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Stainless Steel and Contamination Prevention in Food and Beverage Equipment

Food and beverage design engineers are under constant scrutiny to deliver machines that are both good for the bottom line and that protect the company from devastating product recalls. It is essential for engineers to select materials and components that both meet the functional requirements of the application as well as federal guidelines for safety and contamination prevention

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Jerry Scherzinger, Product Marketing Manager, BimbaJerry Scherzinger, Product Marketing Manager, Bimba

Five years ago, President Obama signed into law the Food Safety Modernization Act (FSMA), the most sweeping reform of our food safety laws in more than 70 years. The rules and standards created by this legislation, along with food safety programs administered by the US Department of Agriculture and the Food and Drug Administration provide the food industry with protocols and best practices that help ensure the safety of our food supply and protect businesses from the devastating costs of product recalls.

Nevertheless, incidents continue to occur. For example, earlier this year, four companies had to recall chunk light tuna products because they may have been undercooked due to an equipment malfunction uncovered during a routine inspection. The FDA said “These deviations were part of the commercial sterilization process and could result in contamination by spoilage organisms or pathogens, which could lead to life-threatening illness if consumed.” And, according to data tracked by Stericyle ExpertSolutions and reported in Food Manufacturing, “An estimated 48 million Americans get sick as a result of one foodborne pathogen or another each year,” with an annual cost in medical treatment, lost productivity and food illness-related mortality of $93 billion.

In short, despite all we know, and despite the enormous hazards, we cannot take for granted the need to select the optimal material and design components for food processing equipment, and the cleaning and disinfection options and procedures for equipment surfaces.

Equipment materials must be chosen with the machine’s ultimate function in mind. Some surface materials, such as stainless steel, are better suited than others for food handing.  Another factor in designing this equipment is that of the machine components and whether they are hydraulic, electric or pneumatic. There are advantages to each, depending on the task, but most often pneumatic components are the best solution for food processing, due to the ease in which they can be cleaned and their lower component cost.

General Design Considerations:

There are two categories of food processing equipment, one with surfaces that come in contact with food products, and one that does not make contact with food products. The surfaces of food equipment also are divided into two categories, one that makes contact with products and one that does not.

A food product contact surface is one the FDA defines as making “direct contact with food residue, or where food residue can drip, drain, diffuse or be drawn.” Obviously, because these surfaces can directly result in food product contamination, rigid sanitary design criteria must be met. Non-product contact surfaces are those that are part of the equipment (for example, the legs, supports and housings), that do not directly contact food. But non-product contact surfaces can still cause indirect contamination of food products so despite the fact that they do not contact food directly, they must not be ignored.

Cleaning and Disinfection:

There is a proper order for cleaning and sanitation of food product contact surfaces areas: Rinse, Clean, Rinse, Sanitize. Even so, this is not sufficient to maintain adequate hygienic levels, since cleaning alone does not necessarily destroy micro-bacterial organisms. It is only through sanitation and disinfection processes that microbial populations can be reduced to levels considered safe enough to avoid food contamination.

Water Chemistry and Quality:

The quality of water used in the cleaning process is often overlooked. It shouldn’t be. Water comprises 95% to 99% of cleaning and sanitizing solutions. It carries the detergent of the sanitizer to the surface and carries soils or contamination away from the surface. If there are impurities in the water, these will drastically compromise the effectiveness of a detergent or sanitizer. Water hardness is the most important chemical property, having a direct effect on cleaning and sanitizing efficiency. Water pH generally ranges from a levels of 5 to 8.5. This range poses no serious consequences but highly alkaline or highly acidic water may require additional buffering agents.

Water can also contain significant numbers of micro-organisms. Water used for cleaning and sanitizing must be potable and pathogen-free. Water impurities can also negatively affect cleaning functions and include oxygen and carbon dioxide (which cause corrosion); bicarbonates and silica (which cause scale); chlorides (which cause scale and corrosion); suspended solids (which cause corrosion and deposition); and unusually high or unusually low pH (which cause mediate corrosion and deposition).

Kinds of Food Soils:

Food soil is another unwanted matter on food contact surfaces. It can be visible or invisible. The source of soil is the food product being handled, but minerals from water or cleaning compound residues also contribute to films left on surfaces.

