EFFECT OF COW PHENOTYPE AND MILK PROTEIN STRUCTURE ON BIOFOULING RATES IN HEAT EXCHANGERS A Master’s Thesis Presented to the Faculty of California Polytechnic State University San Luis Obispo In partial fulfillment of the requirements for the degree of Master of Science in General Engineering with a specialization in Biochemical Engineering By Kamran Ghashghaei December 16, 2003
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EFFECT OF COW PHENOTYPE AND MILK PROTEIN STRUCTURE ON BIOFOULING RATES IN HEAT
EXCHANGERS
A Master’s Thesis Presented to the Faculty of California Polytechnic State University
San Luis Obispo
In partial fulfillment of the requirements for the degree of
Master of Science in General Engineering
with a specialization in Biochemical Engineering
By
Kamran Ghashghaei
December 16, 2003
ii
COPYRIGHT OF MASTER’S THESIS
I grant permission for the reproduction of this thesis in its entirety or any of its parts, without further authorization as long as the author is referenced.
Kamran Ghashghaei Date
iii
MASTER’S THESIS APPROVAL
TITLE: EFFECT OF COW PHENOTYPE AND MILK PROTEIN STRUCTURE ON BIOFOULING RATES IN HEAT EXCHANGERS
AUTHOR: KAMRAN GHASHGHAEI
DATE SUBMITTED: DECEMBER 16, 2003
THESIS COMMITTEE MEMBERS:
Dr. Yarrow Nelson Date:
Dr. Rafael Jimenez Date:
Dr. Dan Walsh Date:
Professor Heather Smith Date:
iv
ABSTRACT
EFFECT OF COW PHENOTYPE AND MILK PROTEIN STRUCTURE ON BIOFOULING RATES IN HEAT EXCHANGERS
KAMRAN GHASHGHAEI
Recent research by the New Zealand Dairy Board suggested that fouling
during milk processing could be reduced by using classified genetic variant phenotype cows that produce specific variants of β-lactoglobulin (BLG). Because of the important role of biofouling in increasing the operating costs of milk processing and possible public health issues, the effect of genetic variants on biofouling was further investigated in a multidisciplinary study between the College of Agriculture and the College of Engineering at Cal Poly. A pilot-scale heat exchanger was assembled and used for measuring biofouling rates for different types of milk from genetically classified Cal Poly dairy cows. This apparatus was used to determine biofouling rates by monitoring both milk and hot water inlet and outlet temperatures using thermocouples connected to a data logger. Biofouling was determined based on the changes in delta T (inlet hot water and milk outlet temperature difference), milk outlet temperature, mass flow and heat transfer rate. Biofouling rate was also analyzed in terms of key components in the biofilm such as protein, mineral, and fat as well as total dry weight. Biofouling, as determined by increases in Delta T and decreases in heat transfer rate was less for BLG BB variant than that of the BLG AA or mixed control, but this difference was not statistically distinguishable at the 95% confidence interval, and large p-values indicated high variability (0.275 for Delta T method, 0.181 for milk outlet temperature method, and 0.508 for heat transfer rate method). No significant different was found between total dried biofilm, and mineral content of the different milk types. However, Kjeldhal and fat analyses suggested that BLG AA contains greater percent protein and fat than the other milk types (BLG BB and control BLG AB) in the biofilm (ANOVA indicated small p-values: 0.054 for the percent protein and 0.095 for the fat content). Therefore, it was possible the low fat and protein content of the BLG BB variant reduced biofouling effects, although this conclusion is difficult to support statistically, more repetitions of these biofouling experiments could be expected to increase the statistical significance of the results.
v
ACKNOWLEDGMENTS
I wish to express my sincere appreciation to the many individuals who
provided help; suggestions and criticism during the development of this work include
the faculties, staffs, and students at Dairy Product Technology Center (DPTC) and the
Department of Dairy Science.
I am indebted to Dr. Yarrow Nelson for his patience, and his willingness to
provide assistance and undertake sometimes thankless and difficult task of
supervising and reviewing of this work. I am grateful to Dr. Rafael Jimenez for his
consistent help, important, thoughtful and constructive input; Dr. Dan Walsh who
influenced the development of this project through his suggestions, encouragement
and his continual support. I would like to thank professor Heather Smith for her
assistance, guidance, and being so helpful in statistical analysis.
