Because so many of our clients are impacted by the current wildfires, we've put together answers to common questions about the options for testing for smoke impact as well as the procedures to follow when sampling. You can also download a printable version of this handout

All smoke samples should be shipped to our St. Helena location (899 Adams Street, Suite A, Saint Helena, CA 94574)

Pre-Harvest Analysis: Grape samples and Microferments

Volatile guaiacol and 4-methylguaiacol in whole berries

(volatile fraction) is the routine pre-harvest screening test for smoke impact at ETS laboratories. Submit approximately 250 berries per sample, undamaged as much as possible. Use preferably hard plastic “Tupperware-style” container - necessary if you are shipping samples. Avoid submitting cluster samples: the additional sample preparation time in the lab will delay results. We do not recommend submitting juice samples.

Guaiacol and 4-methylguaiacol in small scale ferments

(also called “bucket ferments” or “microferments”) is a useful complement to direct grape tests and has gained popularity in recent years. A protocol for preparing microferments can be found here: https://www.awri.com.au/wp-content/uploads/small_lot_fermentation_method.pdf.

At (or near) completion of fermentation (brix <0), transfer fermented wine into a bottle, let settle in fridge for a few hours, decant and submit sample in a 60 mL plastic tube.

Post-Harvest Analysis: Production Wines

Volatile guaiacol and 4-methylguaiacol

Volatile guaiacol and 4-methylguaiacol are useful to assess smoke impact in unoaked wines, starting right at completion of primary fermentation, when quick answers are needed for production wines.

Volatile Markers - Extended Panel

We have temporarily stopped offering this panel during the 2020 wildfire emergency. In addition to guaiacol and 4-methylguaiacol, this panel includes cresols, phenol and syringols.

Glycosylated Markers

We have temporarily stopped offering this panel during the 2020 wildfire emergency. Grape purees can be frozen and analyzed later, as well as wines can be aged in contact with oak and analyzed later, as results which will not be impacted by oak aging.

FREQUENTLY ASKED QUESTIONS:

I WANT TO TEST GRAPES FOR SMOKE, WHAT KIND OF SAMPLE SHOULD I BRING?

The preferred sample for red or white grapes is a representative 250-300 berry sample, with berries as intact as possible. Transport in small rigid “sandwich boxes” works well.

CAN YOU TEST SYRAH?

Yes, but Syrah naturally contains variable amounts of guaiacol, the main smoke marker. This makes it difficult to assess smoke impact, unless exposure to smoke has been relatively severe. One (unperfect) strategy is to use other varieties grown next to Syrah blocks as “proxies”.

WITH WHITE GRAPES, SHOULDN’T I BRING JUICE SAMPLES?

Since smoke compounds are mostly in skins we still prefer whole berry samples for white grapes.

WHEN IS A GOOD TIME TO BRING SAMPLES?

The typical recommendation is about 10-7 days prior to harvest. Keep in mind that the impact of smoke is cumulative and that “negative” results too early may give a false sense of security especially if more exposure to smoke happens.

SHOULD I CRUSH BERRIES AND LET THEM SOAK IN THEIR JUICE BEFORE BRINGING THEM?

We do not recommend this. When we have control of the sample preparation our interpretation guidelines are more applicable.

CAN YOU TEST FOR MORE THAN JUST GUAIACOLS?

For pre-harvest tests, grape or microferments, we are prioritizing volatile guaiacols.

CAN I MIX BERRIES FROM DIFFERENT VARIETIES AND BRING A COMPOSITE SAMPLE?

This is not advisable . We’ve seen in previous years drastic differences in pick-up of smoke compounds between grape varieties, with Petit Verdot often much more impacted than other cultivars.

WHAT IS YOUR TURNAROUND TIME?

For the most accurate turnaround time we recommend taking a look at our website (Analyses - Smoke Markers). We’ll keep our TAT information for grape and wine tests updated regularly.

FOR EVEN MORE INFORMATION, VISIT OUR WEBSITE

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