JUICE EXTRACTION FROM APPLES AND OTHER FRUITS AND VEGETABLES

Presses are the usual and traditional method of removing juice from fr uit and vegetable materials. However, recently diffusion extraction, c entrifugation, and specialized ultrafiltration techniques have been ex plored and have been exploited commercially to a limited extent. Yield efficiency diagrams that relate juice yields to mash feed rates provi de a mechanism for comparing presses and other processes such as enzym e treatments or decanter centrifuges for efficiency under a stated set of circumstances. Diffusion extraction is capable of removing 90 to 9 4% of soluble solids from properly prepared apple slices, but the resu lting juice is diluted with extraction water and is high in extracted tannins. Concentration is necessary to obtain juice solids equivalency , and the resulting juice has sour/astringent flavors that must be rem oved with tannin absorbants to provide acceptable flavor. Currently, d ecanter centifuges are used commercially and have provided an alternat ive to presses under certain circumstances. When naturally colored and flavored (unoxidized) juices are desired, the decanter provides a use ful alternative to presses because it is easily inert gas blanketed. U tilization of a metallic ultrafilter as a press has been patented but has not achieved commercial utilization. The technical literature desc ribing the application of these juice extraction juices, primarily to apples, is reviewed extensively.