Three Filtration Principles to Guide A Food Plant Remodel

From century-old dairy plants in Vermont to pet food startups in California, food manufacturers of all sizes face growing regulation. Of immediate concern is the Food Safety Modernization Act (FSMA) of 2010. Under part of the law phasing in through 2018, most processors must have “hazard analysis and risk-based prevention controls (HARPC)” in place to protect against food-borne illnesses. The U.S. Food and Drug Administration (FDA) has new powers to inspect and fine businesses if controls are inadequate. In this environment, facilities that once counted on grandfather clauses to stay in operation may now be considering a major update.

In any food plant remodel, filtration must be a focal point. It is hard to overstate the importance of sterile liquids, steam and air in food safety. Water is often a universal ingredient and is commonly used to cook, and to sterilize equipment. Compressed air is used to mold bottles, fill packaging, and blanket product in tanks and on process lines. Ambient air is drawn in as product storage tanks empty. These elements are frequent carriers of dirt, particles, oil and microbes, and can transport them into food at multiple points in a process.

International industry groups such as 3-A Sanitary Standards Inc. (3-A SSI) and Safe and Quality Foods (SQF) have established accepted practices and standards to address these risks. It can take time to comply with all applicable guidelines. However, observing just three filtration principles can provide a big head start toward complying with the standards, whether a plant is doing a few improvements or a complete revamp.

Figure 1. A sample filtration plan for a yogurt processing facility. Note the filtration of incoming air and water (points of contaminant generation) and filtration at critical risk points including sterile compressed air cleaning of packaging.

1. Place filtration equipment at the right points in the food and beverage process.

Regardless of how simple or complex a food manufacturing process is, every process owner needs to identify two crucial points for filtration:

  • Points where contamination is first generated or introduced
  • Critical control points where contamination of the product or process is at high risk, or where there’s a “last chance” to remove it

Plants that use multiple ingredients, heat and air treatments, and packaging steps may require a more complex filtration system. But every plant has a common challenge: control incoming contaminants and critical control points.

Points of generation are often where a facility draws in air or water resources, or where steam is created. Plants in industrial areas may pull in dirty air from the surrounding environment, while rural facilities may have more concerns about water quality. As steam is generated in the boiler from the plant’s main water supply, contaminants in the water or boiler will be transported by the steam. Based on best practices outlined by organizations such as 3-A and SQF, a filter or series of filters will be necessary at these sources.

Even in a closed loop system, the process itself can introduce impurities. Common internal points of generation are:

Aging equipment. Prone to leaks and cracks. Air compressors can leak oil, or housings can develop crevices that trap decay.

Carbon steel or iron pipes.A major corrosion risk. 3-A SSI guidelines are unanimous in specifying stainless steel piping and housings for all food contact.

Residual food after cleaning. Potential harbor points for microbes. Even microscopic amounts can be a serious threat as they multiply and travel downstream.

It is an unrealistic goal to remove all contamination sources where they originate. For this reason, sanitary plant design also calls for filtration at critical control points. These are locations in the process where the greatest harm can occur, either because the product is exposed to excessive contaminant, or because ingression would take place too late to be reversed.

To manage critical control points, consider these recommendations:

Place vent filtration on storage tanks. Storage holding tanks are a potential breeding ground for bacteria. As workers draw out product such as syrup to sweeten soda, pressure needs to be equalized to prevent tank collapse. Yet exposure to ambient air can spoil the syrup by introducing harmful substances. Two recommended solutions are purifying the make-up air with a vent filter, and/or blanketing the product with an inert gas, such as nitrogen, that has been filtered.

Install final filtration close to end use. Consider filtration at the last possible processing step to remove surviving contamination, and to prevent the pickup of harmful bacteria just prior to packaging. In water bottling, for example, a final membrane filter will address remaining impurities. If carbonation is injected, the CO2 used should be filtered. Packaging itself can also be a risk. A yogurt maker that applies a foil seal, for example, should first blast the foil with culinary steam to kill microbes that may have collected on the foil during storage or production (Figure 1.)

Add protective prefiltration. Once control points are mapped out, it pays to think about adding lower-cost filters prior to point-of-use final filters. Though this may seem redundant, pre-filters aimed at capturing larger containments will increase the longevity of the more-expensive, small-particulate filters. Process owners who decide not to worry about incoming contamination and rely only on final filtering will expose their entire system to a barrage of contaminants, and overburden the final sterile filter. Prefiltration will help minimize replacement costs and downtime.

