Study of grape juice lyophilisation obtained from rose and white grapes

Abstract

Lyophilization is a fast drying process of grape juice, previously frozen by ice sublimation in a vacuum with controlled heat input. Lyophilization juice is made according to its triple point, the grape juice is in its thr -45 C. For begining we determined the amount of dry substance, the evidence originally obtained with HANNA Instruments HI96801 portable refractometer (% Bx) and we obtained the following values: grape juice rose 15.4% Bx and white grape juice 16.1% Bx. Lyophilization of juice samples was performed at 4 hours and at different temperature ranges (-50, -45, -40, -35, -30, -25, -20, -15, -10, -5, 0 ) and at different pressures, after that is perfo - C for 1 hour under vacuum. In the first phase of lyophilization (4 hours), reduce the amount of water up to 87%, then the secondary drying water quantity is reduced to 2%. This - C values ranging from 77-85% and the amount of dry substance ranging from 15-17%. Lyophilization process used on grape juice has many advantages and disadvantages. It is recommended to use the freeze drying process because does not change the product features and eliminates whereby the greatest amount of water from product.