Food or edible material: processes – compositions – and products – Processes – Packaging or treatment of packaged product
Reexamination Certificate
1998-11-06
2002-10-29
Bhat, N (Department: 1761)
Food or edible material: processes, compositions, and products
Processes
Packaging or treatment of packaged product
C426S232000, C426S233000, C426S521000, C422S003000, C422S026000, C422S109000, C422S111000, C422S307000, C422S308000
Reexamination Certificate
active
06472008
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to controllers for administering batch sterilization processes. In particular, it pertains to such a controller that provides on-line correction of a batch sterilization process when a temperature deviation occurs during the process.
BACKGROUND OF THE INVENTION
Batch sterilization systems are widely used to sterilize shelf stable food products packaged in containers. In a typical batch sterilization system, a batch of these containers is placed inside the batch sterilizer of the system. Then, the controller of the system administers the batch sterilization process that is performed by the batch sterilizer on the batch of containers.
The batch sterilization process has come-up, processing, and cooling phases. These phases deliver a total lethality F to the batch of containers over a total time interval [t
0
, t
c
] covering these phases, where t
0
is the begin time of the come-up phase and t
c
is the end time of the cooling phase. For purposes of this document, an open bracket [or] indicates that the corresponding time is included in the time interval while a closed bracket ( or ) indicates that the corresponding time is not included in the time interval. In order for the food product in the batch to be commercially sterilized, the total lethality actually delivered must satisfy a predefined target total lethality F
targtot
for the food product. The target total lethality may be set by the USDA (U.S. Department of Agriculture), the FDA (Food and Drug Administration), and/or a suitable food processing authority. Furthermore, some batch sterilization systems also include an optional requirement that the come-up and processing phases must deliver a heating lethality F to the batch over a heating time interval [t
0
, t
p
] that meets a predefined target heating lethality F
targh
for the food product, where t
p
is the end time of the processing phase. In this case, the operator sets the target heating lethality on an individual basis for each batch sterilization process.
As is well known, the lethality F delivered to the batch over a particular time interval [t
m
, t
k
] is given by the lethality equation:
Fo
=
∫
t
m
t
k
10
(
T
CS
(
t
)
-
T
REF
)
/
z
ⅆ
t
where t
m
and t
k
are respectively the begin and end times of the time interval [t
m
, t
k
], T
cs
(t) is the product cold spot time-temperature profile of the product cold spot of the batch, z is the thermal characteristic of a particular microorganism to be destroyed in the sterilization process, and T
REF
is a reference temperature for destroying the organism. Thus, the heating lethality F delivered over the heating time interval [t
0
, t
p
]is given by this lethality equation, where t
m
=t
0
and t
k
=t
p
. Similarly, the total lethality F delivered to the product cold spot over the total time interval [t
0
, t
c
] is also given by the lethality equation, but where t
k
=t
c
.
