Olive trees have been cultivated for thousands of years, deeply rooted in the history and cuisine of many cultures. While renowned for their fruit, the question of whether all olives are edible directly from the tree is common. The edibility of olives is complex, involving both the fruit’s natural chemistry and human intervention. Olives require specific preparation to become palatable.
The Raw Reality of Olive Fruit
Raw olives picked directly from the tree are notably bitter and inedible. This intense bitterness stems primarily from oleuropein, a phenolic compound present in high concentrations in the unprocessed fruit. Oleuropein acts as a natural defense mechanism for the olive tree, deterring pests and animals from consuming the fruit. Biting into a fresh olive would result in an astringent taste, making the raw olive unpalatable, despite being non-toxic.
Making Olives Edible: Processing Methods
To transform bitter raw olives into the flavorful items found in stores, a curing process is essential. This process involves various methods designed to remove or significantly reduce oleuropein.
One common technique is brine curing, where olives are submerged in a saltwater solution for an extended period, from several weeks to many months. This method allows the bitter compounds to slowly leach out into the brine, often involving fermentation that contributes to the olive’s flavor.
Other methods include:
- Water curing: This involves soaking olives in plain water, changed frequently, to leach out bitterness. This process can take several days or weeks, after which the olives are typically placed in a salt brine for preservation and flavor development.
- Lye curing: Also known as alkaline treatment, this offers a much faster approach, using a caustic soda solution to quickly break down the bitter compounds. After lye treatment, olives require thorough rinsing to remove any chemical residue before being brined.
- Dry salt curing: This involves packing olives in layers of salt, which draws out moisture and bitterness over several weeks or months, resulting in a wrinkled texture and concentrated flavor.
Diverse Olive Tree Varieties and Their Fruits
All cultivated olive tree varieties (Olea europaea) produce fruit that can be made edible through curing. While all olives require curing, some varieties are better suited for specific uses. For instance, varieties like Arbequina, Frantoio, and Koroneiki are primarily grown for olive oil production due to their high oil content. Their smaller size or less desirable flesh-to-pit ratio makes them less ideal for table olives.
Conversely, varieties such as Manzanilla, Kalamata, and Sevillano are popular for table olives because of their larger size, favorable flesh consistency, and appealing flavor after curing. Some varieties, like Mission or Hojiblanca, are considered dual-purpose, suitable for both oil and table olive production.
What About Other Parts of the Olive Tree?
While the fruit of the olive tree is widely consumed after processing, other parts of the plant are not intended for human consumption. The leaves, bark, wood, and roots are not considered edible. Olive leaves are sometimes used to create herbal teas or extracts, valued for potential medicinal properties rather than as a food source.