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WINERY & VINEYARD EQUIPMENT 90 WINES&VINES January 2018 ambient temperature in the instrument's operation and calculation. The Hanna refrac- tometer can measure percentage Brix from 0 to 85% with a resolution of 0.1% Brix and + /- 0.2% Brix. Rudolph Research Analytics Alcohol and Refractive Index State of the art for high-volume alcohol determinations Rudolph Research Analytics offers a highly accurate refractometer, the J457, and has de- veloped a protocol called Alcotest that com- bines refractometry with densitometry and can quickly and accurately measure the percent alcohol in many alcoholic beverages. The original system was validated for spirits, but wine is a more complex beverage. Alcotest is now available with a wine scale. Its operation is based on a combination of re- fractometry and densitometry. Like the Foss system of infrared analysis, complex systems can be accurately measured once you know the system matrix. Then it is up to the algo- rithm of the analysis to calculate the com- pound or compounds from the complex mixture presented. The refractometer and densitometer in- struments require highly accurate, tempera- ture-controlled environments to carry out the calculations necessary for accurate re- sults. For example, the refractometer is ac- curate to 0.015° Brix and has a resolution of 0.01° Brix. The densitometer is accurate to 0.0001 g/cm 3 and has a repeatability of 0.00005 g/cm 3 . These instruments are rug- ged, splash-proof and designed for high- volume production environments. Editor's note: The author's firm, Tamanend Wine Consulting, worked with Rudolph to help validate its system for wine. Using the equipment: analyses and results The equipment described above was used to conduct the appropriate analyses using the same wine, and each section of results that follow had triplicate analysis of the same sample (see table on pages 88-89). When reviewing these results, it is impor- tant to understand the difference between precision and accuracy. Precision is the mea- sure of the degree of variance in the results. A very low degree in variance has a high preci- sion. However, high precision does not neces- sarily provide high accuracy. Great precision off the target is worse than larger variance on or near the target. The user needs to know what the target (most accurate) is in order to decide if a triplicate measure of + /- 1 is better than + /- 3. For this study, ETS Laboratories provided the target. Another consideration is tolerance. A highly accurate measurement with great pre- cision is likely the best solution, but the cost of that equipment may be too high. The user must then determine their degree of toler- ance—what is good enough—to obtain an affordable result. The third factor is the time needed to get the result. New technology has streamlined analytical procedures, reducing the time needed to get an answer. When compared with traditional equipment, new methods are faster, more repeatable, and many times more accurate. In addition, maintenance and calibration is much easier. Conse- quently, a lab can often run tests in a more timely manner and therefore help you make better wine. Acetic acid: two ways to test Acetic acid is analyzed using enzymes, and the technique does not analyze for anything else. As long as you don't smell the nail polish aroma of ethyl acetate, this reading will be an essentially accurate measure of volatile acidity. The smell of ethyl acetate indicates it has reached the noticeable threshold of 100 to 150 ppm or more in the wine. At that point, the true volatile acidity will be slightly higher, due to the ethyl acetate present. For the CDR WineLab, the procedure adds two reagents to the sample addition. One re- agent is added with a wait time, then the second reagent is added with additional wait time, after which the result is printed. Total time is six minutes for the first test in a series. For the MegaQuant Wave, water, two buf- fers, the sample and two enzymes are added sequentially to the test tube, which is then inserted for the first measurement. The last enzyme with a wait is added for the last mea- surement. The total time is six minutes for the first test in a series. The lowest amount the MegaQuant Wave can detect is 30 ppm; for the CDR WineLab it is 50 ppm. For both instruments, add about 30 seconds for each additional analysis in a series of analy- ses. The same basic procedural steps outlined here are followed with these two instruments when conducting other analyses. The only dif- ferences are the particular enzymes or other reagents, the time of the tests and the amounts of reagents. Once you learn the procedure, you can run all of their tests. Alcohol: ebulliometry goes digital The most common way to analyze for ethanol in wine is by ebulliometry, which is based on the boiling points of water and wine. With the right equipment, the results are accurate enough for regulators for label determinations. For dry wines, accuracy is about + /- 0.1% v/v. This in-house analysis should not be relied upon for decisions where alcohol tax levels change if your wine is within twice the average error. Setup for the first ebulliometer measure- ment takes 15 to 20 minutes for a dry wine with less than 1% residual sugar. Subsequent tests take about seven to eight minutes. As residual sugar levels rise, this test becomes less accurate. Dilution to less than 1% residual sugar helps, but errors increase due to dilution inaccuracy. These errors can only be somewhat tolerated to about 3% residual sugar. Above that, a two-step OPTIONS FOR THE SMALL WINE LABORATORY T here is no one way to select the equipment for a winery lab. The choice depends partly on your starting point: Is this a new winery just getting started? Are you upgrading a legacy laboratory? Are you adding a satellite lab at a remote location or crush pad? These situations and more will influence decisions about winery laboratory equipment. The new technology available provides opportunities for a winery serious about its products and reputation at a cost only slightly more than wet chemistry. The CDR WineLab unit allows a winery to do more than 20 tests in house. There are com- promises that a system like this presents, but having this instrument and using it in the way it is intended will help a winery make better wine. The equipment to complete a lab would include a turbidity meter for heat stability, a conductivity meter such as the Edge from Hanna for cold stability and their refractive index meter for Brix determinations. For greater precision, the MegaQuant Wave should be considered as part of the labora- tory's evolution. This system requires marginally greater attention to technique than the CDR WineLab, and it is important to add certain ancillary equipment to provide the analy- ses that cannot be done with MegaQuant Wave such as the refractive index meter, the Edge pH, electrical conductivity and dissolved oxygen meter and the turbidity meter. When budgetary considerations are paramount, the most important tests to consider are alcohol, SO 2 (total and free), titratable acidity, heat and cold stability. These tests can be added sequentially, which may ease the budget impact. Agápi Lab and Hanna provide this sequential upgrade path for the wine laboratory, as do others.