2. Preparation of matrix sample for Food Testing Laboratory
INTRODUCTION
No
Traceability
NIMT (IDMS
method)
Traceability
to SI unit via
NIMT
TISTR has been designated by NIMT
Be able to
assign true
value using
IDMS
Preservative is widely used in food and beverage
Its use has to be controlled and labeled
“Preservatives added” .
Its amounts has to be declared when submitted to
Authority by TEST REPORT.
In fact, most of laboratories can provide additives
testing in food.
BUT in the condition of ISO/IEC 17025 accredited.
3. Paramee CP 2009
สถาบันวิจัยวิทยาศาสตรและเทคโนโลยีแหงประเทศไทย(วว.)
ti t th
สถาบันวิจัยวิทยาศาสตรและเทคโนโลยีแหงประเทศไทยสถาบันวิจัยวิทยาศาสตรและเทคโนโลยีแหงประเทศไทย((วววว.).)
i hti t th
Spiked benzoic acid in (500mg/kg)
and sorbic acid (250mg/kg) in
70%EtOH
CRM Production : Preservatives in Food
2kg
(40 bags)
Preparation of Matrix food sample containing preservatives content for
food testing Laboratory (PT sample and CRM Production)
4. Characteristic study
Test Items Sample blank Spiked sample
Appearance Red curry smooth paste
pH 5.07-5.10 5.06-5.07
Water activity (%) 0.891-0.917 0.881-0.876
Total plate count
(CFU/g)
3.6x106 12.0x106
5. Homogeneity : Feasibility Study
No of
Prep
SA %RSDSA BA %RSDBA
Lot 1
(2kg)
273 5.3 549 8.1
Lot 2
(10kg)
257 2.2 500 2.5
Lot 3
(10kg)
237 0.7 482 1.2
Lot 1 : Blending No 1
Lot 2 : Blending
No 2Random Sampling : N=10-12 (n=2) by HPLC-UV
Method : Modified Determination of benzoic acid,
sorbic acid and methyl, ethyl, propyl and butyl
parabens by HPLC, SOP No. CLG-BSO.01,
US Department of Agriculture, Food Safety and
Inspection Service, Office of Public Health Science
Lot 3 :Blending
and kneading
ISO 13528 : Statistical methods for use in proficiency testing by inter laboratory comparisons)
6. Sampling N = 12
(Between Sample)
n1 n2
Test portion n=2
(Within sample)
Lot No.3
N2
n1 n2
N3
n1 n2
N4
n1 n2
N5
n1 n2
N6
n1 n2
N1
Homogeneity Study
HPLC UV-VIS
Modified Determination of benzoic acid, sorbic acid and methyl, ethyl, propyl and
butyl parabens by HPLC, SOP No. CLG-BSO.01, US Department of Agriculture, Food
Safety and Inspection Service
8. Short term Stability Study
Storage condition : in Nylon
transparent plastic bag : Dark
color were observed after 3
months at 25OC.
