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									Session 17H-19; Abstract #25657
                                                                Influence of Product-entrapped Air and Venting on Lethal Effect in Model Domestic Pressure Canner                                                                                                              Studies 2

                                                                                                 P. Wambura 1, J.C Anderson and L.T. Walker 1
                                                                       1Dept. of Food & Animal Sciences, Alabama A&M Univ. P.O Box 1628, Normal, AL 35762-1628
                            2This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.




                                                                                                                                                                                    Table 3. Percentages of Lethal Effect of Points outside of Containers based                  EXPERIMENTAL SETUP
                            ABSTRACT                                                    MATERIAL AND METHODS (continued)                                                            upon Temperature Data Relative to Pressure Data
 Effects of entrapped air during thermal processing on lethal effect             Thermocouple output were recorded through the Omega TempScan                                                                   Timed Processing (31 Min.) Process from start to "Finished"
    were evaluated in three domestic canners with seven (7) quart                 1000 data logger.                                                                                              2
                                                                                                                                                                                     Regression r value                  0.2172                         0.2297
    mason jars. Entrapped air volumes in ceramic-bead products were              Reference lethal effects were determined by monitoring pressure                                                          DF F-value Pr > F                 F-value Pr > F
    established with various fillings of water into dry product matrix.           development with a transducer and calculating lethal effect with
                                                                                  conversion of pressure units to temperature by the Clausius-Clapeyron                              Model significance     12   26.75 <.0001 ****              28.75 <.0001 ****
    Alternate periods of venting included none, 5, 10, and 15 min.
                                                                                  equation.
    Lethal effects were determined using thermocouples positioned                                                                                                                    FACTORS               DF Coded t-value                  Coded t-value
    near the bottom, middle, and top of model product and others                 Thermocouple and pressure transducer outputs were recorded through                                 Intercept             1    107.35  30.13      ****       109.26   31.33      ****
                                                                                  the Omega TempScan 1000 data logger. Displaying and recording of
    outside the jars. Process pressure was monitored throughout each              the data logger temperatures and pressures were facilitated with a                                 Vent                  1     -2.23   -0.57     N.S.         -1.61    0.11     N.S.
    of the 72 runs.                                                               personal computer and the Omega TempWin software.                                                  Water                 1      2.66   -5.38     ****          3.57   -5.47     ****
 Two canners (All American and Mirro models) were continuously                                                                                                                       Vent x Vent           1     -0.63   -0.56     N.S.         -2.40   -2.22     *
                                                                                 The beginning of venting time was noted when a constant stream of                                  Vent x Water          1      0.33     0.4     N.S.          1.44    1.82     N.S.
    vented during processes while the third (National Presto) was not             gases were indicated flowing rapidly out of the vent tube and continued
                                                                                                                                                                                     Water x Water         1      6.45    6.06     ****          6.23    6.13     ****
    — but was vented de facto until lid lock moved up under influence             until the vent tube was capped off.
                                                                                                                                                                                     All American          1      5.25    3.59     ***           1.31    0.94     N.S.
    of escaping gases. Nevertheless, venting times and lack of                   Start of processing was taken as the time when the cooker was brought                              Mirro                 1      9.29    6.38     ****          7.39    5.32     ****
    continuous venting demonstrated little impact. The higher lethal              up to pressure indicated when the calibrated-weight gauges would                                   National Presto       0         0 .           N.S.             0 .           N.S.
    effects were noted when least product-entrapped air was modeled.              jiggle at approximately 70 kPa or when the Presto dial gauge reached                               Between               1     -2.38   -1.83     N.S.         -1.96   -1.58     N.S.
    Differences were noted between pressure processes monitored by                the approximate 70 kPa mark (indicated as 10 psi). 31-minute processes                             Dome                  1    -16.17 -10.39      ****        -15.22 -10.25      ****           DISCUSSION
    dial gauge versus calibrated weighted-devices with more variation             were followed by slow cooling with the heat turned off.                                            Dome (not vented)     1     -5.54   -2.47     *            -5.83   -2.73     **
    of the dial gauge system and greater lethal effect due to manual                                                                                                                 Continuous Vent       1    -24.05 -12.21      ****        -22.30 -11.86      ****            Direct thermocouple data transformations to lethal effect analyzed by the
                                                                                 Lethalities (Fo-values) were calculated using the General Method (Tref =                           Non-continuous Vent   1    -12.30   -4.43     ****        -12.48   -4.71     ****             RSREG procedure displayed no design factor significances apart from the
    control basis. Besides lethal effect differences with product-                121.1oC). Kinetic parameter for C. botulinum spore inactivation (Z =                               Girdle                0         0 .           N.S.             0 .           N.S.             unary data of canner model and positions in the jars (Table 1).
