AN OMIC APPROACH TO REVEAL THE CHEMISTRY BEHIND THE COFFEE FLAVOR EVOLUTION OVER TIME

There is nothing more delicious and enticing than the smell of freshly brewed coffee. This is due to the potent flavour and aroma that coffee gives off during the roasting process. Due to the sensory properties of coffee and its high financial value, it is important to preserve and maintain its quality [1]. Coffee quality is a multidimensional attribute influenced by a series of genetics precursors, environmental factors and especially post-harvest processes such as roasting and storage conditions that affect sensory and chemical properties [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), release of CO2, oxidative reactions with the formation of off-notes and the development of rancidity [2,4-6]. Flavor perception is a multimodal assessment of the interaction between different and complex stimuli (ortho retro-nasal, taste, texture, etc.) and the (bio)chemical and physiological responses This work deals with the investigation of a flavomics approach to study the chemistry behind the changes in coffee flavor during storage. 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 (multilayer foil with aluminium barrier (standard) 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% UR and 45°C) and monitored over a period from T0 to T180 for the standard caps and from T0 to T90 for the eco caps. Acidity, peroxide value and p-anisidine were evaluated by spectrophotometric analysis. The sensory tests were carried out by an expert panel. The analytical data of the normalized responses for eco and standard caps show a different behaviour depending on the packaging. A series of volatile compounds were detected in the oxidative 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 colourimetric values (peroxides, p-anisidine and acidity ), the pH and UR % measurements and the VOCs. The results show that the different blends behave differently over time, under stress conditions and in the different packaging.