THE RELATIVE VOLATILITY AND BETA RADIOACTIVITY OF ETHANOL , A COMPOSITE APPROACH TO VARIETAL AUTHENTICATION OF PHILIPPINE WINES.
Raymond J. Sucgang, Soledad S. Castaneda and Fortunato Sevilla III
In cooperation with the Chemists and Educators Support for the Advancement of Relevant Science Education, CESARS Ed, Inc.
keywords: alcohol, ethanol, relative volatility, Carbon 14, beta radioactivity
email: rjsucgang@pnri.dost.gov.ph or cesarsed2002@yahoo.com
Alcoholic beverages vary significantly in their ethanol content and in the feedstock from where they are produced.Several kinds of homemade beverages are prevalent in rural areas in the Philippines. Tuba (coconut wine) is common in coconut growing areas. Tuba can also be made from the sap of buri or nipa palms. In prime coconut provinces such as Laguna and Quezon, tuba is distilled into lambanog or coconut vodka. Lambanog, is a popular Philippine alcoholic beverage and is known for its potency and high alcohol content. Another type, the Basi Wine is a result of fermentation of freshly extracted sugar cane juice. "Tapuy" or 'tapuey" (rice wine) is an indigenous alcoholic drink popular in the Cordillera region and adjacent provinces.
The progression of an azeotropic dehydration of ethyl alcohol, or ethanol from different Philippine-manufactured beverages was monitored and the recovered ethanol was analyzed for carbon -14 activity using low -level liquid scintillation counting.
The relative volatility of ethanol was derived from Dalton, Clapeyron, and Troutons laws. The values for lambanog, tuba, tapuey, and basi were calculated , and taken to represent the degree to which it is viable to separate the mixture by distillation. The relative volatility was found to rise in proportion to the decrease in solute concentration in the alcoholic mixture.
Due to the dissimilarity in composition and therefore in the vapor-liquid pseudo-binary equilibrium, the relative volatility,I, of ethanol likewise fluctuates depending on the composition of the beverage from where it is distilled. The easiness of dehydrating ethanol was validated by constructing the pseudo-binary-ethanol-water plot in order to establish a pattern of the procedure from a thermodynamic viewpoint. By applying Dalton's, Raoult's, Clapeyron and Trouton's Rules, in an effort to relate the boiling temperatures with relative volatility of ethanol in the mixture, the equation :
log I = 8.9 x I"t
TA - TB
was obtained wherein TA and TB are boiling points of ethanol (A) and the residual liquid (B) in degrees Kelvin, K respectively. The relative volatility was found to rise in proportion to the decrease in solute concentrationof the original alcoholic mixture. The degree of ease of obtaining 89.5 mole percent purity ethanol was found to be : lambanog > basi > tapuey > tuba for the selected beverages.
The ethanol derived from the different beverages were subsequently analyzed for Carbon -14 activity, to determine the sensitivity of radiocarbon liquid scintillation counting to detect fossil ethanol adulteration in wines/alcoholic beverages.
The study was able to establish that 14C activity for 100 % biogenic ethyl alcohol from tuba, tapuey, basi and lambanog is between 12-16 disintegrations per minute per gram carbon, dpm/gC, with a mean value of 15.2 1.4 dpm/gC, Based on this, we can set a minimum threshold of 12 dpm/gC for plant derived ethanol at 95% confidence level. Synthetic ethanol or fossil ethanol have zero 14C activity.The I-radioactivity of carbon in ethyl alcohol is a reliable criterion for detection of illegal misrepresentation of authentic liquors with synthetic ethanol mixtures.
