Identifier

etd-04122004-150752

Degree

Master of Science in Biological and Agricultural Engineering (MSBAE)

Department

Biological and Agricultural Engineering

Document Type

Thesis

Abstract

Ohmic heating has been shown to affect the drying rate and texture of foods. This research was designed to determine the effect of ohmic heating on rehydration, color and texture properties of sweet potatoes. Three combinations: 60Hz, 40V, 60Hz, 60V and 1Hz, 40V were applied to ohmically heat sweet potato cubes. The ohmic treated cubes and untreated cubes or controls were stored for six days in four different %relative humidities of 11.15%, 32.73%, 57.70% and 75.32%. Results showed that there was no significant difference in the rehydration properties of ohmic treated samples and control samples. The % moisture gain varied between a minimum of 0.1% and a maximum of 40.7% in the case of ohmically treated samples and 0.71% to 32.41% for control samples. The color lightness values increased with increase in storage time for both ohmically treated and control samples. The 60Hz, 40V ohmically treated samples had less increase compared to control samples. The degree of redness (a*) and degree of yellowness (b*) values were significantly higher for ohmically treated samples during storage. A significant loss of color pigments into rehydrating water was observed during rehydration for ohmically treated samples. The 60Hz, 40V treated samples retained color and appearance compared to other treatments. Texture analysis showed that the ohmic treated samples (60H, 60V) had higher hardness, springiness and chewiness values than the control samples. At lower humidities the firmness or hardness values increased with increase in storage time. Positive correlations were obtained between the moisture content of the samples after rehydration and the hardness and chewiness values. This study demonstrated that ohmic heating played a pivotal role in retaining rehydration properties, color attributes and some of the texture attributes of the sweet potato samples when appropriate combinations of frequency and electrical field strength were used.

Date

2004

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Marybeth Lima

Included in

Engineering Commons

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