Color freeze-dried foods

D.H. Pahner, A.W. Taylor, and M.K. Withers, Flavor, texture and color of air dried and freeze dried vegetables. In Proceedings of the First International Congress on Food Science Technology, Vol. 4, 1965, p. 37. 

Freeze-drying is a food-conservation process that leads to unique product characteristics. The removal of water from a frozen product under vacuum conditions results in a near-perfect preservation of shape and color, and leads to a sponge-like structure that allows a very fast water uptake during rehydration and... 

In general, the quality of microwave dried food products is somewhere between air-dried and freeze-dried products. The reduction of drying times can be quite beneficial for the color and the aroma. Venkatesh and Raghavan (2004) dried rosemary in a household microwave oven with good aroma retention while Krokida and Ma-roulls (1999) measured color and porosity of microwave-dried apples, bananas, and carrots. Khraisheh et al. (2004) compared air-dried and microwave dried potatoes and found a reduction of shrinkage and improved rehydration for the latter. 

Eshtiaghi, M. N., Stute, R., Knorr, D. (1994). High-pressure and freezing pre-treatment effects on drying, rehydration, texture and color of green beans, carrots and potatoes. J. Food Sci., 59,1168-1170. 

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