the release of nickel from stainless steel into cooked foods
TRANSCRIPT
The Release of Nickel from Stainless Steel into Cooked Foods
Kristin Kamerud¹ Kim Anderson² College of Agricultural Sciences¹, Environmental and Molecular Toxicology²
Oregon State University
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
2
Nickel in the Environment
Ubiquitous in environment
Soils, plants, and animals
5th most abundant element (by weight)
84 mg/kg in crust
15-20 µg/L in surface waters
Widely used in industry
Production of stainless steel and other nickel alloys
Nickel in the Environment
Natural and anthropogenic releases of nickel
Weathering of rocks/soil, volcanic emissions, vegetation fires
Combustion of fossil fuels, tobacco smoke, industry and recycling
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
3
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
4
Global Nickel Production
0
50000
100000
150000
200000
250000
300000
Australia Canada Indonesia Philippines Russia
Nic
ke
l (T
on
s)
Global Nickel Mine Production
2009
2010
U.S. Geological Survey, Mineral Commodity Summaries, January 2011
Total global nickel production: 1,550,000 tons
Pathways of Human Exposure
Essential for some species
Not yet proven for humans
Oral exposures through food and drinking water
Estimated Intakes: up to 900 µg/day
Tolerable upper intake level (UL): 1000 µg/day
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
5
Dietary Exposure to Nickel
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
6
Flyvholm, M.-A., G. D. Nielsen, et al. (1984). "Nickel content of food and estimation of dietary intake." Zeitschrift
für Lebensmitteluntersuchung und -Forschung A 179(6): 427-431.
Nickel Toxicokinetics
• Absorption dependent on form of nickel
• 0.09% of nickel metal
• Distribution targets
• Kidney, cardiovascular system, blood, immune system
• Metabolism not well understood
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
7
Effects of Nickel Exposure
Nickel Sensitivity
10% of population
Allergic Contact Dermatitis (ACD)
Oral doses of 3000µg
Recommended to lower
Nickel intake
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
8
Kreciz, Beata. "Systemic Contact Dermatitis to Nickel Present in Cocoa in 14-Year-Old Boy." Pediatric Dermatology 28.3 (2011): 335-36.
Stainless Steel Background
Commonly used in food and beverage industry
316, 304, 420
Chromium oxide surface
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
9
Stainless Steel Background
Chemical composition Ni containing stainless steels
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
10
Stainless Steel Grade
Chromium Mass Fraction (%)
Nickel Mass Fraction (%)
316 16-18 10-14
304 17-19 8-10.5
420 12-14 <0.6
Atlas Steels. "Stainless Steel Grade Chart.“ SPECIALTY STEELS PRODUCT REFERENCE MANUAL. Atlas Steels, n.d. Web.
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
11
Research Questions:
Is nickel released into foods?
Is the amount significant?
What factors contribute to nickel leaching?
Variables Tested:
Grade of stainless steel
Cooking time
Cooking cycles (usage “seasoning”)
Commercial tomato sauces
Hypotheses:
Nickel released is inversely proportional to grade of stainless steel
Nickel released increases with cook time
Nickel released is constant over multiple cook cycles
Nickel content is constant for multiple commercial tomato sauces
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
12
Materials Used
Description Identification Number
Stainless Steel Grade Equivalence
Chemical Composition (mass
fraction %) Cr Ni
316a NIST 121d 316 17.50 11.18
316b NIST 123c 316 17.40 11.34
304 NIST 160b 304 18.37 12.35
Nickel Pellet NI-131 99.9
Saucepan 316
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
13
Four commercially obtained tomato sauces (pH 4.17-4.3)
Study Design
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
14
Methods
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
15
•1g metal
•5g sauce
•Cook process
•Sauce separated
Sampling
•EPA method 3050b
•3mL HNOз
•Heat
•Absence of NO2
Acid Digest • Sample
preparation
• Data analysis
ICP-MS
Multi-Matrix Method Validation
Acid digest and ICP-MS analysis validated with Certified Reference Materials
Tomato leave, oyster tissue, soils and sediment matrices
0.25g of each CRM was digest and analyzed for 16 metals including Ni
Conducted over three different days
Replicates of three each day
Quality Control Samples
Pre-digest fortification
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
16
Method Validation
Precision & Accuracy
Average nickel % recovery: 91.3%
%RSD: 1.35
Average pre-digest sample fortification % recovery: 103%
Limit of Quantification: 0.085µg/L
n=7
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
17
Quality Control Results
• Quality Control Samples
• Meet QC data quality objectives
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
18
Sample Type Concentration (µg/L) % Recovery n Total
Instrument Blank BDL ― 16
Reagent Blank BDL ― 16
10µg/L Check Standard 10.4 ± 0.572 96.0 9
20µg/L Check Standard 21.2 ± 0.399 106 5
Pre-digest Fortification 52.1 ± 1.01 104.2 3
Grade of Stainless Steel
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
19
5g of Tomato Sauce
1g NIST
121d
(11.18% Ni)
1g NIST
123c
(11.34% Ni)
1g NIST
160b
(12.35% Ni)
1g NI
131
(99.9% Ni)
Blank
Tomato
Sauce
Samples were refluxed at 85°C for six hours. Tomato sauce then underwent acid digestion and analysis by ICP-MS.
