Volatiles Retention During Freeze Drying of Synthetic Emulsions

Experimental results are presented for the retention of d‐limonene during freeze drying of sucrose solutions, for 10% and 25% solution concentrations, for fast and slow freezing, and for various levels of d‐limonene addition ranging from below to considerably above the solubility limit. The results show decreasing percentage retentions with increasing initial levels of d‐limonene, reaching an asymptotic value at high initial d‐limonene contents. These results are interpreted quantitatively in terms of both microscopic observations and a simple model which allows for the collection of emulsion droplets at the ice‐concentrate interface during the freezing step, with subsequent loss of those droplets during freeze drying. Retention experiments with n‐hexyl acetate and acetone lend additional support to this interpretation and demonstrate the importance of the ratio of emulsion droplet size to the thickness of the interstitial webs of concentrate.