Changes in texture, microstructure and nutritional quality of carrot slices during blanching and freezing
1999
Kidmose, U. | Martens, H.J.
Thermal processing of vegetables has pronounced effects on the cell structure, often lowering the final textural properties of the product. In order to investigate the effect of thermal processing on carrot, slices were subjected to different blanching and freezing treatments before frozen storage. Microwave-, steam- or water-blanched material was frozen and then stored at -24 degrees C. Steam-blanched carrots were subjected to blast freezing or cryogenic freezing at different temperatures before frozen storage. The influence of these process conditions on the texture (maximum load and slope), microstructure, dry matter, sugars, carotene and drip loss was investigated. Microwave blanching differed from the other blanching methods by resulting in a heterogenic cell structure. The content of dry matter, carotene and sucrose was higher following microwave blanching. Blast freezing resulted in low maximum load which seemed to be caused by major tissue damage. Concerning cryogenic freezing, lowering the temperature from -30 degrees C to -70 degrees C resulted in better preservation of the native microstructure together with an increase in maximum load, which was most pronounced after one month of storage. No significant effect was observed when lowering the temperature from -30 degrees C to -70 degrees C for any of the other measured parameters.
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