Resistance – Thermal Resistance – Thermal and Other and Other

Robert L. BuchananRobert L. BuchananDHHS Food and Drug AdministrationDHHS Food and Drug Administration

Center for Food Safety and Applied Center for Food Safety and Applied NutritionNutrition

Thermal Resistance of Thermal Resistance of E. E. sakazakii – sakazakii – Laboratory TrialsLaboratory Trials Nazarowec-White and Farber (1997)Nazarowec-White and Farber (1997)

Open stainless steel tubes in constant Open stainless steel tubes in constant temperature water bathtemperature water bath

5 pooled food strains and 5 pooled 5 pooled food strains and 5 pooled clinical strainsclinical strains

Edelson-Mammel and Buchanan Edelson-Mammel and Buchanan (2003)(2003) Submerged coil apparatusSubmerged coil apparatus 12 individual strains – food and clinical12 individual strains – food and clinical

Thermal Resistance Thermal Resistance

D-Value:D-Value: Time at a given temperature Time at a given temperature

needed to reduce a microbial needed to reduce a microbial population by 90%population by 90%

Z-Value:Z-Value: Change in temperature needed to Change in temperature needed to

change D-value by 90%change D-value by 90%

2

3

4

5

6

7

8

9

0 500 1000 1500 2000 2500

Heating Time (sec)

Su

rviv

ors

[Log

(CF

U/m

L)]

Thermal Death Time Curves for 2 Thermal Death Time Curves for 2 Enterobacter sakazakiiEnterobacter sakazakii Strains Strains Heated at 58Heated at 58CC

D = 30.5 secD = 30.5 sec

D = 591.9 secD = 591.9 sec

Distribution of DDistribution of D5858°C°C-values for -values for 12 12 Enterobacter sakazakiiEnterobacter sakazakii strainsstrains

0

1

2

3

4

5

6#

of S

trai

ns

0-100 100-200

200-300

300-400

400-500

500-600

D-value (sec)

Comparison of DComparison of D5858°C°C-Values for -Values for Different EnterobacteriaceaeDifferent Enterobacteriaceae

0

100

200

300

400

500

600

D-v

alue

(se

c)E. sakazakii 607

E. coli O157:H7

E. sakazaki N&F-pooledK. pneuomoniae

Salmonella Hartford

E. coli

E. aerogenes

E. sakazakii 51329

Effect of Heating Temperature Effect of Heating Temperature on D-Value for on D-Value for E. sakazakiiE. sakazakii 607 607

1

10

100

1000

10000

55 60 65 70

Heating Temperature (C)

D-V

alu

e (

sec)

Reported Z-valuesReported Z-values

Nazarowec-White and Farber Nazarowec-White and Farber (1997)(1997) Pooled food isolates: 5.6Pooled food isolates: 5.6°C°C Pooled clinical isolates: 6.0 °CPooled clinical isolates: 6.0 °C All: 5.8 °CAll: 5.8 °C

Edelson-Mammel and Edelson-Mammel and Buchanan (2003)Buchanan (2003) Strain 607: 5.6 °CStrain 607: 5.6 °C

Predicted InactivationPredicted Inactivation

Results of these Results of these heating trials heating trials indicate that indicate that heating heating rehydrated infant rehydrated infant formula at formula at 7070°°C C for even a few for even a few seconds will result seconds will result in a substantial in a substantial inactivation of inactivation of E. E. sakazakiisakazakii

0.001

0.01

0.1

1

10

100

65 70 75 80 85 90 95

Temperature (C)Tim

e to

5D

inact

ivati

on (

sec)

Effect of Temperature of Water Effect of Temperature of Water Used to Rehydrate Infant Used to Rehydrate Infant FormulaFormula Inoculated dried infant formula in

baby bottle Add water pre-heated to different

temperatures Cap and agitate periodically for 10

minutes Analyze rehydrated formula for E.

sakazakii

Temperature Decline During Temperature Decline During Rehydration of Infant Rehydration of Infant FormulaFormula

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10

Sample Time (min)

Tem

pera

ture

(C)

Rehydration of Dried Infant Rehydration of Dried Infant FormulaFormula

0

1

2

3

4

5

6Surv

ivors

[L

og(C

FU/m

l)]

