Exploring the effect of Pinus halepensis resin quality on the vinification of Retsina by untargeted profile analysis

Aim: Three factors that affect the chemical composition and perceptible aroma of Retsina—a distinguished Greek wine, crafted by infusing resin harvested from the Aleppo pine (Pinus halepensis Mill.) into the fermentation process of white or rosé wines—were studied: i) the pine forest altitude (resins were harvested from two distinct forests), ii) the resins’ tapping method (two tapping methods were implemented; a conventional one using a paste of sulfuric acid on the pine trunk as an irritating stimulant, and a natural method by not using any chemical stimulant) and iii) the duration of resin extraction in the must (a short and a long extraction time were investigated). Methods: To study these three factors and their respective interactions, nine vinification protocols were carried out. Must and wine samples were collected at different time points during fermentation, maturation and after bottling, and analyzed by both headspace SPME-GC-MS and RP-LC-TIMS-TOF MS techniques. The findings of the chemical analyses were subsequently correlated with those of sensory analysis conducted. Results: In the case of pine resins harvested using the natural method, neither the forest microclimate, nor the employed duration of resin extraction in the must seem to affect the intensity of the oily character in the wine, which remains at low levels. On the other hand, the results showed that when pine resin is harvested by the conventional method, longer contact times release heavier and more oily aromas into the must. Conclusions: In the case of pine resin collected using the natural method, the extraction time in the wine must and the choice of the harvesting area of the resin do not constitute a factor of quality for the produced wine, but rather a matter of style, in contrast to conventionally harvested resin, where these factors are critical for the resulted quality.