DETECTION OF FILTER MEDIA DERIVED HAZE IN APPLE JUICE CONCENTRATE

Haze particles were centrifugally recovered from selected apple juice concentrates produced in the Rio Negro region of Argentina during the production year 1992. Energy dispersive X-ray (EDX) analysis, light an d electron microscopy were combined with a number of haze composition screening tests to characterize the haze morphologically and compositi onally. Screening tests indicated all concentrate samples contained pe ctin, and 6 out of IO isolated haze samples gave indications of protei n. All hazes gave positive responses for polyphenol and iron/tannin co mplexes. Light microscopy proved problematic in that unstained haze ga ve amorphous images that were reddish-brown or varicolored in thicker portions and uncolored/translucent in thinner portions. Electron micro scopy of negatively stained haze particulate showed three major partic le types. Amorphous, positively stained plate-like material containing folds or creases combined with less structured amorphous material coa ting or bridging the plates formed one type of particle. The second gr oup also stained positively, and consisted of fibrous material suggest ive of pectin. The third group of images are of diatom fragments offer ing direct evidence of diatomaceous earth involvement. EDX analysis sh owed major elements present to be silicon and aluminum. Of 10 samples, all contained large quantities of silicon, 3 showed no aluminum, and 7 contained variable, but large, aluminum content. These data are take n to indicate the haze to be derived from filter media. Copyright (C) 1996 Published by Elsevier Science Ltd on behalf of the Canadian Insti tute of Food Science and Technology