Abstract 079
Characterization of haze-active proteins in apple juice
J. Agric. Food Chem. 50 (13): 3828-3834, 2002
L.-C. Wu and K.J. Siebert
The nature of the haze-active protein in apple juice was investigated. Heat treatment removed protein indiscriminately while PVPP treatment was fairly specific for proteins of 15 and 28 kDa. Presumably the PVPP bound to polyphenols, which in turn were complexed with protein. Three candidate apple haze-active proteins (HAP) were isolated. Two were extracted from juice with acetone and fractionated by hydrophobic interaction chromatography and solid phase extraction with C18 (HAP I) or SAX (HAP II) material. Hydroxyproline-rich protein was extracted from apple tissue (HAP III). The order of haze formation with tannic acid was gliadin > HAP III > HAP II > HAP I > BSA, which shows increasing haze formation with increasing proline content. The sizes of HAP I, II and III were 28, 15 and 12 kDa; the first two corresponded to the sizes of proteins removed by PVPP treatment, and are involved in juice haze formation.
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