“The age of thrift is here. You have to do innovation at both ends–premium innovation and innovation for the value consumer.”

— PepsiCo chairman and CEO Indra Nooyi in a recent Q&A with Pattie Sellers. No. 1 on Fortune‘s 2009 Most Powerful Women in Business list (for the fourth year in a row) Nooyi today delivered another quarter of solid earnings. PepsiCo beat analyst expectations with net income of  $1.72 billion, up 9% over last year.

Nooyi is relentless in reinventing a company that many others might have thought didn’t need reinventing. Investing in healthier products, reorganizing her core team, spending billions to acquire Pepsi’s two largest bottlers…the list of changes go on and on. “Any capital we invested in the company has to be rethought,” Nooyi said in the interview, noting, “The bottom line is: Through this downturn, you have to increase your investment, not cut back.” She added, “Now is a wonderful time to look for disruptive models.”

Click here for a series of video clips from Pattie’s interview with Nooyi. –Jessica Shambora