McDonald's product is pictured in a restaurant in Washington, July 23, 2010.
McDonald's product is pictured in a restaurant in Washington, July 23, 2010. Reuters/Molly Riley

Consumers are becoming more wary about fast food chains especially after some of the biggest brands around the world were involved in scandals.

Reportedly, their food products contained inedible or even unthinkable ingredients that resulted to lawsuits worth millions of dollars and threatened to topple the brand completely.

1. McDonald's expired meat

According to Reuters, in China, Yum Brands Inc. the parent brand of McDonald's and KFC apologized to consumers late in July 2014 after it was discovered that Shanghai Husi Food Co Ltd supplied expired meat to the two fast food chains. Records regarding quality control, production and sales were demanded by China's food watchdog and ordered the restaurant to seal over 4,500 boxes of suspected meat products.

2. Taco Bell's beefless taco

A scandal erupted revealing that the famous taco place only filled its popular product with 35% beef. The chain was sued for being dishonest in stating that their mix used 88% beef. The fact is, most of the contents included oats and other fillers.

3. Burger King's horsemeat

Horsemeat is actually edible and regularly eaten in countries like France, Belgium and Canada. However, majority of nations consider eating such a meat source as unthinkable. In the United Kingdom, it was discovered that Burger King used horsemeat in making its burger patties. The chain blamed its supplier in Poland.

4. Fonterra milk bacteria

In 2013, thousands of products sold by Fonterra, a dairy company were recalled after whey products failed in safety tests for showing positive results for botulism-causing bacteria. The contaminated products were forwarded to other producers that make sports drinks and infant formula. About 1,000 tons of the product were recalled.

5. McDonald's pink slime

Jamie Oliver, the master behind the Children's School Dinners Program and Feed Me Better campaign, revealed that the biggest fast food chain used a filler called "pink slime" in its meat. The gooey product has a pink color and is made of meat scraps and fat washed in ammonium hydroxide. It was deemed unfit for human consumption. Ultimately, Oliver won and McDonald's was forced to stop using the filler.

Some scandals resulted to the removal of key executives in the company while others had to pay millions of dollars in damages.