Growing & Winemaking


Keep Instruments Accurate

September 2009
by Paul Franson
Winery labs accuracy
William Jarvis and Dimitri Tchelistcheff confer in the lab at Jarvis Winery in the Napa Valley.

Though winemakers and enologists use many instruments, they don't always pay as much attention to them as they might. Most instruments require periodic maintenance and calibration, but that's easy to forget during the crush of harvest season.

Of course, winery laboratories range from basic to elaborate, with larger winery labs challenging those of universities and West Coast commercial labs like ETS and Vinquiry. We talked to a few to discuss their calibration and maintenance practices.

In winery labs


  • From mid-sized wineries to full-time lab service providers, everyone has a system for keeping their instruments calibrated and in top condition.
  • Though it sounds simplistic, keeping equipment clean and dry is the best way to keep it functioning properly, lab experts say.
  • Laboratory specialists contract third-party firms to affirm weights and other measurements.

Many wineries today do only basic lab work, and they depend on outside labs for anything beyond simple measurements like pH, sugar and TA. Jarvis Winery in Napa Valley is one of these. Winemaker Ted Henry admits that his winery isn't very high tech, but he follows good practice by calibrating his instruments daily using standard solutions. "They don't need much attention," he says.

At Clos LaChance Winery near San Jose, Calif., assistant winemaker Erica O'Brien is charged with maintaining the lab. She calibrates pH meters and pH probes with pH4 and pH7 buffers every morning. "It only takes a couple minutes, but it's very important since the pH electrodes wear out over time, the fill solution may need changing, or the glass bulb could be scratched." She replaces electrodes once per year but has found the actual meter requires no maintenance.

Likewise, O'Brien calibrates the winery's refractometers with both distilled water and 20º Brix sugar solutions before use. "This is also very important, as it seems there's always an adjustment to be made." She adds that you have to make sure the testing solutions are at room temperature.

Finally, she calibrates the densitometer with distilled water before measurement. It requires daily cleaning with detergents, and drying internally with alcohol. The whole process takes a few minutes each day.

Another mid-sized winery is Artesa, the Carneros AVA site where Casey Hass is the lab supervisor. She says Artesa calibrates pH meters daily at the same levels Clos LaChance uses. They check other instruments daily, too, such as the TA meter and alcohol analyzer. She makes up a standard solution of 14%-15% alcohol to verify the latter. The same is true for her ChemWell 2910 autoanalyzer, which she calibrates with known standards.

For some instruments, such as for the Anton Paar digital densitometer, she calls in the vendor. She has a service rep come before harvest to check its calibration and adjust it if needed.

For her turbidity meter, she uses a standard solution every three months and has the company perform preventive maintenance every two years.

Cleanliness comes before calibration

Before detailing the procedures recommended for different instruments, Michelle Bowen, director of laboratory services at Vinquiry in Windsor, Calif., offered some general comments about instrument care.

"Keep everything clean." Clean after use and daily. And store instruments in clean, dry spots. "If any instruments can leak, make sure you place them in a tray to catch the liquids and draw them away. This is especially true of anything containing electric components, which are susceptible to moisture," Bowen noted. "One instrument that is especially troublesome is the segmented flow analyzer, which contains a huge number of tubes that can leak."

She warned that many lab chemicals are very caustic, and many instruments incorporate tubes and reservoirs that may need especially careful cleaning.

Bowen noted that some procedures should be done daily, like cleaning, with more extensive cleaning weekly or periodically, while preventive maintenance might need to be done yearly.

She recommended using standards or known samples daily to make sure the instruments are working properly, and keeping records. "If you see trends, the instruments may need additional cleaning, calibration or even repair."


Constellation and Diageo

It's a big jump from mid-sized wineries to Constellation Brands, which maintains multiple laboratories in the many facilities it has acquired over the years. Gregory Gessner oversees the labs at Icon Estates fine wine group, which includes the California wineries of Robert Mondavi, Franciscan and others. He also works with the corporation's labs at its large wineries and bottling plants such as Mission Bell, Woodbridge and Gonzales.

As you might expect, the various labs collaborate and share some capabilities, with quarterly meetings to coordinate their activities. Gessner says the wineries utilize standards traceable to the National Institute of Standards and Technology, the former National Bureau of Standards.

