Chemical Processing - September 2007 - (Page 61)

>> PROCESS PUZZLER PROCESS PUZZLER < > THIS MONTH’S PUZZLER Our clean-in-place (CIP) system now involves a hot water rinse, followed by a caustic rinse, followed by a biocide in a phosphoric acid solution. The new owners of the plant want to make a change. They propose switching the acid rinse to a steam sterilization step at about 230°F. We are worried about the mechanical seals in process pumps. The pump vendor doesn’t recommend the seals above 225°F and also is concerned about the effect on bearings and pump performance. Do you think agitator seals also will be affected? What improvements do you think are needed to comply with our new owners’ wishes without extensive changes throughout the plant? Keep an acid rinse I would recommend keeping an acid rinse followed by steam sanitization at 220°F. The acid rinse would not only kill organisms but neutralize the residual caustic and dissolve its salt deposits. I wouldn’t recommend keeping the phosphoric acid but rather use of a different acid with biocide. Phosphorous is a key building block in phospholipids formation in the cell membranes/walls of microorganisms. It actually aids in making acid-adapted microorganisms more viable, which could lead to undesirable proliferation. Also, I would be wary of phosphorous polymerizing in the presence of salt deposits in the heat exchanger, leaving behind a pseudo-biofilm on internal surfaces. Biofilms can thermally insulate microorganisms. Be wary of the term sterilization versus sanitization. Sterilization occurs above 250°F as a function of time and heat penetration, at which you’ll be in the killing zone for critical pathogens (e.g., c.botulinum, e. coli). Other thermophilic organisms may survive but are typically non-pathogenic. Of course, since you’re fermenting, microorganism proliferation should be minimal due to competing factors of the organism you’re trying to grow. Ron Johnson, principal engineer PepsiCo, Valhalla, N.Y. Answer other questions first The Puzzler seems to raise more questions that need to be answered before a definitive answer to the question can be given. The first question is why sterilize at 230°F (110°C)? Presumably the new owners wish to eliminate the possibilwww.chemicalprocessing.com http://www.chemicalprocessing.com

Table of Contents Feed for the Digital Edition of Chemical Processing - September 2007

Contents From the Editor Field Notes In Process Energy Saver Compliance Advisor Succeed at Simulation Rethink Your Approach to Process Safety Avoid Blending Blunders Get the Right Cartridge or Bag Filter Wireless Proponents Take HART Membrane Boasts Material Benefits Process Puzzler Plant InSites Chem Show Product Preview ISA Product Preview Equipment & Services Product Spotlight/Classifieds Ad Index End Point

Chemical Processing - September 2007

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