Metals in Foodservice
Metal is everywhere you look in a restaurant, from the stainless flatware in the dining room to steel equipment and aluminum pots in the kitchen. Each metal's unique properties make it better suited for certain applications than others. Below you'll find an explanation of the types of food-grade metals used to build foodservice equipment and how to care for them. We'll also discuss the agency standards that govern foodservice metals, specifically NSF 61 and NSF 51.
The most common metal in foodservice is stainless steel, thanks to its rust resistance and the fact it's easy to clean. Whereas regular steel is made primarily of iron and carbon, stainless steel is an alloy of iron and chromium. Nickel is usually thrown into the mix to increase the metal's hardness, and more exotic elements like molybdenum are sometimes used to create steels for specialty applications.
Stainless steel is strong, sanitary, and attractive. It resists rust, scratching, and denting extremely well. Steel is popular in foodservice for its ability to undergo a fair amount of abuse without being damaged, properties that make it the number one choice for building cooking equipment. Stainless steel can also withstand moderate levels of exposure to moisture, chemicals, and food without corroding or pitting, so it's also a natural choice for prep tables and other equipment that may come in contact with food.
Steel must be at least 11 percent chromium to be called stainless, and it’s the inclusion of that element that makes steel resistant to rust. Chromium allows the outer layer of steel to bind with oxygen to form what's called a passivation layer, an invisible film that prevents the steel from rusting as easily.
You'll find several types of stainless steel being used in foodservice equipment. The differences between the types come down to the elements used to make them and the ratio of each, both of which determine the steel's physical properties. You may encounter two different rating systems used to describe the different types of foodservice stainless. When you're dealing with equipment and fabricated fixtures, you'll most likely see the SAE (Society of Automotive Engineers) ratings used to describe steel. Two SAE steel grades are common in foodservice.
- 300-series stainless steel is made with chromium and nickel, usually 18 percent and 8 percent by mass, respectively. Steel in this series is austenitic, which describes how the alloy's molecules are arranged into their crystal pattern. That arrangement makes most austenitic steels non-magnetic.
- 400-series steels contain chromium, and tiny amounts of nickel and other elements. Because of that molecular makeup, 400-series steel is arranged into a ferritic or martensitic crystal pattern and will always attract a magnet.
Stainless Flatware Grades
When you're shopping for flatware or similar utensils, you're likely to encounter a different steel grading system. These numbers describe how much chromium and nickel are present in each type of steel, which can be used to determine a piece's durability and ability to hold a shine.
- Composed of 18 percent chromium and no nickel, 18/0 steel is used to make economy flatware. It tends to have a dull finish, especially after it's been repeatedly used and washed. Utensils made of 18/0 steel bend more readily than premium flatware.
- Made with 18 percent chromium and 8 percent nickel, 18/8 steelis shiny and resistant to bending and rust, but it can lose its sheen over time. Flatware of 18/8 steel is a good middle-of-the road balance between cost and longevity.
- The highest-quality all-stainless flatware available, that made of 18/10 steel includes 10 percent nickel, which makes it easy to keep polished, and highly resistant to rust and bending. The higher level of nickel makes 18/10 steel easier to work with during the manufacturing process, so flatware made with it can have more intricate patterns.
For a thorough discussion of stainless steel flatware, see our Flatware Buyers' Guide
Taking Care of Stainless Steel
Stainless steel equipment can last for years and even decades when it's properly cared for. Follow these tips to get the most from your stainless steel equipment and supplies.
- Make sure stainless is thoroughly rinsed after it is washed to remove chemicals from detergents that can prematurely wear down the metal.
- A mixture of baking soda and water can be used to gently clean and polish stainless steel.
- When you clean and scrub a stainless steel surface, do so along the steel's polish lines, or "grain," to prevent creating scratches that can damage the equipment's surface.
- Avoid using steel wool and wire brushes to clean stainless steel. Metal cleaning tools can scratch steel's surface and create the potential for rust.
- Avoid exposing steel to materials that contain chlorine, including salty foods, as well as solutions and certain cleaners. Use non-chlorine cleaner only and rinse steel thoroughly after it makes contact with a chlorine-containing substance.
- Prevent hard water deposits, which can play a role in opening the door to rust. Take measures to clean your equipment regularly to keep deposits to a minimum. If your water supply is especially high in minerals, consider installing a treatment system that softens the water on its way to your equipment.