23 50 60 70 80 90 100

Water Temperature (C)

Lower Limit of Detection

Impact of Heating on Impact of Heating on Nutrient ContentNutrient Content

Conducted by Atlanta Center Conducted by Atlanta Center for Nutrient Analysis (ACNA)for Nutrient Analysis (ACNA)

Used boiling water as the worst Used boiling water as the worst case and compared against case and compared against controlcontrol

Analyses done in triplicateAnalyses done in triplicate Results expressed in terms of Results expressed in terms of

units/100 calunits/100 cal

Impact of Heating on Impact of Heating on Nutrient ContentNutrient Content

Formula Formula 11

Formula Formula 22

Formula Formula 33

Formula Formula 44

Vitamin Vitamin AA

300/712300/712

686(-3.7)686(-3.7)300/677300/677

678(+0.1)678(+0.1)300/597300/597

613(+2.7)613(+2.7)300/451300/451

459(+1.8)459(+1.8)

Vitamin Vitamin DD

60/7160/71

73(+2.8)73(+2.8)60/5860/58

53(-8.7)53(-8.7)60/5760/57

63(+10.8)63(+10.8)60/5760/57

55(-2.3)55(-2.3)

Vitamin EVitamin E 1.5/2.91.5/2.9

2.9(0.0)2.9(0.0)2.0/5.22.0/5.2

4.4(-14.0)4.4(-14.0)1.4/3.11.4/3.1

3.0(-3.2)3.0(-3.2)2.0/3.72.0/3.7

3.6(-3.5)3.6(-3.5)

Vitamin Vitamin KK

8.0/17.88.0/17.8

17.9(+0.6)17.9(+0.6)8.0/9.48.0/9.4

9.7(+3.2)9.7(+3.2)8.3/11.88.3/11.8

11.9(+0.9)11.9(+0.9)8.2/15.48.2/15.4

14.8(-3.9)14.8(-3.9)

ThiaminThiamin 100/223100/223

218(-2.2)218(-2.2)80/16880/168

170(+1.2)170(+1.2)100/164100/164

178(+8.5)178(+8.5)60/14160/141

141(0.0)141(0.0)

Impact of Heating on Impact of Heating on Nutrient ContentNutrient Content

Formula Formula 11

Formula Formula 22

Formula Formula 33

Formula Formula 44

RiboflaviRiboflavinn

150/266150/266

261(-1.9)261(-1.9)90/15490/154

143(-7.1)143(-7.1)150/247150/247

257(+4.1)257(+4.1)135/337135/337

308(+8.6)308(+8.6)

Vitamin Vitamin BB66

60/8660/86

81(-6.4)81(-6.4)60/11460/114

116(+1.8)116(+1.8)62.5/13662.5/136

139(+2.2)139(+2.2)75/11875/118

120(+1.7)120(+1.7)

Vitamin Vitamin BB1212

0.25/0.900.25/0.90

0.86(-4.4)0.86(-4.4)0.30/0.720.30/0.72

0.72(0.0)0.72(0.0)0.30/0.400.30/0.40

0.41(+3.3)0.41(+3.3)0.22/0.610.22/0.61

0.62(+2.0)0.62(+2.0)

NiacinNiacin 1050/15031050/1503

1521(+1.21521(+1.2))

1000/14181000/1418

1456(+2.71456(+2.7))

750/1242750/1242

1236(-0.5)1236(-0.5)750/1176750/1176

1282(+9.01282(+9.0))

Folic Folic AcidAcid

15.0/36.015.0/36.0

36.1(+1.0)36.1(+1.0)16.0/32.316.0/32.3

33.3(+3.1)33.3(+3.1)7.5/26.97.5/26.9

28.3(+5.2)28.3(+5.2)15.0/43.915.0/43.9

45.2(+3.0)45.2(+3.0)

Impact of Heating on Impact of Heating on Nutrient ContentNutrient Content

Formula Formula 11

Formula Formula 22

Formula Formula 33

Formula Formula 44

PantotheniPantothenic Acidc Acid

450/1010450/1010

1060(+5.01060(+5.0))

