Use of High Pressure Homogenization to improve sensorial and microbiological features of low-fat yoghurts

In recent year there has been an increasing demand for a new range of dairy product, including yoghurts, which are similar to traditional ones but have a low fat content. However low fat yoghurts has a texture significantly different from that of the full-fat product Different techniques have been tried to improve the body and texture of these yoghurts, most of them by replacing the milk fat by modified starch, gelatin, pectin or by using starter cultures producing exopolysaccharides. Application of High pressure homogenization (HPH) to milk for yoghurt production has been proposed as alternative to the use of additives, which can adversely affect the flavour, aroma and mouthfeel. Aim of this work was to study the effects of HPH on viscosity Water Binding Capacity (WBC) volatile profiles as well as starter stability of low-fat yoghurts produced from homogenized milk (40, 55 and 70 MPa) added of different protein concentrations (3.8 and 4.3%). during the storage at 4\ub0C. Results were compared to data obtained from industrial youghurts having a proteion content of 5%. the 55 MPa treatment, independentely on the protein content , has resulted able to attain viscosity and WBC values not significantly different from the industrial product. Differently, the rheological indexes of yoghurt produced from milk homogenized at 70 Mpa were lower. As far as microbiological data, the straters employed maintained levels at least of 6 log cfu/g at the end of the shelf-life, independently on the protein amount and pressure level, satisfying the FIL-IDF criteria. Moreover , the chromatographic profiles of the volatile compounds, detected at the end of the shelf-life, have shown no significant differences amonf the yoghurts produced from HPH milk with reduced protein contents and industrial product. The results have permitted to select the optimal level of pressure (55MPa) to produce low fat yoghurt characterized by a lower protein content but with with rheological and microbiological features similar to the traditional products