180 ± 1.0 g (100 ± 0.5 g beef, 80 ± 0.5 g gravy, 12–13 mm in thickness).
In filling the tray, about 1/2 of the gravy was evenly spread
on the bottom of the tray, then the pre-treated beef was placed on
the gravy, the rest of the gravy was spread on the top and edges
(Fig. 4). The beef sample was placed close to the front edge of
the tray, and a support frame cut from a polymeric tray was used
to keep the beef sample from moving inside the tray. A thermowell
made from polyimide tubing (MicroLumen Inc., Tampa, FL)
was pre-fixed through the tray wall and placed between the two
central beef slices. The thermo-well was used for inserting a fi-
ber-optic temperature sensor to the cold spot pre-determined with
the model food WPG. Sample trays were sealed with a lick film in a
custom tray sealer for 3 s at 385 F and under 16-in. Hg vacuum.
The trays were conditioned a couple of hours in a low-temperature
storage room (3 ± 1 C) before testing.
To determine processing schedules, experiments were conducted
by operating the system manually. Five trays were treated
in each run. A fiber-optic probe monitored the temperature at the
cold spot in the second tray. The temperature reading and corresponding
F0 were shown on the computer screen during processing.
Trials were conducted with different processing conditions
to develop a schedule for processing samples to reach an expected
final F0 value, 3 min, at the cold spot. In processing using the selected
schedule for F0 = 3 min, sample trays were firstly pre-heated
to 60 C at the cold spot with 122 C water, moved at an adequate
speed through the MW heating cavities for the cold spot of the food
to reach 121 C by the combination of 2.7 kW MW power and hot
water, then held to make F0 to reach around 1 min, and finally
cooled down to 75 C by tap water to gain additional F0 of about
2 min. The schedules for larger F0 values were developed by
extending the holding time based on the schedule for F0 = 3 min.
2.
180 ± 1.0 g (100 ± 0.5 g beef, 80 ± 0.5 g gravy, 12–13 mm in thickness).In filling the tray, about 1/2 of the gravy was evenly spreadon the bottom of the tray, then the pre-treated beef was placed onthe gravy, the rest of the gravy was spread on the top and edges(Fig. 4). The beef sample was placed close to the front edge ofthe tray, and a support frame cut from a polymeric tray was usedto keep the beef sample from moving inside the tray. A thermowellmade from polyimide tubing (MicroLumen Inc., Tampa, FL)was pre-fixed through the tray wall and placed between the twocentral beef slices. The thermo-well was used for inserting a fi-ber-optic temperature sensor to the cold spot pre-determined withthe model food WPG. Sample trays were sealed with a lick film in acustom tray sealer for 3 s at 385 F and under 16-in. Hg vacuum.The trays were conditioned a couple of hours in a low-temperaturestorage room (3 ± 1 C) before testing.To determine processing schedules, experiments were conductedby operating the system manually. Five trays were treatedin each run. A fiber-optic probe monitored the temperature at thecold spot in the second tray. The temperature reading and correspondingF0 were shown on the computer screen during processing.Trials were conducted with different processing conditionsto develop a schedule for processing samples to reach an expectedfinal F0 value, 3 min, at the cold spot. In processing using the selectedschedule for F0 = 3 min, sample trays were firstly pre-heatedto 60 C at the cold spot with 122 C water, moved at an adequatespeed through the MW heating cavities for the cold spot of the foodto reach 121 C by the combination of 2.7 kW MW power and hotwater, then held to make F0 to reach around 1 min, and finallycooled down to 75 C by tap water to gain additional F0 of about2 min. The schedules for larger F0 values were developed byextending the holding time based on the schedule for F0 = 3 min.2.
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