## 1 Introduction  
The quality of any food product is going to worsen after a period of storage time due to various reasons, and changes in terms of safety, nutritional properties and organoleptic characteristics (appearance, odor, flavor, color, texture) are generally observed. Shelf life (SL), which could be considered a synonym of the duration of a consumer's acceptance as a function of a product's stability, differs among foodstuffs, being dependent on inherent features (formulation, microbial population, processing, packaging, etc.) and environmental factors (storage conditions such as temperature, light exposure, etc.) [1, 2]. One main question is: to what extent can the modification of the quality of a product be considered acceptable? It is prohibited to sell foods that are dangerous to health, since they contain microorganisms or toxins or chemical contaminants; in addition, foods unsuitable for human consumption, i.e., with sensory and/or nutritional characteristics below the expected standard, cannot be distributed. In this context, EU legislation (EC Regulation No. 1169/2011) established that the SL of a food, which could be defined as the \"date of minimum durability\", must be labeled as: i) \"best before\" date, related to food quality, which indicates that, after that date, there might be a decline in the organoleptic qualities of the product, but it is still safe to be consumed without risk, preferably as soon as possible, or ii) \"use by\" date, related to food safety, beyond which the food is no longer safe [3]. The manufacturer is responsible for defining the SL duration, also through laboratory tests, even if the legislation does not provide methods of assessment, leaving the arbitrariness of the choice to the producer. The essential aim of an SL study is to assess the time span during which the food quality maintains an acceptable level under specified storage conditions [4], which is a crucial step for both the consumer and the producer, but its correct prediction may be difficult. The quality of a foodstuff with an overestimated SL can indeed be perceived as poor and disappointing, with consequent damage to the image of the company and economical loss. On the other hand, an underestimated SL can generate logistic problems with not only economic consequences but also ethical ones, due to the environmental and social impact deriving from an excess of food waste. According to a recent estimation, the food waste along the distribution chain spans from 25 to 50% of the worldwide food production, with huge economic, environmental but also ethical implications [5]. Several methodologies for SL assessment are available using different approaches, all based on the deep knowledge of food quality decay as a function of storage time [4]. The preliminary step of an SL study requires the individuation of the most crucial chemical, physical, or biological phenomena inducing food quality decay, in order to identify the relevant acceptability limit. When the choice of the acceptability limit is not supported by any regulatory indication, manufacturers must fix the acceptability limits as a function of their strategies and quality target [4,6]. The next step is represented by the study of the quality depletion kinetics, considering how the selected quality marker changes as a function of time during real-time SL testing (under foreseeable storage conditions) or during accelerated SL testing (storage conditions able to accelerate the degradations). The final step is the modeling of data, addressed to estimating SL [4,6]. Considering food regulation, virgin olive oil (VOO) is a unique food, whose quality categories are fixed by distinct international standards (i.e., EU legislation, Codex Alimentarius and International Olive Council (IOC)), all of whom include sensory evaluation [7]. Developed in the early nineties, the \"IOC Panel test\" methodology (IOOC/T.20/Doc. no. 3, 1987) for the classification of sample within a commercial category has been revised many times over the years, to improve its performance.