Consumption of olive oil has steadily increased worldwide over the last 25 years. In fact, Australian consumption of olive oil has tripled since 1991. A portion of the increased consumption can be attributed to consumer interest in “heart-healthy” products. Many believe that olive oil is a healthier alternative to other cooking oils due to the high content of monounsaturated fats. Monounsaturated fats may reduce the risk of stroke and heart disease. In addition, the antioxidants found in olive oils are believed to reduce inflammation in the body.
Like the production of wine, the steps in olive oil processing can vary depending on the desired qualities of the final product. In all cases, processing starts with raw olives. Olives grown for oil production have different flavour profiles and oil content based on the maturity of the olives. Young, green olives typically have strong, bitter flavours but yield less oil compared to mature olives. Mature olives demonstrate mellow flavours and lower antioxidant concentrations than young olives, but yield more oil. When harvesting, it is important to find a balance between flavour and oil yield.
Harvested olives are crushed to produce a paste, which undergoes a process called “malaxation.” This process involves churning and heating the paste to 27 to 30°C for a period of 20 to 60 minutes in order to release more oil and extract flavour from the olive solids. Overheating the mixture can lead to oxidation and a reduced shelf life of the final product. As an alternative, “cold extraction” may be utilised which omits heating the paste. Next, the oil is separated from the mixture typically through centrifugation. If necessary, the oil is then stored in tanks or barrels to allow additional particulates to settle out by gravity. Finally, the oil may be filtered to increase clarity.
In an effort to avoid mislabeling olive oils, the International Olive Oil Council and Standards Australia (AS 5264-2011) have created standards for grading olive oil based on chemical and sensory properties. According to the standards, Extra Virgin Olive Oil must have a free fatty acid (FFA) content of less than 0.8%, while Virgin Olive Oil must contain less than 2% FFA. Olive oil labelled neither extra virgin nor virgin often incorporate refined olive oil. Refined Olive Oil is virgin olive oil that undergoes additional processing to correct defects such as high acidity and/ or poor taste. Due to the strict standards in olive oil labelling, oil testing is critical in ensuring that the oil matches the label claim.
An olive oil manufacturer contacted Hanna Instruments interested in testing their olive oil for free fatty acids. They already had a testing lab set up and wanted an accurate way to quantify the acidity of their product. Hanna Instruments suggested the HI902 Automatic Titrator.
The free fatty acids titration requires a non-aqueous solvent, so Hanna suggested the HI1043B Refillable Double Junction pH Electrode. The HI1043B’s refillable design allows the user to replace the internal electrolyte. In this case, the customer used a lithium chloride in isopropanol electrolyte instead of the conventional potassium chloride in water. The use of a non-aqueous electrolyte provided a quicker and more stable electrode response, shortening the speed of the titration.
The chemically resistant materials of the burette (PTFE valve and tubing) provided the customer peace of mind that their alcohol-based titrant would not damage the equipment. The customer appreciated the large data storage capacity of the titrator which allowed them to easily track the acid content of multiple batches. In addition, the flexibility in configuring the method options gave the customer full control over their testing and enabled them to optimise their titrations to increase overall efficiency. As a result, the HI902 proved to be an excellent fit for the customer’s needs.