| Abstract: | The structure of potato protein precipitates formed by heat treatment or acidification of potato juice was investigated by transmission electron microscopy. Precipitates formed by heat denaturation (3 min at 100°C) consist of electron-dense particles of diameter < 300 nm, aggregated into three-dimensional open networks. Precipitates, formed by acidification to pH 3.0 and holding the acidified juice at room temperature, consist of network-like aggregates of electron-dense particles embedded in thin films which hinder the formation of a dense sediment. This structure explains the high sediment volumes which are typical of this kind of precipitate. By warming the acidified potato juice to 40°C, rapid flocculation and sedimentation of the suspended insoluble protein are observed within a few minutes and a dense sediment is finally obtained. This sediment consists mainly of the network-like aggregates of electron-dense particles and material of low electron density formed by the collapse of the films. Protein films have also been observed in precipitates of heat-denatured bovine serum albumin (BSA). High-methoxyl pectin promotes the formation of protein films on heat denaturation of potato proteins or BSA. |
