RETENTION OF D-LIMONENE DURING FREEZE DRYING OF ORANGE JUICE

Retention of d-limonene during freeze drying of citrus juices from several sources was investigated as a multi-phase problem. Reconstituted to 25 and 10° Brix, commercial frozen concentrates show high retention (between 90 and lOO%), whereas fresh-squeezed juice shows a relatively low retention (about 30%), comparable to that found previously for synthetic emulsions. Retention data for pasteurized fresh juice after substantial agitation and for never-concentrated, commercial pasteurized juices show an intermediate value (between 60 and 70%). Presence and stability of cloud are shown to correlate closely with improved d-limonene retention in commercial frozen concentrates. On this basis, a simple model is developed which predicts the retention level for this type of juice in the asymptotic region. The results for the other types of juice studied are interpreted with the aid of microscopic determinations of oil droplet size and the model derived for synthetic emulsions.