Detection of filter media derived haze in apple juice concentrate

Abstract

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 and electron microscopy were combined with a number of haze composition screening tests to characterize the haze morphologically and compositionally. Screening tests indicated all concentrate samples contained pectin, and 6 out of 10 isolated haze samples gave indications of protein. All hazes gave positive responses for polyphenol and iron/ tannin complexes. Light microscopy proved problematic in that unstained haze gave amorphous images that were reddish-brown or varicolored in thicker portions and uncolored/translucent in thinner portions. Electron microscopy of negatively stained haze particulate showed three major particle types. Amorphous, positively stained plate-like material containing folds or creases combined with less structured amorphous material coating or bridging the plates formed one type of particle. The second group also stained positively, and consisted of fibrous material suggestive of pectin. The third group of images are of diatom fragments offering direct evidence of diatomaceous earth involvement. EDX analysis showed 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 taken to indicate the haze to be derived from filter media.