473:
A broken heating curve is also used in this method when dealing with different products in the same process such as chicken noodle soup in having to dealing with the meat and the noodles having different cooking times as an example. It is more complex than the simple heating curve for processing.
490:. This is usually done by thermal processing and finding ways to reduce the number of bacteria in the product. Time-temperature measurements of bacterial reduction is determined by a D-value, meaning how long it would take to reduce the bacterial population by 90% or one log
94:
that were able to survive the processing; then that these spores' presence depended on the clams' living environment; and finally that these spores would be killed if processed at 250 ˚F (121 ˚C) for ten minutes in a retort.
602:
443:
258:
470:
is the time in minutes required for the straight-line portion of the heating curve plotted semilogarithmically on paper or a computer spreadsheet to pass through a log cycle.
358:
122:. Prescott and Underwood's work was first published in late 1896, with further papers appearing from 1897 to 1926. This research, though important to the growth of
86:, a detailed assignment on what needed to be done. Prescott and Underwood worked on the problem every afternoon from late 1895 to late 1896, focusing on canned
147:) that was determined in the early 1920s. Research continued with inoculated canning pack studies that were published by the NCA in 1968.
518:
710:
697:
75:
380:
195:
452:
is the number of degrees below the retort temperature on a simple heating curve at the end of the heating period,
155:
Thermal death time can be determined one of two ways: 1) by using graphs or 2) by using mathematical formulas.
678:
126:, was never patented. It would pave the way for thermal death time research that was pioneered by Bigelow and
163:
This is usually expressed in minutes at the temperature of 250 °F (121 °C). This is designated as
290:
Prior to the advent of computers, this was plotted on semilogarithmic paper though it can also be done on
759:
170:. Each 18 °F or 10 °C change results in a time change by a factor of 10. This would be shown either as F
692:
A Complete Course In
Canning - Book II: Microbiology, Packaging, HACCP & Ingredients, 13th Edition.
705:
Pioneers in Food
Science, Volume 1: Samuel Cate Prescott - M.I.T. Dean and Pioneer Food Technologist.
131:
67:
55:
325:
63:
730:
Powers, J.J. (2000). "The Food
Industry Contribution: Preeminence in Science and in Application."
648:
which means that processing time will reduce the amount of this bacteria by a factor of 10. The D
51:
461:
is the time in minutes from the beginning of the process to the end of the heating period, and
754:
139:
59:
698:
Food and Drug
Administration (US) information on thermal death time of low-acid canned foods
83:
78:, about losses his company was suffering due to swollen and burst cans despite the newest
8:
656:
is 0.21 minute (12.6 seconds). A 12-D reduction will take 2.52 minutes (151 seconds).
675:
627:
79:
123:
103:
39:
367:= RT (Retort Temperature) − IT (Initial Temperature) and where
319:). It also measures the product temperature rather than the can temperature.
748:
668:
664:
127:
90:. They first discovered that the clams contained heat-resistant bacterial
487:
299:
291:
24:
660:
185:) is also a sterilizing effect at 1 minute at other temperatures with (
306:-axis. This simple heating curve can also determine the lag factor (
35:
727:
D.R. Heldman, Ed. New York: Marcel Dekker, Inc. pp. 1011–1013.
483:
20:
512:-values at different temperatures with its equation shown below:
505:
275:
270:
is the reference temperature, usually 250 °F (121 °C);
137:
Bigelow and Ball's research focused on the thermal death time of
119:
99:
71:
38:, producing salmonella-free feeds for animals (e.g. poultry) and
31:
671:
and is applicable to cosmetic and pharmaceutical manufacturing.
618:-value is affected by pH of the product where low pH has faster
725:
Encyclopedia of
Agricultural, Food, and Biological Engineering.
694:
Timonium, MD: CTI Publications, Inc. pp. 62–3, 71-5, 93-6.
111:
597:{\displaystyle z={\frac {T_{2}-T_{1}}{\log D_{1}-\log D_{2}}}}
482:
In the food industry, it is important to reduce the number of
679:
Computer
Integrated Food Manufacturing Center and Pilot Plant
115:
91:
87:
723:
Juneja, V.K. and L. Huang. (2003). "Thermal Death Time." In
295:
28:
734:
107:
737:
Prescott, L.M., J.P. Harley, & D.A. Klien. (1993).
741:
282:
is the slowest heat point of the product temperature.