Also, I would like to give a special thank to the Office of Naval Research for
funding this research through the C3RP program at Cal Poly.
Finally, I am thankful to our creator who provided me with energy, good
health, an education, and encouraging parents.
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TABLE OF CONTENTS
List of Table…………………………………………………………………………viii
List of Figures………………………………………………………………………...ix
1 INTRODUCTION…………………………………………………………...…….1
2 PROJECT SCOPE…………………………………………………………………5
3 BACKGROUND…………………………………………………………………..6
3.1 Heat treatment in dairy industry…………………………………………….6
3.2 Milk constituents…………………………………………………………….7
3.3 Composition of milk proteins…………………………………………..…...8
3.4 Principal physiochemical properties of milk proteins………………………9
3.5 Major functional properties of milk proteins……………………..………..11
LIST OF TABLES Table 3.1 Common heat treatment applied in the dairy industry………………..6
Table 3.2 Content of major protein component in milk.………………………...9
Table 3.3 Principal physiochemical properties of major protein component in milk…….…………………………………………….10
Table 3.4 Functional properties of main milk proteins…………...……………11
Table 3.5 Positions and amino acid differences in genetic variants of milk proteins………………………………….16 Table 3.6 Comparison of a pre-selected characterization of major whey proteins.……..………………………………………………...19
Table 4.1 Processing conditions in the mix heater- cooler pilot plant- HTST from Processing Machinery & Supply Co…..…..35
Table 4.2 Data indicating quality of milk used and processing conditions……37
Table 5.1 Biofouling rate analysis based on a rise in delta T……………….....45
Table 5.2 Biofouling rate analysis based on decreased milk outlet temperature……………………………………...…………………..45
Figure 5.9 Average percent protein (dry basis) in biofilms formed.
By knowing quantity of dried biofilm samples (Table 5.5) and their percent protein
(Table 5.6), the amount of protein can easily be calculated by multiplying the total
dry weight of the biofilm by the percent protein (Table 5.7). The total protein content
for three different milk types is shown in Figure 5.10. Their trends are similar to the
trend for total dry-weight of biofilm (Figure 5.8). One-way analysis of variance
(ANOVA) determined a p-value of 0.509 for total amount of biofim. Therefore, no
significant statistical difference was observed at the 95% confidence interval.
54
0
5
10
15
20
25
30
35
40
45
50
Control AB BLG BB BLG AA
Milk Type
g pr
otei
n/ m
2
Figure 5.10 Protein quantities per unit area of biofilm samples
Table 5.7 Average quantity of protein in the biofilm
Type Average dried
biofilm g/m2
Average %Protein
Protein g/m2 Stdev
Control AB 93.18 37.33 34.78 2.90
BLG BB 90.59 35.61 32.26 11.06
BLG AA 71.49 38.27 27.36 10.15
55
5.5 Effect of milk type on the fat in biofilm
Fat content in fouling biofilm samples was measured using the Majonnier
method. Results are given in Table 5.8. Greater fat content was observed for BLG AA
type milk compared to the other type (BLG BB and the control BLG AB) (Figure
5.11). Analyses of these data with a one-way ANOVA resulted in a p-value of 0.095.
The difference between BLG AA type milk and the two other types was statistically
significant.
