Effect of Thermal Treatment on the Quality of Cloudy Apple Juice

• Published in: Journal of agricultural and food chemistry 2006-07, Vol.54 (15), p.5453-5460
• Main Authors: Krapfenbauer, Gottfried, Kinner, Mathias, Gössinger, Manfred, Schönlechner, Regine, Berghofer, Emmerich
• Format: Article
• Language: English
• Subjects: apple juice; Beverages - analysis; Biological and medical sciences; Carboxylic Ester Hydrolases - metabolism; catechol oxidase; Catechol Oxidase - metabolism; cloudy apple juice; Color; enzymatic browning; enzyme activity; enzyme inactivation; Food industries; food processing; Fruit; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; heat inactivation; heat treatment; high temperature short time heat treatment; high temperature treatment; Hot Temperature; Humans; Hydrogen-Ion Concentration; Maillard Reaction; Malus; Nephelometry and Turbidimetry; pectinesterase; Sensation; turbidity
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf0606858

Apple juice from eight different varieties of apples was heated at high-temperature (60−90 °C) and short-time (20−100 s) (HTST) combinations. To determine the effect of heating conditions on enzymatic browning and cloud stability in apple juices, the activity of polyphenol oxidase and pectinesterase was analyzed and correlated with the thermal treatment conditions and the quality of the juice. Additional investigations included the measurement of pH value, soluble solid content, titratable acidity, color, and turbidity after 3 and 6 months. The results showed that HTST treatment at 80 °C already inactivated polyphenol oxidase, whereas pectinesterase activity was reduced to half and could even at 90 °C not be inactivated completely. In fact, highest residual pectinesterase activity was found at 60 °C. Heating at 70 °C caused stable pectinesterase activity and even a slight increase for 50 and 100 s heating times. Turbidity and lightness increased after HTST treatment. In particular, differences in cloud stability between the varieties were measured. HTST parameters did not correlate with the residual cloud stability after 6 months. The sensory evaluation revealed that only a few combinations were distinguishable. The best stability of cloud and color in relation to heat impact was achieved by HTST treatment between 70 °C/100 s and 80 °C/20 s. Keywords: Cloudy apple juice; pectinesterase; polyphenol oxidase; cloud stability; color difference