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In conventional processes, such as evaporation, higher levels of concentration can be reached compared with freeze concentration or membrane techniques. However, the advantage of the freeze concentration technique is based on the quality of the product obtained due to the low temperatures used in the process, which makes it a very suitable technology for the processing of fruit juices. There are two basic methods for concentrating solutions by freezing: suspension and film freeze concentration. Suspension freeze concentration systems (FCS) already have operating equipment in the food industry, while film FCSs, also called layer crystallization, is still at an experimental stage. This review summarizes the most important studies relating to the suspension and film freeze concentration in fruit juices and sugar solutions, illustrating the different possibilities that freeze concentration has in the fruit juices industry; it also presents trends and suggests improvements for the future development of this technology. It is noted that most recent publications refer to the film FCS. The technology used to design, build and maintain layer crystallization equipment is simple and it can be available to any operator in the food industry, layer systems will be used in the future if their results can be improved in terms of ice purity and degree of fluid concentration.

Coffee extract was freeze-concentrated using the total block technique. The effects of four parameters\ud were evaluated: the initial coffee mass fraction (5 and 15% w/w), the cooling temperature ( 10 and\ud 20 C), the heating temperature (20 and 40 C) and the freezing direction (parallel and counter-flow\ud to the thawing direction). The solid concentration was measured during the thawing stage to quantify\ud the solute recovery and the concentration index for one stage of freeze concentration. The coffee mass\ud fraction, the freezing direction and the cooling temperature significantly influenced the solute recovery.\ud A concentration index between 1 and 2.3 was obtained in one cycle. The effect of block freeze concentration\ud on the bioactive compound concentration and the antioxidant activity was measured. The coffee bioactive\ud compounds were distributed in proportion to the total solid content in the ice and liquid.\ud Therefore, block freeze concentration is an effective technique to preserve functional properties of coffee\ud extracts.Postprint (published version

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