Table 5.8 Analysis of fat content in biofilm
Type Test Weight of
dish g
Weight of Sample
g
Dried weight of dish + Fat
g
Weight of fat g
% Fat Average % Fat
Stdev
1 27.9061 8.206 28.0039 0.0978 1.1918
2 41.732 8.1718 41.7987 0.0667 0.8162 Control AB
3 30.2605 8.2005 30.3797 0.1192 1.4536
1.1539 0.32
1 30.3995 8.0092 30.5102 0.1107 1.3822
2 28.0679 8.4195 28.1417 0.0738 0.8765 BLG BB
3 29.9589 8.3018 30.0629 0.1040 1.2527
1.1705 0.26
1 33.964 7.795 34.0777 0.1137 1.4586
2 29.9544 7.8901 30.0853 0.1309 1.6590 BLG AA
3 28.0438 3.5254 28.1115 0.0677 1.9203
1.6793 0.23
56
0.0000
0.5000
1.0000
1.5000
2.0000
2.5000
Contro
l AB
BLG B
B
BLG A
A
Milk Type
Ave
rage
% F
at in
bio
film
Figure 5.11 Analysis of milk type on the fat in biofilm 5.6 Effect of milk type on the mineral content of biofilms
Mineral content in biofilm samples was measured by using ash analysis
(Table 5.9). Figure 5.12 shows the effect of milk type on mineral content in biofilm.
Lower mineral content was observed for BLG AA than BLG BB or Control BLG AB.
However, the difference between milk-type was not statistically significant at the 95
% confidence with a p-value of 0.447 (analyzed by ANOVA method).
57
Table 5.9 Mineral content in biofilm
Type Test Crucible Wt. g
Wt. of samples
g
Ashed wt. of cru + samples
g
Wt. Of Ash
g % Ash Average
Ash % Stdev
21.0635 0.1126 21.0748 0.0113 10.0355 1
22.9429 0.107 22.9532 0.0103 9.6262
22.1221 0.1039 22.13 0.0079 7.6035 2
28.1103 0.1071 28.1195 0.0092 8.5901
18.8595 0.1074 18.867 0.0075 6.9832
Control AB
3 23.831 0.1067 23.8416 0.0106 9.9344
8.7955 1.29
25.8714 0.104 25.8817 0.0103 9.9038 1
17.2819 0.1053 17.2897 0.0078 7.4074
28.2977 0.1052 28.3092 0.0115 10.9316 2
27.2234 0.1123 27.2336 0.0102 9.0828
18.7367 0.117 18.7441 0.0074 6.3248
BLG BB
3 22.9151 0.1063 22.9226 0.0075 7.0555
8.4510 1.80
25.9036 0.1297 25.912 0.0084 6.4765 1
24.564 0.1052 24.5698 0.0058 5.5133
27.3213 0.1124 27.3294 0.0081 7.2064 2
28.1572 0.114 28.166 0.0088 7.7193
17.3481 0.1055 17.3574 0.0093 8.8152
BLG AA
3 26.1574 0.1107 26.1668 0.0094 8.4914
7.3703 1.24
58
0
2
4
6
8
10
12
Control AB BLG BB BLG AA
Milk type
Ave
rage
ash
%
Figure 5.12 Analysis of milk-type on the mineral in biofilm
5.7 Result of gel electrophoresis of milk and biofilm proteins
Results of protein analysis by gel electrophoresis are shown in Figure 5.13
and Figure 5.14 for whole milk and bifim samples, respectively. Identifications were
made by comparing the position of the different protein bands obtained from the
whole milk and the biofilm samples to the position of pre-stained standard protein
bands. By this means it was possible to establish that protein fraction of the fluid
whole milk and biofilm was composed of α-LA, BLG, caseins (several kinds), bovine
serum albumin, high molecular weight proteins, and protein containing disulphide
bonds (Figure 5.13 a, and Figure 5.14a). Resolution of principal globular proteins of
whole milk by SDS-PAGE is shown in Figure 5.13. Relatively weak staining of the
bands for BLG BB of whole milk samples was observed (Figure 5.13 a and b).
59
Interaction between κ-casein and BLG also was also observed in biofilm
samples after extreme heat processing under non-reducing condition due to relatively
high concentrations of caseins (Figure 5.14a). Intensity of bands for BLG was nearly
similar for all the milk types (Figure 5.14 b).
60
Figure 5.13 SDS-PAGE pattern of proteins in whole milk under: A) non-reducing and B) reducing conditions. Each lane contains 15 µL of the sample.
