Date of Award
Level of Access
Master of Science (MS)
Food Science and Human Nutrition
Second Committee Member
L. Brian Perkins
Third Committee Member
Highbush and lowbush blueberries were pretreated with high frequency ultrasound before freeze drying and were compared with berries that were freeze dried only, in order to determine the effects on freeze drying time, anthocyanins, total free phenolics, ORAC values, BRIX, Titratable acidity, moisture, water activity, rehydration ratio and color. There was no difference in drying time for highbush berries, however, drying time for lowbush berries was decreased. Moisture content was directly related to whether the berries were dried to a point below 50mTorr in difference between capacitance manometer and pirani gauge readings. Sonication significantly (p<0.05) decreased total acids and ORAC values and color fading in both highbush and lowbush berries. In lowbush berries, sonication decreased total anthocyanins, total free phenolics and increased BRIX values.
The decreased quality of sonicated lowbush berries was determined to be a result of the sonication process itself. Therefore, it is recommended to further investigate different methods of treating with ultrasound that will not result in juice loss of the berries. It is also recommended that increasing frequency and time of treatment for highbush berries to better penetrate their thicker skin, may result in a significant difference in drying time.
Young Johnson, Connie Jean, "The Effect of High Frequency Ultrasound Pretreatment on Highbush and Lowbush Blueberries' Freeze Drying Time, Anthocyanins, Phenolics, and Other Chemical Qualities" (2013). Electronic Theses and Dissertations. 1942.