Morning Business Memo:

Diet Pepsi is quietly changing its sweetener as it looks for new ways to compete against Coke. Diet Pepsi used to contain only the sweetener aspartame, which is sensitive to heat and breaks down more easily. Now it also contains another sweetener, acesulfame potassium, that's used in a wide range of foods including baked goods, chewing gum and gelatin desserts. The goal of sweetener switch is to help the soda maintain its potency longer. Pepsico has been looking to reinvigorate its brands after losing market share to Coca Cola in recent years. Although the Diet Pepsi switch is only intended to help prevent the taste from degrading over time, companies are often sensitive to public perceptions that they might be tinkering with major brands.

What's going with Apple? The share price of the world's leading technology company fell 3.8 percent Friday after a big financial firm reduced its price estimate. Analysis from UBS Financial cited worries of slowing demand for the iPhone and iPad. Apple shares are down 25 percent from their peak of more than $700 in September, but for the year Apple is still up 26 percent.

At last, signs of movement in the fiscal cliff talks. A fresh proposal from House Speaker John Boehner would mean that tax rates of the wealthiest tax payers would go up January 1. Those earning over $1 million would see their marginal rates rise. President Obama proposed that higher income tax rates would begin when income reaches $250,000. Boehner is also offering to raise the debt ceiling for a year. In return the speaker wants$1 trillion in spending cuts from benefit programs including Medicare. Democrats rejected the offer and say an increase in the Medicare eligibility age is a non-starter. But the new proposals suggest a potential compromise framework for avoiding the fiscal cliff.

Natural gas looks set to replace coal as the world's second biggest energy source by 2025. The forecast comes from oil giant ExxonMobil in its latest energy report. According to Oil and Gas Journal, demand for gas will grow by 65 percent by 2040, and 20 percent of global production will be in North America. Electricity demand will account for more than half the global energy demand increase over the next few decades, with gas, nuclear and renewable energy meeting more power generation demand as coal and oil meet less, according to ExxonMobil's 2013 outlook.

Many in the energy industry are unhappy about soot pollution standards announced by the EPA. Soot particles have been linked to thousands of cases of lung, heart disease and asthma attacks. The New York Times reports the EPA acted under a court deadline, setting "an annual standard of 12 micrograms per cubic meter of air, a significant tightening from the previous standard of 15 micrograms, set in 1997." A federal court found the higher amount wasn't sufficient to protect public health.

Richard Davies Business Correspondent ABC News Radio abcnews.com Twitter: daviesabc