As a food equipment manufacturer serving customers from all over the world, we used to be bewildered by the different requirement on the stainless steel material.  After sending our equipment for various food contact tests, and reading over the norm from NSF, we have found the answer of which grade of stainless steel is suitable for food contact.  

Grade of stainless steel and their magnetic property

There are three commonly used grades of stainless steel, namely 304, 201 and 430; 430 is generally known in Hong Kong as 不锈鐵.  304 is the most expensive among the three, with the best anti-corrosion property.   201 comes next, and the cheapest is 430 with the least anti-corrosion.

Unless they are a food equipment manufacturer, people generally rely on their magnetic property to differentiate stainless steel

  • 304: non-magnetic
  • 201: non-magnetic
  • 430: magnetic

201 has replaced 304 in many applications

About two decades ago, when 201 was still not generally available in the market, magnetic property is reliable enough to tell whether the stainless steel is 304 or not. If it is magnetic, it is 430; otherwise it is 304. After another non-magnetic stainless steel 201 is introduced to the market, the magnetic test cannot differentiate 304 from 201.

Since 201 has similar non-magnetic as 304, it has since been adopted to replace 304 in many applications.  201 is cheaper than 304 and has a better anti-corrosion property than 430.  A lot of work tables in the kitchen are now made of 201.  In an oily environment such as the fryer vat where corrosion is highly unlikely, 201 is more than adequate.

Sanitization and misconceptions

You may hear people say “only 304 can be used in contact of food”.  Is it so?

NSF norm (NSF-51) states that stainless steel of a minimum 16% chromium content is required for application in food zone, which thus includes all three types of stainless steel.  304 has a chromium content of 18%, while both 201 and 430 have 16-18%.

In other words, in addition to 304, NSF approves 201 and even 430 to be used in food zone.

Magnetic properties of 430

Come to think of that, it makes perfect sense.  In an induction cooker, the pot needs to be magnetic to enable the magnetic energy from the cooktop to be converted into heat energy on the pot.   Neither 304 nor 201 has this property to make it usable in an induction oven.  Up until a few years ago 430 stainless steel is our only option to cook with an induction oven (though now we have 304 cladded with 430).  The pot needs to be made of 430 stainless steel to cook with induction.  Had 430 stainless steel not met sanitization requirement, the whole world would have known about it.   This was clearly not the case.   It is irrefutable that 430 can be used in food zone.  

Despite the clear explanation from NSF, people are still bound by tradition and demand that only 304 be used in areas of food zone.  As a result, fryers approved by world renowned fast food chains have their frypot (vat) made of 304 and the other areas made of 201 if cost is a concern.

Non stainless steel can also be used in food zone

Some fryer manufacturers in the western world use nickel plated steel for their frypot (steel electrodeposited with nickel on the surface).  While not stainless steel, the material is still approved by NSF.

  • NSF 5.2.1 says that metallic coatings … may be used to render a material corrosion resistant.
  • Annex A of NSF 5.2.1 mentions nickel electrodeposited coatings applied according to ASTM is approved for use.

In other words, whether 304 is required has more to do with conventional preference than a consideration out of sanitization.   Different countries have different preference.   If 304 is still required in your trade, do not hesitate.   Just do it in 304.