An apparatus for partial ice-melting to improve yield in progressive freeze-concentration

A small test apparatus was made for partial melting of ice at controlled conditions in temperature and stirring speed. Ice cubes from 10 wt% sucrose were partially melted in this apparatus at 4 temperature and 4 stirring speeds. At the lower temperature with relatively faster stirring speed, the initially-melted fractions effectively contained the higher concentration of solute than the later-melted fractions. The partial ice-melting technique was combined with progressive freeze-concentration (PFC) to improve the yield in PFC. Apple juice with 13.7 degrees Brix was concentrated up to 25.5 degrees Brix by PFC using a tubular ice system. Then, the partial ice-melting was applied for the ice formed by PFC to improve the yield from 63.8% to 85% by recovering the initial 30% melted fraction. The partial ice-melting was also applied to pear (La France) juice flavor condensate. After 2.36 times concentration of flavor component (butyl acetate) by PFC, the yield was improved from 86.7% to 95% by recovering the initial 35% melted fraction in the partial ice-melting process. Partial ice-melting technique will overcome the major drawback of PFC, in which the yield decreases with an increase in solute concentration because of the solute inclusion in the ice. (C) 2014 Elsevier Ltd. All rights reserved.