Texture and microstructure of foods frozen by electro-magnetic freezing system

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 13680166
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 食生活
• Research Institution: Tokushima Bunri University
• Principal Investigator: TAMURA Sakie Tokushima Bunri University, Faculty of Human Life Sciences, Professor, 人間生活学部, 教授 (30033632)
• Co-Investigator(Kenkyū-buntansha): MATSUSHITA Junko Tokushima Bunri University, Faculty of Human Life Sciences, Lecturer, 人間生活学部, 講師 (20289317)
• Project Period (FY): 2001 – 2002
• Keywords: electro-magnetic freezing / chicken breast / pumpkin / carrot / asparagus / fracture property / microstructure

Research Abstract

In order to investigate the effect of electro-magnetic freezing, chicken breasts, pumpkin fleshes with different specific gravity, carrot roots and asparagus stems were frozen at - 45℃ by rapid freezing system with frequencies from 5 to 40Hz (ABI, INC.) and samples for the controlled group were frozen by conventional rapid freezer at the same temperature. After thawing, fractural properties of samples were examined by Creepmeter (RE-33005) and the microstructure was observed by light and transmission electron microscope. The ratios of cavities showing the trace of ice crystals to the tissues were determined by image analysis.
When chicken breasts were frozen by electro-magnetic freezer with. 30Hz, no remarkable difference was observed after one week storage, but after 6.5 month storage, big cavities, which were observed in the muscular fibers of the samples frozen by conventional rapid freezer, were clearly suppressed in those of the samples frozen by electro-magnetic freezer. When the pumpkin with relatively high value of specific gravity was frozen with 30Hz, extracellular and intracellular cavity spaces were smaller than those frozen by the conventional rapid freezing. Moreover even after storing for 3 months the quality was less deteriorated in those frozen by the electro-magnetic freezing. In the parenchyma tissues of frozen-thawed carrot pieces, cavities showing the traces of ice crystals were seen in the intercellular spaces surrounded by the concave cells, and the volume ratio of the cavities to the tissue was slightly decreased by freezing with 20Hz. In the asparagus stems frozen by both freezing methods, big cavities were observed in the parenchyma tissue surrounding vascular bundles. It is considered therefore that, as far as we examined, it was difficult to provide effective results when vegetables containing high levels of volume of water were frozen by electro-magnetic freezing.