The chemistry behind the coffee flavour evolution over time: an omic approach

Rationale Coffee quality is a multidimensional attribute influenced by a series of genetic precursors, environmental factors and especially post-harvest processes such as roasting and storage conditions that affect sensory and chemical properties [1,2,3]. Storage is strongly influenced by various environmental conditions: moisture, temperature and oxygen are the basic dynamic forces that play a fundamental role in a number of deterioration processes, such as volatilisation of odour molecules (VOCs), the release of CO2, oxidative reactions with the formation of off-notes and the development of rancidity [2,4-6]. This work deals with the investigation of a flavoromics approach to study the chemistry behind the changes in coffee flavour during storage. Methods The chemical data of the investigated coffee samples were obtained by analysing both volatile and non-volatile profiles (i.e. lipids and phenolic fractions including alkaloids) using HS-SPME-GC-MS and HPLC-UV/DAD. Different commercial coffee capsules in different packaging, namely standard (multilayer foil with aluminium barrier) (and eco-capsules, batches (3 batches each) and blends (P and B, 100% Arabica and I 50/50% Arabica/Robusta) were analysed. Samples were stored under stress conditions (65% RH and 45°C) and monitored over a period from T0 to T180 days for the standard caps and from T0 to T90 days for the eco caps. Acidity, peroxide value and p-anisidine were evaluated by spectrophotometric analysis. In parallel, the sensory tests were carried out by an expert panel. Results: A series of volatile compounds were detected in the oxidized samples, including 3 VOCs exhibiting pungent, rancid and acidic notes and appearing in sensory unacceptable samples independently from blends, batches and packaging. The phenolic fraction and alkaloids do not vary significantly (p > 0.05). The fraction is very stable over time regardless of packaging and mixture. The evolution of the free fatty acids (FFAs) was correlated with the peroxides, p-anisidine and acidity values, the pH and UR % measurements and the VOCs. Conclusions&perspectives: The results show that the different blends behave differently over time in the standard packaging with respect to Eco-caps the latter presenting a shorter shelf-life