Effect of UV irradiation on enzymatic activities and physicochemical properties of apple juices from different varieties

• Published in: Food science & technology Vol. 44; no. 1; pp. 115 - 119
• Main Authors: Falguera, Víctor, Pagán, Jordi, Ibarz, Albert
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 2011; Elsevier
• Subjects: Apple juice; ascorbic acid; Biological and medical sciences; catechol oxidase; color; Colour; energy; enzyme activity; enzyme inactivation; Food industries; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; irradiation; lamps; mercury; Peroxidase; pigmentation; pigments; Poyphenol oxidase; soluble solids; Ultraviolet irradiation; ultraviolet radiation; vitamin content; Peroxidase; Poyphenol oxidase; Ultraviolet irradiation; Apple juice; Colour; Fruit; Enzyme; Fruit product; Fruit juice; Apple; Peroxidases; Enzymatic activity; Oxidoreductases; Variety; Physicochemical properties
• ISSN: 0023-6438; 1096-1127
• DOI: 10.1016/j.lwt.2010.05.028

The influence of ultraviolet irradiation (UV) on some quality attributes (colour, pH, soluble solids content, formol index, total phenolics, sugars and vitamin C) and enzymatic activities (polyphenol oxidase, peroxidase and pectinolytic enzymes) of fresh apple juice was investigated. Apple juices made from four different varieties (Golden, Starking, Fuji and King David) were irradiated during 120
min with a high-pressure mercury lamp of 400
W that emits in a range between 250 and 740
nm with a resulting incident energy of 3.88·10
−7 E·min
−1. The treatment was effective in the inactivation of the assayed enzymes. Polyphenol oxidase was inactivated in 100
min, while peroxidase was completely destroyed in only 15
min in all the four varieties. No variations were observed in pH, soluble solids content, formol index, total phenolics and sugars. The colour of the juice made from King David was unvariable during all the experiment. In the ones made from Golden, Starking and Fuji, UV radiation impaired some of the pigments present in the juice, either initially present or the ones formed later. This fact can be especially observed in the increase of the CIELab parameter L*, which increased from 23.2 to 24.6 in Fuji juice. The content of vitamin C in juices from Golden, Starking and Fuji slightly changed during the experiment, decreasing a 4.0% in Fuji juice, 5.7% in Golden one and 5.6% in Starking one. Meanwhile, in the juice from King David the loss was 70.0%. This significant difference can be attributed to the lack of pigmentation of this juice.