Since soils vary widely in composition, no one detergent is capable of removing all types. But in general, acidic cleaners dissolve alkaline soils and alkaline cleaners dissolve acidic soils and food wastes.

Types of Cleaning Compounds, Their Uses and Hazards:

Once the type of soil that needs need to removed has been identified, we need to understand the effects of different types of cleaners and their potential uses and hazards. For example, strong alkalis like sodium hydroxide destroys microbes and dissolve proteins, but they are corrosive. Heavy-duty alkali like sodium carbonate removes fats but is slightly corrosive. Mild alkali such as sodium bicarbonate can be applied to lightly soiled areas with no real hazard, while strong acids like phosphoric and hydrofluoric acids are effective in dissolving surface mineral deposits but they are corrosive to concrete, metals and fabrics.

Materials for Machine Designers in the Food Equipment Industry:

The greatest challenge for machine designers in the food equipment industry is to identify the most effective, least dangerous cleaning and disinfection solutions. Many factors must be considered when making surface material selections. Stainless steel is specified in many industry and regulatory standards as the preferred surface for food equipment. For example, the 300 series stainless steel has been identified as the preferred surface for use in the milk industry. Other grades of stainless steel are more appropriate for handling high fat products or meats. And for products containing high levels of acid, salt or other corrosive elements, common-resistance materials like titanium are preferred.

“Softer” metals such as aluminum, brass, copper or mild steel are also used, though these materials are generally less corrosion-resistant. Aluminum, for example, is readily attacked by acidic and highly alkaline cleaners, which can render the surface impossible to clean, due to corrosion. Plastics are subject to stress cracking and clouding from prolonged exposure to corrosive food materials or cleaning agents.

The Case for Stainless Steel:

In addition to its excellent resistance to corrosive elements, stainless steel has other attractive qualities that influence its popular usage across industries:

In terms of health and safety, stainless steel has no negative impact on individuals who handle the material throughout its production process, use or ultimate disposal. The emissions footprint of stainless steel as related to carbon, water and air is minimal. Stainless steel is highly reusable and also recyclable. Its low maintenance costs and long life mean stainless steel has minimal impact on the planet. Industries that produce stainless steel show long-term sustainability and growth, provide excellent reliability and quality for their customers and ensure a solid and reliable supply-chain to the end consumer.

Pneumatics in Wash-Down Applications:

Design engineers are faced with numerous decisions when designing equipment for use in wash down applications. One of the first is to decide the type of technology that will provide the motion and “muscle” required to do the work.

Pneumatic, hydraulic and electrical components all provide unique advantages and disadvantages.  Typically, a combination of all three may be required for complex equipment. Most systems specifically require electric components because the use of motors, valves and switches provide the necessary control flexibility for today’s modern equipment.

Hydraulics are usually utilized in applications that require high pressure and force. For applications where only low to moderate force is required, pneumatics is preferable. Pneumatics possess a few distinct advantages over hydraulics, such as: lower component cost, lighter weight, cleanliness of air versus hydraulic fluids; and simplicity of design and control.

When selecting pneumatic components such as actuators, valves and air preparations, consideration should first be given to the construction materials. As noted earlier, the use of stainless steel components should be considered whenever possible. Depending on the chemistry of the wash down solution, other non-corrosive metals may also be considered, as well as plastics such as acetyl resin. For example, pneumatic cylinders are usually designed with stainless steel bodies, end caps and piston rods. Properly designed components will also reduce the presence of small crevices in component geometries, which can foster growth of bacteria by trapping food product in hard to clean areas.

Other design features that make cylinders optimal for use in wash down applications include rod wipers, which limit the potential for external contamination during pressure spraying, and corrosion-resistant bearing and bushing materials such as PTFI (Polytetrafluoroethylene).

In conclusion:

Food and beverage design engineers are under constant scrutiny to deliver machines that are both good for the bottom line and that protect the company from devastating product recalls. It is essential for engineers to select materials and components that both meet the functional requirements of the application as well as Federal Guidelines for safety and contamination prevention. It is also paramount that the proper protocols are followed for the maintenance and sanitation of equipment surfaces.

The bottom line is hard to miss. Recalls due to contamination can be avoided. Taking the initiative to ensure that your company is not only aware of but effectively adhering to industry guidelines for food safety is critical to the maintenance of a viable business.

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