Noncaustic Cleaning in the Brewery


Fred Holzhauer and Dana Johnson, Birko
The New Brewer, March/April, 1996

In one brewery’s experience, noncaustic cleaners can be as tough on brewery soil as their harsh counterparts, but kinder and gentler to employees, vessels and the bottom line.

In cleaning the mashtun and brewkettle, brewers are concerned with two principal types of soil: proteins and carbohydrates.

Protein Chemistry

A protein is a series of amino acid groups. Under alkaline or oxidizing acid conditions, hydrolysis (a fancy way of saying decomposition occuring in and with water) of protein into smaller amino acid groups can occur. The effective pH ranges for protein hydrolysis are less than 2 and greater than 11. Caustic cleaners take advantage of hydrolysis at pH above 13.

There is a solubility function of amino acid groups with pH. This is frequently the basis for wastewater pretreatment in food plants. (see Figure 1.)

beerstone) and ammonia, which evolves as a gas. The reaction is not reversible. The reaction for the alkaline formation of beerstone goes like this:

2 H2O + 4 H2NCOO- => 2 Ca(COO)2 + 4 NH3(g) + 2 SO42- + O2(g)

High pH conditions such as those in caustic cleaning promote the “setting” of beerstone, which is evident as a discoloration of the brewkettle. In Brewspeak, water + protein stains and gypsum = beerstone not exclusively, but especially under caustic conditions. The implications here are:

Carbohydrate Chemistry

Carbohydrate soils in the brewery are principally starches and unfermentable sugars (maltodextrins). These soils are soluble or dispersible in water, especially at low pH (in acid environments). Generally, any detergent system that can remove protein and fat can also handle carbohydrates.

The Non-Caustic Approach to Cleaning

Until now, conventional wisdom in brewery cleanup has been to apply hot caustic solutions to surfaces for soil breakdown, then to follow with an acid solution for a neutralizing rinse. But given the aforementioned facts about the nature of the typical brewery soils, it would make sense to use an acid product first in a challenging C.I.P. situation. We can follow with a non-caustic alkaline stage. This was our hypothesis when we began to develop a noncaustic cleaner for use in the brewery.

We figured that if acid were to be used first, it would adequately decompose the protein, and also provide-in the first stage-solubility for hardness salts, softening them instead of setting them. In this way, we could avoid the insoluble portion of the amino acid pH response by emptying the vessel and proceeding to alkaline cleaning without a rinse.

George Ellington, Brewer at Breckenridge Brewery in Denver, with a container of BRU-R-EZ™

Metallurgically speaking, acid leaves a clean and active surface that is an ideal medium for soil adhesion, and very subject to corrosive attack. The acid source can be a cleaning stage of a C.I.P. program, or the beer itself. However, this acid metal surface is also a good candidate for alkaline passivation. Passivation is accomplished by reacting, under oxidizing conditions, the surface metal molecules with appropriate anions so that the resulting salts formed are self limiting, corrosion resistant, and relatively “adhesion neutral”. The protective molecular layer that is formed can be termed a conversion coating. For example, aluminum forms a conversion coating naturally in air.

When we set out to develop a nonalkaline cleaner for use in the brewing industry, we wanted to design it so that it would displace the acid softened proteins and also form the protective conversion coating necessary for long life and good health of the metal brewing vessels. We know that a successful cleaner would have to address soft metals such as aluminum and copper, as well as mild or stainless steels, and that it would have to produce a conversion coating not leachable by the natural acids in beer. It would have to have excellent rinsability. (Caustic cleaners are notorious for their poor rinsability, hence the requirement of an acid neutralizing rinse.)

You can easily check the residual of alkaline or acid cleaners in your brewery. Simply immerse a pH strip in the rinsate leaving a vessel. Next, check vessel walls. Neutral wet surfaces indicate a successful rinse.

Once you have established a successful rinse, you can evaluate the sheeting action of water. Water will continuously wet a clean surface, while residual soil appears as a dry island on the surface. But be careful: caustic solutions tend to attach to soil whether or not the soil is removed, giving the sheeting appearance of a clean surface. Therefore, both the pH test and a sheeting surface are necessary to proof the vessel.

The Safety Issue

Employee safety is paramount in considering which cleaners to use in the brewery. How many of you have and use adequate safety gear for the handling of hot caustic solutions and high percentage caustic formulations? Are safety showers accessible? We determined that the successful non-caustic alkaline cleaner must present an adequate pH to do its job, yet be safely and conveniently handled and used.

The Method Used by Breckenridge Brewery

Breckenridge Brewery in Denver, Colorado helped us refine our noncaustic cleaner so it can be used to CIP the mashtun and brewkettle. Instead of using caustic first, Breckenridge now first uses a phosphoric-nitric acid formulation to remove the beerstone and loosen the protein soil. By using the acid first, the beerstone is removed on the first pass rather than plating it to the metal. The protein soil is either removed or loosened by the action of the acid. The acid is then discarded and followed by the noncaustic cleaner BRU-R-EZ™, without a rinse in between. Since the noncaustic rinses well, an acid neutralization step is not necessary.

For the acid step, Breckenridge charges its brewkettle with approximately 100 gallons of hot water and applies steamed. Two gallons of the acid is added to the water and the mixture is allowed to circulate throughout the brewkettle lines and sprayballs. When the temperature of the solution reaches 140 degrees F (60 degrees C) the steam is shut off and the solution continues to circulate for about 25 minutes. The solution is then pumped into the mashtun and the circulation continues for 15 to 20 minutes. After circulation is completed in the mashtun, the solution is discarded.

After the acid solution is dumped, rinsing is not needed prior to using the noncaustic cleaner we developed. A rinse would only serve to reset the protein soil and lessen the efficacy of the next step.

In the noncaustic step, the brewkettle is again charged with 100 gallons of water. Once the temperature reaches 140 degrees F (60 degrees C), 20 pounds of predispersed BRU-R-EZ™. is added and the circulation begins. The circulation is allowed to proceed for 45 minutes and temperature is maintained at around 180 degrees F (80 degrees C). The solution is then pumped to the mashtun and five additional pounds of BRU-R-EZ™ is added to the solution. The circulation of the mashtun runs for approximately 30 minutes, then the solution is dumped and a hot rinse is applied to the brewkettle and mashtun.

The pH of the vessel walls and rinsate water is checked with indicator paper to ensure that the cleaner has been removed. When the pH is found to be neutral on the vessel walls and the rinsate water, the procedure is completed and the equipment is ready for brewing.

Since this method was perfected by Breckenridge, the noncaustic approach to cleaning brewing vessels has been tried at other Denver-area breweries – Tabernash Brewing Co. and Eldorado Brewing Co. included. It is a method that should be considered by breweries that want a cleaning program that is kind to employees, the metal brewing vessels, and the environment.

References:

  1. Butler, James Newton, Ionic Equilibrium, A Mathematical Approach. Addison-Wesley Publishing Co., Inc., 1964.
  2. The Merck Index, 11th Edition. Susan Bud-avari, Ed. Merck & Co., Inc., 1989.
  3. Metcalf and Eddy Wastewater Engineering: Treatment, Disposal, and Reuse, 3rd Edition. Revised by George Tchobanoglous and Frank Burton. McGraw-Hill, Inc., 1972.

Fred Holzhauer was an R&D chemist for Birko. He holds a degree in Metallurgical Engineering from the Colorado School of Mines.

Dana Johnson has been with Birko since 1979 and is manager of the CON-TACT-IT® Bacteria Detection System. He has authored several articles on cleaning and sanitizing in the brewery.