4. Conclusions
A microwave (MW) sterilization process for sliced beef in gravy
prepackaged in 7-oz polymeric trays was developed in this
study. For processing schedule development, sliced beef was
pre-treated for 4 min in boiling water with 0.5% salt before processing
to limit possible movement of samples inside trays and
make it possible to monitor temperatures at cold spots. Whey
protein gel (35% Whey Alacen 878, 1% D-ribose, 0% salt, and 64%
water) was chosen as a model food to emulate the pre-treated
sliced beef for heating pattern and cold spot determination. The
model and real foods had matched dielectric properties. Cold
spots were determined to be 18 mm away from the front and rear
edges in the middle layer of the tray using a chemical makeraided
computer vision method. Processing schedules to achieve
different lethality levels (F0 = 3, 6, and 12 min) were established
for treatment of the pre-cooked beef in gravy in 7-oz trays with
the pilot-scale MW sterilization system developed at Washington
State University. The developed processing schedules were veri-
fied by inoculated pack studies using C. sporogenes PA 3679
spores. The results suggested that the 915-MHz single-mode
MW sterilization technology was effective for processing of the
inhomogeneous food. The techniques provided in this study
may be used for developing MW sterilization processes for other
packaged inhomogeneous foods, such as fish in gravy in pouches
and chicken meat in gray in trays. The engineering data collected
in this study could be used for scaling-up the MW system for
industrial application.
4. ConclusionsA microwave (MW) sterilization process for sliced beef in gravyprepackaged in 7-oz polymeric trays was developed in thisstudy. For processing schedule development, sliced beef waspre-treated for 4 min in boiling water with 0.5% salt before processingto limit possible movement of samples inside trays andmake it possible to monitor temperatures at cold spots. Wheyprotein gel (35% Whey Alacen 878, 1% D-ribose, 0% salt, and 64%water) was chosen as a model food to emulate the pre-treatedsliced beef for heating pattern and cold spot determination. Themodel and real foods had matched dielectric properties. Coldspots were determined to be 18 mm away from the front and rearedges in the middle layer of the tray using a chemical makeraidedcomputer vision method. Processing schedules to achievedifferent lethality levels (F0 = 3, 6, and 12 min) were establishedfor treatment of the pre-cooked beef in gravy in 7-oz trays withthe pilot-scale MW sterilization system developed at WashingtonState University. The developed processing schedules were veri-fied by inoculated pack studies using C. sporogenes PA 3679spores. The results suggested that the 915-MHz single-modeMW sterilization technology was effective for processing of theinhomogeneous food. The techniques provided in this studymay be used for developing MW sterilization processes for otherpackaged inhomogeneous foods, such as fish in gravy in pouchesand chicken meat in gray in trays. The engineering data collectedin this study could be used for scaling-up the MW system forindustrial application.
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