    entrapped air, the three positions of thermocouples registered least          10Co) was selected. Relative lethal effects were noted as percentage of                                                                                                                         However, results from this data displayed non-significant differentiation
    thermal effect at top portions of the jars. All manufacturers of              the pressure-based lethal effects.                                                                                                                                                               based on the three pressure canners (as desired) only when the data values
    domestic canning kettles emphasize periods of venting to eliminate                                                                                                              Table 4. Percentages of Lethal Effect of Points inside Containers based upon
                                                                                                             31    (Ti  T ref )                                                                                                                                                   were made relative to pressure data (Table 2).
    air in the canners prior to the timed processing but this study only
                                                                                                     Fo =  10
                                                                                                            i 1
                                                                                                                        Z
                                                                                                                                   t i                                             Temperature Data Relative to Pressure Data Contrasting Categories of Venting Time             When the data were considered relative to pressure, a linear dependence
    reflected suppressed lethal effects when containers manifested                                                                                                                                                                                                                 upon water level suggested improved lethal effects whenever the air-
    product-entrapped air.                                                                                                                                                                                      Timed Processing (31 Min.) Process from start to "Finished"        entrapped challenge for process was reduced. -- Prediction by this regression
                                                                                Statistics                                                                                                      2                                                                                  is an ~ 23% [2 X ~ 11.5 coded term] increase of lethal effect from the most
                                                                                                                                                                                    Regression r value                   0.4752                         0.4622
                                                                                Three-by-three design space factors (venting times and water fill levels)                                                                                                                          air-entrapped model product to the least air-entrapped model product.
                                                                                                                                                                                                           DF F-value Pr > F                 F-value Pr > F
                       INTRODUCTION                                                were regressed with the RSREG procedure employing co-variables
                                                                                                                                                                                    Model significance      8    52.29 <.0001 ****              49.63 <.0001 ****                 Positions in the jars were basis for differing lethal effects with the top
 Consumption of under-processed food constitutes a significant risk of             of unary types for the three canners and the thermocouple positions                                                                                                                             position experiencing the least while the bottom indicated as 5% (3% for
    food-borne illness. It is estimated that food-borne diseases cause             using the SAS for Windows software (Copyright (c) 1999-2001 by                                                                                                                                 total process) and the middle position indicated as 6% (7% for total process)
                                                                                                                                                                                    FACTORS                DF Coded t-value                  Coded t-value
    approximately 76 million illnesses, 325,000 hospitalizations, and              SAS Institute Inc., Cary, NC).                                                                                                                                                                  greater than the top position (Table 2).
                                                                                                                                                                                    Intercept              1    53.18     6.42 ****             61.46    11.3 ****                When only the points monitored outside the jars were considered, no
    5,000 deaths in the United States each year (Mead et al., 1999).                                                                                                                water                  1    11.94     3.43 ***              10.87    1.97 *
 Air is a poor heat transfer fluid since it has low specific heat and thermal                                                                                                                                                                                                      significant departure of lethal effect compared to the ―Girdle‖ sites strapped
                                                                                RESULTS AND DISCUSSION                                                                              water*water            1     -0.78   -0.71 N.S.              0.72    0.71 N.S.                 to the jars was evident for the points suspended in spaces ―Between‖ the jars
    conductivity. Recommendations have been published seeking to                Table 1. Lethal Effects in Minutes based upon Direct Thermocouple                                   All American           1     -1.02   -0.82 N.S.             -1.77   -1.53 N.S.                 (Table 3).
    ensure adequate venting of air from the pressure canner in manners             Temperature Data                                                                                 Mirro                  1      2.31    1.82 N.S.              2.28    1.94 N.S.                The points in the lid dome area whether by the vent or away were much less
    similar to commercial practices where particularly for flexible                                                                                                                 National Presto        0         0 .       N.S.                 0 .       N.S.                 exhibiting of lethal effect (Table 3).
