1. Obscuration Mare-Loe Prinsloo Technical Manager Primary Production Spirits

2. What is obscuration? Definition: Variatian in alcohol concentration due to the presence of dissolved substances – Indication of non-volatile soluble solids (extract- sugar and non sugar extract) Relevance of SG – SG (gravity of substance relative to water at 20ºC) Hydrometer Pycnometer (mass & specific volume - P = m/v) DMA (SG & conversion factor – alcohol %) Why is obscuration important?

3. What is obscuration?

4. How is obscuration determined? Determination of obscuration Calculation (high concentration spirit BDY application) -Hydrometer -Distilled spirit, seen as true strength (no extract present e.g. 96.4% abv) -SG used to read alcohol strength from alcohol table after temp correction -If difference between before and after distillation -% Obs = DS – TS (% abv prior to dist - % abv after dist) Evaporation -Weigh constant volume e.g. 100 ml, evaporate & dry to constant mass -Extract = sugars, fixed acids, salts and phenols -Extract in g/100 ml correlated to SG and sugar content - alcohol % Distillation & Picno or DMA -Weigh volume, transfer to distilling flask and distill, weigh in picno before and after -Extract = sugars, fixed acids, salts and phenols

5. Problems with SG measurements Disadvantages Hydrometer -Relatively large sample required -Air bubbles -Human error reading meniscus, repeatability -Calibration and “maintenance” of hydrometers & thermometers Evaporation -Volume and weight to be determined -Heating not controlled in absolute manner -Time consuming, drying to constant mass -Many variables Distillation & Picno or DMA -Weight, volume, DISTILLATION -Time consuming -Relatively large sample -Low concentrations problematic, accuracy

6. What is obscuration? Requirements Accuracy -Eliminate need for distillation -Need for analysis of alcoholic products at a wide range of concentrations and consistency e.g. milk based liqueurs -NO interaction of the extract on analytical method Speed & Ease of operation Cost Possibilities -GC -NIR (winescan) -Alcoholizer

7. What is obscuration? CG analysis Benefits -High level of accuracy & repeatability -Low detection limits -Wide range of alcohol concentrations and product range -Least amount of interference by other compounds Disadvantage -Sample prep -Run time -Chemical waste -Running cost- cost of instrument and maintenance, gaslines, columns etc.

8. What is obscuration? NIR (Wine Scan) Benefits: -Complex alcoholic beverages -Limited interference by other wine constituents -Fast and accurate -Small sample required -No chemical waste Disadvantages: -Calibration with known compounds required - Different product types require unique and different calibration curves -Eliminate need for distillation -Need for analysis of alcoholic products at a wide range of concentrations -Initial cost of instrument

9. What is obscuration? Alcoholizer Benefits: -Specialized NIR (1150 -1200 nm) -Free of interference by other wine/spirit constituents -Fast and accurate -No chemical waste -Adjustment to zero point by single binary alcohol sample that work for different products Disadvantages: -Calibrated once a year by supplier -Initial cost

10. What is obscuration? Questions?