Understanding Olive Oil Acidity
Contrary to a common misconception, the term "acidity" in olive oil does not refer to a sour taste or its pH level. Olive oil is a fat and does not contain a measurable pH like water-based liquids. Instead, olive oil acidity is a quality parameter that measures the percentage of free fatty acids (FFAs), a direct indicator of the oil's quality and freshness. The FFAs are fatty acids that have broken away from their glycerol backbone, a process known as hydrolysis or lipolysis. This chemical breakdown is undesirable because it leads to a shorter shelf life and a decline in overall quality. A low FFA count signifies that the olives were healthy and handled with care from tree to bottle, while a high count suggests damage, poor storage, or a delay in processing. It is important to note that you cannot change the acidity of olive oil at home after it has been produced. The focus must be on preventing its increase.
What Causes High Acidity?
Several factors contribute to the increase of free fatty acids in olive oil:
- Damaged or overripe olives: Bruised, diseased, or insect-infested olives contain enzymes that accelerate the breakdown of triglycerides into FFAs. Using olives that are overripe can also lead to higher acidity.
- Delayed processing: A significant delay between harvesting and milling allows the olives to begin fermenting, causing a rapid rise in acidity.
- Poor storage of olives: If harvested olives are stored in piles or sacks for extended periods, the weight and lack of air circulation can cause damage and fermentation.
- Oxidation during extraction: Allowing the olive paste to be exposed to too much oxygen or high temperatures during the malaxation (mixing) stage can increase FFA levels.
- Contact with water and solids: If the oil is not adequately separated from the water and solid olive particles, enzymatic activity can continue, increasing acidity.
How Producers Control Acidity at the Source
The journey to a low-acidity olive oil begins long before the oil reaches your kitchen. Producers of high-quality, especially extra virgin olive oil, follow strict protocols to minimize FFA formation.
Best Practices for Harvesting
Producers prioritize the health and integrity of the olives:
- Harvesting at optimal ripeness: Harvesting olives when they are perfectly ripe, rather than overripe, yields oil with lower acidity.
- Gentle harvesting techniques: Minimizing bruising during harvesting, whether by hand-picking or using gentle mechanical means, protects the olives from damage.
- Rapid transport to mill: Olives are transported quickly and efficiently to the mill, often in shallow, aerated crates, to prevent bruising and fermentation.
The Importance of Immediate Processing
Speed is crucial during processing to maintain low FFA levels. The milling process typically happens within hours of harvesting, preventing the olives from degrading. Additionally, modern mills are equipped with temperature control features to keep the malaxation process under 30°C (86°F), further protecting the oil's quality.
Role of Filtration
After extraction, the oil is often filtered. Filtration removes fine particles of olive pulp, water, and other impurities. These suspended solids contain enzymes that can cause ongoing hydrolysis and rancidity during storage. Filtering the oil makes it more stable, thereby helping to maintain its low acidity over a longer period. Unfiltered olive oil, or "olio nuovo," contains more of these particles and should be consumed more quickly.
How Consumers Can Prevent Acidity Increase at Home
Once you have purchased a high-quality, low-acidity extra virgin olive oil, the responsibility shifts to you to prevent its degradation. Proper storage is paramount to keeping its acidity low and preserving its freshness.
The Enemies of Olive Oil: Light, Air, and Heat
- Light: UV and visible light are major catalysts for oxidation, a process that increases FFA levels and causes rancidity.
- Air (Oxygen): Oxygen is a key component of oxidation. Each time a bottle is opened, air enters, accelerating the degradation process. Limiting air exposure is critical.
- Heat: High and fluctuating temperatures speed up the chemical reactions that cause oil to break down. Never store oil next to the stove.
The Best Storage Practices
- Store in a cool, dark place: A closed pantry or cabinet, away from heat sources like the stove or oven, is ideal. Aim for a consistent temperature between 57°F and 70°F.
- Use opaque containers: Always choose olive oil in dark glass bottles, ceramic vessels, or metal tins, as these block light effectively. If you buy oil in a clear bottle, transfer it to a light-proof container or wrap the bottle in foil.
- Ensure a tight seal: Always close the lid tightly after each use to minimize oxygen exposure.
- Buy appropriate sizes: If you don't use olive oil quickly, buy smaller bottles. This reduces the amount of oil exposed to air over time. For bulk oil, transfer it into several smaller, airtight containers.
Comparison of Olive Oil Storage Containers
| Container Type | Light Protection | Air Protection (Sealed) | Durability | Longevity for Bulk Storage |
|---|---|---|---|---|
| Dark Glass Bottle | Good | Good | Fair | Not ideal for long-term bulk |
| Stainless Steel Fusti | Excellent | Excellent | Excellent | Excellent |
| Opaque Metal Can | Good | Good | Good | Good, but can corrode if not coated |
| Clear Plastic/Glass | Poor | Variable/Poor | Variable | Poor (Accelerates degradation) |
Conclusion
While you cannot actively decrease the free acidity of olive oil once it has been bottled, the key is to prevent it from rising. This involves making informed purchasing decisions and following meticulous storage practices. By choosing high-quality Extra Virgin Olive Oil from a reputable producer who emphasizes early harvest and rapid processing, you start with the best possible product. Afterwards, protecting that oil from its primary enemies—light, air, and heat—ensures its longevity and preserves its low acidity, flavor, and health benefits. Proper storage allows you to enjoy the full quality of your olive oil until the last drop. For further details on official standards, refer to the International Olive Council guidelines.
Remember, a low-acidity olive oil is a testament to quality production and careful preservation, ensuring you get the freshest and most flavorful oil possible.
