Food Protection Trends - November/December 2017 - 417

and L. monocytogenes (P < 0.05) (Table 2). Breidt et al. (4)
found that thermal inactivation rates of E. coli O157:H7 and
L. monocytogenes in pickle brine (pH 4.1) were identical,
while S. enterica was significantly less heat tolerant. Similarly,
Mazzotta (16) found that, in heated fruit juices (pH 3.9),
S. enterica was heat sensitive while E. coli O157:H7 was
heat resistant. Acidification of a product reduces the heat
resistance of vegetative cells and reduces the possibility of
recovery from sub-lethal injury (24). In acidified tomato
purée samples, all three pathogens were significantly more
heat tolerant when purée was acidified with citric acid rather
than with acetic acid (P < 0.05; Table 2). When tomato
purée was acidified to pH 3.8 with acetic acid rather than
with citric acid, the average D54°C -values were 7.34 min, 8.53
min, and 5.19 min lower for E. coli O157:H7, S. enterica,
and L. monocytogenes, respectively. In heated cucumber
purée, Bae et al. also found that E. coli O157:H7, S. enterica
and L. monocytogenes were more resistant to citric acid than
to acetic acid (3). The antimicrobial effects of citric and
acetic acid are dependent on their pKa values (23). Acetic
acid (pKa 4.76) is a stronger acid than citric acid, which is a
triprotic acid (pKa1 3.13, pKa2 4.77, pKa3 6.39). In acidified
tomato-based foods with pH 4.5 and below, acetic acid has
a greater proportion of undissociated acid than citric acid
has, and acetic acid is more likely than citric acid to diffuse
into the cell, lower cytoplasmic pH, and inhibit metabolic
reactions (1, 17). While this phenomenon may at least
partially explain our findings, our experimental design
was aimed only at achieving a target pH-value and did not
take into account either buffering capacity of the system
or actual quantity of acid added. For industrial food safety
applications, it is advantageous to use organic acids with
a pK a near the pH of the food environment. However, the
amount and concentration of acid required to achieve the
target pH value, the associated flavor characteristics, and
the labeling provision of an acidulant are also important
factors to consider when selecting acidulants for product
formulation (12).
In previous work from our laboratory, pathogen inactivation in unacidified tomato purée (pH 4.5) was modeled over
a range of temperatures (52-58°C) using the re-parameterized Weibull method and the shape of the inactivation curve
(β) was evaluated, with nonlinearity frequently observed
(10). In the current study, when pathogen inactivation was
modeled in acidified tomato purée (pH 4.2 and 3.8) as
compared to unacidified purée, nonlinearity in heat inactivation curves increased from 31% to 59% of trials (data not
shown), suggesting that a nonlinear curve-fit model, such
as the Weibull method, may be of even greater utility when
establishing accurate thermal processing parameters in low
pH food systems.
Using data derived from a cucumber juice medium,
Breidt et al. (6) calculated thermal processing parameters for pathogen destruction in acidified cucumber juice

across a wide range of potential processing temperatures
(60.6-82.2°C/141-180°F) and showed that L. monocytogenes
was more heat resistant than E. coli O157:H7 and S. enterica
at temperatures below 74°C (166°F), but E. coli O157:H7
was the most heat resistant at temperatures above 74°C. The
present work found that when 5-log reduction values were
plotted against a wide range of typical processing temperatures, data lines for E. coli O157:H7 and L. monocytogenes
intersected at 65°C; E. coli O157:H7 was the most heatresistant pathogen at temperatures below 65°C (149°F), but
L. monocytogenes was the most heat resistant above 65°C
(Fig. 2). While the physiological explanation for this difference in z-values between the two pathogens is not completely
understood, the difference in z-values is important to consider when calculating processing time/temperature combinations. Therefore, to establish a single set of parameters that
ensure lethality of vegetative pathogens across a wide range
of relevant temperatures, a straight line was created that
ensured at least a 5-log pathogen reduction across all temperatures. The linear equation that defined the straight line was
used to generate a table of calculated time-temperature pairs
(Table 5) that would ensure at least a 5-log reduction for all
pathogens tested, similar to the method of Breidt et al. (6).
Processors of tomato-based acidified foods should consult a
competent process authority to determine additional heating
requirements beyond the minimal recommended here, to
account for formulation effects on thermal processing, to address spoilage, and/or to address destruction of acid-resistant
microbiota and other relevant factors in the establishment of
the scheduled process.
RECOMMENDATIONS
Using the re-parameterized Weibull model, we have
calculated time/temperature conditions that ensure at least
a 5-log reduction of vegetative pathogens of concern in
tomato-based acidified canned foods (pH ≤ 4.5).
* Processing time and temperature combinations were
calculated that can be applied to acidified products
with tomato as the primary ingredient/formulation
base. These recommendations support safety while
avoiding over-processing. Processors will wish to take
into account product formulation and the potential
presence of spoilage organisms in using these minimal to
establish operational processing parameters.
* Acidification of tomato-based canned foods using
citric or acetic acid will increase pathogen lethality
across all heating temperatures, with acetic acid having
greater antimicrobial activity than citric acid.
* Processing times and temperatures achieve at least
a 5-log pathogen reduction across a wide range
of anticipated processing conditions. Modeling
pathogen survival across typical commercial processing
temperatures indicated that the target organism depends
on temperature; E. coli O157:H7 had the greatest

