Effect of Freezing Rate on the Onion Cell Deformation Evaluated by Digital Image Correlation
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Effect of Freezing Rate on the Onion Cell Deformation Evaluated by Digital Image Correlation Xiaochuan Zhang 1,2 & Xinqing Chu 1 & Hongwei Ji 1,3 & Yabo Wang 1,2
Received: 10 December 2015 / Accepted: 4 April 2016 # Springer Science+Business Media New York 2016
Abstract Cell deformation induced by freezing is a phenomenon that is affecting food quality. In this paper, digital image correlation (DIC) was used to investigate the effect of freezing rate on onion cell deformation. In order to improve the measurement accuracy of DIC, a micro-scale speckle pattern was formed on the onion cell surface by evenly coating CuO nanoparticles before performing a freezing test. Then, freezing tests were carried out in three different frozen conditions and DIC analysis was performed. Test results show that the cell deformation is nonhomogenous. Relatively larger deformation usually occurs in the region near the cell wall, and the deformation in the central region of a cell is usually relatively smaller. Moreover, the range of the cell deformation field decreases with an increase in freezing rate. The relationship between the cell deformation and the freezing rate shows that a relatively smaller range of cell deformation corresponds to a better preservation quality of the onion. The deformation analysis presented in this study can be used to evaluate the quality of vegetables after being frozen.
Keywords Deformation . Onion cell . Freezing rate . Digital image correlation (DIC)
* Hongwei Ji [email protected]
1
School of Mechanical Engineering, Tianjin University of Commerce, No. 409, Guangrong Road, Beichen District, Tianjin 300134, China
2
Tianjin Key Laboratory of Refrigeration Technology, Tianjin University of Commerce, Tianjin 300134, China
3
Department of Mechanics, Tianjin University, Tianjin 300072, China
Introduction With the development of the frozen storage equipment, a number of vegetable storage schemes can be formed by changing frozen-related parameters (e.g., freezing rate, thawing rate, storage temperature, and storage time). Because a specific frozen storage scheme has a significant effect on vegetable quality, studies have focused on the selection of an optimal frozen storage scheme (Czarnowska and Gujska 2012; Giannakourou and Taoukis 2003; Lisiewska and Kmiecik 2000). However, proper evaluation of vegetable quality is essential in selecting an optimal storage scheme. Generally, vegetable quality has been evaluated by analyzing the freezing-induced changes on the microstructure, color, composition, and other freezing-sensitive parameters (Chassagne-Berces et al. 2009; Luscher et al. 2005; Sun and Li 2003). Indeed, cell deformation is inevitable for the frozen vegetables and may correspond to cell injury. However, few studies have investigated cell deformation and this can be attributed in part to the unavailability of suitable experimental techniques to measure cell deformation. Digital image correlation (DIC) (Bruck et al. 1989; Pan et al. 2009b) is a deformation measurement method with the advantages of
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