Implications on quality of energy savings in the concentration of foods

Abstract

Most foods contain components which are chemically unstable and can be damaged at elevated temperatures. The volatile aromas can be lost with the vapour in evaporation or with the permeate in membrane concentration. Because of this, measures aimed at the reduction of energy consumption — such as increasing the number of effects in evaporation — generally also affect the quality and, therefore, the economic value of foods. A survey is given of the various energy saving measures in evaporative concentration, membrane processes and freeze-concentration on both quality degrading (thermal) chemical reactions and the physical loss of volatile aromas. It is shown that quality losses are highest in multi-effect evaporators and lowest in freeze concentration. The energy consumption of the latter process compares with an evaporator composed of 5 to 10 effects, this depending on the depression of the freezing temperature.