CO2 processing and hydration of fruit and vegetable tissues by clathrate hydrate formation

Abstract CO 2 hydrate can be used to preserve fresh fruits and vegetables, and its application could contribute to the processing of carbonated frozen food. We investigated water transformation in the frozen tissue of fresh grape samples upon CO 2 treatment at 2–3 MPa and 3 °C for up to 46 h. Frozen fresh bean, radish, eggplant and cucumber samples were also investigated for comparison. X-ray diffraction indicated that after undergoing CO 2 treatment for several hours, structure I CO 2 hydrate formed within the grape tissue. Phase-contrast X-ray imaging using the diffraction-enhanced imaging technique revealed the presence of CO 2 hydrate within the intercellular spaces of these tissues. The carbonated produce became effervescent because of the dissociation of CO 2 hydrate through the intercellular space, especially above the melting point of ice. In addition, suppressed metabolic activity resulting from CO 2 hydrate formation, which inhibits water and nutrient transport through intercellular space, can be expected.