November/December Food Protection Trends

417



Table of Contents for the Digital Edition of Food Protection Trends - November/December 2017

The Cleanliness of Resusable Water Bottles: How Contamination Levels are Affected by Bottle Usage and Cleaning Behaviors of Bottle Owners
Impact of Carcass Anatomical Location on the Microbiological Profile of Beef Trimmings
Thermal Processing Parameters to Ensure a 5-log Reduction of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in Acidified Tomato-based Foods
Experimental Evaluation of Performance of Sampling Techniques for Microbiological Quantification on Carcass Services
Effect-based Analytics for Toxicological Screening - Concepts for Future Developments
Beyond the Bio - John Luchansky
PDF Highlight - Food Chemical Hazards and Food Allergy PDG
IAFP 2017 In Review
Industry Products
Coming Events
Food Protection Trends - November/December 2017 - Cover1
Food Protection Trends - November/December 2017 - Cover2
Food Protection Trends - November/December 2017 - 385
Food Protection Trends - November/December 2017 - 386
Food Protection Trends - November/December 2017 - 387
Food Protection Trends - November/December 2017 - 388
Food Protection Trends - November/December 2017 - 389
Food Protection Trends - November/December 2017 - 390
Food Protection Trends - November/December 2017 - 391
Food Protection Trends - November/December 2017 - The Cleanliness of Resusable Water Bottles: How Contamination Levels are Affected by Bottle Usage and Cleaning Behaviors of Bottle Owners
Food Protection Trends - November/December 2017 - 393
Food Protection Trends - November/December 2017 - 394
Food Protection Trends - November/December 2017 - 395
Food Protection Trends - November/December 2017 - 396
Food Protection Trends - November/December 2017 - 397
Food Protection Trends - November/December 2017 - 398
Food Protection Trends - November/December 2017 - 399
Food Protection Trends - November/December 2017 - 400
Food Protection Trends - November/December 2017 - 401
Food Protection Trends - November/December 2017 - 402
Food Protection Trends - November/December 2017 - Impact of Carcass Anatomical Location on the Microbiological Profile of Beef Trimmings
Food Protection Trends - November/December 2017 - 404
Food Protection Trends - November/December 2017 - 405
Food Protection Trends - November/December 2017 - 406
Food Protection Trends - November/December 2017 - 407
Food Protection Trends - November/December 2017 - 408
Food Protection Trends - November/December 2017 - Thermal Processing Parameters to Ensure a 5-log Reduction of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in Acidified Tomato-based Foods
Food Protection Trends - November/December 2017 - 410
Food Protection Trends - November/December 2017 - 411
Food Protection Trends - November/December 2017 - 412
Food Protection Trends - November/December 2017 - 413
Food Protection Trends - November/December 2017 - 414
Food Protection Trends - November/December 2017 - 415
Food Protection Trends - November/December 2017 - 416
Food Protection Trends - November/December 2017 - 417
Food Protection Trends - November/December 2017 - 418
Food Protection Trends - November/December 2017 - Experimental Evaluation of Performance of Sampling Techniques for Microbiological Quantification on Carcass Services
Food Protection Trends - November/December 2017 - 420
Food Protection Trends - November/December 2017 - 421
Food Protection Trends - November/December 2017 - 422
Food Protection Trends - November/December 2017 - 423
Food Protection Trends - November/December 2017 - 424
Food Protection Trends - November/December 2017 - 425
Food Protection Trends - November/December 2017 - 426
Food Protection Trends - November/December 2017 - 427
Food Protection Trends - November/December 2017 - 428
Food Protection Trends - November/December 2017 - 429
Food Protection Trends - November/December 2017 - Effect-based Analytics for Toxicological Screening - Concepts for Future Developments
Food Protection Trends - November/December 2017 - 431
Food Protection Trends - November/December 2017 - 432
Food Protection Trends - November/December 2017 - 433
Food Protection Trends - November/December 2017 - 434
Food Protection Trends - November/December 2017 - 435
Food Protection Trends - November/December 2017 - 436
Food Protection Trends - November/December 2017 - 437
Food Protection Trends - November/December 2017 - Beyond the Bio - John Luchansky
Food Protection Trends - November/December 2017 - 439
Food Protection Trends - November/December 2017 - 440
Food Protection Trends - November/December 2017 - PDF Highlight - Food Chemical Hazards and Food Allergy PDG
Food Protection Trends - November/December 2017 - 442
Food Protection Trends - November/December 2017 - 443
Food Protection Trends - November/December 2017 - 444
Food Protection Trends - November/December 2017 - IAFP 2017 In Review
Food Protection Trends - November/December 2017 - 446
Food Protection Trends - November/December 2017 - 447
