Phenolics from walnut (Juglans regia L.) kernels: antioxidant activity and interactions with proteins

DIANA LABUCKAS; DAMIÁN MAESTRI; MILTON PERELLO; MARCELA MARTÍNEZ; ALICIA LAMARQUE

Food Chemistry

Elsevier

Año: 2008 vol. 107 p. 607 - 612

Walnut (Juglans regia L.) kernels have an important amount of phenolic compounds. The objectives of the work were twofold: a) to extract the phenolic fraction from hulls and walnut flour, and to examine its antioxidant capacity b) to evaluate the effect of hull removal on solubility of protein fractions from walnut flour. In accordance with their higher total phenolic content, hull extracts had stronger antioxidant activity than flour extracts. The presence of phenolic compounds decreased protein solubility in walnut flour obtained from whole kernels. Dehulling kernels improved significantly protein recovery but this fact was strongly affected by the solvent system employed. Proteins from whole kernels, especially those extracted with water and NaCl solution had a reduced solubility, indicating that phenolics bind to proteins when they are dispersed in aqueous media at neutral pH. The results are discussed in the light of the different complex-forming mechanisms that bind phenolics to proteins.