Minimising Volatile Acidity Risk in Wineries: Temperature-Verified Cleaning
Volatile acidity (VA) is one of the most commercially damaging defects in wine. Caused primarily by the activity of acetic acid bacteria — particularly Acetobacter and Gluconobacter species — VA manifests as a sharp, vinegary character that is perceptible even at very low concentrations and escalates rapidly if conditions allow the bacteria to continue growing. A wine with elevated VA that reaches the palate of a consumer, retailer buyer, or critic will be rejected as defective — and the damage to the producer's reputation can far outlast the loss of any single batch of wine.
The most effective strategy for VA control in the winery is prevention rather than remediation. Once VA has developed beyond a low threshold, the options for correction are limited and costly. The foundation of VA prevention is rigorous cleaning and sanitation of all surfaces that come into contact with wine and wine-producing microorganisms — and the effectiveness of that cleaning depends critically on achieving the correct temperature during the hot water and caustic phases of the cleaning cycle. Temperature indicating labels provide a simple, documented method of verifying that your winery's cleaning programme is achieving the temperatures required to control acetic acid bacteria across all parts of the cleaning circuit.
Understanding Volatile Acidity: Sources and Thresholds
Volatile acidity in wine is measured as grams of acetic acid per litre (g/L). All wines contain some acetic acid as a normal by-product of yeast fermentation, and levels below approximately 0.6 g/L in white wines and 0.8 g/L in red wines are generally below the threshold of consumer detectability. UK and EU regulations set maximum permitted levels of 1.2 g/L for white and rosé wines, and 1.5 g/L for red wines, with stricter limits applying for wines seeking quality appellation designations. These regulatory thresholds represent the upper limit of the legally acceptable range — many winemakers target significantly lower levels as a matter of quality management.
The primary pathways for VA development in the winery are the activity of Acetobacter and related bacteria during fermentation, particularly when oxygen exposure is inadequate control and the wine temperature is suboptimal; post-fermentation development in wine held in contact with air in inadequately filled tanks or barrels; and the activity of residual acetic acid bacteria on insufficiently cleaned equipment surfaces — including pump bodies, hoses, valve seats, filter housings, and barrel stave interiors — that provide a persistent reservoir of inoculum.
This last pathway — the equipment surface reservoir — is the one that rigorous cleaning and sanitation most directly addresses, and it is the pathway where temperature indicating labels provide the most direct monitoring value.
The Role of Temperature in Controlling Acetic Acid Bacteria
Acetobacter species are generally less heat-resistant than the lactobacilli that cause lactic acid spoilage, but they are still significantly more resistant to heat than they appear. Vegetative cells of Acetobacter aceti are inactivated at 60°C within a few minutes, but populations attached to surfaces in biofilm formations — the mode of growth that makes equipment surfaces a persistent contamination reservoir — can be considerably more resistant. Effective cleaning must therefore achieve not just the target temperature, but must maintain it in contact with the surface for sufficient time to penetrate and inactivate the biofilm community, not just the planktonic cells in the cleaning solution.
For hot water sanitation targeting acetic acid bacteria in winery environments, achieving 65–70°C at the surface being cleaned for a contact time of five minutes is a commonly recommended target. Where Brettanomyces is also a concern (as it is in most red wine facilities), 70°C or above is more appropriate, as Brett is somewhat more heat-resistant than Acetobacter under biofilm conditions.
How Temperature Indicating Labels Are Used for VA Risk Management
The principle is simple: attach a temperature indicating label to a representative point on the surface being cleaned, run the hot water cleaning cycle, and read the label afterwards. A label that has changed to confirm the target temperature was reached confirms that the cleaning cycle was thermally effective at that point. A label that has not reached the target temperature identifies a performance gap in the cleaning programme — perhaps a point in the circuit where temperature is lost, a vessel zone that receives inadequate hot water flow, or a piece of equipment where the CIP cycle needs to be adjusted.
Common placement positions for VA risk management monitoring include the lowest point of fermentation and storage vessel interiors, where hot cleaning solution may stratify and cool; the pump body inlet and outlet ports, which are in direct contact with wine and are a primary Acetobacter colonisation site; transfer hose interiors; barrel interior surfaces (accessible via the bunghole, using a carrier label or a stainless steel probe carrier); and the interior faces of valve bodies, filter housings, and other fittings with complex internal geometries that provide protected niches for biofilm development.
