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Recent advances in the
infrared analysis of milk
Steve Holroyd Directorate of Science & Technology
Confidential to Fonterra Co-operative Group
April 2015
Page 2 Confidential to Fonterra Co-operative Group
Overview
• Infrared analysis of milk
• Mid infrared spectroscopy
– Measurement of minor components
–Targeted and non-targeted analyses
– Instrument developments
• Near infrared - current applications
• A vision of future applications
Page 3 Confidential to Fonterra Co-operative Group
Principle of IR-Spectroscopy
d
I 0 I
Light-Source
Detector
Transmission T = —
1
T
I 0
I
Sample
Absorption = A = log — = · c · d
I = intensity of reference beam 0
I = intensity of sample beam
d = sample thickness
c = concentration
= molar absorption coefficient
Page 4 Confidential to Fonterra Co-operative Group
What’s in liquid milk?
• Evolved as a complete food
• Complex mixture of fat, protein
and carbohydrates
• Extensive microstructure 1-100µm
• Fat globules and casein micelles
Page 5 Confidential to Fonterra Co-operative Group
Milkfat globules – scatter light
0
2
4
6
8
10
12
14
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10
Volume (%)
Size (µm)
Page 6 Confidential to Fonterra Co-operative Group
MIR and NIR
• Mid IR
- Transmission through thin sample
- Discrete peaks
- More sensitive
• Near IR
- Good for reflectance
- Broad overlapping peaks
- More potential light scattering
Page 7 Confidential to Fonterra Co-operative Group 7
Near vs. mid infrared for milk
• Mid IR
– Transmission through 37-50um cells using Fourier transform infrared (FTIR) wavelength range 1000-4000cm-1
– Widely used for liquid dairy products
– Both in- and at-line
– Traditionally measures fat, protein and lactose
• NIR
– FTNIR, diode array and dispersive systems, wavelength range 700-2500nm
– Reflectance or transmission at- or in-line
– Widely used for solid and semi-solid products, also for liquids
– Traditionally measures moisture, fat and protein
Page 8 Confidential to Fonterra Co-operative Group
Where infrared spectroscopy fits in….
Final product
grading
In process
Before processing
For payment
Page 9 Confidential to Fonterra Co-operative Group
Mid IR spectroscopy
1. Measurement of “minor components” in
milk
2. The use of targeted and untargeted
calibration models to assess milk quality
3. The development of lower cost
instrument platforms
Page 10 Confidential to Fonterra Co-operative Group
Mid IR spectra of liquid milk
0.0
0.1
0.2
0.3
0.4
1000 1100 1200 1300 1400 1500 1600
wavenumber
ab
so
rba
nce
Page 11 Confidential to Fonterra Co-operative Group
1. Measurement of “minor components” in milk
• 1980-90s: Traditional quantitative calibration are for
gross composition
–Fat, protein, lactose, total solids, solids not fat
• 2000: Major fractions of fat and protein
–Casein, saturated and unsaturated fatty acids
• 2010: Individual fatty acids and proteins
• Adulterants at concentrations below 1000ppm
–What is the correlation model (calibration) based on
–Beware of covariance!
Page 12 Confidential to Fonterra Co-operative Group
MIR new applications 2014-5 published
• Estimation of genetic parameters by FTIR – energy balance (Journal of Dairy Science
98, McParland et al, 2014)
• Detection of whey in milk/whey quality (Food chemistry, 174/176, de Carvalho et al and
Kucheryavkiy et al 2014)
• Within milking variation of milk composition and fatty acid profile (Journal of Dairy
Science, 97/7, Rico et al 2014)
• Estimation of genetic and cross breeding parameters of fatty acid concentrations in milk
fat (Journal of Dairy Science, 81/3, Holroyd et al, 2014)
• Screening methods for detection of five adulterants by FTIR (Food chemistry, 181, 31,
Botelho et al 2015)
Page 13 Confidential to Fonterra Co-operative Group
2. The use of targeted and untargeted
calibration models
• Melamine crisis (2008) with contaminated milk powder
• Liquid milk deliberately adulterated for economic gain
• Collaborative project between Fonterra, Arla and Foss
• Resulted in development of targeted and untargeted models for detecting milk
adulteration at economic levels
• In 2014 Foss has commercial release of FTIR models using abnormal
spectrum module (ASM) as well as targeted models for specific adulterants
Page 14 Confidential to Fonterra Co-operative Group
1. Quantitative (targeted analysis)
C:\valhalla\MSCFT2\PCA\DK\New Folder\pre0
0 100 200 300 400 500 600 700 800 900 1000
0
100
200
300
400
500
600
700
800
900
1000
RMSEP=28.111 SEP=28.158 SEPCorr=28.237 SDrep=12.757 Mean=338.09
Predicted (Melamine F/C=9/22)
Act
ual
57 samples in 3 replicates
%CV: RMSEP=8.31 SEP=8.33 SEPCorr=8.35 SDrep=3.77
