Chapter 12 - Athermal Membrane Processes for the Concentration of Liquid Foods and Natural Colors

Abstract

Liquid foods (fruit juices and natural colors) are gaining importance in the food industry because they contain components beneficial for human health. Both fruit juices and natural colors, when extracted from their sources, have a low solid content, color strength, and a high water load. Water, being the major constituent of liquid foods/natural colors, contributes to the growth of microorganisms. Concentrating liquid foods provides a reduction in transport, packaging, and storage costs. The juice industry has developed a complex recovery of essence, careful process control, and blending techniques to produce a good quality concentrate that is acceptable to consumers. However, it is still easily distinguishable from fresh juice. Natural colors are heat sensitive (they show changes in color intensity), hence it is necessary to concentrate dilute solutions using methods that operate at ambient temperature. Many efforts have been reported regarding improved methods such as freeze concentration, sublimation concentration, and concentration by using membranes such as ultrafiltration, nanofiltration, and reverse osmosis for the concentration of liquid foods (fruit juices and colors). The most promising alternative is membrane-based concentration, which does not involve any heat or pressure driven processes, as do osmotic membrane distillation or direct osmosis. The merits and demerits of these membrane processes, along with the possibilities for integrating them with existing processes are discussed in this chapter.