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Exchange-traded funds offer a convenient way to invest in sectors or niches that interest you. If you'd like to add some food and beverage companies to your portfolio but don't have the time or expertise to hand-pick a few, the PowerShares Dynamic Food & Beverage ETF (NYSEMKT:PBJ) could save you a lot of trouble. Instead of trying to figure out which stocks will perform best, you can use this exchange-traded fund to invest in lots of food and beverage companies simultaneously.

Why this ETF and why food and beverage companies?
The food and beverage industry is rather defensive, as eating isn't optional for any of us. Still, the industry faces some headwinds, too. At Deloitte, Pat Conroy pointed to deteriorating brand loyalty and "consumers' prolonged recessionary mind-set" as two examples. Still, those aren't necessarily permanent problems, and as our planet's population keeps growing, it will need more food, which will have to be grown on less available land. That gives the industry some solid long-term growth prospects.

ETFs often sport lower expense ratios than their mutual fund cousins. This ETF is no exception, with an annual fee of 0.63%. It has outperformed the world market over the past three and five years.

A closer look at some components
On your own you might not have selected The Andersons (NASDAQ:ANDE) or WhiteWave Foods (NYSE:WWAV) as food and beverage companies for your portfolio, but this ETF included them among its 30 holdings.

The Andersons
The Andersons is a food company and much more. Along with storing and trading grains, making and selling crop nutrients, and operating specialty food stores, it also manages a fleet of more than 22,000 railcars, makes cat litter, and deals in ethanol, among other things (whew!).

The company's top and bottom lines are growing at a good clip (five-year annual average rates of 13% and 23%, respectively), and dividends have grown at an average annual rate of 13% over the past five years. (The stock recently yielded 0.8%.) The Andersons' last quarter left a little to be desired, though, with revenue and earnings both significantly missing estimates. Revenue dropped 21%, but while earnings per share were disappointing, they still clocked in nearly 80% higher than year-ago levels. A harsh winter and falling grain prices were cited as major factors. Still, The Andersons offers operational diversification and stands to benefit from growth in rail traffic as our economy heats up -- the last quarter already featured record operating income from the rail division -- and its ethanol business has been enjoying fatter profit margins, too.

With its current and forward P/E ratio near 15 and growth having slowed some recently, the stock doesn't appear to be a compelling bargain at the moment, but you might at least want to add it to your watchlist in case there's a drop in price.

WhiteWave Foods
WhiteWave Foods is a 2012 fast-growing spinoff from Dean Foods, with a focus on organic fare and plant-based foods. Its offerings sport brand names such as Silk, International Delight, Land O'Lakes, Horizon Organic, TruMoo, and Earthbound Farm.

In its first quarter, revenue jumped 36% over year-ago levels. Management also upped its near-term projections, and a joint venture in China is expected to boost business -- there's strong dairy demand in China these days.

Some see WhiteWave as an attractive acquisition target due to its strong brands, but investment decisions shouldn't be based on speculation. WhiteWave Foods' top line has been growing slowly and steadily, while its bottom line has bounced around more. Free cash flow has been lumpy, too, in part due to growing capital spending as the company beefs up its production capacity due to stronger-than-expected demand. Its stock seems a bit pricey, with a current P/E of 51 and a forward one of 27.5. It's true that WhiteWave's robust growth rates help justify its premium pricing, but investors seeking undervalued stocks with margins of safety might want to wait for a pullback in price before buying.

The big picture
It makes sense to consider adding some food and beverage companies to your portfolio. You can do so easily via an ETF. Alternatively, you might simply investigate its holdings and then cherry-pick from among them after doing some research on your own.