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.
Determination of Carboxymethylcellulose with Chromotropic Acid
Abstract Chromotropic acid (1,8-dihydroxynaph-thanene-3,6-disulfonie acid) in concentrated sulfuric acid was used to determine carboxymethylcellulose (CMC) isolated from milk, chocolate milk, chocolate and vanilla ice cream, and other products. For maximum color development, the reagent must be dissolved in concentrated H 2 S0 4 and the CMC—reagent mixture must be heated for 60 to 90min at 99±1C. The characteristic purple color developed has maximum absorbance at 570nm. Color density increased as the degree of substitution of the CMC increased. Of 30 different food gums and related substances tested, only pectin and pectic acid gave the characteristic purple color. The reagent is more specific but less sensitive than the 2,7-naphthalenediol reagent. Interference from chocolate ingredients is less than when the 2,7-naphthalenediol and anthrone reagents are used and much less than with the phenol-H 2 S0 4 reagent. In addition, determination is more rapid than with 2,7-naphthalenediol. Recoveries from various products were 88% and upwards, based on the addition of CMC added to water and carried through the entire and identical isolation procedure. The method will detect CMC in food products at 0.025% (w/w).
The ultramicro determination of inorganic sulphte.
Unfortunately there was also a large increase in control reading under this circumstance and further lowering of the ethanol concen- tration was not feasible. The recovery of 0-25-2- 5eg. of SO42- ion/10p1. of sample was tested in the presence of a number of anions and cations, sulphatase substrates and tissue and enzyme preparations. In general, the findings of Lloyd (1959) were repeated except that recovery of low sulphate concentra- tions was 5-15% too high in the presence of 0-02 M-PO43-ions. At concentrations of P04"- ion below 0-01 M no interference was observed.