The second-most-common food-grade metal you'll find is aluminum. Aluminum is less expensive than stainless steel, but it's also softer and able to withstand less abuse. Aluminum is used for its light weight, low cost, and rust resistance, and is prized in cookware for the speed with which it heats. Like steel, the aluminum used to build restaurant equipment is alloyed with other elements to give it strength and durability. There are three main types of aluminum used to build restaurant equipment and kitchen supplies, each of which includes the addition of manganese, silicon, iron, and copper. The percentages present in each of those elements determine a grade's physical properties.
- The softest type you'll find in foodservice is 1100 aluminum. Its softness makes it easy to form into a variety of shapes, but leaves the material prone to scratching, warping, and denting.
- The higher concentration of manganese in 3003 aluminum makes it harder, more durable, and ideal for medium-duty cookware.
- The heaviest-duty aluminum used in foodservice is 3004 aluminum, which is made with at least 1 percent manganese and about as much magnesium, which further bolsters the metal's strength.
Aluminum is often used for exterior parts of equipment that aren't exposed to abuse, such as the sides and backs. Aluminum can be finished to match surrounding stainless steel for a uniform look.
Economy cookware is made from aluminum for its low cost, light weight, and ability to heat quickly and evenly. See our article on cookware materials for a deeper discussion of aluminum and other types of cookware.
Aluminum is also added to ceramic to make china. Aluminum makes china stronger, enabling it to be made very thin without becoming fragile.
Anodized aluminum is finished with a process that thickens and strengthens its passivation layer, making it more resistant to corrosion and sometimes giving it a smoother finish. That process is often accompanied by a step to dye the surface of the aluminum to add a decorative sheen. Another advantage to aluminum is that, if the passivation layer is every damaged, it will gradually rebuild itself.
Caring for Aluminum
- Acidic products like vinegar, lemon juice, and cream of tartar work to remove stains from aluminum surfaces.
- Avoid using steel wool and metal brushes that can scratch soft aluminum and create a rough surface that food is prone to stick to.
- Avoid exposing aluminum to salt and chemicals that contain chlorine, which can cause the metal to pit.
Manufacturers employ a number of methods to form metal into the final components they use to build restaurant equipment. Like the materials themselves, each one of these methods has benefits and drawbacks.
Casting is the process of pouring molten metal into a mold and allowing it to cool to form the desired shape. This is the process that gives cast iron its name. Cast pieces tend to be dense and heavy, so casting is the ideal process for creating heavy-duty components like burners, grates, and handles.
Bending involves folding sheet metal along straight edges to form it into simple shapes. This process is widely used to form panels for equipment cabinets and fixtures like tables.
Deep drawing is the process of using a punch to push a piece of sheet metal through a die to form a shape. This is a popular method for forming containers like steam table pans and sink bowls, and is especially beneficial when sanitation is a priority because deep drawn components can be made to have no sharp edges or corners where food can become trapped.
Stamping involves cleanly cutting two-dimensional shapes out of sheet metal. This process is used to press out components like brackets for fixtures and is sometimes used to form the blades of economy knives.
Other Foodservice Metals
While stainless steel and aluminum are by far the most popular food grade metals used in foodservice, a few other materials play important roles in the industry.
- Cast iron is a simple alloy of iron and carbon that's used to form rugged, heavy components including gas burners, grates, and radiants. Cookware is the most well-known application for cast iron outside the commercial kitchen, but restaurants do occasionally employ cast iron servingware to provide a rustic tabletop presentation.
- Copper is a metal that's prized for its superior ability to conduct both heat and electricity. All electric equipment includes copper wire circuits, and copper cookware is common in high-end restaurants, especially where kitchens are open for customers to see.
- Galvanized steel is a type of economy steel that that has been treated with a coating of zinc to make it impervious to rust. Galvanized steel is often used to build the bottom panels of cooking equipment, legs and support components of economy work tables, and to form utility containers like pails and trash cans.
Sanitation and Safety Standards
The same way the NSF certifies certain types of foodservice equipment to be easy to keep clean and sanitary, it certifies certain materials used to make that equipment as safe for contact with food. Two NSF standards are directly concerned with the materials foodservice equipment is made of.
NSF Standard 51 defines which types of materials, including metals, and finishes are considered safe to make contact with food. These criteria are intended to ensure that equipment and supplies are easy to clean and sanitize, and pose no risk of transferring harmful substances to food that makes contact with them.
NSF Standard 61 regulates any material that comes in contact with drinking water at any point. This includes pipes, fittings, faucets and other fixtures, sink basins, and other containers. Like NSF 51, this standard is intended to prevent unsafe chemicals, particularly lead, from getting into consumers' food and drinks.