Organoleptic quality of freeze‐dried foods can be improved by increasing the solids content of the food material to levels of 25–35%. This also results in a reduction of the water load to the freeze‐drier, which greatly improves the economics of the process. For solid foods, such as fruit slices, the increase in solids concentration is achievable by an osmosis process. Sucrose has generally been the solute of choice, but economic considerations are indicating that the suitability of new osmosis solutes should be evaluated. Several mixed osmosis solutes were evaluated for their effectiveness in concentrating apple slices prior to freeze‐drying. Kinetics of water loss and solute uptake were determined for solutions of differing composition and concentration. Several of the osmotically preconcentrated freeze‐dried apple slices were evaluated for organoleptic acceptability.

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The chemical and physical characteristics of the different types of amorphous silicon dioxide contribute to the versatility of these compounds in a variety of commercial applications. Traditionally, silicas have had a broad spectra of product usage including such areas as viscosity control agents in inks, paints, corrosion-resistant coatings, etc. and as excipients in pharmaceuticals and cosmetics. In the food industry, the most important application has been as an anticaking agent in powdered mixes, seasonings, and coffee whiteners. However, amorphous silica has multifunctional properties that would allow it to act as a viscosity control agent, emulsion stabilizer, suspension and dispersion agent, desiccant, etc. The utilization of silicas in these potential applications, however, has not been undertaken, partially because of the limited knowledge of their physiochemical interactions with other food components and partially due to their controversial status from a toxicological point of view. The main goal of this review is to compile current information on the incorporation of amorphous silicon dioxide as a highly functional and viable additive in the food processing industry as well as to discuss the most recent toxicological investigations of silica in an attempt to present some of the potential food applications and their concomitant toxicological implications. Some of the more significant differences between various silicas and their surface chemistries are presented to elucidate some of their mechanisms of interaction with food components and other biological systems and to aid in the prediction of their rheological or toxicological behavior.

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