Procedure for studying the enzyme urease to catalyze the hydrolysis of urea.

No abstract

Sodium hypochlorite has been tested for destruction of aflatoxins during the preparation of peanut protein isolates from raw peanuts and defatted peanut meal. The treatments were evaluated by determination of the aflatoxins in the products by thin layer chromatography. Effects of sodium hypochlorite concentration, reaction pH, temperature, and time were studied. Results show that both the sodium hypochlorite concentration and pH are important factors in reducing the concentration of aflatoxins in the protein isolates to nondetectable levels. The treatment with 0.4% sodium hypochlorite at pH 8 produced protein isolates with trace amounts of aflatoxins B1 and B2 from ground raw peanuts containing 725 ppb aflatoxin B1 and 148 ppb aflatoxin B2, whereas untreated protein isolates contained 384 ppb aflatoxin B1 and 76 ppb aflatoxin B2. At pH 9, 0.3% sodium hypochlorite reduced the aflatoxin B1 content in the protein isolates from 300 ppb to below detectable quantities and the aflatoxin B2 content from 52 ppb to 2 ppb. Similar results were obtained at pH 10 for 0.3% sodium hypochlorite concentration. In the case of defatted peanut meal which contained 136 ppb aflatoxin B1 and 36 ppb aflatoxin B2, 0.25% sodium hypochlorite concentration at pH 8 (0.20% at pH 9; 0.15% at pH 10) reduced both the aflatoxin B1 and B2 contents to below detectable quantities in protein isolates as compared to aflatoxin levels of ca. 75 ppb B1 and 17 ppb B2 in the untreated protein isolates. Reaction temperature and time did not affect the destruction of aflatoxins significantly.

This article highlights why it is sometimes desirable to select organic solvents when carrying out enzymatic reactions, criteria for solvent selection, effects of organic solvents on enzymes, applications, and future prospects.

The present investigation is the first definitive study of the distribution of aflatoxins in a wet-milling process of raw peanuts. The results show that the majority of the aflatoxins originally present in the peanuts remained in the solid fractions, particularly the protein fraction, during wet-milling. In the protein concentrate preparation, the concentrates carried 81-89% of the total toxin; crude oil, 5-8%; and whey fraction, 3-14%. In the case of protein isolate preparation, 51-56% of the total toxin remained with the isolates, 22-26% with the residue, 11-17% with the whey, and 7-8% with the crude oil. Distribution of aflatoxins in the preparation of protein isolates from defatted peanut meal showed that 55-65% of the total toxin originally present in the meal remained with the protein isolates, 20-28% with the residue, and 10-20% with the whey fraction. Changes in extraction pHs for the preparation of protein isolates either from raw peanuts or defatted meal did not alter the distribution pattern mentioned above. A new approach based upon charge-transfer (electron acceptor-donor) complex formation is suggested to shift this aflatoxin distribution from protein products to disposable whey or residue fraction during the processing of raw peanuts and defatted meal for protein products.