Detection of water-binding additives in canned mushrooms

Abstract

Since 1 October 1987 the use of additives to prevent too much shrinkage of preserved mushrooms has been prohibited in the Netherlands. Therefore, methods have been developed to control canned mushrooms for the presence of these water-binding additives (e.g. egg-white, starches, gums, alginates). Physical methods (viscosity, filtration flow rate) tentatively studied did not give sufficiently reliable results. Microscopic, immunochemical and chromatographic methods were more successful. These methods were developed using reference samples of canned mushrooms with various water-binding agents and were finally tested with blind samples. The methods developed proved to be complementary. With microscopical methods starches can be detected by staining but, among others, alginates are indistinguishable from proteins using a staining technique. Other additives, such as guar gum and microcrystalline cellulose, can be morphologically identified using microscopy. An immunoblot method for the determination of ovalbumin was adapted in order to determine small amounts of ovalbumin in the surrounding liquid of the mushrooms. The presence of polysaccharides containing water-binding additives such as alginates, pectins and xanthan gum can be detected with gel permeation chromatography. Confirmation by gas chromatography is necessary but is hindered by a naturally occurring polysaccharide in the mushrooms.