pH
The Power of Hydrogen, or pH, is a measure of how acidic (<7) or basic (>7) a solution is on a logarithmic scale. It’s the most fundamental analysis in all of winemaking informing us of microbial inhibition, chemical speciation, and tartrate stability.
At wine pH (~pH 3-4), there are no dangerous pathogens to human life, and this has largely shaped the traditions and legislature around winemaking. Since the risk of food born illness is very low, winemakers have far more leeway with winery sanitation than with other food products. Nevertheless, pH helps winemakers understand the proclivity of wine towards spoilage, thus giving them a framework for sanitary demand. Rather than thinking of sanitation as an absolute, we can discuss its relevance as a stylistic tool depending on varying pH values. Furthermore, pH also influences the speciation of chemicals in wine, most notably sulfur, phenolics, and metals, and their roles in antimicrobial and antioxidant activity.
The limits for cleaning and sanitation are well-defined:
Clean: removal of soil and 90% reduction of colony forming units.
Disinfection: a reduction of 99.9% of colony forming units.
Sanitation: a reduction of 99.999% colony forming units.
Sterilization: a reduction of 99.9999% colony forming units. Chemical sterilants include 0.2% peracetic acid (PAA) and 7.5% hydrogen peroxide (H2O2) (Mohapatra, 2017).
As a biological transformation, winemaking exists within a grey area of the this spectrum. Ultimately, the level of cleanliness in a winery is subject to a winemaker’s microbiome of desire. For instance, premium Cabernet Sauvignon producers with high pHs tend to have immaculate cellars with strict sanitation and risk adverse protocols like inoculating with cultivated yeast, whereas small lot Pinot Noir producers tend to take more risks with spontaneous fermentations in porous vessels with less sulfur. How we determine the design and practices for each wine style will be based on sanitary demand, the primary function of pH. It is important to note, however, that there is no definitive limits for these decisions. Spontaneous fermentations can be executed at pH 4.5 as well as at pH 3.5. The most important distinction is one’s careful attention to detail.
To learn more about Free SO2 and its importance in winemaking, become a Bound advising client.
References
Colantuoni, G., McLeod, S. WINEXRAY LLC. https://www.winexray.com/
Gawel, R. (1998). Red wine astringency: A review. Australian Journal of Grape and Wine Research, 4(2), 74–95. https://doi.org/10.1111/j.1755-0238.1998.tb00137.x
Jenkins, T. W., Howe, P. A., Sacks, G. L., & Waterhouse, A. L. (2020). Determination of Molecular and “Truly” Free Sulfur Dioxide in Wine: A Comparison of Headspace and Conventional Methods. American Journal of Enology and Viticulture, 71(3), 222–230. https://doi.org/10.5344/ajev.2020.19052
Kallithraka, S., Bakker, J., & Clifford, M. N. (1997). Effect of pH on Astringency in Model Solutions and Wines. Journal of Agricultural and Food Chemistry, 45(6), 2211–2216. https://doi.org/10.1021/jf960871l
Mohapatra, S. (2017). Sterilization and Disinfection. Essentials of Neuroanesthesia, 929–944. https://doi.org/10.1016/B978-0-12-805299-0.00059-2
Singleton, V. L. (1987). Oxygen with Phenols and Related Reactions in Musts, Wines, and Model Systems: Observations and Practical Implications. American Journal of Enology and Viticulture, 38(1), 69–77. https://doi.org/10.5344/ajev.1987.38.1.69
Smith, C. (2013). Postmodern Winemaking: Rethinking the Modern Science of an Ancient Craft. University of California Press.
Sotres, J., Lindh, L., & Arnebrant, T. (2011). Friction Force Spectroscopy as a Tool to Study the Strength and Structure of Salivary Films. Langmuir, 27(22), 13692–13700. https://doi.org/10.1021/la202870c
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FAQs
Frequently Asked Questions
Supplies
- We supply 50 mL centrifuge tubes and labels upon request.
Sample
- Sample your wine in a way that is most representative of the entire lot (i.e. practice flushing your sample valve, collecting after movements like pumpovers, stirring your barrel, etc.).
Label
- Label each sample appropriately with your Client ID, Sample Date, and Sample ID. Samples for Phenolics analysis also require a Crush Date, Varietal, and Appellation. The analysis cannot be performed without the applicable information for each sample.
- Mark the sample type. ”Juice” applies to grapes and juice samples before fermentation. ”Must” applies to samples undergoing primary fermentation. ”Wine” applies to samples after fermentation.
- Select “Standard” for our corresponding juice, must, and wine panels, or select “Phenolics” for our phenolics panel. SO2 analysis can be included with the standard panel by selecting “with SO2”. Individual parameters can be added at the bottom of the label. A full list can be found on our ANALYSES page.
Clients are able to submit samples by scheduling a pickup, delivering directly to our lab, or via the mail.
To arrange for pickup, clients must be located near Lompoc, Buellton, Santa Ynez, Goleta, or Santa Barbara and notify us by 11 am for same-day retrieval. Established clients can also use our quick scheduling function by clicking the “LAB CLIENTS” tab on the bottom right hand corner of the screen. Be sure to select the correct date and provide all necessary details including instructions for pickup or requests for sampling supplies. Please contact us for more information.
- We provide same-day results by 7 pm with a guaranteed turnaround within 24 hours of sample receipt.
- Samples that are not analyzed same-daly are refrigerated overnight and analyzed first thing the next morning.
- Results are delivered via email in PDF format and uploaded to your account.
- Our invoices are sent via email and are due upon receipt.
- Your payment is securely processed through Bound’s website using one of the most trusted e-commerce platforms in the world.
- You can also opt-in to our invoice autopay feature by clicking “SIGN UP FOR AUTOPAY” on your account page.
To ensure their stability, we ask our clients either freeze or boil their juice / fermenting wine samples before shipment. Please note that boiling or freezing your samples may influence your results and we cannot guarantee their validity. Please contact Bound with any additional questions about sample preparation before shipment. We recommend expedited same-day to one-day shipping with a tracking number included.
Frozen
Samples can be placed in a freezer 24-hours in advance and shipped with an ice pack. Do not over-fill the polypropylene tubes or use glass containers as the frozen liquid will expand and could pose a safety concern. Freezing samples is a better alternative to boiling when analyzing compounds like ethanol, volatile acidity, free sulfur, and phenolics. Label each sample as "FROZEN".
Boiled
We generally do not recommend boiling your samples as it can significantly alter the chemistry of your sample. If necessary, samples can be boiled in their 50 mL polypropylene centrifuge tubes with a loosely fitted cap on top. Polypropylene tubes can be boiled up to 10 minutes, but be sure not to over boil as exposure to high temperatures can change your results. Label each sample as "BOILED".
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