Fundamentals of Enology - VWT 172 Bryan Avila

1. Fermentation Analyses Fundamentals of Enology - VWT 172 Bryan Avila

2. Overview Fermentation Basics Brix and Temperature Sensory Record Keeping

3. Fermentation Basics Microbial cell growth follow a similar growth curve

4. Elements of Alcoholic Fermentation End of Pre-Ferm Inoculation 105 cells/mL) Lag Phase Log Phase (108 cells/mL) Nutrient Addition - DAP - Complex Nutrients Brix Time (Days)

6. Fermentation

7. 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)

9. 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)

10. 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

11. Clinitest Kit

12. Enzymatic Analysis of Fermentable Sugars The enzymatic kits are used to determine the precise amount of fermentable sugars in a fermentation 100 mg of G+F/100ml (Other commonly used residual sugar units: 1g/L or 1%) Widely recognized as an official method as a measure of dryness for Alcoholic Fermentation Aka – RS, GLU/FRU

13. Sensory • Brief sensory analysis is taken at the time of sampling by the lab tech or winemaker • The fermentation sensory is checking for • Sulfides • Ethyl acetate • VA • Unexpected aromas

14. Ebulliometer The ebulliometer evaluates the boiling point of different types of liquids. Based on the fact that alcohol boils at 78.4 °C, a lower temperature than water The boiling point of alcohol-water mixtures change as a function of their concentration. The boiling point of any liquid depends on the atmospheric pressure thus the zero point has to be set against the boiling point of pure water prior to starting each test. +/- 0.5% Alcohol http://www.winegrowers.info/wine_making/Alcohol.htm

15. Ebulliometer

16. Usual order of fermentation sampling operations Sanitize valve/bung and sampling apparatus Pull sample Take temperature Check brix Smell wine Return wine??? Re-sanitize valve/bung and sampling apparatus