corrective measure of the pastiness in dry-cured ham

Resumo

This doctoral thesis tried to contribute to solving one of the quality defects whose high incidence leads to great economic losses in the ham industry. In spite of an exhaustive control in the process, 10% of the finished hams present pasty textures, causing technological problems and quality reductions. For this, 200 hams were cured, in which the development of pasty textures was facilitated, being able to carry out the tests of this research work. The objectives were, in a first instance to study the relationship between the proteolysis index and the appearance of texture defects, identifying possible biomarkers associated with proteolytic activity, and also an instrumental determination of its organoleptic consequences. Secondly, from an analytical point of view, to study the effect of two selected non-invasive techniques applied as texture defects corrective measures (power ultrasound and high pressures) on protein structures and organoleptic attributes. At first, adhesiveness and nitrogen fractions were determined to calculate the proteolysis index, being able to classify hams in three intervals: low (<32), medium (32-36) and high (> 36) proteolysis index. Subsequently, free amino acid profile, volatile compound profile and a proteomic study were determined. From the results, it was shown that a high proteolysis index was related to a more adhesiveness as much as an increment in bitter taste and important aromatic losses. The use of power ultrasound could reduce the adhesiveness but it was observed that the taste of samples was turned sweeter, bitterer and more rancid, as well as the typical fatty odour of dry-cured ham could be decreased causing quality reductions. On the other hand, the treatments with high pressures in combination with high temperatures caused intense modifications in the profile of free amino acids and volatile compounds, especially at temperatures of 35 °C. These modifications gave rise to hams apparently with a greater sweet, acid and rancid taste, being the rancid aroma enhanced due to the increased content of aldehyde compounds (especially the hexanal content). However, it was observed that such impact can be minimized when the use of high pressures is combined with temperatures in the range of 0 20 °C. Regarding the proteomic analysis, the main evidence that can be highlighted were the identification of MYH1 and MYH4 protein fragments as suitable proteolysis biomarkers as well as non-fragmented sarcoplasmic proteins namely FABP4 / H, PRDX6, SOD, CBR1 and ACY1 as independent candidate biomarkers of ultrasound treatment. Finally, it was observed that the application of high pressures could promote actin fragmentation.