Shelf Life of Extra Virgin Olive Oil and Its Prediction Models
Table 1
Critical chemical parameters used in olive oil shelf-life prediction model development.
Parameter
Determination
Indicator
Methodology
Free fatty acids (FFA)
Free fatty acids are formed by the hydrolysis of triglycerides during ripening, processing and storage
An elevated level of free fatty acid indicates hydrolyzed fruits and/or poor quality oil made from unsound fruit, improperly processed or stored oil
Analytical titration
Peroxide value (PV)
Peroxides are primary oxidation products that are formed when oils are exposed to oxygen, producing undesirable flavors and aroma
An elevated level of peroxides indicates oxidized and/or poor quality oil
Analytical titration
Ultraviolet absorbance (UV)
Conjugated double bonds are formed from natural nonconjugated unsaturation in oils upon oxidation. The measures primary oxidation products and measures secondary oxidation products
An elevated level of UV absorbance indicates oxidized and/or poor quality oil
UV spectrophotometry
1, 2-Diacylglycerols (DAGs)
Fresh EVOO contains a high proportion of 1,2-diacylglycerols to 1,2- and 1,3-diacylglycerols, while olive oil from poor quality fruits and refined olive oils have higher level of 1,3-DAGs than fresh EVOO
A low ratio of 1,2-diacylglycerols to 1,2- and 1,3-diacylglycerols is an indicator for oil that is hydrolyzed, oxidized, and/or of poor quality
Gas chromatography (GC)
Pyropheophytins (PPP)
Chlorophyll pigments break down to pheophytins and then pyropheophytins upon thermal degradation and aging of olive oil
An elevated ratio of pheophytin a to pyropheophytins is an indicator for oil that is oxidized and/or adulterated with refined oil
High performance liquid chromatography (HPLC)
Sensory evaluation
Sensory refers to flavor and aroma attributes
Sensory evaluation can help identify oils that are of poor quality, oxidized, and/or adulterated with other oils
A recognized panel of 8–12 people evaluates oils for sensory characteristics
Induction time
The oxidation process is accelerated by means of heating up the reaction vessel while passing air continuously through the sample
Oxidative stability (in hours) denotes the resistance of oils to oxidation. The longer the induction time, the more stable the oil
Rancimat
Total phenols
The sum of up to 30 individual phenols which have antioxidative ability
A low level of total phenols can indicate a shorter shelf life while a high level of total phenols can indicate a longer shelf life
Volatile compositions change during oxidation. For example, as the oil oxidizes, the concentration of hexanal decreases while concentration of nonanal increases
The ratios of hexanal/nonanal and E-2-hexenal/hexanal can indicate oxidized oil
Headspace-gas chromatography (GC)
Fatty acid profile (FAP)
Saturated and unsaturated fatty acids consist of the principal components of fats. Fatty acid profiles are distinguishable markers between olive oils and some seed/nut oils (FAPs vary slightly depending on the varieties and growing region of olives)
Analysis of the fatty acid profile provides information on the authenticity of the olive oil and can be used as an indicator for adulteration
