Stability of Extra Virgin Olive Oil and Other Edible Oils Under Deep-Frying and Storage Stress: A Multivariate Study of Instrumental and Sensory Data

This thesis, structured in eight chapters, comprehensively investigates olive oil stability and enrichment. Chapter One introduces objectives. Chapter Two reviews olive oil significance and advanced spectroscopic techniques. Chapter Three details novel hydroxytyrosol-based enrichment protocols and non-destructive detection. Chapter Four confirms enhanced EVOO stability during deep-frying with enrichment. Chapters Five and Six comparatively analyze diverse oils under frying, highlighting hydroxytyrosol's antioxidant role and introducing robust NIRS-based quality quantification. Chapter Seven examines storage effects on EVOO cultivars and applies NIRS for monitoring. Chapter Eight concludes, discussing key findings, scientific contributions, and practical implications. ABSTRACT: The degradation of extra virgin olive oil (EVOO) during high-temperature deep-frying and prolonged storage—leading to loss of sensorial quality and health-benefiting polyphenols—poses a significant challenge. This doctoral thesis presents a comprehensive, interdisciplinary study to enhance olive oil thermo-oxidative stability. The research investigated EVOO under continuous deep-frying (170–210 °C, 0–48 hours) and long-term storage (up to 360 days) under both natural and accelerated aging conditions (40 °C). A central hypothesis was that phenolic compounds, especially hydroxytyrosol (HTyr), are crucial for oxidative resistance and health benefits. Analyses included chromatography (HPLC, GC), physicochemical, sensory, and spectroscopic methods, augmented by big data and advanced chemometrics. A key outcome is the development of a natural fortification approach using HTyr-rich olive fruit extract (OFE). Fortifying EVOO and various other olive oil types with HTyr significantly improved their oxidative and thermal stability during deep-frying compared to unfortified oils and reference sunflower oils. Fortified oils showed lower peroxide values, improved UV absorbance indices (K232, K270), and reduced total oxidation (TOTOX), while preserving functional quality. HTyr and tyrosol exhibited the highest thermal stability among phenolics. Sensory analysis confirmed that fortified oils maintained desirable attributes (fruitiness, bitterness, pungency) and minimized off-flavors, presenting a clean-label alternative to synthetic antioxidants. Optimal deep-frying conditions were identified as 3 hours at 170 °C with HTyr supplementation. Certain EVOO cultivars (e.g., Royuela, Picual) demonstrated exceptional thermal stability. A major methodological innovation is the application of near-infrared spectroscopy (NIRS) combined with SELECTOLS regression. This enabled rapid, non-destructive, and highly accurate (R = 0.86–0.99) prediction of quality parameters (fatty acid profiles, phenolics, pigments, antioxidant capacity, sensory attributes) using minimal wavelengths (5–30). This method offers a cost-effective, scalable, and eco-friendly solution for real-time quality control, nutritional labeling, and fraud prevention. EVOO consistently showed superior oxidative stability, with HTyr fortification broadly enhancing performance across oil types, supporting circular economy goals. Big data analytics further identified NIR spectral signatures for degradation. Long-term storage evaluation ( various EVOO samples, 5 cultivars, 2 harvest stages, up to 12 months) revealed that oils with higher phenolic content (e.g., Picual, Picudo) exhibited greater oxidative resistance, while low-phenolic samples (e.g., Arbequina) degraded rapidly, often losing EVOO classification. NIRS-based predictive models were effective for estimating EVOO shelf life, enabling optimization of storage and conservation strategies. In conclusion, this thesis provides a robust framework for fortifying EVOO with natural antioxidants, integrated with advanced analytical and big data techniques to preserve oil quality, safety, and sustainability. The research delivers scalable strategies to enhance product value, monitor shelf life, and maintain nutritional integrity, contributing significantly to food science, analytical chemistry, lipid research, and sustainability with broad implications for the edible oil industry.

Grantor dc:publisher

Universidad de La Rioja (España)

Year dc:date

2025

Author dc:creator

• Abdellatif, Taha Mehany Hussein

Contributors dc:contributor

• González Sáiz, José María (Universidad de La Rioja)
• Pizarro Millán, Consuelo (Universidad de La Rioja)

Statement dc:rights

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Language dc:language

eng

Repository record dc:identifier

https://dialnet.unirioja.es/servlet/oaites?codigo=394335

OAI identifier oai:identifier

oai:dialnet.unirioja.es:TES0000023202