Quantitative Colorimetric Assay for Total Protein Applied to the Red Wine Pinot Noir

• Published in: Journal of agricultural and food chemistry Vol. 59; no. 13; pp. 6871 - 6876
• Main Authors: Smith, Mark R, Penner, Mike H, Bennett, Samuel E, Bakalinsky, Alan T
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 13.07.2011
• Subjects: absorbance; acetone; Analytical Methods; beta-fructofuranosidase; Biological and medical sciences; Chemical Precipitation; cold; colorimetry; Colorimetry - methods; dye binding; dyes; Fermented food industries; Food industries; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; Membrane Glycoproteins - analysis; protein content; proteins; Proteins - analysis; red wines; Sensation; trichloroacetic acid; Wine - analysis; Wines and vinegars; yeasts; mannoprotein; Pinot noir; invertase; red wine protein; glycoprotein; grape; yeast; Yeast; Fruit; Enzyme; β-Fructofuranosidase; Glycoprotein; Colorimetry; Red wine; Protein; Glycosylases; Assay; Alcoholic beverage; Glycosidases; Grape; Hydrolases
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf200547u

A standard method for assaying protein in red wine is currently lacking. The method described here is based on protein precipitation followed by dye binding quantification. Improvements over existing approaches include minimal sample processing prior to protein precipitation with cold trichloroacetic acid/acetone and quantification based on absorbance relative to a commercially available standard representative of proteins likely to be found in wine, the yeast mannoprotein invertase. The precipitation method shortened preparation time relative to currently published methods and the mannoprotein standard yielded values comparable to those obtained by micro-Kjeldahl analysis. The assay was used to measure protein in 48 Pinot noir wines from 6 to 32 years old. The protein content of these wines was found to range from 50 to 102 mg/L with a mean value of 70 mg/L. The availability of a simple and relatively rapid procedure for assaying protein provides a practical tool to quantify a wine component that has been overlooked in routine analyses of red wines.