The company has some older autoanalyzers that were developed for the medical industry, and Gessner finds that th ey aren't as robust as the newer products. The labs are looking at their future needs now, in fact. Ironically, he says they've found more problems with the electronics in the instruments than the mechanical parts. "We have to replace the circuit boards."

One of Constellation's current focuses is improving measurements of dissolved gases, as the importance of these readings becomes more widely appreciated. Gessner doesn't have a metrologist--a specialist in measurement--on his staff, but he is hoping that will come.

Like Gessner, Pamela Borreson works with a number of laboratories at different sites. She is the technical services manager for Diageo's Beaulieu, Sterling and Rosenblum wineries in California.

Each winery has a lab, but the one at Beaulieu Vineyard is the most sophisticated, and it is becoming a focal point for development. Other Diageo sites such as Provenance and Chalone have basic facilities for everyday measurements such as pH and TA, but they turn to the lab at BV for more demanding work.

Borreson recently hired two people; one a Ph.D, to help the labs institute "ISO-like" procedures. "We don't need to be ISO-certified," she says, "but we want to have similar traceability and procedures. If we really need traceable work, we can send it to ETS," the St. Helena, Calif., wine lab.

Along with the usual steps, the lab keeps a log on each instrument, with changes and calibration and maintenance noted. Borreson says that typically only the older instruments require adjustment, though they obviously clean the instruments as required. "In general, the newer instruments are cleaner in design and operation, so they don't need as much troubleshooting as older designs."

Changes in instruments are a challenge for labs like hers. "Even 2-year-old instruments can be outdated." The lab recently acquired a Fourier Transfer IR spectrometer, for example, and it cost more than $100,000. "It's expensive, but it can do 19 tests at the same time in 30 seconds."

Likewise, she has a gas chromatograph mass spectrometer, an expensive instrument, but one she says is becoming a standard tool for wineries this size.

The new instruments help deal with new challenges, but she still would like to be able to run tests on microbiological concerns such as Brett and TCA. "They're expensive to do--in-house or at a lab--but we'd like to be able to do them here." She notes that ETS has a new test it calls Scorpion, which can count the actual contaminant cells. "It's rather sophisticated to do, however, and we're just a winery lab."

On her horizon are expected new federal and European requirements, including limits on ethyl carbamate (urethane). She also anticipates possible labeling requirements for allergens such as eggs and fish, and wants to be able to test for them. That would add new calibration requirements as well.

Vinquiry's approach
If anyone is more dependent on their instruments than winery winemakers, it's the lab services that assist the industry. Michelle Bowen is the director of laboratory services at Vinquiry in Windsor, Calif. Vinquiry is ISO certified, so it requires even more stringent procedures than most winery labs--but some of those maintain ISO certification, too.

Vinquiry uses many instruments--including some found only in the largest winery laboratories--and it also provides calibration services and maintenance on some instruments. It also arranges calibration and hosts periodic calibration workshops by manufacturers or registered calibration services.

In most medium to large winery laboratories, equipment needing attention would include a variety of instruments, including some used in the field or cellar as well as the labs themselves. Thermometers and hydrometers are pretty reliable, but they need to be checked occasionally with a standard or a certified service. 

Oxygen meters and probes, as well as pH meters and probes, tell you when it's time for maintenance. The usual fix is to change the probe membrane. "Warm-up times are very important, too--as is keeping it clean. You should follow the instructions in the manual, and if you find that inadequate, call the supplier. They'll have someone who can help," Bowen says. She also notes that you need to clean and calibrate them daily, especially the electrodes.

Vinquiry has a specialist come in once a year to clean, adjust and calibrate its microscopes.

Many customers bring in refractometers for checking, particularly before harvest. "For digital meters, zero and clean, and check against standards. Vinquiry uses 20º, 22º and 25º Brix standards. The readings must match within 0.2. And keep a log." The company also sells the standard solutions.

Bowen says people often bring in old hand-held refractometers for service. "We try to fix them if we can," she says.

Vinquiry uses both hand-held and laboratory-based Anton Paar densitometers; the supplier's representative visits to maintain and calibrate the equipment. Bowen notes that the instruments sometimes need recalibration after intense environmental conditions like exceptionally stormy weather.

"We can calibrate the hand-held unit ourselves if we carefully follow the directions in the manual," she says. "The idea of taking it apart scares a lot of people--a lot of people in the wine business don't have strong technical backgrounds--and it looks fragile, but it's built to take apart and clean."

