Estimatation of alcohol by specific gravity method

/Estimatation of alcohol by specific gravity method
Estimatation of alcohol by specific gravity method2018-02-26T11:55:03+00:00

Estimatation of alcohol by specific gravity method

Introduction

This method provides an approximation of alcohol content. Specific gravity is the density of a substance relative to the density of water or it is the ratio of density of a substance compared to the density of fresh water at 4°C (39° F). At this temperature the density of water is at its greatest value and equal 1g/ml. Since specific gravity is a ratio, so it has no units. An object will float in water if its density is less than the density of water and sink if its density is greater than that of water. Similarly, an object with specific gravity less than 1 will float and those with a specific gravity greater than one will sink. Specific gravity values for a few common substances are: Au-19.3; mercury-13.6; alcohol-0.7893; benzene- 0.8786. Note that since water has a density of 1g/cm3, the specific gravity is the same as the density of the material measured in g/cm3. The method assumes that the difference in Specific Gravity before and after fermentation is due solely to the conversion of sugars before fermentation into alcohol after fermentation.

* The method relies on –

all the wines measured, starting with the same sugar levels
all the sugars being fermented, with the wine finishing dry
the unfermentable sugars being the same for all wines
The method assumes that the difference in Specific Gravity before and after fermentation is due solely to the conversion of sugars before fermentation into alcohol after fermentation.

Requirements

  1. Sample containing alcohol
  2. Hydrometer
  3. Pipettes
  4. Water bath
  5. Test tubes

Procedure

  1. Take the initial reading with hydrometer. It should be read by noting the level at which the surface of the fluid contacts the glass when the hydrometer is floating in the liquid.
  2. The first reading should be taken before the addition of yeast, and at 60 degrees F.
  3. The second reading should be taken after fermentation is complete, that is, before bottling, and before adding priming sugar.
  4. The following is a sample for determinin both alcohol by weight (a.b.w.) and alcohol by volume (a.b.v.).
  5. Your first reading (original gravity [O.G.]) = 1.045
  6. Your second reading (final or finishing gravity) = 1.010
  7. Subtract final from original. 1.045 – 1.010 = 0.035 multiply this figure by 105. 0.035 x 105 = 3.68% a.b.w.
  8. Therefore, you have a brew of 3.68% alcohol by weight.
  9. To get Alcohol by volume simply multiply your figure for % a.b.w. by 1.25
    1. x 1.25 = 4.6% a.b.v.
    2. %v/v alcohol = (SG2 – SG1) / 0.0074
Go Back to Access Protocol Library
Go Back to Fermentation Protocols

News Updates

  • An MoU was signed between Orbit Biotech and Govt of Punjab during the Progressive Punjab Invest Summit 2015.
  • Registrations open for the biotech industrial training program starting April/May/June/July 2018. For registrations contact us at +91. 85 91 87 1105
error: Content is protected !!