Starbucks' (Nasdaq: SBUX) first-quarter earnings hit a high note on many metrics, but its margins took a hit as commodity price pressures continue to be an issue. However, investors should refrain from cutting this twist on the caffeine habit from their portfolios.

First-quarter net income increased 10% to $382.1 million, or $0.50 per share. Total revenues increased 16.4% to $3.44 billion. Global same-store sales perked an impressive 9% higher, with a 7% traffic boost and a 2% jump in their average ticket.

If investors must search for something to fret about, it would be Starbucks' margins. Quarterly operating margin fell to 16.2% from 17% this time last year. The 80-basis-point decrease is attributed to the high price of commodities, particularly coffee.

On the other hand, Starbucks' recent partnership with Green Mountain Coffee Roasters (Nasdaq: GMCR) is alive and kicking pretty hard; Starbucks said it shipped more than 100 million Starbucks- and Tazo-branded K-Cups in the first quarter, helping drive its consumer product group sector's revenue 72% higher.

In addition, Starbucks' international expansion is progressing. The coffee giant has opened 241 new stores across the world, reaching 500 stores in China and Latin America.

Apparently a theme is popping up amongst food- and beverage-related companies like Starbucks. Quarterly resultsfor McDonald's (NYSE: MCD) earlier this week didn't exactly thrill investors, and lower margins also cast a shadow over an otherwise good quarter.

Although Starbucks hit a new 52-week high recently, it's still cheaper than some coffee peers. Starbucks' PEG ratio of 1.48 compares quite favorably to Peet's (Nasdaq: PEET) PEG ratio of 2.14 and Caribou's (Nasdaq: CBOU) PEG ratio of 1.74. Plus, Starbucks' growth plans, including its Evolution Fresh acquisition, give investors good reason to believe in heady future growth.

In September, I purchased shares of Starbucks for the real-money Rising Star portfolio I'm managing for, and I'm pleased with its performance so far, and potential investors could view today's weakness as a good buying opportunity. Starbucks remains a solid stock for the long haul.

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