500/793500/793

803(+1.3)803(+1.3)450/633450/633

649(+2.5)649(+2.5)450/770450/770

755(+1.9)755(+1.9)

BiotinBiotin 4.4/9.94.4/9.9

10.4(+5.1)10.4(+5.1)3.0/4.63.0/4.6

4.2(-8.0)4.2(-8.0)5.5/6.65.5/6.6

6.7(+2.1)6.7(+2.1)2.2/4.32.2/4.3

4.3(+1.9)4.3(+1.9)

Vitamin Vitamin CC

9.0/16.69.0/16.6

11.5(-11.5(-30.7)30.7)

12.0/26.212.0/26.2

9.0(-65.6)9.0(-65.6)8.3/10.78.3/10.7

10.1(-5.6)10.1(-5.6)8.0/18.38.0/18.3

15.0(-15.0(-18.0)18.0)

Thermal Resistance of Thermal Resistance of E. E. sakazakii sakazakii – Pilot Plant– Pilot Plant

Nazarowec-White et al. (1999)Nazarowec-White et al. (1999) Pooled strains?Pooled strains? HTST pasteurizerHTST pasteurizer

Effectiveness of Effectiveness of PasteurizationPasteurization

3 sec3 sec 10 sec10 sec 16 sec16 sec 30 sec30 sec 60 sec60 sec

5959°C°C 100100 100100

60 60 °C°C 6363 5050

61 61 °C°C 100100 7979 5050 2020

62 62 °C°C 100100 4040 3.23.2 3.23.2

63 63 °C°C 38.838.8 50.150.1 2020 0.630.63 0.400.40

64 64 °C°C 39.839.8 1616 5.05.0 0.0130.013 0.0400.040

65 65 °C°C 31.631.6 2.02.0 0.200.20 0.00040.0004

66 66 °C°C 6.316.31 0.200.20 0.0790.079

67 67 °C°C 0.3980.398

68 68 °C°C 0.0630.063

Resistance to Other Resistance to Other TreatmentsTreatments

Great deal of information available Great deal of information available about about EnterobacteriaceaeEnterobacteriaceae in general in general

Resistances If Like Other Resistances If Like Other EnterobacteriaceaeEnterobacteriaceae Not heat resistantNot heat resistant Moderate acid resistance if adaptedModerate acid resistance if adapted Moderate alkali resistance if adaptedModerate alkali resistance if adapted Low to moderate chlorine resistanceLow to moderate chlorine resistance Low to moderate irradiation Low to moderate irradiation

resistanceresistance Will remain viable in refrigerated and Will remain viable in refrigerated and

frozen products for extended periods, frozen products for extended periods, particularly if neutral pHparticularly if neutral pH

Moderate to good resistance to dryingModerate to good resistance to drying

Resistance to Other Resistance to Other TreatmentsTreatments

Little published Little published information available information available specifically about specifically about E. E. sakazakiisakazakii

Even less available on Even less available on distribution of resistancesdistribution of resistances

Other ResistancesOther Resistances

Isolation from dried foods indicates Isolation from dried foods indicates resistance to dryingresistance to drying

Isolation from seeds treated with Isolation from seeds treated with hypochlorite suggest that at least hypochlorite suggest that at least some strains may be relatively some strains may be relatively resistant to chlorine (Okuda et al., resistant to chlorine (Okuda et al., 1994)1994)

Relatively sensitive to the growth Relatively sensitive to the growth inhibiting effects of chitosans (No et inhibiting effects of chitosans (No et al., 2002)al., 2002)

Resistance to DehydrationResistance to Dehydration

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

0 2 4 6 8 10

Storage Time (mon)

Surv

ivin

g P

opula

tion

[Log(C

FU/m

L)]

SummarySummary

Not a particularly thermally Not a particularly thermally resistant microorganismresistant microorganism

Substantial diversity in thermal Substantial diversity in thermal resistance among strainsresistance among strains

Good agreement among studiesGood agreement among studies Inactivation at temperatures above Inactivation at temperatures above

7070°C, even for a few seconds °C, even for a few seconds Specific information on its Specific information on its

resistance to other treatments is resistance to other treatments is generally lackinggenerally lacking