According to Official Guinness Records,
The most gas rings on a hob is 50 and was achieved by Nardi Elettrodomestici, with a special cooking hob created in celebration of the company's 50th anniversary, at the Science and Technology Museum in Milan, Italy, on 19 May 2008.
The cooking top was created with best practices and approved by the security institute for such devices. It features a variety of gas rings (in shape and capacity). Nardi is considering giving the cooking top away as a present to a charity or to a school for chefs.
For a complete list of 2008 records, please visit 2008 Guinness Records in Italy.