Quality of yogurts prepared from UHPH-treated milk
Special Symposium - Innovations in Food Technology (LMC Congress)
Meals - Convenience, Gastronomy & Quality (Food-1a)
Keywords: ultra-high pressure homogenisation, yogurt, texture, syneresis, rheology
The effects of ultra-high pressure homogenisation (UHPH) on cow’s milk were investigated and its suitability for yogurt manufacturing was compared with the conventional process currently applied in the yogurt industry. Yogurts were prepared from UHPH-treated milks at 200 and 300 MPa at 40ºC, and yogurts prepared from heat-treated milk at 90ºC, 90s, homogenised at 15 MPa and enriched with 3% of skim milk powder were used as control samples. This study included microbiological analysis, determination of titrable acidity, determination of syneresis (spontaneous and forced by centrifugation) and textural and rheological evaluation of gels. In order to follow the evolution of yogurts during the storage at refrigeration temperature (4-6ºC), the analysis were carried-out weekly (1, 7, 14, 21 and 28 days).
S. termophilus counts were very similar between the treatments studied, and cell loads were almost constant during the storage while L. bulgarcius counts decreased at the end of the shelf-life. Yogurts prepared from heat-treated milk presented higher titrable acidity values than yogurts prepared from both UHPH treatments at 200 and 300 MPa, however, the amount of lactic acid/100 g of milk was almost constant along the storage in all samples. Syneresis results, either spontaneous or forced by centrifugation, reflected that yogurts from UHPH-treated milk showed lower values, especially those from milk treated at 300 MPa, than yogurts prepared from heat-treated milk enriched with SMP. Firmness values were almost constant during cold storage in all treatments, but yogurts prepared from UHPH-treated milk at 300 MPa were the firmest ones all along the storage. Rheological measurments showed that G’ and the yield point increased until day 14 of storage, and were similar between the treatments studied.
Presented Wednesday 19, 16:35 to 16:50, in session Meals - Convenience, Gastronomy & Quality (Food-1a).
