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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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