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ARS Home » Northeast Area » Kearneysville, West Virginia » Appalachian Fruit Research Laboratory » Innovative Fruit Production, Improvement, and Protection » Research » Publications at this Location » Publication #317011
Title: Influence of vacuum impregnation and pulsed electric field on the freezing temperature and ice propagation rates of spinach leaves

Author
item DYMEK, KATARZYNA - Lund University
item DEJMEK, PETR - Lund University
item GOMEZ GALINDO, FEDERICO - Lund University
item Wisniewski, Michael

Submitted to: Journal of Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2015
Publication Date: 5/19/2015
Citation: Dymek, K., Dejmek, P., Gomez Galindo, F., Wisniewski, M.E. 2015. Influence of vacuum impregnation and pulsed electric field on the freezing temperature and ice propagation rates of spinach leaves. Journal of Food Science and Technology. 64:497-502.

Interpretive Summary: Determining factors that impact the temperature at which plants or plant material will freeze and how ice propagates through the plant material remains an important question for the development of frost protection measures and also for the food processing industry. Maintaining the quality of food material that has been frozen as part of processing is essential, and methods to maintain the quality of sensitive food products is the subject of research by academic and industry researchers. In the present study, USDA-ARS expertise in the use of infrared thermography was utilized to visualize the freezing process of spinach leaves that had been infiltrated with a sugar solution. The leaves were simultaneously exposed to an electric field to facilitate the penetration of the sugar solution into the cell. Results demonstrated the impact of the infiltrated solutions on the freezing process and indicated that the pulsed electric field had no impact on the freezing process. The study further confirmed the use of infrared technology to visualize the freezing process and will continue to be used in further USDA-ARS research on developing frost protection strategies.

Technical Abstract: Efforts are currently directed towards improving the quality of sensitive tissues of fruits and vegetables after freezing and thawing. One of the methods under investigation is the combination of vacuum impregnation (VI) with cryoprotectants and pulsed electric field (PEF) applied to the plant tissue prior exposure to freezing. The influence of these processes on the freezing temperature and ice propagation rate of spinach baby leaves are studied here. Leaves impregnated with trehalose, sucrose, glucose and mannitol exhibited significantly lower ice propagation rates and higher freezing temperatures in comparison to non-treated controls. Leaves subjected to PEF also showed increased freezing temperatures compared to the non-treated leaves; however, the ice propagation rate was not influenced by PEF for the cryoprotectants used in the study, except for leaves impregnated with trehalose, where it was significantly increased, and water, where it was significantly decreased. The combination of VI and PEF resulted in comparable freezing temperatures and ice propagation rates as the leaves subjected only to VI.