# Presentation: 748945

## Resistance – Thermal and Other 

**Robert L. Buchanan**
**DHHS Food and Drug Administration**
**Center for Food Safety and Applied Nutrition**

## Thermal Resistance of E. sakazakii – Laboratory Trials

**Nazarowec-White and Farber (1997)**
**Open stainless steel tubes in constant temperature water bath**
**5 pooled food strains and 5 pooled clinical strains**
**Edelson-Mammel and Buchanan (2003)**
**Submerged coil apparatus**
**12 individual strains – food and clinical**

## Thermal Resistance 

**D-Value:**
**Time at a given temperature needed to reduce a microbial population by 90%**
**Z-Value:**
**Change in temperature needed to change D-value by 90%**

## Thermal Death Time Curves for 2 Enterobacter sakazakii Strains Heated at 58C

**Thermal Death Time Curves for 2 *****Enterobacter sakazakii***** Strains Heated at 58********C**

**D = 30.5 sec**

**D = 591.9 sec**

## Distribution of D58°C-values for 12 Enterobacter sakazakii strains

## Comparison of D58°C-Values for Different Enterobacteriaceae

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

## Reported Z-values

**Nazarowec-White and Farber (1997)**
**Pooled food isolates: 5.6****°C**
**Pooled clinical isolates: 6.0 °C**
**All: 5.8 °C**
**Edelson-Mammel and Buchanan (2003)**
**Strain 607: 5.6 °C**

## Predicted Inactivation

**Results of these heating trials indicate that heating rehydrated infant formula at ********70****°****C for even a few seconds  will result in a substantial inactivation of *****E. sakazakii***** **

## Effect of Temperature of Water Used to Rehydrate Infant Formula

**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 Rehydration of Infant Formula

## Rehydration of Dried Infant Formula

**Lower Limit of Detection**

## Impact of Heating on Nutrient Content

**Conducted by Atlanta Center for Nutrient Analysis (ACNA)**
**Used boiling water as the worst case and compared against control**
**Analyses done in triplicate**
**Results expressed in terms of units/100 cal**

## Impact of Heating on Nutrient Content

|  | Formula 1 | Formula 2 | Formula 3 | Formula 4 |
| --- | --- | --- | --- | --- |
| Vitamin A | 300/712
686(-3.7) | 300/677
678(+0.1) | 300/597
613(+2.7) | 300/451
459(+1.8) |
| Vitamin D | 60/71
73(+2.8) | 60/58
53(-8.7) | 60/57
63(+10.8) | 60/57
55(-2.3) |
| Vitamin E | 1.5/2.9
2.9(0.0) | 2.0/5.2
4.4(-14.0) | 1.4/3.1
3.0(-3.2) | 2.0/3.7
3.6(-3.5) |
| Vitamin K | 8.0/17.8
17.9(+0.6) | 8.0/9.4
9.7(+3.2) | 8.3/11.8
11.9(+0.9) | 8.2/15.4
14.8(-3.9) |
| Thiamin | 100/223
218(-2.2) | 80/168
170(+1.2) | 100/164
178(+8.5) | 60/141
141(0.0) |

## Impact of Heating on Nutrient Content

|  | Formula 1 | Formula 2 | Formula 3 | Formula 4 |
| --- | --- | --- | --- | --- |
| Riboflavin | 150/266
261(-1.9) | 90/154
143(-7.1) | 150/247
257(+4.1) | 135/337
308(+8.6) |
| Vitamin B6 | 60/86
81(-6.4) | 60/114
116(+1.8) | 62.5/136
139(+2.2) | 75/118
120(+1.7) |
| Vitamin B12 | 0.25/0.90
0.86(-4.4) | 0.30/0.72
0.72(0.0) | 0.30/0.40
0.41(+3.3) | 0.22/0.61
0.62(+2.0) |
| Niacin | 1050/1503
1521(+1.2) | 1000/1418
1456(+2.7) | 750/1242
1236(-0.5) | 750/1176
1282(+9.0) |
| Folic Acid | 15.0/36.0
36.1(+1.0) | 16.0/32.3
33.3(+3.1) | 7.5/26.9
28.3(+5.2) | 15.0/43.9
45.2(+3.0) |

## Impact of Heating on Nutrient Content

|  | Formula 1 | Formula 2 | Formula 3 | Formula 4 |
| --- | --- | --- | --- | --- |
| Pantothenic Acid | 450/1010
1060(+5.0) | 500/793
803(+1.3) | 450/633
649(+2.5) | 450/770
755(+1.9) |
| Biotin | 4.4/9.9
10.4(+5.1) | 3.0/4.6
4.2(-8.0) | 5.5/6.6
6.7(+2.1) | 2.2/4.3
4.3(+1.9) |
| Vitamin C | 9.0/16.6
11.5(-30.7) | 12.0/26.2
9.0(-65.6) | 8.3/10.7
10.1(-5.6) | 8.0/18.3
15.0(-18.0) |

## Thermal Resistance of E. sakazakii – Pilot Plant

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

## Effectiveness of Pasteurization

|  | 3 sec | 10 sec | 16 sec | 30 sec | 60 sec |
| --- | --- | --- | --- | --- | --- |
| 59°C |  |  |  | 100 | 100 |
| 60 °C |  |  |  | 63 | 50 |
| 61 °C |  | 100 | 79 | 50 | 20 |
| 62 °C |  | 100 | 40 | 3.2 | 3.2 |
| 63 °C | 38.8 | 50.1 | 20 | 0.63 | 0.40 |
| 64 °C | 39.8 | 16 | 5.0 | 0.013 | 0.040 |
| 65 °C | 31.6 | 2.0 | 0.20 | 0.0004 |  |
| 66 °C | 6.31 | 0.20 | 0.079 |  |  |
| 67 °C | 0.398 |  |  |  |  |
| 68 °C | 0.063 |  |  |  |  |

## Resistance to Other Treatments

**Great deal of information available about *****Enterobacteriaceae***** in general**

## Resistances If Like Other Enterobacteriaceae

**Not heat resistant**
**Moderate acid resistance if adapted**
**Moderate alkali resistance if adapted**
**Low to moderate chlorine resistance**
**Low to moderate irradiation resistance**
**Will remain viable in refrigerated and frozen products for extended periods, particularly if neutral pH**
**Moderate to good resistance to drying**

## Resistance to Other Treatments

**Little published information available specifically about *****E. sakazakii***
**Even less available on distribution of resistances**

## Other Resistances

**Isolation from dried foods indicates resistance to drying**
**Isolation from seeds treated with hypochlorite suggest that at least some strains may be relatively resistant to chlorine (Okuda et al., 1994)**
**Relatively sensitive to the growth inhibiting effects of chitosans (No et al., 2002)**

## Resistance to Dehydration

## Summary

**Not a particularly thermally resistant microorganism**
**Substantial diversity in thermal resistance among strains**
**Good agreement among studies**
**Inactivation at temperatures above 70****°C, even for a few seconds **
**Specific information on its resistance to other treatments is generally lacking**