Stainless vs. Aluminum: Is Your Food Packaging Equipment 100% Wash-Down Certified?

Maintaining a pristine production and packaging environment is mission-critical for food manufacturers. First of all, they are highly regulated by the Food and Drug Administration (FDA), the U.S. Department of Agriculture (USDA), and other governing bodies in specific food sectors.

Maintaining a pristine production and packaging environment is mission-critical for food manufacturers. First of all, they are highly regulated by the Food and Drug Administration (FDA), the U.S. Department of Agriculture (USDA), and other governing bodies in specific food sectors. Also, unsanitary food manufacturing can be disastrous to public health. The Centers for Disease Control and Prevention (CDC) report approximately 76 million cases of food borne illness a year, with an estimated 200 deaths resulting from food-induced anaphylaxis. Not to mention the impact of a contaminated food product recall on a company’s reputation and sales – the average cost of a food product recall is upwards of $540,000.


Globalization, international trade, new regulations, and increased consumer demand for safer food have pushed the food industry worldwide to create and standardize improved safety practices. Just this year, the International Organization for Standardization (ISO) published a new auditable standard (ISO 22000) that defines HACCP’s role in food safety and states the requirements for companies that desire to exceed the regulations for food safety. In addition, a report by Industrial & Institutional Cleaning Chemicals shows that disinfectants and sanitizers are expected to record the fastest growth among industrial and institutional cleaning chemical types through 2008. I&ICC predicts that gains will be drive by heightened safety and health concerns over the spread of infections diseases and risks associated with foodborne pathogens.

It’s easy to see why food manufacturers have set the standard for cleanliness in industry. One of the key features that they look for when purchasing processing and packaging equipment is that it be 100% “wash-down certified.”

In many food processing plants, especially meat packaging, wash-down means the equipment must withstand a rigorous cleaning process, which entails using hot (minimum 140° F), high-pressure (up to 1000 psi) water sprays, and caustic, acid-based detergents dispensed through spray and foam systems in addition to hand cleaning. “Ease of cleaning and durability are top priorities when we select equipment to purchase,” explained Mark Nouvel, director of poultry engineering for Gold Kist, Inc (Atlanta, GA). Gold Kist is one of the nation’s largest poultry farms with more than 2,300 family farms in the Southeast producing more than 14 million chickens a week.

What makes equipment wash-down certified?

The main criterion for wash-down certified packaging equipment is stainless steel construction. Some equipment manufacturers claim their products are “wash-down,” when only some parts, if any, of the equipment is fabricated out of stainless steel. More commonly, the equipment is constructed from substandard, albeit economical, aluminum.

In contrast to anodized aluminum, stainless steel resists corrosion and localized chloride attacks from both cleaning agents and aggressive ingredients such as high levels of chloride salts and high acid contents like those found in tomato paste and ketchup. Stainless steel can be electro-polished for a uniquely flat, mirror-like surface. James Fritz, phD in Corrosion Engineering and NACE-certified Materials Selection Design Specialist from TMR Stainless, explains “the surface metal is first mechanically polished, then immersed in a polishing solution, followed by the application of an external electric current. This process levels the microscopic highs and lows on the surface of the metal and results in very low Ra values (i.e., roughness). A smoother surface is clinically cleaner because bacteria have little to ‘cling’ to on the surface of the metal.”

Easy to Clean

There’s a direct correlation between ease of cleaning and productivity – the easier it is to clean and sterilize plant processing and packaging equipment, the more productive the plant.

Whether it comes in direct contact with food or only indirect contact, all processing and packaging equipment must be cleaned frequently – often at the end of every line change, shift, and workday. In the USDA’s Food Safety Inspection Service directive it states, “all food and non-food contact surfaces of facilities, equipment, and utensils used in the operation of the establishment must be cleaned and sanitized as frequently as necessary to prevent the creation of unsanitary conditions and the adulteration of product.” Depending on the size of the plant, type of food produced, and number of shifts, this could add up to 15 to 20 hours or more of mandatory cleaning each week.

The ability to clean in place is another important characteristic for food equipment. “With stainless steels, standard CIP solutions and procedures can be used,” says Fritz. “It takes less time and effort to clean stainless steel equipment in place plus aluminum would be less resistant to some of the standard solutions used for CIP,” he said.

Durable for a Long Life

Another advantage of stainless steel over aluminum is strength. According to Jack McGurn, technical consultant for the Nickel Institute, “an aluminum alloy like 1100, which is a common marketplace alloy, would have a yield strength of 5,000 pounds per square inch versus an equivalent stainless steel alloy like 304, which is commonly used in the food industry. Type 316 is considered where the threat of pitting is possible. Both alloys have a yield strength of about 30,000 pounds per square inch,” said McGurn.

Due to its lower strength, the surface of aluminum alloys is more vulnerable to scrapes, dents, and nicks which can be more difficult to clean and serve as initiation sites for corrosive attack by cleaning agents used in the food industry. If the cleaning agent or food ingredient penetrates the normal protective oxides of the metal, bare metal is exposed and there is an increased likelihood for further pitting of the metal. “Once pitting occurs, catastrophic corrosion starts and the metal will deteriorate. It may absorb dangerous bacteria and pathogens from the food, and metallic ions from the alloy will contaminate any food products that come in contact with the equipment,” said McGurn.

In a technical brief (NiDI Technical Series #10 079) from the Nickel Development Institute entitled Sanitation of stainless steel and other food preparation surfaces, it states “the inherent mechanical strength and resistance to surface damage exhibited by stainless steel makes it a superior material when effective cleaning and sanitizing are a high priority during its use.” Another related technical brief (NiDI Technical Series #10 046) from the Nickel Development Institute and reprinted in The Journal of Applied Bacteriology concluded “stainless steel, although not as cleanable as glass or china, is more cleanable than aluminum.”

Overall, the life cycle cost advantages of stainless steel over aluminum outweigh the incremental additional cost. When it comes to wash-down applications, Gold Kist prefers stainless. If aluminum is involved, sometimes there are problems, plus costly, OEM-specific cleaning agents are required. Over time, aluminum corrodes no matter what you do and it must be replaced; while stainless steel can last beyond a line’s life expectancy.

Satisfies the Strictest Requirements

The American Society of Mechanical Engineers (ASME) has approved various grades of stainless steel for use in bioprocessing equipment. Aluminum has not met the same ASME standards. Other standards that stainless steel has met include:

• NSF International – a not-for-profit, non-governmental organization in standards development, product certification, education, and risk-management for public health and safety
• A-3 Sanitary Standard for Stainless Steel
• International Association for Food Protection
• U.S. Public Health Service
• Dairy Industry Committee
• U.S. Dept of Agriculture-Dairy Programs

Cleanliness that Meets Customers Inspection

Stainless steel has increased in volume every year for the last decade or more – and not just because it’s easier to clean in industrial environments. “It’s the metal of choice,” says Fritz. “It’s durable, easy to clean and maintain, easily fabricated, recyclable, approved by most governing agencies, and – let’s face it – more aesthetically pleasing. It just looks cleaner.”

Most companies’ customers are the driving force behind their purchasing decisions. Even for equipment that has little-to-no direct contact with foodstuff, it’s vital to present a good image to customers, demonstrating that the company is doing everything it can to put forth as hygienic a product as possible.