Now is the time in Portugal when olive harvest takes the center stage. Across the country, families and communities come together to harvest olives, a tradition that has both cultural and economic significance. Yesterday, in the Science & Wine family, we participated in this timeless ritual, an experience that reminded me of the importance of preserving the quality of olives from tree to table. In my search for ways to innovate in olive oil production, I came across a fascinating paper authored by Nabat Atamyradova, S. Yusra Özkılıç, and Derya Arslan, titled “Blanching of Olive Fruits Before Storage at Different Conditions: Effects on Oil Yield, Lipase Activity, and Oxidation.” The insights in this study offer potential solutions to one of the most critical stages in olive oil production, post-harvest storage.
In this blog post, I share the key findings of the study, explore its implications for olive oil producers, and discuss how its recommendations could influence practices in Portugal and other olive-growing regions.
The Importance of Post-Harvest Storage
The time between harvest and processing is crucial in olive oil production. Olives are highly perishable and improper storage can lead to significant losses in both yield and quality. Traditionally, farmers store harvested olives under ambient conditions, often in woven sacks or bulk piles, before transporting them to mills. Although this method has been used for generations, it can expose olives to microbial contamination, increased lipase activity, and oxidative processes that degrade the quality of the oil.
Atamyradova et al.. addressed these challenges by exploring an innovative technique: blanching olives before storage. Blanching involves immersion of olives in hot water for a short duration. The authors aimed to assess how this process, combined with different storage conditions, affects key parameters of extra-virgin olive oil, such as oil yield, oxidative stability, and phenolic content.
The Study at a Glance
The researchers conducted experiments on olives of the Edremit cultivar manually harvested from an orchard in Turkey. The olives were divided into groups based on whether they were blanched or not, and stored in two types of containers: perforated plastic crates and woven sacks. These groups were then kept at two storage temperatures: ambient (around 25°C) and cold (8–10°C)for 10 days. Here is what they found:
1. Oil Yield
Blanching did not negatively affect the oil yield. Under ambient conditions, blanched olives stored in perforated crates had the highest oil yield (26.4%), which was attributed to moisture loss during storage. However, cold-stored olives, especially those in crates, exhibited lower yields, likely because of reduced dehydration.
Oil yield (%) obtained from blanched or unblanched olives stored under different conditions.
2. Lipase Activity
Lipase hydrolyzes triglycerides, leading to increased levels of free fatty acids, a marker of lower oil quality. Blanching significantly inhibited lipase activity, maintaining levels close to those of freshly harvested olives, even after 10 days of storage. In unblanched samples stored under ambient conditions, lipase activity was double that of blanched samples.
Lipase enzyme activity in olive paste from blanched or unblanched olives stored under different conditions.
3. Oxidative Stability
Oxidative stability is a critical factor in determining the shelf-life and health benefits of olive oil. Oils extracted from blanched olives stored under cold conditions had lower peroxide values and K232 (a measure of secondary oxidation), indicating better stability. In contrast, oils from unblanched olives stored in woven sacks exhibited higher levels of oxidation.
4. Phenolic Content
Phenolic compounds contribute to the antioxidant properties and sensory profile of olive oil. The study revealed that while storage in woven sacks increased the phenolic content, it negatively affected the oxidative stability and oil yield. Cold storage generally preserves phenolic compounds better than ambient conditions, with oils from blanched and cold-stored olives retaining the highest antioxidant activity.
Total amount of phenolic substances in oils extracted from blanched or unblanched olives stored under different conditions.
Implications for Olive Oil Production
This study offers valuable insights for olive oil producers, especially those facing challenges in managing harvest during peak seasons. Here are some practical takeaways:
- Blanching as a Pre-Treatment: Blanching olives at 100°C for 3 min before storage could be a game changer. It reduces lipase activity and oxidative degradation, while preserving phenolic compounds. This simple, low-cost intervention has the potential to significantly improve the oil quality.
- Cold Storage in Perforated Crates: Combining blanching with cold storage in perforated crates is an optimal approach for high-quality oil production. Although this method may slightly reduce the oil yield, the trade-off is justified by the superior quality of the oil.
- Limitations of Woven Sacks: Although woven sacks promote higher phenolic content, they compromise the oxidative stability and yield. Producers should reconsider their use, especially in warm climates or when cold storage is not available.
Relevance to Portugal’s Olive Oil Industry
Portugal is one of the world’s leading producers of olive oil and renowned for its high-quality extra-virgin olive oil. However, traditional methods of storing and processing olives could benefit from modernization, particularly as the demand for premium olive oil increases. The findings of this study align well with Portugal’s push toward sustainable and high-quality agriculture:
- Preserving Tradition While Innovating: Adopting blanching and improved storage methods do not conflict with the rich traditions of Portuguese olive oil production. Instead, these techniques enhance the quality of the final product, ensuring that traditional practices meet the modern quality standards.
- Climate Adaptation: With rising temperatures due to climate change, cold storage will become increasingly important for preserving olive quality. This study reinforces the need for investment in cold storage infrastructure, particularly in regions where harvest volumes often exceed processing capacities.
- Promoting Research and Collaboration: Portugal’s olive oil sector can benefit from collaboration with researchers and producers in other Mediterranean countries. Sharing knowledge and implementing evidence-based practices such as those presented in this study can drive the industry forward.
Final Thoughts
As olive harvest continues across Portugal, it is an opportune moment to reflect on how innovation can complement tradition. The study by Atamyradova et al. sheds light on a promising technique that could revolutionize the storage and processing of olives. By adopting practices, such as blanching and cold storage, producers can ensure that their oils meet the highest standards of quality and sustainability.
At Science & Wine, we are passionate about exploring the intersections of science and tradition, and this paper is a perfect example of how research can inspire change. As I look back on yesterday’s harvest, I am excited about the potential to integrate these findings into our own practices and share this knowledge with the wider community.
Read all at: Atamyradova, N., Özkılıç, S. Y., & Arslan, D. (2024). Blanching of olive fruits before storage at different conditions: Effects on oil yield, lipase activity and oxidation. Journal of Agriculture and Food Research, 101509.https://doi.org/10.1016/j.jafr.2024.101509