Modified method for the determination of pyruvic acid with dinitrophenylhydrazine in the assessment of onion pungency
نویسندگان
چکیده
Modifications to the commonly used Schwimmer and Weston procedure for determining pyruvic acid in onions are proposed. These modifications involve changes in the concentrations and volumes of the reagents and the use of 515 rather than 420 nm as the wavelength for measurements. These changes improve both the linearity and the sensitivity of the assay and eliminate interference from coloured material found in yellow onions. With these changes, more reliable determinations of pyruvic acid and thus of onion pungency should be possible. 2003 Society of Chemical Industry
منابع مشابه
Postharvest Flux and Genotype × Environment Effects for Onion-induced Antiplatelet Activity, Pungency, and Soluble Solids in Long-day Onion during Postharvest Cold Storage
Two mild and two pungent onion (Allium cepa L.) selections (hereafter referred to as cultitypes), W420B, W424B, MSU8155B, and Exhibition, were grown at two locations in two states (Wisconsin and Oregon) during 1994 and 1995. Onion bulbs were harvested, stored at 4 °C and sampled for antiplatelet activity, pungency, and soluble solids 10 days after harvest and every 40 days during a 210-day post...
متن کاملPhenylalanine Ammonia-lyase, Peroxidase, Pyruvic Acid and Total Phenolics Variations in Onion Bulbs During Long-term Storage
Phenylalanine ammonia-lyase (PAL) and peroxidase (POD) enzyme activities, total phenolics and pyruvic acid (PA) (as pungency indicator) were measured in onion bulb tissues (c.v. Rouge Amposta) during storage at 4 and 20 3C. After 2 wk, PAL activity increased at 4 3C, but decreased at 20 3C, and after 4 wk, PAL activity at 20 3C was higher than activity observed at 4 3C. Peroxidase activity was ...
متن کاملAutomated Determination of Serum Glutamic Oxalacetic and Glutamic Pyruvic Transaminase.
The determination of serum glutamic oxalacetic and glutamic pyruvic transaminase has been simplified by the use of automated analysis. The flow diagrams, concentration of reagents, and calculation of the color unit in terms of the Karmen unit are shown for 2,4-dinitrophenylhydrazine and 6-benzamido-4-methoxy-m -toluidine diazonium chloride as the reacting dyes. Advantages of both methods are co...
متن کاملPyruvic acid is attached through its central carbon atom to the amino terminus of the recombinant DNA-derived DNA-binding protein Ner of bacteriophage Mu.
Ner protein of bacteriophage Mu, produced by recombinant DNA techniques in Escherichia coli, has been found to possess a molecule of pyruvic acid attached covalently through carbon-2 to the amino-terminal cysteine residue. The intact protein and the amino-terminal chymotryptic peptide were found by mass spectrometry to be 70 mass units heavier than expected. The modified peptide was unstable un...
متن کاملMetabolism of l-ascorbic acid, dehydro-l'ascorbic acid, and diketo-l-gulonic acid in the guinea pig.
The interrelationships of L-ascorbic acid (AsA) and dehydro-L-ascorbic acid (DHA) have been investigated both in viva and in vitro by numerous workers, with especial emphasis upon the conversion of DHA to AsA by the animal body (l-8). The conversion of DHA to diketo-L-gulonic acid (DKA) in vitro has been shown by Herbert and coworkers (3), by Borsook (l), and by Penney and Zilva (6), and this c...
متن کامل