    pouches in stacks the call is to remove air from container external                                     Timed Processing (31 Min.) Process from start to "Finished"
                                                                                                                                                                                    Bottom                 1      5.05    4.02 ****              2.49    2.15 *                   Differences were noted for the continuously vented systems of ~ 22 – 24%
                                                                                            2
    contact surfaces (Ramaswamy and Grabowski, 1996).                           Regression r value                    0.4285                                0.3021
                                                                                                                                                                                    Middle                 1      5.85    4.36 ****              5.95     4.8 ****                 less at the vent area and ~ 15 – 16% less in the space away from the vent and
 Several studies that have been carried out on evaluating the effect of air                          DF    F Value Pr > F                        F Value Pr > F
                                                                                                                                                                                    Top                    0         0 .       N.S.                 0 .       N.S.                 appeared to represent a reduced transfer of heat in areas away from boiling
    entrapped in flexible packages (retortable pouches) reported that air       Model significance    9       28.83 <.0001 ****                     16.64 <.0001 ****                                                                                                              water within which the jars were heated (Table 3).
                                                                                                                                                                                    Not Vented             1     -6.28   -4.98 ****             -3.99   -3.42 ***
    leads to decrease in the heating rate, reduction in heat transfer rate,                                                                                                                                                                                                       Greater depression of thermal effect for points by the vent may reflect a
                                                                                FACTORS              DF    Coded t-value                         Coded t-value                      Vented 5 minutes       1     -3.33   -2.64 **               -0.81   -0.69 N.S.
    and reduction in the accumulated lethality (Weintraub et al., 1989;                                                                                                                                                                                                            presence of air (that reduced the water vapor pressure and its associated
                                                                                Intercept            1         5.78    3.54               ***        9.56    4.16       ****        More than 5 min.       0         0 .       N.S.                 0 .       N.S.
    Campbell and Ramaswamy, 1992; Ramaswamy and Grabowski,                                                                                                                                                                                                                         temperature equivalent).
                                                                                Vent                 1         0.34    0.85               N.S.       0.00    1.69       N.S.
    1996; Brennan et al., 1976).                                                                                                                                                                                                                                                  Evidences by the coded water term of the greater mass of water enabling
                                                                                Water                1         1.19    0.59               N.S.       1.53   -0.88       N.S.        Notes: **** indicates significance p<0.0001; *** indicates significance p<0.005;
 The main objectives of this study were to contrast canner types and to                                                                                                                                                                                                            greater heat capacity to retain temperature in the vicinity of the jars by the
                                                                                Vent x Vent          1         0.05     0.3               N.S.      -0.09   -0.32       N.S.        ** indicates significance p<0.01; * indicates significance p<0.05; N.S. indicates not
    evaluate temperature distributions within model product with                                                                                                                                                                                                                   ―Girdle‖ positions were seen in the regression (Table 3).
                                                                                Vent x Water         1        -0.21    -1.9               N.S.      -0.86   -4.16       ****        significant                                                                                   By three categorical terms of ―not vented‖, ―vented 5 minutes‖, and ―vented
    variation of three levels of product-entrapped air (three water-fill        Water x Water        1         0.30    1.91               N.S.       1.09    3.74       ***
                                                                                                                                                                                                                                                                                   more than 5 min.‖ the indication came through that not vented at all was
    levels) within the three pressure canners during cooking cycles             All American         1        -1.35   -7.42               ****      -1.49   -4.49       ****
    preceded by three venting schedules.                                        Mirro                1        -0.46   -2.45               *         -0.17    -0.5       N.S.        PRESSURE COOKERS USED                                                                          significantly less in lethal effect than 5 or more minutes (~4% less for the
                                                                                                                                                                                                                                                                                   full process) (Table 4).
                                                                                National Presto      0            0 .                     N.S.          0 .             N.S.
                                                                                Bottom               1         0.53    2.91               **         0.52    1.56       N.S.                                                                                                      For the shorter (31 min.) timed portion of the process by categorical groups
                MATERIAL AND METHODS                                            Middle               1         0.71    3.61               ***        1.23    3.42       ***                                                                                                        the longer vent times were also ~3% more effective than the 5 min. vent
                                                                                                                                                                                                                  TRANSDUCER                                                       time (Table 4).
