Polyphenol Degradation Estimator

How it works

The estimator treats one reported phenolic-content number as a single pool and uses a pseudo-first-order approximation:

P(t) = P₀ × e^{−k × t}

where P(t) is the estimated content after t days, P₀ is the starting value, and k is an effective rate constant. Some studies found pseudo-first-order behaviour for total phenols and secoiridoid derivatives, but individual compounds do not all behave this way: simple hydroxytyrosol and tyrosol can initially increase as larger secoiridoids hydrolyse, and different oils can have materially different rates.

Temperature is represented with an Arrhenius-type sensitivity:

k(T) = k_ref × exp[(E_a,app / R) × (1 / T_ref − 1 / T)]

Below 15°C the rate is held at the 15°C value. Longterm storage work found similar initial secoiridoid loss at 5 and 15°C, with a distinct increase from 25°C, so a plain Arrhenius curve from 25 °C would overstate how much a refrigerator slows phenolic number loss. The result then applies illustrative relative multipliers for light and oxygen exposure. These multipliers are scenario controls. Light intensity and spectrum, pigments, bottle colour, headspace, closure, and opening frequency all contribute.

Model anchors:

• Midpoint k_ref = 0.0022 day⁻¹ at 25 °C. This is a phenolic-content rate: the mean 42% loss after 12 months at 20 °C in darkness (160 oils), Arrhenius-shifted to 25 °C. This doesn't report the slower antioxidant activity rates sometimes reported for closed bottles, which persist while secoiridoids hydrolyse to hydroxytyrosol.
• Sensitivity band k_ref = 0.0007–0.0035 day⁻¹ at 25 °C. This spans slower high phenol oils and faster oleacein/oleocanthal-rich oils rather than a tight antioxidant activity interval.
• Apparent E_a = 57 500 J·mol⁻¹, the mean of the total phenol Arrhenius fits reported for 25–60 °C (about 51–68 kJ·mol⁻¹ depending on the oil).
• R = 8.314 J·mol⁻¹·K⁻¹; T_ref = 298.15 K (25 °C); T_floor = 288.15 K (15 °C).
• Light multipliers: dark (1.0), ambient room light (1.5), direct sunlight (2.5).
• Oxygen multipliers: inert gas/minimal headspace (0.75), air headspace in a sealed bottle (1.0), frequently opened/large headspace (1.5).

Use the same analytical method for any before-and-after comparison. “Total phenolics”, an HPLC sum, and hydroxytyrosol plus its derivatives are not interchangeable measurements. This tool cannot determine whether an olive oil still meets the EU hydroxytyrosol health-claim threshold; that requires the relevant laboratory measurement.

The model is most useful for comparing scenarios and identifying the storage conditions likely to matter. It should not be used as an expiry date, a guarantee of health-claim retention, or a substitute for testing.

Related: Smoke point scenario model.

Sources

• Castillo-Luna, Criado-Navarro, Ledesma-Escobar, López-Bascón & Priego-Capote (2021), The decrease in the health benefits of extra virgin olive oil during storage is conditioned by the initial phenolic profile — 160 EVOOs, 12 months, darkness, 20 °C; mean phenolic-content loss 42.0 ± 24.3%, with faster loss in oleacein/oleocanthal-rich oils.
• Mousavi, Mariotti, Stanzione, Pandolfi, Mastio, Baldoni & Cultrera (2021), Evolution of Extra Virgin Olive Oil Quality under Different Storage Conditions — 18- and 36-month storage; 4 °C preserved phenols better than ambient temperature, argon helped mainly to 18 months, and loss after opening accelerated in every treatment.
• Lavelli, Fregapane & Salvador (2006), Effect of Storage on Secoiridoid and Tocopherol Contents and Antioxidant Activity of Monovarietal Extra Virgin Olive Oils — closed, dark bottles at 25 and 40 °C; pseudo-first-order antioxidant-activity rates of 0.8–1.5 × 10⁻³ day⁻¹ at 25 °C, slower than typical phenolic-content loss because hydrolysis can preserve radical-scavenging activity.
• Krichene, Salvador & Fregapane (2015), Stability of Virgin Olive Oil Phenolic Compounds during Long-Term Storage (18 Months) at Temperatures of 5–50 °C — secoiridoid degradation was pseudo-first-order; initial rates were similar at 5 and 15 °C, rose at 25 °C, and were faster still at 50 °C. Oxygen availability and the starting phenolic profile also mattered.
• Mancebo-Campos, Salvador & Fregapane (2022), Modelling Virgin Olive Oil Potential Shelf-Life from Antioxidants and Lipid Oxidation Progress — total phenols and secoiridoids fitted pseudo-first-order kinetics; hydroxytyrosol and tyrosol fitted pseudo-zero-order. Apparent E_a for total phenols was about 51–68 kJ·mol⁻¹ (mean used here: 57.5 kJ·mol⁻¹).
• Psomiadou & Tsimidou (2002), Stability of Virgin Olive Oil. 1. Autoxidation Studies and 2. Photo-oxidation Studies — foundational storage studies on oxidation and light.
• Caponio et al. (2005), Influence of the Exposure to Light on Extra Virgin Olive Oil Quality during Storage — demonstrates that light exposure changes storage stability and losses of antioxidant pigments and tocopherols.
• Ferreiro et al. (2025), Assessing the Shelf-Life of Olive Oil Under Different Storage Conditions: A Review of Predictive Models — recent review of the strengths and limitations of kinetic and empirical models.