Determination of alginate in dairy products.
Abstract Comprehensive study was made of the precipitability of several hydrocolloids and other related compounds by divalent cations and, specifically, of the optimum conditions for recovering alginate from milk and dairy products by precipitation as calcium, strontium, and manganese salts. In aqueous dispersion, these cations selectively precipitated alginate, pectinic acids, and pectic acid. Alginate was recovered from milk, chocolate milk, ice cream, cheese spreads, cream cheese spreads, and other products by predigesting the mixture with papain, clarifying the digest with Celite 535 and charcoal, filtering and converting any pectin, pectinic acid, and pectic acid to galacturonic acid by pectinmethylesterase (pectinesterase) and polygalacturonase. Then, calcium chloride was added to the filtrate. The calcium alginate precipitate was washed free of sugars, dispersed by sodium hexametaphosphate, and the amount of alginate in the dispersion determined by the phenol-sulfuric acid test. Recoveries obtained were 96-101% for water dispersions, 92-96% for milk, 90-95% for ice cream, and 85-95% for cheese products.
Detection of water-binding additives in canned mushrooms
ZusammenfassungDie Anwendung von Zusatzstoffen zur Verbesserung des Wasserbindungsvermögens von Champignons ist in den Niederlanden seit Oktober 1987 verboten. Deshalb wurden Methoden zur Kontrolle auf die Anwesenheit dieser Wasserbindungsmitteln (z. B. Eiklar, Stärke, Gummi, Alginate) in Champignonkonserven entwickelt. Einleitende Experimente zeigten, daß physikalische Methoden (Viscositdt, Filtriergeschwindigkeit) nicht genügend zuverlässige Resultate lieferten. Mikroskopische, immunchemische und chromatographische Methoden waren erfolgreicher. Diese Methoden wurden getestet mit Referenzproben, bei denen Champignonkonserven mehrere Wasserbindungsmittel zugesetzt worden sind und schließlich gegen Blindproben geprüft. Es stellte sich heraus, daß die Bestimmungsmethoden sich gegenseitig ergänzen. Mit mikroskopischen Methoden sind Stärken durch Färbung nachweisbar, während zum Beispiel Alginate and Eiklar durch Färbung nicht zu unterscheiden sind. Andere Zusatzstoffe wie Guargummi and mikrokristallinische Cellulose sind morphologisch and mikroskopisch erkennbar. Eine Immunblot-Methode zum Nachweis von Ovalbumin wurde so modifiziert, daß die Bestimmung von kleinen Mengen in der Flüssigkeit der Champignonkonserven möglich ist. Es zeigte sich, daß mit der Gelpermeations-Chromatographie Wasserbindungsmittel auf Polysaccharidbasis wie Alginate, Pectine, Xanthangummi nachweisbar sind. Eine Bestätigung mit Hilfe der Gaschromatographie ist notwendig, aber diese wird durch ein in Champignons von Natur vorkommendes Polysaccharid erschwert.SummarySince 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.
Method validation in pharmaceutical analysis
Method validation in pharmaceutical analysis , Method validation in pharmaceutical analysis , کتابخانه دیجیتال جندی شاپور اهواز