Slope: 1.0013
Intcpt: -1.8636
r: 0.9969
Bias : -1.4116
FTIR predicted melamine (ppm)
Refe
ren
ce
te
st m
ela
min
e (
pp
m)
Page 15 Confidential to Fonterra Co-operative Group
Qualification (untargeted analysis)
• Defines a single “good” group
• Anything outside is by definition
“abnormal”
• Advantage – you can find what you
are not looking for
Page 16 Confidential to Fonterra Co-operative Group
Untargeted evaluation of spectra
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
-5 -4 -3 -2 -1 0 1 2 3
Scor
e on
pri
ncip
al c
ompo
nent
2
Score on principal component 1
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
-5 -4 -3 -2 -1 0 1 2 3
Scor
e on
pri
ncip
al c
ompo
nent
2
Score on principal component 1
New sample
Normal
Short distance
New sample
Abnormal
Long distance
Page 17 Confidential to Fonterra Co-operative Group
Results – untargeted analysis of liquid milk
by FTIR
Threshold
Page 18 Confidential to Fonterra Co-operative Group
Fingerprint FTIR analysis of NZ milk
0
1
2
3
4
5
6
7
8
9
10
145
89
133
177
221
265
309
353
397
441
485
529
573
617
661
705
749
793
837
881
925
969
101
3105
7110
1114
5118
9123
3127
7132
1136
5140
9145
3149
7154
1158
5162
9167
3171
7176
1180
5184
9189
3193
7198
1202
5206
9211
3215
7220
1224
5228
9233
3237
7
AS
M s
co
re
Sample number
FT2 - ASM Score 07.01.13
Page 19 Confidential to Fonterra Co-operative Group
Challenge with untargeted analyses
0
200
400
600
800
1000
1200
0 1 2 3 4 5
Limit o
f Det
ectio
n (p
pm)
% Acceptable false positives
Melamine
Ammonium sulphate
Urea
Page 20 Confidential to Fonterra Co-operative Group
Combining Untargeted and Targeted models
Does the untargeted (FTIR)
model indicate a deviating
sample?
Is there a targeted (FTIR) model
indicating the nature of the
deviation?
The sample is most likely
adulterated Confirmatory chemistry
Is there a targeted (FTIR) model
indicating adulteration with a
specific adulterant?
No Yes
Yes Yes
The deviating sample
must be investigated
further with confirmatory
chemistry
The sample is normal
No No
Page 21 Confidential to Fonterra Co-operative Group
3. FTIR instrument platforms
• Traditional FTIR based instruments
– Foss FT1, FT2, FT+
– Bentley DairySpec
– Delta Lactoscope
• Highly accurate (0.02% for fat and
protein)
• Automated flow/cleaning system with
temperature control and precise
homogenisation for consistent sample
presentation
• In widespread use
Page 22 Confidential to Fonterra Co-operative Group
Lower cost mid IR/FTIR
• Smaller, less automated = substantially cheaper
• Measure gross composition, but less accurate
• Use proprietary technology to reduce interference
from lack of homogenisation
• IndiFoss MilkoScreen
• MIRIS - The Dairy Milk Analyser (filter instrument)
• Foss MilkoScan Mars
Images from Foss and MIRIS
Page 24 Confidential to Fonterra Co-operative Group
Prevention of economically motivated adulteration
• Use FTIR to manage risks
associated with accessing
larger part of global milk pool
• Business support systems for
effective decision making
Page 25 Confidential to Fonterra Co-operative Group
NIR for liquid milks
• More commonly used for solids and semi-solids
• Liquid milk applications can be challenging
• NIR used a number of applications
– On farm analysis of composition
– Differentiation of milk from cows with different diets
– Organic/non-organic milk
– Different calibration protocols for dealing with light
scattering effects due to fat globule size
– Scattering shown to contribute to 50% total absorbance
in a liquid milk sample
– Milk coagulation
– Somatic cell detection
Source - The use of NIR on milk and milk products (Holroyd,
Journal of NIR, 21/5 2013)
Page 26 Confidential to Fonterra Co-operative Group
Liquid Sampling Module (LSM)
26
Attachment to existing NIR system
LSM features
• Homogenizer for raw milk
• Peristaltic pump for high viscousity dairy
products, e.g. concentrates and premixes
• Flow cell with 1mm (1000mm) pathlength
• Automated sampling and repeated
measurements
• Basic and advanced cleaning (0.5 and 2%
detergent)
• Similar accuracy to FTIR systems
Info courtesy of Bruker Optics
Page 27 Confidential to Fonterra Co-operative Group
Vision of the future
• Mid IR - wide range of FTIR systems with accuracy
dependent upon value chain in specific location
– Cost vs accuracy
– Calibration models used for range of quality parameters
– Targeted and non targeted models common
• Near IR systems fill niche roles
– Single instrument for multiple uses, liquids and solids
– On farm applications
• Used with guidance from international standard setting
groups
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