DescriptionHigh hydrostatic pressure (HHP) processing has been shown to infuse small size molecules into food materials much faster than does osmosis-based transport. The accepted mechanism is that HHP permeabilizes cells which increases the mass diffusivity of the food matrix. Hence, infusion is enhanced when foods are treated under high pressure. In this study we investigated, using a model system, HHP driven infusion of quercetin into cranberries. The main objectives of the study were to test whether enhanced infusion of quercetin can be achieved using HHP and to test whether the commonly accepted mechanism of cell permeabilization is operative in this model system. Two systems were used in this study - fresh cranberries, cells of which are intact and frozen-thawed cranberries, cells of which get permeabilized during freeze-thawing process. Under HHP, infusion of quercetin was enhanced, compared to infusion at ambient conditions (control), in both fresh and frozen-thawed cranberries. While the amount of quercetin infused under pressure was 3-5 times that in control, it was independent of the applied pressure in a broad range (5-551 MPa). Low pressure of 5 MPa was sufficient to cause enhanced infusion in frozen-thawed cranberries. Furthermore, pressure cycling treatment (2 cycles and 5 cycles) significantly increased the amount of quercetin infused. Unlike other studies, no additional cell permeabilization was observed in frozen-thawed cranberries after HHP, although amount infused was higher. This result suggested that the commonly accepted mechanism of cell permeabilization may not be the only cause of enhanced infusion. Additionally, while both fresh and frozen-thawed cranberries showed similar cell-membrane permeability after HHP, fresh cranberries had about two times greater amount of infused-quercetin than in frozen-thawed cranberries after HHP. If cell-membrane rupture were the only mechanism of infusion, then the amount infused into both, fresh and frozen-thawed cranberries, should have been equal. These results suggest that HHP infusion is not just cell-permeabilization based but may be caused by pressure driven flow (Darcy flow in porous media). Understanding the actual mechanisms of transport under pressure may enable to develop process guidelines that will help the food industry to develop value-added foods.