How to preserve rosemary

In this brief guide, we are going to answer the question “how to preserve rosemary” and discuss the different methods of preserving rosemary.

How to preserve rosemary

Rosemary (Rosmarinus officinalis L.) grows wild in the Mediterranean basin, where it is appreciated for its aromatic, antimicrobial and antioxidant properties. Like in most leaves, during storage, the high level of moisture provides the perfect breeding ground for the growth of microorganisms. Preservation methods are required to extend the shelf life of herbs (1).

Rosemary can be preserved by :

  • Refrigerating
  • Freezing
  • Drying
  • Infusing in olive oil

Rosemary is a well-known herb used for seasoning a variety of dishes ranging from meat and vegetables to cocktails.

How to refrigerate rosemary for preservation

Refrigerating is the easiest method to preserve rosemary. Refrigerated rosemary will have the same flavor and texture as fresh rosemary. The only drawback is that refrigerated rosemary must be used within 2 weeks.

To refrigerate rosemary:

  • Wash the rosemary in clean water.
  • Remove the excess water by using a salad spinner or paper towels.
  • Wrap the rosemary in a damp towel.
  • Place the towel inside a plastic bag or an airtight container.
  • Label and refrigerate for up to 2 weeks.

How to freeze rosemary for preservation

In a study, three stabilization methods were compared for the shelf life extension of rosemary: air drying, freezing and freeze-drying. Freezing at -20°C (-4°F) for 12 months seems to have given the best results, allowing the best retention of 6 important compounds (1,8-cineole, bornyl acetate, a-terpineol, terpinen-4-ol, terpinolene, myrtenol) (1).

Freezing preserves rosemary for about 1 year. You can use frozen rosemary straight from the freezer without thawing.

To freeze rosemary sprigs:

  • Wash the rosemary sprigs in clean water. 
  • Remove the excess water by using a salad spinner or paper towels. 
  • Place the rosemary sprigs on a tray lined with parchment paper.
  • Freeze the rosemary sprigs for a few hours.
  • Transfer the rosemary sprigs inside a ziplock bag and squeeze out all the air. 
  • Seal, label and return it to the freezer.

To freeze rosemary in an ice cube tray:

  • Wash the rosemary sprigs in clean water. 
  • Remove the excess water by using a salad spinner or paper towels. 
  • Chop up the rosemary.
  • Place a small amount of chopped rosemary inside each cubicle of the ice cube tray and top up with water. Be sure to use as little water as possible. Olive oil l can be added instead of water. Rosemary frozen in oil will melt sooner when added to dishes.
  • Place the tray in the freezer until all the cubes are frozen.
  • Transfer the frozen cubes into a ziplock bag.
  • Squeeze out the air, seal, label and return it to the freezer.

How to dry rosemary for preservation

Drying is the most commonly used method to preserve rosemary. However, hot air-drying can result in thermal damage and can severely alter the volatile composition and color of the herbs. Some volatile compounds evaporate during air-drying, whereas others are partially retained, and some oxidation products appear during drying, depending on temperature used for drying (1).

Rosemary retains its flavor, texture and aroma when dried. However, a study showed that air drying at 38°C (100°F) was the worst method evaluated for rosemary preservation, thus more volatile compounds were lost, compared with freezing and freeze-drying (1). After drying, rosemary leaves can be removed from the sprigs before storing. Dried rosemary can also be ground into a powder before storage, however, this will result in more loss of flavor and aroma over time.

Rosemary takes longer to dry than other herbs due to the thick texture of the leaves. Air-drying takes the longest time. Using a food dehydrator takes at least 2 to 3 days to completely dry the rosemary

Always store dried rosemary in an airtight container in a cool, dark place away from direct sunlight. Properly stored dried rosemary will preserve well for several years.

Rosemary can be dried in one of 3 ways:

Air-drying

  • Wash the rosemary sprigs in clean water. 
  • Remove the excess water by using a salad spinner or paper towels. 
  • Tie up the rosemary sprigs using twine and hang them to air-dry in a warm room. 

Oven-drying

  • Wash the rosemary sprigs in clean water. 
  • Remove the excess water by using a salad spinner or paper towels. 
  • Spread out the rosemary sprigs in a tray lined with parchment paper.
  • Set the oven to the lowest possible temperature setting and dry the rosemary sprigs.

Using a food dehydrator

  • Wash the rosemary sprigs in clean water. 
  • Remove the excess water by using a salad spinner or paper towels. 
  • Spread out the rosemary sprigs in a tray lined with parchment paper.
  • Set the food dehydrator to the lowest possible temperature setting and dry the rosemary sprigs.

How to preserve rosemary by infusing with olive oil

Dried rosemary can be infused with olive oil to produce rosemary-infused olive oil. Rosemary-infused olive oil can be used to season dishes as well as for hair treatment. The only ingredients you need to make rosemary-infused olive oil are dried rosemary and olive oil.

Dry herbs or their extracts are used in oils or lipid-containing foods to retard oxidative deterioration. The antioxidant effect of rosemary is related to the presence of carnosic acid, carnosol and rosmarinic acid and its derivatives. Other compounds identified in rosemary extracts are rosmaridiphenol and rosemary quinone or more hydrophilic compounds, such as luteolin and derivatives. When rosemary is immersed in the oil, the amount of phenolic compounds are increased and consequently, the oxidation of the fatty acids is delayed (2).

There are 2 methods to produce rosemary-infused olive oil. The hot-infusion method and the cold-infusion method. The cold-infusion method produces the best results however, it takes about 2 weeks for the infusion to complete.

Regardless of the method used, rosemary-infused olive oil must be used within 3 months.

Shelf-life of preserved rosemary

Refrigerating: Refrigerating will preserve fresh rosemary for about 2 weeks.

Freezing: Freezing will preserve fresh rosemary for a  maximum of 1 year. If rosemary is frozen in ice cube trays with water or olive oil, it is better to use them within 6 months.

Drying: Drying will preserve rosemary for several years when stored properly.

Infusing in olive oil: Rosemary infused with olive oil has a shelf-life of about 3 months.

Conclusion

In this brief guide, we answered the question “how to preserve rosemary” and discussed the different methods used to preserve rosemary.

If you have any questions or comments, please let us know.

References

  1. Usai, Marianna, et al. Influence of different stabilizing operations and storage time on the composition of essential oil of thyme (Thymus officinalis L.) and rosemary (Rosmarinus officinalis L.). LWT-Food Sci Technol, 2011, 44, 244-249.
  2. Damechki, Mayada, Sofia Sotiropoulou, and Maria Tsimidou. Antioxidant and pro-oxidant factors in oregano and rosemary gourmet olive oils. Grasas y Aceites, 2001, 52, 207-213.

Hi, I am Charlotte, I love cooking and in my previous life, I was a chef. I bring some of my experience to the recipes on this hub and answer your food questions.