Compression of foods during freeze-drying: water plasticization at the ice-dry layer interface.
The compressive mechanical properties of freeze-dried green beans show a pronounced decrease in rigidity when moisture content and/or temperature are increased. There exist several temperature and moisture combinations which give common values for mechanical properties. These combinations also give a common compressive behavior. Using this information on mechanical properties, it is possible to predict a stress-strain relationship, if given either a temperature, a moisture content, or the value of a pertinent mechanical property. It is shown that the moisture contents and temperatures that exist in the dry layer during freeze-drying result in mechanical properties that are suitable for compression of the dry layer. From studies on compression behavior during freeze-drying, it is shown that applied compressive pressure is the main determinant of final degree of compression. Increasing the compressive pressure gave a higher compression effect and gave a more rapid drying, presumably due to improved heat transfer in the compressed dry layer. From the above information, a simple method to predict compression behavior during freeze-drying was developed.
Emami
C
C
Dunkin' Donut, Braintree, MA 02184.
Flink
J M
JM
D007887:Fabaceae; D005502:Food; D005612:Freeze Drying; D055585:Physical Phenomena; D010825:Physics; D010946:Plants, Medicinal; D013696:Temperature; D014867:Water / Q000032:analysis
D014867:Water