Seasonal and Batch Monitoring Programmes
For VA risk management purposes, the timing of temperature monitoring should reflect the periods of highest risk and the seasonal pattern of the winery's operations. Pre-harvest deep cleaning and sanitisation of all fermentation and processing equipment is the highest-priority monitoring event, since the cleanliness of equipment at the start of harvest directly determines the microbial load with which the incoming vintage begins fermentation. Temperature indicating label monitoring of every vessel and major circuit component during pre-harvest CIP provides documented evidence that the start-of-vintage cleaning programme was thermally effective.
During harvest and active fermentation, the pace of operations makes comprehensive cleaning monitoring more challenging, but spot-check monitoring of high-risk equipment — pumps, transfer lines, and filler components — provides ongoing assurance that cleaning standards are being maintained under production pressure. Post-harvest cleaning and wine movement monitoring, as wines are racked, filtered, and moved between vessels, is the second major monitoring window.
Integration with VA Monitoring Programme
Temperature indicating label records should be integrated with the winery's VA monitoring programme — the routine measurement of VA levels in all wines at defined points in their development. A correlation between high VA readings in wines from specific vessels and inadequate cleaning temperatures at the corresponding vessel positions identifies the equipment-level contamination source, enabling targeted remedial action rather than general investigation. This integrated approach — measuring both the cleaning process (temperature) and the product outcome (VA level) — provides a comprehensive quality management picture that supports both VA control and the documentation requirements of quality certifications.
Frequently Asked Questions
What VA levels should trigger a review of cleaning and sanitation procedures?
Any upward trend in VA levels across a wine that is still under development should prompt a review of equipment sanitation for the vessels and circuits that have been in contact with that wine. A VA level approaching 0.6 g/L in a white wine or 0.8 g/L in a red wine still in tank or barrel warrants investigation, as these levels indicate active acetic acid bacteria activity. A wine already showing 1.0 g/L or above may have limited remediation options, and a full review of sanitation procedures is indicated to prevent recurrence.
Are temperature indicating labels effective for monitoring barrel interiors?
Yes — labels can be applied to the interior stave surface via a carrier probe introduced through the bunghole before steaming. The label is recovered after the steam treatment and read to confirm whether the stave surface temperature reached the target level. For barrels with established Brett or Acetobacter contamination, steam temperatures of 70°C or above at the stave surface are targeted. Barrel-by-barrel steaming temperature monitoring is time-intensive but provides the documentation required for wineries producing premium wines where barrel hygiene is a key quality control measure.
Can VA be removed from wine that has already developed it?
Options for reducing established VA in wine are limited. Blending with low-VA wine can reduce the overall level if sufficient low-VA wine is available. Reverse osmosis treatment can reduce VA, but the capital cost and potential impact on wine character make it appropriate only for high-value wines. The most effective approach is prevention: a rigorous sanitation programme that eliminates acetic acid bacteria from equipment surfaces before they can colonise wine.
Does controlling cleaning temperature eliminate all VA risk?
Controlling cleaning temperature is one of the most important elements of VA prevention, but it is not the only one. Oxygen management during fermentation and post-fermentation handling, SO2 management, temperature control during storage and ageing, and the integrity of closures during bottling all contribute to VA control. A thermal sanitation programme verified by temperature indicating labels addresses the equipment contamination vector; the other elements of VA control require separate management attention.
How should temperature indicating label monitoring records be retained?
Records should be retained as part of the winery's quality management documentation, linked to the specific vessel, circuit, and cleaning event they document. For wineries under SALSA certification, records should be retained for at least two years. For wineries operating under longer-duration certification or supplying customers with extended documentation requirements, retain records for the shelf life of the wine produced in the cleaned equipment plus one year as a minimum.
About Temperature Indicators Ltd
Temperature Indicators Ltd is a specialist global distributor solely focused on temperature-sensitive labels, tags, and indicators for cold chain monitoring, process validation, and regulatory compliance. With 35 years of experience and operations shipping to over 50 countries worldwide, we supply food manufacturers, pharmaceutical distributors, sterile services departments, and logistics providers with the temperature monitoring solutions they need to maintain compliance. Contact us for expert guidance on temperature monitoring for your application.
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The information provided in this article is for general guidance only. Temperature Indicators Ltd makes no warranties, express or implied, regarding the accuracy or completeness of this content. Product specifications, regulatory requirements, and industry standards may change over time. Always verify current requirements with the relevant regulatory authority and consult a qualified professional before making decisions based on information contained in this article. Temperature Indicators Ltd accepts no liability for actions taken in reliance on information provided here.
- Temperature Indicators Staff
