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

• Apparatus was made for partial ice-melting with controlled temperature and stirring.
• Solute enrichment effect was observed for the initially melted fractions.
• Partial ice-melting was effectively combined with progressive freeze-concentration.
• Apple juice and pear flavors were successfully freeze-concentrated with good yields.
• Partial ice-melting overcomes weakness in 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 °Brix was concentrated up to 25.5 °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.