Resumen de Influence of high pressure treatments on goat’s milk cheese for the improvement of its sensory and commercial characteristics
Natàlia Nicolau Villellas
The overall goal of the present PhD thesis was to study some factors related to the choice of pressure intensity (100, 200 or 300 MPa) and the moment of high-pressure (HP) treatments application (before or after brining; BS and AS respectively) that could influence water binding, textural characteristics and sensory profile of pressurized goat¿s milk cheeses compared with the control cheeses. First of all several cheese making productions were carried out in order to tune up the manufacture conditions, especially pursuing the goal of major water binding by conventional methods. Different pressure and time conditions were tested during pressing, two different brining times and two different relative humidity values in the ripening room were studied. From these works, the best conditions retaining higher moisture content were chosen and applied to cheese manufacturing. Results indicated that pressure intensity was the variable which most affected goat¿s milk cheeses, and in a lesser extent the moment of application. In regards to physic-chemical characteristics, 300 MPa HP-treated cheeses showed highest pH values and moisture content. Additionally, these cheeses appeared as much more ripened than others, probably due to color enhanced characteristics and higher proteolysis values. In relation to textural parameters, pressurized cheeses at 300 MPa were less firm and account for higher strain values compared with the control and the rest of pressurized cheeses. Significant differences referring to high-pressure treatments at different moments of brining appeared in 100 and 200 MPa cheeses, resulting AS samples in lower fracture stress (¿ t) values at day 30 of ripening. Micrographs were quantified and the microstructure of cheese analyzed obtaining a different microstructure determined by low levels in porosity, especially in 300 MPa cheeses. At the end of ripening, higher lipidic area was another characteristic attributed to 300 MPa cheeses compared to the rest of cheeses. Cheeses high-pressure treated at 300 MPa received a significantly higher overall grade than did other samples respect to the sensory analysis, mostly with regards to textural parameters, leading to better mouthfeel cheeses as punctuated by panelists. Internal moisture profiles of goat¿s milk cheeses were affected in a great manner by pressure intensity applied and in a lesser extent, by the moment of HP application. 300 MPa cheeses showed greater amounts of W1 (free water) released at all sampling points during ripening. Although little oscillations of W3 were found at first stages of ripening, 300 MPa samples finished their ripening with major amounts of W3, together with the control cheese, showing both samples a better binding of water at the optimum ripening point compared with 100 and 200 MPa cheeses. Most of samples reached the equilibrium in regards to the salt content between inner and outer parts of cheese at the determinate optimum ripening point for cheeses in this study (day 30). Regarding the pressure effect, HP samples, especially 300 MPa cheeses revealed a greater penetration of salt at day 1, showing higher values than control and the rest of pressurized cheeses in the inner part of cheese. While control or other pressurized cheeses did not reach salt uptake equilibrium before day 30, 300 MPa cheeses revealed a faster diffusion of salt during ripening obtaining similar values between both cheese parts studied (inner and outer) at day 7 of ripening. No large effect can be observed in high-pressure treated-samples respect to the moment of brining and the salt content. In this study, HP-treatments caused several changes on the overall amount of volatile compounds found in goat¿s milk cheeses. While pressures of 300 MPa seemed to increase total amount of volatile compounds, cheeses treated at 100 and 200 MPa revealed lower levels compared with the control cheese leading to an impoverished volatile profile. The absence or presence of several compounds in 300 MPa treated-cheeses modified their volatile profile enhancing it by minimizing the mouldy or sharpness and goaty notes of 300 MPa cheeses. It can be drawn that novel textures and flavors, certainly due to the better water binding could be developed by HP processing applying 300 MPa HP-treatment. This technology may provide new textures to traditional cheeses or even the possibility to create novel types of cheese enhancing their commercial characteristics being more appealing to consumers and providing beneficial factors, economically speaking.