98:
These studies prompted the similar research of canned
521:
383:
328:
198:
508:
is used to determine the time values with different
707:
Trumball, CT: Food & Nutrition Press. pp 22–28.
626:-value at an unknown temperature can be calculated
374:It is also determined in the equation shown below:
82:technology available. Sedgwick gave his assistant,
596:
438:{\displaystyle \log g=\log jI-{B_{B} \over f_{h}}}
437:
352:
252:
494:at a given temperature. This D-value reference (D
746:
253:{\displaystyle L=10^{(T-T_{\mathrm {Ref} })/z}}
720:New York: Chapman & Hall. pp. 342–6.
640:The target of reduction in canning is the 12-
633:-value at a given temperature provided the
150:
19:is how long it takes to kill a specific
711:History about Underwood Canning Company
298:would be shown on the x-axis while the
747:
718:Modern Food Microbiology, 4th Edition.
498:) point is 250 °F (121 °C).
76:Massachusetts Institute of Technology
58:, a food company founded in 1822 at
681:put Ball's formula online for use.
158:
13:
231:
228:
225:
27:. It was originally developed for
14:
771:
371:is constant for a given product.
285:
477:
353:{\displaystyle j={jI \over I}}
237:
210:
34:and has found applications in
1:
684:
622:values on various foods. The
486:in products to ensure proper
713:- Accessed October 28, 2006.
700:- Accessed November 5, 2006.
611:is temperature in °F or °C.
132:National Canners Association
7:
178:= 10 minutes (Fahrenheit).
174:= 10 minutes (Celsius) or F
10:
776:
739:Microbiology, 2nd Edition.
732:A Century of Food Science.
45:
130:from 1921 to 1936 at the
68:William Thompson Sedgwick
56:Underwood Canning Company
703:Goldblith, S.A. (1993).
64:Watertown, Massachusetts
62:and later relocated to
52:William Lyman Underwood
690:Downing, D.L. (1996).
598:
439:
354:
302:would be shown on the
254:
599:
440:
355:
255:
151:Mathematical formulas
140:Clostridium botulinum
60:Boston, Massachusetts
519:
381:
326:
196:
84:Samuel Cate Prescott
760:Microbiology terms
716:Jay, J.M. (1992).
659:This is taught in
637:-value is known.
594:
435:
350:
250:
74:department at the
17:Thermal death time
676:Purdue University
592:
433:
348:
310:) and the slope (
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181:A lethal ratio (
159:Graphical method
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124:food technology
70:, chair of the
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40:pharmaceuticals
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294:programs. The
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286:Formula method
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23:at a specific
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674:In 2001, the
672:
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646:C. botulinum,
644:reduction of
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755:Food science
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669:microbiology
665:food science
658:
654:C. botulinum
653:
645:
641:
639:
634:
630:
629:knowing the
623:
619:
615:
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608:
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509:
501:
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481:
478:Applications
472:
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315:
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145:C. botulinum
144:
138:
136:
128:C. Olin Ball
97:
49:
16:
15:
663:courses in
488:food safety
300:temperature
292:spreadsheet
25:temperature
749:Categories
685:References
661:university
579:
573:−
560:
542:−
409:−
400:
388:
217:−
50:In 1895,
36:cosmetics
21:bacterium
484:microbes
112:tomatoes
104:sardines
506:z-value
276:z-value
274:is the
134:(NCA).
120:spinach
100:lobster
72:biology
54:of the
46:History
32:canning
607:where
448:where
363:where
278:, and
263:where
118:, and
92:spores
80:retort
614:This
88:clams
667:and
652:for
296:time
116:corn
108:peas
29:food
576:log
557:log
504:or
397:log
385:log
268:Ref
189:).
176:250
172:121
751::
492:10
207:10
114:,
110:,
106:,
102:,
42:.
650:R
642:D
635:Z
631:D
624:D
620:D
616:D
609:T
587:2
583:D
568:1
564:D
550:1
546:T
537:2
533:T
526:=
523:z
510:D
502:z
496:R
467:h
463:f
458:B
454:B
450:g
429:h
425:f
419:B
415:B
406:I
403:j
394:=
391:g
369:j
365:I
346:I
342:I
339:j
333:=
330:j
316:h
312:f
308:j
304:y
280:T
272:z
265:T
246:z
242:/
238:)
232:f
229:e
226:R
221:T
214:T
211:(
203:=
200:L
187:T
183:L
168:0
165:F
143:(
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