Exploration of Super-chilling Technology of Fresh-cut Celery

Significance 

Celery is a herb specie containing natural components such as flavonoids that are considered significant for human health. They can help reduce the risk of some diseases like cardiovascular infections and tumors. As such, the global consumption of celery has rapidly increased over the years. To ensure the availability and undisrupted supply chain of celery products, the development of specific and highly efficient preservation techniques is a prerequisite. Among the available preservation technologies, super chilling that involves storing food below their freezing temperature, has been identified as a promising technology for celery preservation. Relative to freezing and refrigeration methods, super-chilling can largely maintain the biological cells’ living state, extend food shelf life, and consume less energy. However, whether super-chilling can be used to preserve fresh-cut celery effectively remains unclear.

In super-chilling preservation, the ice crystals formed within the foods provide the desired cooling to maintain the temperature balance and enhance the mechanical properties of the tissues. However, the ice crystals also influence the quality and structure of the preserved foods. They are affected mainly by the cooling rate. Several technologies, including immersion freezing techniques, have been employed to increase the freezing rate and improve food quality. For preserving fresh-cut celery, however, it is imperative to understand the impact of accelerating the cooling rate of fresh-cut celery through low immersion temperatures during super-chilling processes.

To this note, a team of researchers from Qufu Normal University: Dr. Cong-Cong Xu, Master De-Kun Liu, Dr. Chun-Xiao Guo, and Yu-qing Wu (Undergraduate) recently investigated the influence of cooling rates and super-chilling temperatures on ice crystals characteristics, cell structures, and quality of super-chilled fresh-cut celery. In this approach, different cooling rates at different immersion temperatures of -35°C, -45°C, and -55°C, as well as different super-chilling temperatures of 1-2 °C below the freezing temperature, were taken into consideration. Their work is currently published in the journal, International Journal of Refrigeration.

Based on the results, the average freezing temperature of fresh-cut celery was -0.48 ±0.08 °C, with a super-chilling degree freezing as -1.5°C and -3.0°C. The ultralow immersion temperatures significantly shortened the super-chilling temperatures and increased the cooling rate of fresh-cut celery. Interestingly, super-chilling to -1.5°C at -55 °C was reported to be the best for maintaining the cell structure and physicochemical quality of tissues attributed to the improved size, morphology, and uniformly distributed tiny ice crystals inside and outside the numerous cells. Moreover, the tissues exhibited enhanced mechanical strength that ensured adequate resistance to kinetic damages associated with packages and transport. On the other hand, other treatments resulted in larger and irregular ice crystals leading to severe deterioration of the cell structures and decreased quality.

In a nutshell, Dr. Cong-Cong Xu and colleagues examined the effects of cooling rates and super-chilling temperatures on the general quality of fresh-cut celery preserved through the super-chilling method. The obtained results provided evidence that supper-chilling can be applied to fresh-cut celery preservation under a combination of a super-chilling temperature of -1.5°C and a cooling rate of -55 °C conditions. These optimal conditions would be significant for achieving the desired qualities of super-chilled fresh-cut celery products.

Super-chilled fresh-cut celery-Advances in Engineering
Figure legend: Scanning electronic microscopy (SEM) images of super-chilled fresh-cut celery tissues. Control: raw tissues, A, C, and E: tissues super-chilled to –1.5 °C at respective immersion temperatures of –35 °C, –45 °C, and –55 °C; B, D and F: tissues super-chilled to –3.0 °C at respective immersion temperatures of –35 °C, –45 °C, and –55 °C. IC: intracellular ice crystals; EC: extracellular ice crystals; SC: small ice crystals; LC: large ice crystals; SP: small pores.

About the author

Dr. Congcong Xu received Ph.D. degree from the Department of Food Science and Engineering, Shanghai Jiao Tong University, Shanghai in 2015. She is currently an associate professor of food quality and safety in the Qufu Normal University, Qufu, China. Currently, her main research interests include low temperature cold chain technology and quality control mechanism of fresh-cut fruits and vegetables, super-chilling technology, active packaging technology, and product development of ready to eat fresh-cut vegetables and foodborne antifreeze peptides.

She has published more than 20 technical papers in reputable journals such as Journal of Food Engineering, Food Control, Food Chemistry, LWT-Food Science and Technology, International Journal of Refrigeration, etc. and 1 authorized national invention patents. Her research results obtained the funding support from the National Natural Science Foundation of China, Natural Science Foundation of Shandong Province, the Project of Constructing High-level Applied Specialty (group) of Shandong-Biological Engineering Specialty Group, and so on. She was invited as a reviewer of LWT-Food Science and Technology more than 20 times and was rewarded 3 times because of excellent work.

About the author

Dekun Liu received Bachelor and Master degrees from the School of Life Science, Shandong University, Shandong, China in 2010 and 2014, respectively. He is currently an experimentalist of biological science in the Qufu Normal University, Qufu, China. Currently, his main research interests include plant molecular biology, the development of food biotechnology, biological foundation of botanical food quality control.

He has published 7 review and research papers (e.g. in Journal of Food Engineering, International Journal of Food Properties, LWT-Food Science and Technology, International Journal of Refrigeration). He has participated in several important research programs, such as 4 National Science Natural foundations, 1 the Project of Constructing High-level Applied Specialty (group) of Shandong-Biological Engineering Specialty Group. And he also held 1 Experimental Technology Research Project of Qufu Normal University.

About the author

Dr. Chunxiao Guo received a PhD degree in the field of Microbiology from Sichuan University, China, in 2012. She is currently a lecturer of food quality and safety in the School of Life Science, Qufu Normal University, Qufu, China. Her main research interests include food microbiology, food fermentation technology and microbial diversity. She has participated in 11th Five-Year Major Project “the Research and development of large edible and medicinal fungus” and the Project of Development of Science and Technology of Sichuan Province in China “Functional evaluation of bacterial species resources of the resource-microorganism sharing platform”.

She published several papers in reputable journals, such as General Assembly International, International Journal of Biological Macromolecules, Journal of the Institute of Brewing, Bulletin of microbiology, and participated in 2 authorized national invention patents.

About the author

Yuqing Wu is currently an undergraduate of food quality and safety in the School of Life Science, Qufu Normal University, Qufu, China. As an important member, she devotes herself to researching the development of super-chilling technology of fresh-cut celery and quality control mechanism of fresh-cut vegetables.

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Reference

Xu, C., Liu, D., Guo, C., & Wu, Y. (2020). Effect of cooling rate and super-chilling temperature on ice crystal characteristic, cell structure, and physicochemical quality of super-chilled fresh-cut celery. International Journal of Refrigeration, 113, 249-255.

Go To International Journal of Refrigeration

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