Ice morphology modification and solute recovery improvement by heating and annealing during block freeze-concentration of coffee extracts

• Crystal morphology was affected by annealing in the block freeze-concentration of coffee extracts.
• Applying annealing at −5 °C increases the amount of solute recovered during the block freeze-concentration of coffee extracts.
• Applying annealing increase the circularity and the size of the crystals during block freeze-concentration of coffee extract.

Several treatments on ice blocks can be applied during block freeze-concentration to increase the solute recovery from the ice. In the present study, the changes in the ice block’s temperature and the application of annealing during the block freeze-concentration of aqueous coffee extracts were studied. The ice block was subjected to heating and annealing prior to the thawing stage. The effect of coolant temperature during ice block heating (T = −10 and −5 °C) and the application of annealing (+, −) on solute recovery and ice structure morphology was evaluated. The use of annealing during block freeze-concentration modified the ice crystal morphology and increased the solute recovery only when it is applied at the highest temperature. In general, the annealing process increased the size and circularity of the ice crystals, consequently improving the solute recovery. Thus, annealing can be used to increase the solute recovery during block freeze-concentration.