Those handy packages of pre-washed, already mixed greens are easy choices for summer salads. But experts warn they may not be as safe, fresh or healthy as loose greens.

Bagged greens go through more processing steps than loose greens, food safety expert and culinary sanitation professional Gevork Kazanchyan tells Martha Stewart.

“When weighing purely absolute risk, bagged greens have been linked to more outbreaks in recent years,” Kazanchyan, from Cal State University reveals. He explains that the greens may come from multiple sources and are chopped, washed and mixed before they are packaged. Once the greens are chopped they become more vulnerable to bacteria. Even triple-washing won’t solve the problem.

Fresh greens, like a head of romaine, last longer than bagged greens. Experts say that buying greens that are packaged in clamshells instead of bags can improve the safety and longevity of the product. But always check for brown spots and other signs that reveal the greens may be past their prime. 

Here’s how to properly wash and store greens loose greens, according to experts at the University of Wisconsin :

• Wash your hands for 20 seconds with soap and water and clean surfaces before and after preparing leafy greens.

• Inspect the leafy greens and get rid of any torn or bruised leaves. Also, get rid of the outer leaves of cabbages and lettuce heads that can tend to trap dirt and harmful microorganisms

• Rinse the remaining leaves under clean, running water. Use your hands to gently rub them to help get rid of germs and dirt. Kitchen vinegar and lemon juice may be used, but there is no evidence to show either are any better than plain running water. Do not wash leafy greens or other produce with soap, detergent, or produce wash. Do not use a bleach solution or other disinfectant to wash produce.

• Dry leafy greens with a clean cloth, paper towel, or use a salad spinner. Wrap with paper towels and store in a container in the refriegerator.

• Don’t wash pre-washed greens again because this process can introduce more contaminants.

• Keep greens away from ethylene-producing fruits such as apples and bananas to prevent premature spoilage.

• Choose brands you trust when buying bagged greens.

While packaged greens are decidedly more convenient they do carry a slightly higher risk of contamination so in the long run, loose greens are a healthier choice.