Microwave heat treatment of apple before air dehydration - effects on physical properties and microstructure

Research output: Contribution to journalJournal articleResearchpeer-review

  • Tomas Funebo
  • Ahrné, Lilia
  • Siw Kidman
  • Maud Langton
  • Christina Skjöldebrand

Golden delicious apple cubes were heated with microwave energy of high intensity (20 W/g), as a pre-treatment before air-dehydration at 40 °C, 60 °C and 80 °C. After the microwave treatment extending for 0.75 up to 5 min, the cubes were finish-dried with only forced air at 2 m/s. Dehydrated and rehydrated samples were analyzed with a puncture test using a texture analyzer. The microstructure of the samples was studied with confocal laser scanning microscopy (CLSM). Dried apple pieces were harder and more shrunk when pre-treated with microwaves, compared to only air dehydration. Despite the shrinkage and increased firmness, the rehydration capacity of microwave `blanched' apple cubes was higher than when they were only air-dehydrated. Image analysis of the rehydrated apples showed that large voids (up to 0.5 mm in diameter) had developed, and that these increased with air temperature. Higher magnification of the images revealed cell separation and disruption of cell walls, caused by the microwave heating.

Original languageEnglish
JournalJournal of Food Engineering
Issue number3
Pages (from-to)173-182
Number of pages10
Publication statusPublished - 2000
Externally publishedYes

ID: 202135224