(a) Non-reducing whole milk
21
Caseins
β-LG (BLG)
α-LA
3 5 6 7 8 9 10
High mass
BSA
203
86 135
43
30
20
14.4
Weight (KD)
(b) Reducing whole milk
4
21
Caseins
α-LA
3 5 6 7 8 9 10
High mass
BSA
203
86 135
43
30
20
14.4
Weight (KD) 4
BLG
Standard Control BLG AB BLG BB BLG AA
Control BLG AB BLG BB BLG AA Standard
61
Figure 5.14 SDS-PAGE patterns of proteins in biofim samples under:A)
non-reducing and B) reducing conditions. Each lane contains 15 µL of the sample.
(a) Non-reducing Biofilm
(b) Reducing Biofilm
21
Caseins
BLG
α-LA
3 5 6 7 8 9 10
High mass
BSA
203
86 135
43
30
20
14.4
Weight (KD) 4
21
Caseins
BLG
α-LA
3 5 6 7 8 9 10
High mass
BSA
203
86
135
43
30
20
14.4
Weight (KD) 4
Control BLG AB BLG BB BLG AA Standard
Standard Control BLG AB BLG AA BLG BB
62
CHAPTER 6
DISCUSSION
6.1 Strategy for reducing biofouling
To control the fouling problem, the most straightforward approach is to
develop a quantitative model for fouling and then use the model to optimize the
process conditions with respect to equipment and possibly the milk itself. The model
should account for all knowledge of the physical and chemical influences on of the
fouling mechanism. The model can then be used to optimize the process conditions
with respect to the fouling rate of the equipment. In the chemical industry this has
been a general approach for many years. However, a large number of variables can
affect milk biofouling due to the fact that milk is a complex substance, and interaction
of its components on the surface of the heat exchanger and with each other is a
reflection of the net deposition.
The study at New Zealand concluded that milk from beta-lactoglobulin BB
phenotype cows has a much lower fouling rate than milk from beta-lactoglobulin AA
phenotype cow. They also concluded that BLG BB type whole milk powder results in
significantly lower fouling rates than whole milk powder made from control AB and
BLG AA for milk powder manufacture under UHT (Ultra-High Temperature)
Processing (Hill et al. 1998). In that study the biofouling rate was only determined by
63
monitoring the rise in the temperature difference (Delta T) between milk and hot
water for a total run time of 8 hours under UHT plant operating conditions. The UHT
processor had a preheat temperature of 75 ˚C and then was raised to 140 ˚C.
This Cal Poly study also found that biofouling by the BLG-BB variant was
less than that of the BLG-AA or mixed control, but this difference was not
statistically distinguishable at the 95% confidence interval with moderately large p-
values (Table 5.3), when using the same Delta T method. In the current Cal Poly
study, biofouling was also measured using changes in milk outlet temperature versus
time and changes in heat transfer rates. Comparison between BLG variants by these
methods indicated less biofouling for the BLG-BB variant, but again these differences
were not statistically significant. Results may be different because the New Zealand
study was under UHT conditions (140 ˚C), while the Cal Poly study was not under
UHT processing conditions (maximum milk outlet temperature up to 97 ˚C).
Differences in results could also be due to variation between the milk used in the
respective experiments since this study was conducted using milk from U.S. dairy
herds.
6.2 Effect of milk type on protein, fat, and mineral content of biofilms
It is interesting that there was apparently less biofouling (in terms of Delta T
and milk outlet temperature) for the BLG-BB variant milk even though there
appeared to be more biofilm mass for the BLG-BB milk. While these observations
were not statistically significant at the 95% confidence level, it is still worthwhile to
64
interpret this result. With less heat exchanger biofouling caused by biofilms of greater
total mass, it is likely that the composition of the biofilm has an important influence
on biofouling. In these experiments bifilm of BLG AA phenotype, which caused
more biofouling, contained higher percent protein compared to BLG BB and Control
BLG AB with considerable statistical significance (Figure 5.8). The order of percent
protein was as AA>AB>BB (Figure 5.8). Additionally, analysis of fat content
determined that there was greater fat content in biofilm of BLG AA milk type
compared to BLG BB and control BLG AB and this was also statistically significant.
Trends in total dried biofilm mass and mineral content (Figure 5.7 and Figure 5.9) are
similar. It is obvious larger number of replication can improve the statistic.
