Cleaning and Sanitizing Winery Equipment: Stainless Steel, Barrels, Bottling Lines

By Dr. Molly Kelly, Enology Extension Educator, Department of Food Science

As we approach harvest, we should be reviewing our sanitation protocols both in the vineyard and winery. In this article we will focus on effective cleaning and sanitizing in the winery, specifically winery equipment to make sure certain objectives are met:

  • To continually improve wine quality 
  • To reduce quality concerns
  • To ultimately operate cost-effectively…by annually producing both a quality wine and reaching the targeted financial return
  • To reduce food safety concerns

Stainless Steel Winery Equipment

During normal service, all grades and finishes of stainless steel may in fact stain, discolor, or attain an adhering layer of grime.  What considerations should one take regarding maintaining stainless steel equipment and the related use of cleaners and sanitizers?  The frequency and cost of cleaning stainless steel is lower than for many other materials and often out-weighs the higher acquisition costs. Generally, the frequency of cleaning should be determined by the objective to “clean the metal when it is dirty in order to restore its original appearance.”

So, the degree of cleaning depends on the condition of stainless steel equipment:

  • Routine Maintenance – mild cleaning
  • Mildly aggressive cleaning to remove minor surface dirt:  use sponge or bristle brush with a non-abrasive cleaner and warm water; towel dry. To prevent compromising the integrity of the protective oxide coating on stainless steel, only soft-bristle brushes should be used in the case where scrubbing is required.
  • More aggressive, for example, grease:  repeat above, then use a hydrocarbon solvent such as acetone or alcohol.
  • Aggressive cleaning to remove stains or light rust:  use a chrome, brass, silver cleaner and mild non-scratching creams and polishes.
  • Most aggressive to remove stubborn mineral deposits:  use phosphoric acid (10-15% solution) – apply with a soft cloth and let stand; no rubbing.  Follow with ammonia and water rinse; rinse with hot water.  Note that nitric acid is effective too but tends to degrade gasket material.

General Cleaning and Sanitizing Sequence: 

1. Begin with a cold water, high-pressure rinse.  Cleaning with high-pressure is most effective when the spray is directed at an angle to surface being cleaned.  One may also use warm water (100-109 F) in high-pressure systems; this tends to reduce time.

2.  Use a strong inorganic alkaline solution; such alkaline cleaners effectively dissolve acid soils and food wastes. Examples of alkaline cleaning agents are caustic soda (NaOH), soda ash (KOH), trisodium phosphate (TSP) and sodium metasilicate.  Carefully follow instructions because such alkalis are very corrosive to stainless steel if used incorrectly.  A mild acid (citric) will neutralize alkaline detergent residues, dissolve the mineral deposits and prevent spotting.  As a rule, soda ash (KOH) rinses better than caustic soda (NaOH).

3. Continue with a cold water, high-pressure rinse.

4. Sanitizer Options:  

a.  Water and Steam

  • Hot water (180 F) and steam are ideal sterilants:  they are noncorrosive, penetrative of surfaces, and effective against juice/wine microorganisms.  
    • Use hot water for 20 minutes (at 180 F).
    • If steam, use until condensate from valves reaches 180 F for 20 minutes.

b.  Quaternary ammonium compounds (QACs), combined with peroxyacetic acid.  

Note that “acid-anionic” sanitizers such as peroxyacetic acid are effective at lower than ambient temperatures; remove biofilms; and are effective against bacterial spores. The low foam characteristics make them ideal for Clean-in-Place (CIP) applications.  Although peroxyacetic acid must be used in well-ventilated area, it is ecologically harmless by decomposing into acetic acid, oxygen, and water.

  • Rinse: QAC solutions may leave objectionable films on equipment and should be rinsed off with fresh cold water, high-pressure rinse.
  • Final rinse: a hot water, high-pressure rinse. Ideally, heat-sterilized water should be used for this final rinse.  
  • Ozone treatment (optional)
  • NOTE: Remember to remove tank valves, take apart and clean prior to harvest.

Barrels

There are many different barrel cleaning methods:

  • High-pressure water, hot or cold
  • Steam
  • Caustic chemicals
  • Ozone
  • SO2 (in any form: wicks, liquid, gas)
  • Dry ice blasting
  • Ultrasound
  • Shaving

In selecting which method to use, consider the effects on aroma/flavor extraction, tartrate removal, microbial reductions, water usage, power usage, worker safety, and cost.

The following are recommended cleaning and sanitizing sequences, based on barrel status.

New Barrels/Fault-Free Barrels

  • Cold water, high-pressure rinse, 1-3 minutes
  • High-pressure steam rinse, 1-3 minutes
  • Repeat cold and steam rinses twice more
  • Either refill with clean wine or
    • Fill with water
      • add ozone, if available
      • follow with water + 45 ppm SO2/90 ppm citrate
  • After 1-4 days, empty and refill with wine or empty and burn sulfur wick, re-bung, and store; or, if using the gas, inject SO2for three to five seconds.
  • If the barrel is to be long-term stored, dissolve and add 45 grams of potassium metabisulfite (KMS) and 180 grams of citric acid; then top the barrel with water. Be sure to top the barrel with plain water every couple of weeks. When you’re ready to use the barrel, empty and rinse twice; then fill with wine.

