Fruit juice concentrates- hard pear, soft pear, fig, prune, raisin, white grape, and pineapple, and sweeteners-invert beet, invert cane, and high fructose corn syrup (HFCS) were characterized by sugar profiles, nonvolatile acid profiles, UV spectral profiles, and mineral content. These fruit juices and sweeteners were also used to adulterate commercial apple juice at levels of 40%, 20%, and 10%. Sugar and nonvolatile acid analyses were performed by HPLC and isotopic carbon analyses were applied to selected samples. Data analysis included the application of Pattern Recognition methods and Chi-square test. Analysis by Pattern Recognition was restricted to sugar profiles because of the availability of an extensive data base on sugar composition of authentic apple juice, the compositional data base for the other components being limited. The "potential adulterants" were clearly distinguished from the cluster of authentic apple juice. Apple juice samples adulterated at 40% were at the perimeter and also distinguishable from the cluster, while the samples adulterated at 20% and 10% were intermingled within the cluster. Pattern Recognition methods were also used for classification of the authentic apple juice data base obtained from Mattick and Moyer (1983). Apple samples were classified by variety and geographical origin. Sucrose, glucose/fructose ratio, and sorbitol were important variables in the separability of the samples. Pattern Recognition methods are effective in classification of authentic juices and show potential as a powerful technique in discriminating between adulterated and authentic apple juice. / Graduation date: 1987

In order to prevent enzymatic oxidation of phenols during the centrifugal extraction of juice from apple purée, a sulfite or ascorbic acid treatment followed by blanching has been proposed. However, juice from blanched puree is more turbid and difficult to clarify than juice processed without blanching. In order to better understand the effect of blanching on juice turbidity as well as to provide more information concerning the effect of cultivar, post-harvest storage and enzyme treatment on juice quality, the chemical and physical properties of apple juice and apple juice particulate from fresh and stored McIntosh, Red Delicious and Spartan apples processed with and without enzyme digestion and with and without blanching were examined. Analysis of juice included measurement of: soluble solids, total sugars (by HPLC), sucrose, glucose, fructose, sorbitol, pH, titratable acidity, total acidity (by HPLC), citric acid, galacturonic acid, malic acid, quinic acid, succinic acid, pectin (as anhydrogalacturonic acid by HPLC) and turbidity (as absorbance at 600 nm). Analysis of particulate included measurement of dry matter weight, pectin, protein and zeta potential as well as thin sectioning, negative staining and shadow casting transmission electron microscopy. Chemical analysis of apple juice showed that the levels of organic acids, sugars and soluble pectin differed between cultivars. However, no varietal differences were observed in the chemical or microscopic analysis of cloud material. Blanching of apple puree, on the other hand, increased apple juice turbidity by increasing the amount of particulate suspended in the juice. Furthermore, blanching stabilized suspended particulate by what appeared to be the formation of a protective colloid which prevented particle aggregation through electrostatic repulsion. Post-harvest apple storage also resulted in changes to juice particulate, which were observed as gel formation during juice storage at 0°C and as a web-like aspect in the microscopic appearance of juice particulate. Treatment of apple purée with Ir-gazyme 100 decreased juice turbidity, resulting in the concomitant decrease in both the level of soluble juice pectin and the amount of suspended cloud material. Use of enzyme treatment and blanching in the processing of apple juice was demonstrated by stepwise discriminant analysis to allow production of four unique apple juice products. / Land and Food Systems, Faculty of / Graduate