1g
316a 1g
316b
1g
304
Stainless Steel Grade
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
20
n=5; samples deemed significant at p=<0.05 * Statistical difference between one or more samples
Stainless Steel Grade
Nic
ke
l C
on
ce
ntr
atio
n (
mg
/kg
)
0
2
4
6
8
60
70
Tomato
SauceSS 316b SS 304 SS 316a NI 131
*
*
*
Stainless Steel Grade
Nic
ke
l C
on
ce
ntr
atio
n (
mg
/kg
)
0
2
4
6
8
60
70
Tomato
SauceSS 316b SS 304 SS 316a NI 131
*
*
*
Discussion Expectations:
316a and 316b about equal
304 high response
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
21
Results show 316b and 304 equivalent
Protective properties of Cr
Percent Nickel Released
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
22
Experimental Tomato Sauce
Sample
Chemical Composition (mass fraction %)
Cr Ni
Average Ni Leached
(µg)
% Ni Leached
316a 17.50 11.18 3.11 2.78
316b 17.40 11.34 5.71 5.04
304 18.37 12.35 5.1 4.13
Nickel Pellet ― 99.9 65.8 6.59
Grade of stainless steel experimental samples
n=5
Cooking Time
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
23
5g of Tomato Sauce
1g NIST
123c
(11.34% Ni)
Blank
Tomato
Sauce
Samples were refluxed at 85°C for two, six, or twenty hours. Tomato sauce then underwent acid digestion and analysis by ICP-MS.
1g
316b
Cooking Time
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
24
n=4; samples deemed significant at p=<0.05 * Statistical difference between one or more samples
Cook Time (Hours)
Tomato Sauce 2 Hours 6 Hours 20 Hours
Ni C
on
ce
ntr
atio
n (
mg
/kg
)
0
2
4
6
8
10
*
Cooking Cycles
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
25
5g of Tomato Sauce
1g NIST
123c
(11.34% Ni)
Blank
Tomato
Sauce
Samples were refluxed at 85°C for six hours. Tomato sauce was washed off, and replaced with fresh sauce.
Tomato sauce from the third, sixth, and tenth cooking cycle underwent acid digestion and analysis by ICP-MS.
1g
316b
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
26
Cooking Cycles
n=4; samples deemed significant at p=<0.05 * Statistical difference between one or more samples
Cooking Cycle
Nic
kel Conce
ntr
ation (
mg/k
g)
0
2
4
6
TomatoSauce
1stCycle
3rdCycle
6thCycle
10thCycle
*
*
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
27
Commercial Tomato Sauces
5g of Tomato Sauce
1g NIST
123c
(11.34% Ni)
Blank
Tomato
Sauce 1-4
Samples were refluxed at 85°C for six hours. Tomato sauce then underwent acid digestion and analysis by ICP-MS.
1g
316b
Commercial Tomato Sauce
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
28
C.
Commercial Tomato Sauce
Sauce A Sauce B Sauce C Sauce D
Nic
kel C
on
cen
trat
ion
(m
g/kg
)
0.00
0.25
4.00
6.00
8.00 Tomato Sauce
Tomato Sauce & SRM 123c
*
n=4; samples deemed significant at p=<0.05 * Statistical difference between one or more samples
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
29
Saucepan
571g of Tomato Sauce
Grade 316
Stainless Steel
Saucepan
Sauce was refluxed at 85°C for twenty hours. 5g aliquots were taken and underwent acid digestion and analysis by ICP-MS.
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
30
Saucepan
n=5; samples deemed significant at p=<0.05 * Statistical difference between one or more samples ** 20 hour cook time
Stainless Steel Grade
Nic
kel C
on
ce
ntr
ation
(m
g/k
g)
0
2
4
6
8
60
70
Tomato
SauceSS 316b SS 304 SS 316a NI 131 Saucepan **
(316)
*
*
*
*
Grade 316: 316b and Stainless Steel Saucepan
Would have expected similar nickel concentrations
~50% less nickel leached from saucepan than 316b
However, tomato sauce to stainless steel surface area ratios different
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
31
Surface Area
316b Avg. nickel released after
20h cook time: 7.63mg/kg
Saucepan
Avg. nickel released after 20h cook time: 3.84mg/kg
~50% less than 316b
Sauce : Stainless steel ratio
1:0.6
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
32
Stainless steels used a good surrogate for cookware and cooking variable assessment
Sauce : Stainless steel ratio
1:5
Would expect a nearly a 10 fold difference, but we observed only a 2 fold difference
Ni per Serving of Tomato Sauce
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
33
Nickel per Serving of Tomato Sauce Contribution to Total Nickel Intake
Cooking Time Cooking Cycles
0
400
800
1200
1600
2000
Daily UL2
Estimate Daily
Nickel Intakes3
TomatoSauce
Saucepan(20 Hours)
20 Hours 1st Cycle 10th Cycle
Nic
kel (µ
g)
Conclusions Hypothesis: Nickel released is inversely proportional to grade of stainless steel
Nickel is leached into tomato sauce
316b and 304 showed no statistical difference
Protective properties of Cr
316a statistically different than 316b and 304
316b showed greatest response
Dependent on chemical composition
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
34
Hypothesis: Nickel released increases with cook time
Nickel increase with cook time
Hypothesis: Nickel released is constant over multiple cook cycles
Nickel is still leaching after 10 cook cycles but the amount is less than the early cook cycles
Hypothesis: Nickel content is constant for multiple commercial tomato sauces
No significant difference were seen between multiple commercial tomato sauces in their effect on nickel leaching
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
35
Conclusions
Stainless steel cookware contributes to total nickel intakes
Avoidance of stainless steel cookware may decrease total nickel exposure
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
36
Conclusions
Acknowledgements
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
37
Kim Anderson, Ph.D.
Kate Field, Dan Sudakin
FSES
Kevin Hobbie, Norman Forsberg
Friends & Family
Thank you for your attention. Any Questions?
Nove
mb
er
26
th 2
01
2
Kristin
Ka
me
rud
38