Ultrastructure of denaturated potato proteins

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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.