  Temperature distribution profiles on the central axes of one-quart           Top                  0            0 .                     N.S.          0 .             N.S.
   mason jars (946 ml) filled with ceramic beads and three (3) water
   level fills were conducted with three domestic pressure canners (an
   All American model 921, a Mirro model 0522, and a National Presto            Table 2. Percentages of Lethal Effect of Points inside the Jars based
   model 01780).                                                                   upon Temperature Data Relative to Pressure Data
                                                                                                                                                                                                                                                                                 CONCLUSION
                                                                                                                                                                                                                                                                                  Manufacturers of domestic canning kettles emphasize periods of venting (7
  Temperature distribution during venting was measured by copper-                          2
                                                                                                            Timed Processing (31 Min.)           Process from start to "Finished"
                                                                                                                                                                                                                                                                                   to 10 min.) to eliminate air in the canners prior to the timed processing.
   constantan thermocouples placed in specific location in each.                Regression r value                   0.4336                                  0.4185
                                                                                                     DF   F-value Pr > F                         F-value   Pr > F                                                                                                                 Five minutes venting was a good as 10 min. in this study.
  Seven (7) Ecklund Harrison thermocouples were placed into the                Model significance    9      29.43 <.0001 ****                       27.67 <.0001 ****                                                                                                            Published recommendations appeared to give adequate margins of safety.
   seven (7) mason jars to monitor temperature profile development                                                                                                                                                                                                                Nevertheless, this synthetic product model did not represent the full range of
   inside the jars.                                                             FACTORS              DF   Coded    t-value                       Coded     t-value                                                                                                                 potential foods that could be considered to qualify the recommendation.
  The twelve (12) bare thermocouples and 5 more Ecklund-Harrison               Intercept            1       52.19       1.76             N.S.      60.86         4.9   ****
   models were placed in specific locations around the inside of the            Vent                 1        2.39       0.47             N.S.        0.42       0.95   N.S.
   cooker to monitor temperature development inside the pressure                Water                1       11.48       3.99             ****      10.34        2.11   *                                                                                                        SELECTED REFERENCES
   cooker.                                                                      Vent x Vent          1        0.48       0.37             N.S.       -0.41      -0.34   N.S.
                                                                                                                                                                                                                                                                                  Brennan, J.G., Butlers, J.R., Cowell, N.D., and Lilly, A.E.V. 1976. Food
                                                                                Vent x Water         1       -1.07      -1.16             N.S.       -1.42      -1.66   N.S.
  Three levels of product-entrapped air were conducted with each of the        Water x Water        1       -2.17      -1.66             N.S.        0.58       0.48   N.S.
                                                                                                                                                                                                                                                                                   Engineering Operations, Second edition, Applied Science Publisher Limited,
   All American, Mirro and National Presto pressure canners.                    All American         1        0.38       0.25             N.S.       -0.52      -0.38   N.S.                                                                                                       London.
                                                                                                                                                                                                                                                                                  Campbell, S. and Ramaswamy, H.S. 1992. Heating Rate, Lethality and Cold
  Jars (946ml) were filled with a 910g of dried ceramic beads.                 Mirro                1        1.60       1.04             N.S.        1.44       1.02   N.S.
                                                                                National Presto      0           0    .                   N.S.           0    .         N.S.                                                                                                       Spot Location in Air-Entrapped Retort Pouches During Over-Pressure
  Jars were filled in turn with water to one of the three levels (120, 240     Bottom               1        5.16       3.42             ***         2.96       2.13   *                                                                                                          Processing. Journal of Food Science, 57: 485-489.
   and 360g) at room temperature and closed with lids and rings before                                                                                                                                                         National                                           Mead, P.S., Slutsker, L., Dietz, V., McCaig, L.F., Bresee, J.S., Shapiro, C.,
                                                                                Middle               1        6.44       3.97             ****        7.01       4.69   ****                                                                              Mirro
   being loaded into the cookers. Rings were not severely tightened so as       Top                  0           0    .                   N.S.           0    .         N.S.                  All American                     Presto                                              Griffin, P.M and Tauxe, R.V. 1999. Food-Related Illness and Death in the
   to allow air to escape.                                                                                                                                                                                                                                                         United States. Journal of Emerging Infectious Diseases, 5 (10): 607-625
  Experiments were conducted in random orders with venting times of            Notes: **** indicates significance p<0.0001; *** indicates significance p<0.005;                                                                                                                  Ramaswamy, H.S. and Grabowski, S. 1996. Influence of Entrapped Air on the
   5, 10, and 15 min. Another series of experiments were done with no              ** indicates significance p<0.01; * indicates significance p<0.05; N.S. indicates                                                                                                               Heating Behavior of a Model Food Packaged in Semi-Rigid Plastic Containers
   venting throughout.                                                             not significant                                                                                                                                                                                 during Thermal Processing. Journal of Food Technology. 29: 88-93. Academic
                                                                                                                                                                                                                                                                                   Press Limited.

								
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