2. Identify correct filter technologies for food plant remodel.

Two areas of potential confusion about microfiltration exist: ratings and construction. Here are some facts for more-informed product selection:

Look beyond microns. Not all filters rated for the same micron size are equal. It is vital to consider not only the particulate size a filter is rated for, but also the efficiency at which it is able to capture the particulate. Efficiency is crucial in knowing how much contaminant the filter captures (percentage) at a given micron size and larger. When selecting a filter, it is also important to know if the filter is absolute or nominal. An absolute filter is comprised of higher quality filtration media that can provide an efficiency of 99.98 percent or greater at a specific micron rating. On the other hand, a nominal filter is a lower-quality filter that typically provides only 60 to 98 percent efficiency at that same micron level.

Without this information, it is impossible to select the right element for a specific demand. In fact, it can be dangerous. Whereas one filter may be only 85 percent efficient at 1 micron for final water filtration for lemonade, another 1-micron filter may deliver 99.99999 percent (7-log) efficiency. The reverse can also be true. A 10-micron filter at 5-log efficiency (99.999 percent) might be overkill for early stages of dirty-water processing, and may require frequent replacement (Figure 2).

3 Filtration Principles to Guide a Food Plant Remodel

Figure 2. Three filters, all with 1-micron labels, can deliver different levels of efficiency. All graphics courtesy of Donaldson Company Inc.

Once a manufacturer has identified the right efficiency level at a given micron rating, they can move on to consider depth-loading capacity (retention), the number of sterilization cycles the element can safely tolerate, and how often the element will need changing (filter life). Along with flow rates, which drive energy costs, these factors drive total cost of ownership.

Consider newer filter options. Two common depth loading filter element types are traditional melt-blown technology and pleated-media filters. Melt-blown filters are cylindrical blocks of porous media, and are commonly used because of their lower price. Pleated elements pack a cartridge with densely folded specialty media and have more than twice the surface area and depth-loading capacity of a melt-blown counterpart. This difference translates to pleated elements having a longer service life and capturing more contaminants (Image 1).

Although pleated elements may cost more up front, they provide a lower cost of ownership than a comparable melt-blown element, since they are more efficient and last longer. Heavily contaminated water, for example, can quickly saturate a 10-micron melt-blown filter. A better option would be a 10-micron pleated pre-filter with a longer life that can greatly reduce downtime and labor expenses, netting a cost savings for the facility.

An effective filtration plan depends greatly on what the plant is bringing in to its process. With treated city water, extensive prefiltration may not be necessary. Plants pulling water from a local river, on the other hand, may start with a bag filter to screen out debris, proceed to a 50- or 100-micron nominal filter, then use a succession of pleated pre-filters rated 50, 20, and 10 microns before a final membrane filter of .1 to .2 microns. Untreated ambient air will need prefiltration before it can be used in a compressor, and again as the compressor injects air to texturize food such as ice cream, or to apply packaging. Without filtration, moisture and oils can be transferred into the process.

Safe and cost-effective liquid, steam and air filtration is all about filter staging: the right efficiency at the right micron size in the right location. There are thousands of filter combinations, and every plant and process is unique.

3. Understand the difference between “certified” and “compliant” products.

A third filtration principle is to look for equipment and products that display the 3-A certification symbol. Process certification is voluntary, but having the designation “will provide assurance to regulators and buyers that a credible, objective, third party has verified that the processing system conforms to the applicable 3-A Accepted Practices,” per 3-A Sanitary Standards Inc.’s Manual for Third Party Verification. Without the authorization, a product is not guaranteed to have a sanitary design, which reduces the number of harbor points where bacteria can gather and multiply.

“Compliant” is merely a manufacturing claim and is not the same as certified. The differences between “certified” and “compliant” equipment can involve connections, welding methods, and polish ratings not always visible to the naked eye. Some examples are:

  • Poor welds that are rough and create contaminate harbor points
  • Bead-blasting a surface rather than electropolishing it
  • A lower grade surface finish than required
  • Pipe joints with a flange or national pipe thread (NPT) instead of a sanitary connection such as Tri-Clamp sanitary clamps

Food processors should understand the risk to their brands if they use a supplier without certification and with little track record in producing sanitary equipment. Recently, 3-A SSI issued a warning to the industry to beware of Chinese manufacturers using the 3-A certification symbol without authorization. A list of the companies is available on the website.  The leadership of 3-A is taking steps, with their international trade counsel, to stop the infringing behavior and prevent the entry of unlicensed products into the U.S.

Conclusion: Plan food plant remodel with a trusted partner

Process owners manage a great deal of risk when retrofitting, and face multiple challenges, including cost and supply constraints. Without the time to research industry standards and best practices, it can be easy to fall back on familiar technologies. However, what is familiar may no longer be appropriate or the most efficient solution.

Bringing in a trusted partner who can correctly answer those questions will help significantly in the long run to manage both risks and costs.

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