PT  - JOURNAL ARTICLE
AU  - Karen Slinkard
AU  - Vernon L. Singleton
TI  - Total Phenol Analysis: Automation and Comparison with Manual Methods
AID  - 10.5344/ajev.1977.28.1.49
DP  - 1977 Jan 01
TA  - American Journal of Enology and Viticulture
PG  - 49--55
VI  - 28
IP  - 1
4099  - http://www.ajevonline.org/content/28/1/49.short
4100  - http://www.ajevonline.org/content/28/1/49.full
SO  - Am J Enol Vitic.1977 Jan 01; 28
AB  - A fully automated-continuous flow 40-sample/ hour procedure was adapted from the Singleton-Rossi method of analysis for total phenols in wine and other plant extracts. It was compared with small-volume manual and semiautomated versions of this analysis. The agreement in mg of gallic acid equivalent phenol (GAE) per liter among a series of dry wines was excellent by all three procedures. The coefficients of variation in replicate analyses averaged 5.8% for the manual, 6.2% for the semi-automated and 2.2% for the automated procedure. This greater reproducibility, plus savings of about 70% in labor and up to 40% in reagents, makes the automated procedure attractive for laboratories doing enough total phenol analyses to recoup the cost of the automating equipment. For continuous flow, color development with the Folin-Ciocalteu reagent in alkaline solution must be hastened by heating compared to slower room temperature development for the manual methods. Heating of sugar-containing samples in the alkaline solution gives interference presumably from endiol formation. Examples are given of corrections which were used successfully to estimate the true phenol content of sweet wines.