Is Coke still following its 127-year-old 'secret fizzy formula'?

Coca-Cola, which is known for touting the roots of its recipes, claims that their formulae are sacred and unchanging.

In the 1994 book Secret Formula, which drew from interviews with former executives and access to Coca-Cola's corporate archives, reporter Frederick Allen noted that multiple changes were made to the formula over the years, News.com.au reported.

For example, Allen noted that the soft drink once contained trace amounts of cocaine as a result of the coca leaves in the ingredients, as well as four times the amount of caffeine.

However, in an emailed statement, Coca-Cola said its secret formula has remained the same since it was invented in 1886 and that cocaine has "never been an added ingredient" in its soft drink.

In the 1980s, Coca-Cola along with PepsiCo switched from sugar to high-fructose corn syrup, a cheaper sweetener.

The companies last year also said they'd change the way they make the caramel colouring used in their soft drinks, while claiming that doing so does not alter the basic formulas or taste for their soft drinks.

The sweeter formula was marketed as an improved replacement for the flagship soda, and the company points to the outrage that ensued as proof of how much people love the original.

According to the emailed statement from Coca-Cola, that's the only time the company ever tried changing its formula.