Other researchers have reported effects of intrinsic factors such as age of the
milk and its composition (mainly protein and mineral) on biofouling rates (De Jong
1997). Many investigators have also confirmed the correlation between protein
denaturation in milk and fouling of heat exchangers (Lalande et al. 1984; Fryer 1989;
De Jong et al. 1992).
Two distinct types of deposits as the result of milk biofouling were described
by Burton (1968): protein deposit, at temperature up to 100 ˚C (a soft white
voluminous spongy deposit) and the second mineral deposit, formed at temperatures
above 100 ˚C (a gray brittle structure). Experimental results have been shown that
BLG plays a dominant role in the fouling process of heat exchangers. It appears that
the denaturation of BLG and the formation of deposits occur simultaneously as the
milk flows through the heat exchanger (De Jong et al. 1992). The heat stability of
65
milk is affected by BLG variant (Feagan 1979; Hillier et al. 1979; McLean et al.
1987) as well as temperature and pH (Ng-Kwai-Hang et al. 1992). Hiller et al. (1979)
reported that at temperatures below 90 ˚C, BLG A was more heat stable than BLG B,
but at temperatures above 90 ˚C, the situation was reversed. Differential scanning
calorimetric measurements in phosphate buffer at pH 6.8 indicated that BLG BB had
a higher denaturation temperature than either AB or AA phenotype (Imafidon 1990).
This may explain why the BLG BB variant milk caused significantly less biofouling
in the New Zealand study because their experiments were done at very high
temperatures associated with UHT processing.
6.3 Composition identification of by SDS-PAGE method
This electrophoresis analysis provides qualitative rather than quantitative
results. Results of SDS-PAGE suggest that the BLG BB whole milk contains less
whey protein than the other milk types (BLG AA and control BLG AB), as shown in
Figure 5.12 a and b. This agrees with reported literature (Hill et al. 1998). Protein
containing disulfide bonds interact and aggregate with each other in non-reducing
conditions (Figure 5.13 a), but under reducing conditions these disulfide interchange
bonds were disrupted by adding mercapto ethanol and consequently results in
revealing bands of whey proteins and caseins (Figure 5.13 b). It is reported that when
whey protein is denatured, it will associate with the casein (Lewis et al. 2000). It is
also reported that in absence of casein, whey protein are susceptible to coagulation.
66
CHAPTER 7
CONCLUSIONS
The genetic variant milk with BLG BB produced the least biofouling in terms
of loss of thermal conductivity in the heat exchanger but this difference was not
statistically significant at the 95% confidence level. In contrast, the total amount of
biofilm produced by BLG AA milk on a dry-weight basis was lower than that
produced by BLG BB milk (again, not significant at 95% confidence level).
However, the percent protein and percent fat was lower for the biofilms produced by
BLG AA milk. This suggests that the composition of the biofilm may play an
important role in determining the severity of biofouling. Using SDS-PAGE appeared
similar protein composition for all the milk type. Overall, this study suggested that
the BLG BB milk results in a small reduction in biofouling, but this advantage was
not statistically significant because of the large experimental variability of
temperature measurements. The results of this work agree with the findings of New
Zealand Dairy Board, which also reported a lower fouling rate of BLG BB compared
to BLG AA phenotype cows.
