Glucosinolates, a group of naturally occurring thioglucosides, are significant factors impairing the nutritional quality of rapeseed and postextraction rapeseed meal, restricting its use as high-quality protein animal feed. Currently, the European Community standards and Canola definition are being brought in line recommending cultivation and marketing of rapeseed with a glucosinolate content below 18 micromol of total glucosinolates per gram of seeds. Furthermore, some glucosinolates are of increasing interest in Brassica vegetables due to their proven cancer-preventing activities. A novel approach to the analysis of total glucosinolates is reported in this paper based on their alkaline degradation and subsequent reaction of released 1-thioglucose with ferricyanide. The reaction was followed spectrophotometrically using sinigrin and glucotropeaolin as model glucosinolates. The applicability of the method was demonstrated using rapeseed extracts after reducing the interfering effect of phenolics by their adsorption onto polyvinylpolypyrrolidone. Good agreement with official ISO methods was shown.
A comparison is, made of potentiometric and amperometric sensors. For amperometric sensors there are advantages in using the wall-jet system with ring-disc or packed-bed electrodes. Particular applications to the determination of proteins, root death, total iron and the concentration of NO; are described. Enzyme electrodes using organic salts are capable of the direct oxidation of the enzyme itself. A theoretical description is presented. Experiments with glucose oxidase show that the transport of glucose through the membrane is the rate-limiting step. By contrast with a sensor for choline, using choline oxidase, we find that the transport of substrate through the membrane and the unsaturated enzyme kinetics are each partially ratelimiting. Electrodes, made of conducting organic salts, also oxidise NADH. For an ethanol sensor, using ethanol dehydrogenase, we find that the rate-limiting steps are those involving homogeneous enzyme kinetics.
Methodologies for the determination of vitamin B(2) in food matrixes and a premix using simple sample conditioning steps coupled with a convenient and cheap electrochemical sensing device are presented. Electrochemical analysis based on differential pulse voltammetry (DPV) coupled to carbon electrodes gave a well-defined reduction peak at -0.42 V versus a Ag/AgCl quasi-reference electrode. Using a straightforward sample preparation step, vitamin B(2) can be measured successfully in a nutritional premix and food products. Standard additions of riboflavin were used to confirm the analyte concentrations and to provide precision data.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.