Amazon’s $13.7 billion takeover of Whole Foods became official this week, and prices on 15 products at the upscale grocer immediately took a plunge.

Some apples saw a 43 percent drop per pound, with avocados, salmon and bananas not far behind with a 30 percent-plus price decrease.

How is Amazon going to change the culture at Whole Foods, particularly what customers experience? And is the supermarket environment about to get even more competitive, including for the Valley-based Sprouts?

For more, we spoke to Joe Dobrow, former head of marketing for Whole Foods and Sprouts. He’s also author of the book "Natural Prophets."