ySod.BA@4C = -0.0625x + 503.78 R² = 0.0672 y Sod.BA@25C= -0.2285x + 494.93 R² = 0.20
ySA@4C = -0.3473x + 254.96 R² = 0.7725
ySA@25C = -0.9157x + 244.88 R² = 0.8918
Instability of sorbic acid
9. PT Food Sample : Stability Study
Stability study and shelf life for short term study (3months)
Data
(Na.benzoate)
25C 4C Remark
Slope (b1) -0.2285 -0.0625
Intercept(b0) 494.931 503.779
S2 (sd of the point
among the line)
662.56 822.16
S(b1) (uncertainty
associated with the
slope)
0.175 0.195
Significant of slope
(t0.95, n-2=26 ,=2.056)
0.228<0.360 0.062<0.401
2
)(
1
2
110
2
−
−−
=
∑=
n
xXbbY
s
n
i
i
∑=
−
=
n
i
i XX
s
s
1
2
)(
)( 12,95.01 bxstb n−<
No instability was observed at 25C and 4C of storage condition for 90days
ISO Guide 35 – Reference materials-General and statistical principles for certification (Annex B5)
10. PT(Local Labs) : Sodium benzoate in curry paste
MTC-PT-1000-2550
-assigned value from 6 Labs (ISO/IEC
17025 accredited),
- Evaluation of the PT is according to
ISO 13528 : Statistical methods for use
in proficiency testing by inter laboratory
comparisons)
-Reference Standards were from
NIST, RMIPO, ACROSS, BDH, Carlo
Erbra, Fluka, MERCK, Riedel-
dehaenAG, SIGMA Aldich, Supelco,
UNILAB,and USP
Oct 2007-Feb 2008
77.11175.0553.9509.5120.4 2222
=+++=PTu
2222
stabPTwbbPT uuuuu +++=
Sodium benzoate PT Sample =474+24 mg/kg
U= 4.9%
where k = 2 is the coverage factor for a 95 %
confidence level and uCRM is the combined standard
uncertainty calculated according to ISO Guide 35
22
hom* assignoPT uuu +=
12. CRM Production : Benzoic acid in curry paste
Material No of bags
(50g)
PT Sample 40
CRM needed 50
Feasibility study 20
Characteristic study 20
Homogeneity study 10
Stability study 60
10kg
Gamma radiation
Eliminate bacteria*
*Curry paste samples were sterilized by gamma ray irradiation at Thailand Institute of Nuclear and
Technology (TINT)
•Decreasing of sorbic acid was observed and inhomogeneity was found.
•Study on stability was found that 39.5% of sorbic acid was decreased @
1000 mg/l) after 1h at 105C.
•Therefore sorbic acid was not considered for the APMP.QM-P14
*the homogeneity were carried on before and after radiation
13. Analysis Blank sample PT sample
Benzoic acid Not detected
(less than 3 mg/kg)
See homogeneity study
pH (10%w/v) 5.09 5.02
Water activity 0.89% 0.88%
Total plate count 1.0x106 CFU/g 4.2x106 CFU/g (before irradiation)
8.3x103 CFU/g (after irradiation)
Solubility 80% w/w
Non soluble matter 4% w/w on 1 micron membrane filter
16% w/w on 22 micron membrane filter
Characterization Study : Benzoic acid in curry paste
Result is similar to the previous study
15. Figure 1: Participants’ results for benzoic acid content in curry paste sample. The
horizontal blue lines represent the proposed reference value (median) and its associated
uncertainty. The horizontal brown line is the arithmetic mean value and its associated
uncertainty.
assigned Value for CRM =378 mg/kg
U=12 mg/kg
16. CRM Stability Study : Benzoic Acid in Curry Paste
BA -22C
Slope (b1) 0.262
Intercept(b0) 379.334
S
2
(sd of the point among the line) 9.162
S(b1) (unc associated with the
slope)
0.143
Significant of slope
(t0.95, n-2=10 ,=2.776)
0.261<0.396
)( 12,95.01 bxstb n−<
No instability was observed at -22C for 2 years
17. CRM : Benzoic acid in curry paste
22222
ltsstsassignedwbbCRM uuuuuu ++++=
Sources of unc ui
ui
2
usts 0.175 0.031
ults 0.143 0.020
u(assigned)
6.500 42.250
Sbb
2.928 8.572
S within gr
3.097 9.591
SQRT(ui
2
combined) 7.776
U (k=2) 15.6
%U 3.2
Benzoic acid = 378 +15.6 mg/kg
•The certified value is based on isotope dilution mass
spectrometry method which is analysed by National
Metrology Institute of Thailand
•Benzoic acid SRM is used for matrix matching
standard curve
CRMCRM kxuU
•uncertainty is the combined standard uncertainty
multiply by k calculated according to ISO Guide 35,
•where k = 2 is the coverage factor for a 95 %
confidence level
=
18. ACKNOWLWDGEMENT
Dr. Chainarong Cherdchu NIMT
Dr. Charun Yafa NIMT
Ms.Pranee Phukphatthanachai NIMT
Dr. Luxsamee Plungsangmas TISTR
Mr. Cheumsak Sinchaisri TISTR
Ms.Vilaval Pongpitak et.al. TISTR (BCL)
Ms.Thippaya Junvee Fortune et.al. TISTR (ACL)
