ANALYSIS AND ECONOMIC EVALUATION OF CONCENTRATION ALTERNATIVES FOR LIQUID FOODS — QUALITY ASPECTS AND COSTS OF CONCENTRATION

ABSTRACT In the selection of concentration processes the net added value of the concentrate with respect to the capital invested should be maximized. The net added value expressed per unit weight of feed is the difference between the gross added valve, being the increase in product value due to concentration, and the costs of concentration. The main factors affecting the gross added value and the concentration costs are treated systematically. The main factors influencing the gross added value are: thermal quality degradation by chemical reactions; loss of volatile aromas; and the concentration that is obtained in the process. The first two factors generally affect the gross added value negatively. The thermal effects of the various processes are shortly summarized. In revaporative concentration and reverse osmosis, aromas can usually be recovered by steam stripping and distillation if the aromas in the food are at least a factor of three more volatile than water. For liquids containing aromas with a relative volatility close to or smaller than unity only freeze concentration can be used, if the quality is to be fully retained. The approximate costs of concentration are given for dewatering capacities in the range of 1 to 50 tons per hour and 2000 to 7000 operational hr per year. As energy costs increase further, only concentration processes with a relatively low energy consumption will, at least for higher capacities, remain economically justified. The energy consumptions expressed in steam equivalents vary widely, viz. evaporation 0.16–1.3, freeze concentration 0.25–0.5, and membrane processes 0.01–0.48.