ConAgra Foods, which manufactures Egg Beaters liquid eggs, has filed a patent-infringement lawsuit to block rival Michael Foods adding cheese to its better’n Eggs product.

According to a report in US newswire Bloomberg News, Michael Foods is introducing two new products – three cheese and ham and cheese – to its Better’n Eggs line. Better’n Eggs already includes a cheese and chives variety.

ConAgra has claimed that this infringes its 1989 patent for liquid egg substitutes combined with cheese.

The egg substitute market in the US is currently worth US$197.7m and has expanded in recent years as consumers seek more low-cholesterol egg substitutes. ConAgra claims that its Egg Beaters is the best selling liquid egg substitute, with about a 50% market share.