Previous studies (Pandit et al., 2007a) revealed that cold spots
(obtaining the least thermal processing) located in the middle layer
of the sample. This was caused by the limitations of the microwave
power penetration and heat conduction. In this study, only the
heating patterns of the middle layer in the MW treated WPG samples
were analyzed (Fig. 8). Red and blue colors in two cylindrical
samples served as the minimum and maximum values for the color
scale used to analyze digital color images of the microwave treated
WPG samples. Red represents the highest color value (255) for
WPG samples saturated with chemical maker M-2; and blue de-
fines the lowest color value (0) to fresh WPG samples. Although
having different shapes, being placed at different positions and
sealed in trays with different amounts of gravy, the four WPG samples
had similar heating patterns during the MW process. More
intensive heating occured at the central area than at the areas close
to the front and rear edges of the sample. Heating patterns were
repeatable among the experimental replicates. The lowest and
highest color value regions were defined as the cold spot and hot
spot, respectively.
The cold spots were located at the points 18 mm away from the
front and rear edges of the sample tray. The specified cold spots
were considered as the ones of the pre-shrunk sliced beef in gravy,
since the WPG and the beef matched each other with dielectric
properties and had similar heating behavior in MW processing.
The location of cold spot in a real food was validated by Pandit
(2006), using a number of fiber-optic temperature sensors, to be
the same location of cold spot pre-determined inside the model
food
Previous studies (Pandit et al., 2007a) revealed that cold spots
(obtaining the least thermal processing) located in the middle layer
of the sample. This was caused by the limitations of the microwave
power penetration and heat conduction. In this study, only the
heating patterns of the middle layer in the MW treated WPG samples
were analyzed (Fig. 8). Red and blue colors in two cylindrical
samples served as the minimum and maximum values for the color
scale used to analyze digital color images of the microwave treated
WPG samples. Red represents the highest color value (255) for
WPG samples saturated with chemical maker M-2; and blue de-
fines the lowest color value (0) to fresh WPG samples. Although
having different shapes, being placed at different positions and
sealed in trays with different amounts of gravy, the four WPG samples
had similar heating patterns during the MW process. More
intensive heating occured at the central area than at the areas close
to the front and rear edges of the sample. Heating patterns were
repeatable among the experimental replicates. The lowest and
highest color value regions were defined as the cold spot and hot
spot, respectively.
The cold spots were located at the points 18 mm away from the
front and rear edges of the sample tray. The specified cold spots
were considered as the ones of the pre-shrunk sliced beef in gravy,
since the WPG and the beef matched each other with dielectric
properties and had similar heating behavior in MW processing.
The location of cold spot in a real food was validated by Pandit
(2006), using a number of fiber-optic temperature sensors, to be
the same location of cold spot pre-determined inside the model
food
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