Cloud stability of apple juices in relation to their particle charge properties studied by electro-optics

Turbidity, cloud stability, pulp and pectin contents, and particle charge properties of apple juices were studied depending on the normal atmosphere cold storage of four apple cultivars. Cloud stability and adsorbed pectin content increased after the cold storage, while coarse/fine pulp ratio decreased. The rise of stability was correlated well (R = 0.92) with the increase of particle electric polarizability determined by electric light scattering. The latter effect is probably due to the enhanced amount and reduced degree of esterification of the adsorbed pectin. The results of the present study clearly demonstrate the advantage of the electro-optics for elucidation of the cloud stability mechanism. Moreover, the processing of apples after their cold storage is shown to be worthwhile, allowing an improvement of cloud stability.