The time intervals [t
0
, t
p
] and [t
0
, t
c
] and the product cold spot time-time-temperature profile T
cs
(t) must be such that the target lethalities F
targh
and F
targtot
are met by the heating and total lethalities F over [t
0
, t
p
] and F over [t
0
, t
c
]. In order to ensure that this occurs, various mathematical simulation models have been developed for simulating the product cold spot time-temperature profile T
cs
(t) over the come-up, processing, and cooling phases. These models include those described in Ball, C. O. and Olson, F. C. W.,
Sterilization in Food Technology; Theory, Practice and Calculations
, McGraw-Hill Book Company, Inc., 1957; Hayakawa, K.,
Experimental Formulas for Accurate Estimation of Transient Temperature of Food and Their Application to thermal Process Evaluation
, Food Technology, vol. 24, no. 12, pp. 89 to 99, 1970;
Thermobacteriology in Food Processing
, Academic Press, New York, 1965; Teixeira, A. A., Innovative Heat Transfer Models: From Research Lab to On-Line Implementation in
Food Processing Automation II
, ASAE, p. 177-184, 1992; Lanoiselle, J. L., Candau, Y., and Debray E., Predicting Internal Temperatures of Canned Foods During Thermal Processing Using a Linear Recursive Model,
J Food Sci
., Vol. 60, No. 4, 1995; Teixeira, A. A., Dixon, J. R., Zahradnik, J. W., and Zinsmeister, G. E., Computer Optimization of Nutrient Retention in Thermal Processing of Conduction Heated Foods,
Food Technology,
23:137-142, 1969; Kan-Ichi Hayakawa, Estimating Food Temperatures During Various Processing or Handling Treatments,
J. of Food Science,
36:378-385, 1971; Manson, J. E., Zahradnik, J. W., and Stumbo, C. R., Evaluation of Lethality and Nutrient Retentions of Conduction-Heating Foods in Rectangular Containers,
Food Technology,
24(11):109-113, 1970; Noronha, J., Hendrickx, M., Van Loeg, A., and Tobback, P., New Semi-empirical Approach to Handle Time-Variable Boundary Conditions During Sterilization of Non-Conductive Heating Foods,
J. Food Eng.,
24:249-268, 1995; and the NumeriCAL model developed by Dr. John Manson of CALWEST Technologies, licensed to FMC Corporation, and used in FMC Corporation's LOG-TEC controller. A number of approaches have been developed for using these models to meet the target lethalities F
targh
and F
targtot
.
Referring to
FIG. 1
, a conventional approach is to use such a simulation model only for off-line (i.e., prior to administering the batch sterilization process) definition of a scheduled total time-temperature profile T
sRT
(t)
0
for the batch sterilization process. In this approach, the controller of the batch sterilization system uses the simulation model to simulate a scheduled product cold spot time-temperature profile T
cs
(t)
0
that is predicted to occur over the come-up, processing, and cooling phases. This simulation is based on a pre-defined come-up time-temperature gradient T
uRT
(t), a scheduled processing retort temperature T
pRT
0
, and a pre-defined cooling time-temperature gradient T
cRT
(t). The gradients T
uRT
(t) and T
cRT
(t) are based on heating and cooling temperature distribution tests conducted on the batch sterilizer and may include segments defined by endpoint temperatures and time durations.
The lethality equation described earlier is then used, where t
m
=t
0
and t
k
=t
p
0
, F=F
0
, and T
CS
(t)=T
CS
(t)
0
, to compute a heating lethality F
0
that is predicted to be delivered over a scheduled heating time interval [t
0
, t
p
0
] and is based on the scheduled product cold spot time-temperature profile T
CS
(t)
0
. Similarly, a total lethality F
0
that is predicted to be delivered over a scheduled total time interval [t
0
, t
c
0
] is computed based on the profile T
CS
(t)
0
using the lethality equation, except where t
k
=t
c
0
. As alluded to earlier, this is done so that the heating and total lethalities will meet the target lethalities F
targh
and F
targtot
.
By simulating the scheduled product cold spot time-temperature profile T
CS
(t)
0
and computing the scheduled heating and total lethalities F
0
over [t
0
, t
p
0
] and F
0
over [t
0
, t
c
0
] in this way, the controller defines the scheduled total time-temperature profile T
sRT
(t)
0
for which the target lethalities F
targh
and F
targtot
are satisfied. This profile T
sRT
(t)
0
includes come-up, processing, and cooling portions over scheduled come-up, processing, and cooling time intervals [t
0
, t
u
0
], (t
u
0
, t
p
0
], (t
p
0
, t
c
0
], respectively. The come-up and cooling portions comprise the portions of the gradients T
uRT
(t) and T
cRT
(t) over the corresponding scheduled come-up and cooling time intervals [t
0
, t
u
0
] and (t
p
0
, t
c
0
], respectively. Similarly, the processing portion comprises the constant scheduled processing retort temperature T
pRT
0
over the scheduled processing time interval (t
u
0
, t
p
0
]
Bhat N
FMC Technologies Inc.
Knauer Stephen M.
Mendenhall Larry
LandOfFree
Method for administering and providing on-line correction of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for administering and providing on-line correction of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for administering and providing on-line correction of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2945442