HTI has developed an innovative membrane technology for the concentration of products which are sensitive to heat and require special handling. The technology is a form of osmosis known as Forward Osmosis Concentration. HTI’s systems can concentrate products containing a wide range of suspended solids with no prefiltration requirements. The FO process removes water from the product by contacting an osmotic agent solution with higher solids content on the other side of a semipermeable membrane. A typical flow scheme is shown on the attached diagram. The nonfouling properties of the system design also permits ease of cleaning. The technology concentrates products at low temperatures (5-20°C) and low pressures (10-30 psig). The products obtained are normally concentrated up to 40-50°Brix.
Product degradation and loss of quality are major concerns for the food and beverage industry when evaluating concentration processes. Standard evaporation techniques detrimentally affect some key flavor compounds in fruit and vegetable juices and purees, as well as other food products. This is especially true of tropical fruits. Evaporators also cause loss of aroma and volatile components that are essential to maintaining the characteristics of freshness in premium quality concentrates. The rejection properties of FO membranes ensure that virtually all of the important components remain in the product.
HTI's pilot equipment has concentrated a wide range of products. The attached table provides a list of sample concentrates produced for potential end users. HTI has also designed a tomato puree concentration process where the Draw Solution (DS) evaporator is replaced with an outdoor-open tank. In this case, the reconstitution of the DS (salt brine solution) is made possible with solar evaporation. This eliminates the need for fuel and greatly lowers energy consumption. The variety of products that can be processed with FO demonstrates the versatility of the technology. Therefore, the FO technology is suitable for concentration of products which are seasonal in nature.
The operating results from HTI's FO pilot system have demonstrated that the cold temperature concentration technology is capable of providing improved quality products economically and on a large scale. Although the capital cost of FO may be higher than standard evaporators, the improved quality of the product compensates for the cost difference. For products that command a premium price for quality, the technology is highly suitable.