Balances should be calibrated daily, and again, keep track of variation. Vinquiry is fortunate to have a metrologist on staff to perform this service, and it also owns National Institute of Standards and Technology (NIST)-certified weights. "If it's not within specs, it usually needs cleaning," Bowen advises. She also recommends Heusser Neweigh, a calibration service based in Concord, Calif. "They can certify instruments and accessories." She adds that they will make calls if necessary.

Bottletop burettes need to be calibrated regularly. Vinquiry has every burette and pipette calibrated on a schedule, and it always has backups available.

Though Vinquiry doesn't use electric ebulliometers, Bowen notes that customers sometimes bring them in for service. She finds that they often contain liquids that have led to corrosion. &qu ot;When we get them in, it's usually because they weren't stored properly.

"You do need to calibrate them with a standard every day," she warns. She uses standard liquids of 13.5% and 15%, which the company also sells.

Centrifuges don't need much attention except keeping them clean, though occasionally the gaskets must be replaced. Bowen does note that centrifuges come with a bottle of graphite, which should be applied to the cups occasionally.

Keep spare parts handy
Among the most sophisticated instruments in many winery labs are spectrophotometers, which have internal calibration systems. Actual calibration is usually only needed after something goes wrong and they need to be repaired. The most common failure is the lamps; Bowen warns users to keep spares on hand, as they always seem to fail at inconvenient times.

She says always to use the checks and standards when performing enzymatic analysis, and keep a record so you can note if readings are drifting. Other than that, "Keep it clean and run cleaning solution like Tergazyme through it after use." Along with the daily cleanings, she recommends a more intense weekly cleaning. Periodically, Vinquiry also replaces lamps, tubing and sample needles.

The lab director says that every year she buys a preventive maintenance contract for her spectrometers, adding that it's a huge comfort to know they're taken care of. "It saves a lot of time and money down the road," she says. Her lab includes a Varian gas chromatography and mass spectrometry, Perkins Elmer high performance liquid chromatography system and Anton Paar near-infrared optical spectrometer.

One "instrument" that many labs may not think of is the fume hood. "They have to be periodically cleaned and calibrated, Bowen notes.

Vinquiry schedules regular calibration service days for pH meters, refractometers, balances, microscopes and automatic pipettors. Various service levels are available, and custom services can be created for the equipment. Calibration is available for both one- and two-channel pH meters. Basic service levels for pipettors include verification and validation at multiple volumes, adjustment of the instrument into tolerance, and leak checks. Both single channel and multi-channel pipettes are accepted. Instrument repair is also available and priced on a per-project basis.

Some suppliers even offer free calibration. For example, Thermo Scientific (Orion Products) provides complimentary service on pH, oxygen and conductivity meters occasionally at Vinquiry.

ETS has outside assessor
Another large lab that services the wine business is ETS Laboratories, headquartered in St. Helena. Ken Stoub is an independent assessor who serves as a senior consultant to the firm on metrology. Stoub notes that some winemakers would love to be able just to buy an instrument and use it, but that's not good practice. "You can't just whip it out of the box and start using it," he warns. "You need to calibrate even hand-held refractometers and pH meters."

Stoub emphasizes the elaborate steps labs like ETS must take. Balances are used constantly, for example, and the lab calibrates them with weights traceable to NIST, which they send out every five years to an accredited calibration lab. It then uses these weights to calibrate working weights. Fortunately, he says, they see very little change in the weights.

The lab also has experts clean and calibrate the balances annually.

For an atomic absorption spectrometer, which is used for analysis of metals, the lab buys reference materials from an accredited reference materials producer for each metal of interest. Then it makes up different concentrations and compares the results, which can be used to generate a calibration curve.

It also performs a calibration on autoanalyzers and checks them during the day after every 10 samples. Stoub says that if ETS finds a problem, they re-run the tests.

As an independent assessor of labs, Stoub finds that labs run by analytical chemists tend to be most careful in their calibration and maintenance. He says, "They (ETS) follow the most rigorous procedures I see."

As a final note, Michelle Bowen says that Vinquiry schedules a lot of calibration and maintenance in July and August to be ready for harvest. She agrees that the extensive schedule that Vinquiry and other large labs follow may not be practical for smaller winery laboratories, but she reminds us, "Things tend to go out when you most need them."

Of course, in that case, commercial labs are happy to help out.

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