Likely Fault-Free Barrels, but Unsure

  • Sodium percarbonate washes (Proxycarb) are an excellent option for addressing potential off-flavors.  Citric acid washes are then used to neutralize residual chemicals.  Once the barrel has been cleaned, allow the barrel to dry completely on a rack with the bunghole facing down.  Sodium percarbonate is better than hydrogen peroxide: it is more stable at application concentration (100-200 mg/L), has improved compatibility with hard water, and reduced foaming tendencies.
  • When the barrel is dry, burn 10-20 grams of sulfur wick per barrel; or, if using the gas, inject SOfor three to five seconds.  
  • Place either a paper cup, wooden shipping bung, or other in the bunghole.
  • Check sulfur level every 3-4 weeks and re-sulfur as necessary.

Tannin and Tartrate Deposit Removal

  • Removal of tannins:  Alkaline solutions (soaking with 1% sodium carbonate) are most effective in removing tannins from new barrels.  If further treatment is necessary, steam and several rinses should be applied.
  • Removal of tartrate deposits:  scraping is labor intensive and may injure wood. Instead, use a circular spray head. For stubborn deposits, soaking with 1 kg of soda ash and caustic soda in 100 L of water is effective.

Faulty Barrels

  • Option 1: Remove from winery and sell for non-wine uses
  • Option 2: Clean, sterilize, and re-use, if worth the cost
    • Use same rinse cycles as per barrels without faulty aromas or tastes.
    • Fill with water, put steam wand in water and bring water to 160-180°F, steam periodically to maintain temperature for 4-6 hours and
      • add ozone, if available
      • follow with water + 45 ppm SO2/90 ppm citrate
    • After 1-4 days, empty and burn sulfur wick, re-bung, and store.
    • After 1-4 weeks, rinse and fill with clean water; after 1 week, take samples and then add 90 ppm SO2/180 ppm citrate while doing microbiological assay of samples.
    • If samples are negative for spoilage microorganisms, re-use barrel, but sample periodically.

Bottling Room Equipment

The bottling and packaging function is one of the most critical steps in wine production because there are many opportunities for problems (people with different responsibilities, multiple wines to bottle, and operation and maintenance of multiple equipment stations).

Are sterile bottling rooms necessary?  No, but the bottling area should be screened-off from fermentation areas and excessive air movement, and the room itself should have easily sanitized floors, walls, and ceilings.

General Cleaning and Sanitizing Sequence: 

  • Cold water, high-pressure rinse
    • Mild alkaline detergent solution
    • Cold water, high-pressure rinse
    • Quaternary ammonium compounds (QACs), combined with peroxyacetic acid.  
    • Cold water, high-pressure rinse
    • Sanitization: Hot water and steam used to sanitize bottling line
      • 80-90F for 30 minutes
      • 180F for 20 minutes; or
      • Ozone for 20-30 minutes; or
      • Use of iodophors (iodine-based sanitizers): broad-spectrum – active against bacteria, viruses, yeasts, molds, fungi.  Follow instructions carefully to avoid potential TCA problems; follow with a hot water, high-pressure rinse.

Prior to bottling, add enough SO2to ensure enough free SO2for 0.8 ppm molecular SO2. Add a little bit extra – to account for free SO2loss during bottling. Generally, target a free SO2that is 10 to 15 ppm higher than the level of free SO2needed for 0.8 ppm molecular SO2.  Also, target more or less depending on trauma of bottling method (O2pick up)

Recommendations during operation of the bottling line:

  • Wine spills as a source of contamination should be countered by regular and proper cleaning
  • Filter-pad trays should be emptied often, and related wine spills quickly rinsed away with a sanitizing agent
  • Fill bowls: Mist filler spouts with 70% ethanol to inhibit microbial growth
  • Corker: will likely have spilled wine, so use ethanol misting of corker jaws during bottling
  • Floor drain gutters should be kept clean by frequent rinsing
  • Activity: Limit number of people around the filling/corking area
  • Daily sanitation…hot water or steam…20 minutes at 180F
  • At least weekly, clean with caustic cleaners followed by hot water sanitation.
  • Collect bottles for analysis hourly and immediately after start-up and breaks.

References:

Butzke, C., Barrel Maintenance, Dept. of Food Science, Purdue University, 2007.

Carter, James, There’s a Right Way to Clean and Sanitizing your Facility, Food Quality.com

Donnelly, David M, Airborne Microbial Contamination in a Winery Bottling Room, Am. J. Enol Vitic, Vol 28, #3, 1977

Fugelsang, Kenneth; Edward, Charles G. Wine Microbiology, 2nd Edition, 2010. Springer-Verlag New York Inc. (Chapter 9, Winery Cleaning and Sanitizing)

Marriott, Norman G.; Gravani, Robert B.  Principles of Food Sanitation, 5thEdition, 2006. Springer Science + Business Media, Inc. (pp 361-367)

Howe, P., ETS Laboratories, SOWI “Current Issues” Workshops March 2011. 

Menke, S., Cleansers and Sanitizers, Penn State Enology Extension, 2007.

Tracy, R. and Skaalen, B. Jan/Feb 2009. Bottling-last line of microbial defense. Practical Winery and Vineyard

Worobo, Randy W., Non-chlorine Sanitizer Options for the Wineries, 33th Annual New York Wine Industry Workshop

Zoecklein, B. et al, Wine Analysis and Production, Aspen Publishers, 1999.

Barrel Care  http://www.boswellcompany.com/barrel-care/

Maintaining and Cleaning Stainless Steel  http://www.evapco.eu/sites/evapco.eu/files/white_papers/40-Cleaning-Stainless-Steel.pdf

Stainless Steel – Cleaning, Care and Maintenance  http://www.azom.com/article.aspx?ArticleID=1182

Taking Care of Your Barrels   https://barrelbuilders.com/wp-content/uploads/2016/06/06-16-Barrel-Care.pdf

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