Food Protection Trends - November/December 2017 - 448
Food Protection Trends - November/December 2017 - 449
Food Protection Trends - November/December 2017 - 450
Food Protection Trends - November/December 2017 - 451
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Food Protection Trends - November/December 2017 - 453
Food Protection Trends - November/December 2017 - 454
Food Protection Trends - November/December 2017 - 455
Food Protection Trends - November/December 2017 - 456
Food Protection Trends - November/December 2017 - 457
Food Protection Trends - November/December 2017 - 458
Food Protection Trends - November/December 2017 - 459
Food Protection Trends - November/December 2017 - 460
Food Protection Trends - November/December 2017 - 461
Food Protection Trends - November/December 2017 - 462
Food Protection Trends - November/December 2017 - 463
Food Protection Trends - November/December 2017 - 464
Food Protection Trends - November/December 2017 - 465
Food Protection Trends - November/December 2017 - 466
Food Protection Trends - November/December 2017 - 467
Food Protection Trends - November/December 2017 - 468
Food Protection Trends - November/December 2017 - 469
Food Protection Trends - November/December 2017 - 470
Food Protection Trends - November/December 2017 - 471
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Food Protection Trends - November/December 2017 - 473
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Food Protection Trends - November/December 2017 - 475
Food Protection Trends - November/December 2017 - 476
Food Protection Trends - November/December 2017 - 477
Food Protection Trends - November/December 2017 - 478
Food Protection Trends - November/December 2017 - 479
Food Protection Trends - November/December 2017 - 480
Food Protection Trends - November/December 2017 - 481
Food Protection Trends - November/December 2017 - 482
Food Protection Trends - November/December 2017 - 483
Food Protection Trends - November/December 2017 - 484
Food Protection Trends - November/December 2017 - 485
Food Protection Trends - November/December 2017 - 486
Food Protection Trends - November/December 2017 - 487
Food Protection Trends - November/December 2017 - 488
Food Protection Trends - November/December 2017 - 489
Food Protection Trends - November/December 2017 - 490
Food Protection Trends - November/December 2017 - 491
Food Protection Trends - November/December 2017 - 492
Food Protection Trends - November/December 2017 - 493
Food Protection Trends - November/December 2017 - 494
Food Protection Trends - November/December 2017 - 495
Food Protection Trends - November/December 2017 - 496
Food Protection Trends - November/December 2017 - 497
Food Protection Trends - November/December 2017 - 498
Food Protection Trends - November/December 2017 - 499
Food Protection Trends - November/December 2017 - 500
Food Protection Trends - November/December 2017 - 501
Food Protection Trends - November/December 2017 - 502
Food Protection Trends - November/December 2017 - 503
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Food Protection Trends - November/December 2017 - 505
Food Protection Trends - November/December 2017 - 506
Food Protection Trends - November/December 2017 - 507
Food Protection Trends - November/December 2017 - 508
Food Protection Trends - November/December 2017 - 509
Food Protection Trends - November/December 2017 - 510
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Food Protection Trends - November/December 2017 - 513
Food Protection Trends - November/December 2017 - 514
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Food Protection Trends - November/December 2017 - 517
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Food Protection Trends - November/December 2017 - 519
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Food Protection Trends - November/December 2017 - 523
Food Protection Trends - November/December 2017 - 524
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Food Protection Trends - November/December 2017 - 529
Food Protection Trends - November/December 2017 - 530
Food Protection Trends - November/December 2017 - 531
Food Protection Trends - November/December 2017 - 532
Food Protection Trends - November/December 2017 - 533
Food Protection Trends - November/December 2017 - Industry Products
Food Protection Trends - November/December 2017 - 535
Food Protection Trends - November/December 2017 - 536
Food Protection Trends - November/December 2017 - 537
Food Protection Trends - November/December 2017 - 538
Food Protection Trends - November/December 2017 - 539
Food Protection Trends - November/December 2017 - 540
Food Protection Trends - November/December 2017 - 541
Food Protection Trends - November/December 2017 - 542
Food Protection Trends - November/December 2017 - 543
Food Protection Trends - November/December 2017 - Coming Events
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Food Protection Trends - November/December 2017 - Cover4
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