Fermentation Analysis: Brix, Temperature, and Sensory Evaluation in Winemaking, Slides of Winemaking

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Fermentation Analyses

Overview

• Fermentation Basics

• Brix and Temperature

• Sensory

• Record Keeping

Fermentation

Brix Hydrometer

• Since Glucose and Fructose compose 90% of the soluable solids in juice - Allows hydrometry to be used as a reasonable measurement
• Operation of the hydrometer is based on Archimedes' principle that a solid suspended in a fluid will be buoyed up by a force equal to the weight of the fluid displaced.
• Aka Saccharometer
• Multiplying the Brix by the conversion rate (0.55 for example) will give the potential alcohol number.

Schematic drawing of a hydrometer. The lower the density of the fluid, the deeper the weighted float B will sink; the depth can be read off the scale A. (Wikipedia)

Temperature in winemaking

• Measurement of average heat given off of a substance
• The liquid expands and contracts with changes in temperature
• A thermometer has two important elements: the temperature sensor and the scale
• Temperature measurements should be taken immediately after the sample is drawn
• Indicator of fermentation performance/kinetics
• Indicator of cooling system performance
• All ferments should be kept below 104F to avoid stuck fermentation
• Temperature affects the flavors that are developed in fermentation. (ie. Hot temp may result in cooked fruit characters)

Clinitest

• Is a copper reduction test that reacts with

reducing sugars

• The color change indicates sugar

concentrations below 1%

• Used because it measures trace levels of sugar

and is unaffected by the alcohol level.

• Not recommended to be used as the final

sugar analysis because it does have a slight

interraction with phenolics

Ebulliometer

• The ebulliometer is a measuring device that is designed to

evaluate the boiling point of different types of liquids.

• It's use in the wine industry is based on the fact that alcohol

boils at 78.4 °C, a lower temperature than water

• The boiling point of alcohol-water mixtures changes as a

function of their concentration.

• The boiling point of any liquid depends on the atmospheric

pressure, so the zero point has to be set against the boiling point of pure water prior to starting each test.

• +/- 0.5% Alcohol

Ebulliometer