Hydroxymethylfurfural Formation and Sensory Implications in Raisins: Effects of Cultivar, Extra Virgin Olive Oil Pretreatment, and Storage Temperature

Hydroxymethylfurfural (HMF) is a well-established marker of heat-induced reactions in sugar-rich foods. However, its accumulation in raisins in response to clean-label pretreatments and its association with consumer sensory perception remain unclear. This study investigated the influence of extra virgin olive oil (EVOO) pretreatment, cultivar (BRS Clara and BRS Vitoria), and storage conditions (4, 25, and 35 °C) on HMF formation in raisins and on their sensory implications. Cultivar influenced physicochemical properties, but neither cultivar nor pretreatment significantly affected HMF levels after drying. During storage, HMF formation followed predominantly zero-order reaction kinetics, with Q10 values (7.33–8.39) confirming strong temperature dependence, and pronounced accumulation at 35 °C. Sensory analysis showed that flavor was the main driver of consumer perception, with burnt sugar notes more frequently cited as a disliked attribute in samples stored at higher temperatures, whereas samples stored at lower temperatures retained attributes closer to time zero. Pearson correlation analysis confirmed a strong positive association between HMF and the burnt sugar descriptor (r = 0.86, p < 0.001). These findings demonstrate that EVOO pretreatment can improve drying efficiency without promoting HMF formation, and highlight the value of the combined chemical–sensory approach to assess quality changes in raisins from tropical-adapted grape cultivars.