A new approach for the preservation of apple tissue by using a combined method of xenon hydrate formation and freezing

• Xenon hydrate formation was used for reduction of bulk water in apple tissue.
• The combined method of xenon hydrate formation and freezing (CXF) was used for preservation of apple tissue.
• CXF could maintain firmness, turgor pressure, and cell membrane integrity of apple tissue.
• CXF was compared with conventional freezing process.
• CXF could better preserve quality of the apple tissue than conventional freezing process.

Freezing usually causes cell and tissue damage in frozen fruits. This study attempted to use a combined method of xenon hydrate formation and freezing (CXF) for the preservation of apple parenchyma tissue and to compare it with the freezing alone process (FAP). CXF included two steps. The first step was to initiate a certain amount of xenon hydrate by introducing the apple parenchyma tissue to the xenon gas at 1.0 MPa and 1 °C for 0, 1, 2, 3, 4, 5, 6 and 7 d. It was found that the amount of xenon hydrate in apple parenchyma tissue increased with storage time and 2 d was optimum to obtain the certain amount of xenon hydrate. In the second step, the sample with optimum xenon hydrate formation was frozen at − 20 °C. The results showed that CXF was more effective in maintaining firmness, turgor pressure, and cell membrane integrity of the apple parenchyma tissue than FAP. A typical restricted diffusion phenomenon which indicates that water molecules are maintained in the apple parenchyma cells was found in the CXF samples, while the FAP samples showed an unrestricted diffusion phenomenon. In addition, firmness, turgor pressure, cell membrane integrity, and restricted diffusion phenomenon of the CXF samples were similar to those of the fresh samples. The CXF could preserve the apple parenchyma tissue because of the bulk water inside the cells and the water surrounding the cells which transformed to ice crystals is limited. Thus, cell and tissue damage due to the formation of ice crystals was reduced. The obtained results indicated that the CXF is effective for the preservation of the apple parenchyma tissue.Industrial relevanceThere has been an attempt to improve the quality of frozen fruit by using innovative techniques, in opposition to simply freezing. This present work proposed xenon hydrate formation for the reduction of bulk water before freezing in order to reduce freezing damage due to a large amount of ice crystal formation. The combined method of xenon hydrate formation and freezing has been proved to be able to reduce cell membrane damage usually occurring in frozen fruit. Thus this new technique has potential to be used for improving the quality of frozen fruit. The xenon hydrate formation is considered as an innovative technique for the preservation of fruit, which is expected to be useful for the frozen food industry.