28-9 |
Low-fat yogurt manufacture using high hydrostatic pressure and thermal processing |
F. M. HARTE1, L. O. Luedecke, B. G. Swanson, and G. V. Barbosa-Cánovas. (1) Biological Systems Engineering Dept., Washington State Univ., Grimes St. - Smith Hall, Pullman, WA 99164-6120 Due to syneresis and lack of adequate texture, thickeners and stabilizers are added during the manufacture of low-fat yogurt. Since yogurt is a product associated with healthy diets, it is expected that the manufacture of a low-fat, additive-free yogurt (currently not available in the market) will boost the interest from consumers. The objective of the study was to determine the effect of high hydrostatic pressure combined with thermal processing in the viscoelastic and microstructural properties of yogurts made from fortified skim milk. Fortified (4% low heat skim milk powder) raw skim milk was subjected to high hydrostatic pressure (up to 636 MPa) alone and combined with thermal treatment (85°C, 30 min). Set yogurts were made using traditional methods, stored at 4°C for 36 hours, and then subjected to oscillatory testing (0.1% strain), normal force penetration, and transmission electron microscopy observation. Yogurts made from high hydrostatic pressure (600 MPa) and thermally treated fortified skim milk showed increased storage modulus and resistance to normal penetration when compared to those obtained from thermally treated milk. High hydrostatic pressure (676 MPa) promoted extensive disruption of casein micelles even in yogurts from previously heated skim milk. The combination of high hydrostatic pressure and thermal treatment has shown to remarkably affect the rheological and microstructural properties of low-fat yogurt. Although further research is needed, high hydrostatic pressure can be potentially used for the development of an additive-free yogurt. A provisional US patent application for the use of combined high hydrostatic pressure and thermal treatment in the manufacture of yogurt was obtained.
Session 28, Dairy Foods: Developments in microbiology and chemistry of cheese
|