Effect of separation and thawing mode on block freeze-concentration of coffee brews

Coffee brews were freeze-concentrated using block technique to evaluate the effect of thawing temperature, thawing mode and separation mode on solute yield. Samples were frozen and solute recovered using different thawing and separation conditions. Three thawing temperatures (20, 4 and 1 degrees C), two thawing modes (microwave assisted and free thawing) and two liquid fraction separation modes (gravitational and vacuum assisted) were tested. Solute yield was evaluated as a function of thawing ratio. Data were fitted to a monomolecular model to compare separation quality by means of the solute recovery ratio for each treatment. A combination of microwave assisted thawing and vacuum separation showed the best results in terms of solute recovery ratio. On the other hand, applying microwave assisted thawing or vacuum separation individually did not significantly enhance the solute recovery ratio. Additionally a thawing temperature effect on the solute recover ratio was also found. These results show that it is possible to improve the separation quality of Block PC by combining this technology with vacuum-assisted separation microwave heating. These results suggest that block freeze-concentration has potential industrial application. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.