Kroger Co., parent company of King Soopers and City Market, on Wednesday announced it's bolstering private label organic food offerings in a challenge to the onetime exclusive domain of Wild Oats and Whole Foods.

The nation's largest supermarket chain will add about 60 products, including waffles, milk and peanut butter, under the "Private Selection" label by the end of September. The products will be available throughout the store, not just in the natural foods aisle.

"This is an easy way for consumers who want to try organic foods to do so at their own pace," said Linda Severin, Kroger's vice president of corporate brands.

Kroger's announcement comes as the size of the organic market is a central issue in federal antitrust authorities' attempt to block Whole Foods' proposed $671 million purchase of Boulder-based Wild Oats.

A federal judge is currently weighing the Federal Trade Commission's argument that the combination of the two stores would lead to less competition and higher prices for organic foods consumers, while Whole Foods counters that plenty of other supermarkets sell natural and organic food.

Some 53 percent of organic shoppers purchased foods and beverages at traditional grocery stores last year, making it the leading source of organic products, according to the Natural Marketing Institute's Health & Wellness Trends Database.

Store-brand labels can cost less than specialty brands, making the products attractive to consumers who have avoided organic products because of the higher price.

Safeway sells more than 150 certified organic products under its "O" private label, and expects to post more than $300 million in sales this year. SuperValu, which purchased Albertsons, has said it plans to offer 300 organic products under its Nature's Best label this year.

Sales of organic foods grew 22 percent last year to reach $16.9 billion, according to the Organic Trade Association.

"Organics is probably the hottest thing going in the food market right now," said Ted Taft, managing director of the Meridian Consulting Group. "The conventional grocery channel has seen that growth and seen that as something they need to have."

Cincinnati-based Kroger introduced its Naturally Preferred natural and organics foods line five years ago. The line includes 300 products that use all natural and organic ingredients.

Kroger operates more than 100 King Soopers and 38 City Markets in Colorado.

Chemical-free's broadening appeal

Organic food sales in the United States over the past decade:

1997 sales   $3.6 billion

2001 sales   $7.4 billion

2006 sales   $16.7 billionSource: Organic Trade Association

davisj@RockyMountainNews.com or 303-892-2514. The Associated Press contributed to this report.