67
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APPENDIX A
“Raw Temperature data for Delta T methods as a function of time for each run”
74
2) Control BLG AB (Test2)
y = 0.1294x + 3.1416R2 = 0.7779
00.5
11.5
22.5
33.5
44.5
0.000 2.000 4.000 6.000 8.000
Time (hr)
Del
ta T
(F/
hr)
Figure A.1,2,3 Linear regression plot of Delta T versus time
1) Control BLG AB (Test1)
y = 0.0688x + 2.8383R2 = 0.7702
2.7
2.8
2.9
3
3.1
3.2
3.3
3.4
0.000 2.000 4.000 6.000 8.000
Time (hr)
Del
ta T
(F
/hr)
3) Control BLG AB (Test 3)
y = 0.1707x + 3.923R2 = 0.8886
0
1
2
3
4
5
6
0.000 2.000 4.000 6.000 8.000
Time (hr)
Del
ta T
F/h
r
75
5) BLG BB (Test2)
y = 0.1327x + 3.3058R2 = 0.7163
00.5
11.5
22.5
33.5
44.5
0.0000 2.0000 4.0000 6.0000 8.0000
Time (hr)
Del
ta T
(F)
6) BLGBB (Test3)
y = 0.0506x + 2.7588R2 = 0.5557
2.6
2.7
2.8
2.9
3
3.1
3.2
3.3
0.0000 2.0000 4.0000 6.0000 8.0000
Time (hr)
Del
ta T
(F)
Figure A.4,5,6 Linear regression plot of Delta T versus time
4) BLG BB (Test1)
y = 0.02x + 2.8138R2 = 0.1283
2.6
2.7
2.8
2.9
3
3.1
3.2
0.0000 2.0000 4.0000 6.0000 8.0000
Time (hr)
Del
ta T
(F)
76
7) BLG AA (Tes1)
y = 0.1814x + 2.99R2 = 0.8974
00.5
11.5
22.5
33.5
44.5
0.000 2.000 4.000 6.000
Time (hr)
Del
ta T
(F)
8) BLG AA (Test2)
y = 0.1008x + 2.7152R2 = 0.8898
0
0.5
1
1.5
2
2.5
3
3.5
4
0.0000 2.0000 4.0000 6.0000 8.0000
Time (hr)
Del
ta T
(F)
9) BLG AA (Test3)
y = 0.1324x + 3.5759R2 = 0.7912
00.5
11.5
22.5
33.5
44.5
5
0.0000 2.0000 4.0000 6.0000 8.0000
Time (hr)
Del
ta T
(F)
Figure A.7,8,9 Linear regression plot of Delta T versus time
77
APPENDIX B
“Data for milk outlet temperature as a function of time for each run”
78
1) Control BLG AB (Test 1)
y = -0.203x + 200.94R2 = 0.7688
199.4199.6199.8
200200.2200.4200.6200.8
201201.2201.4201.6
0.000 2.000 4.000 6.000 8.000
Time (hr)
Milk
out
let (
F)
2) Control BLG AB (Test 2)
y = -0.2699x + 200.44R2 = 0.8062
198.5
199
199.5
200
200.5
201
201.5
0.000 2.000 4.000 6.000 8.000
Time (hr)
Milk
out
let (
F)
3) Control BLG AB (Test 3)
y = -0.3903x + 200.67R2 = 0.8863
198
198.5
199
199.5
200
200.5
201
201.5
0.000 2.000 4.000 6.000 8.000
Time (hr)
Milk
out
let (
F)
Figure B.1,2,3 Linear regression plot of milk outlet temperature versus time
79
4) BLG BB (Test1)
y = -0.0631x + 201.11R2 = 0.2433
200.4
200.6
200.8
201201.2
201.4
201.6
201.8
0.0000 2.0000 4.0000 6.0000 8.0000
Median Time (hr)
Med
ian
milk
out
let (
F)
5) BLG BB (Test2)
y = -0.2059x + 199.61R2 = 0.5223
198
198.5
199
199.5
200
200.5
201
0.0000 2.0000 4.0000 6.0000 8.0000
Median Time (hr)
Med
ian
milk
out
let (
F)
6) BLG BB (Test3)
y = -0.1299x + 200.46R2 = 0.7033
199.4
199.6
199.8
200
200.2
200.4
200.6
200.8
201
0.0000 2.0000 4.0000 6.0000 8.0000
Median Time (hr)
Med
ian
milk
out
let (
F)
Figure B.4,5,6 Linear regression plot of milk outlet temperature versus time
80
7) BLG AA (Test1)
y = -0.2375x + 200.62R2 = 0.8743
199.2199.4199.6199.8
200200.2200.4200.6200.8
0.000 1.000 2.000 3.000 4.000 5.000 6.000
Time (hr)
Milk
out
let (
F)
8) BLG AA (Test2)
y = -0.1377x + 200.97R2 = 0.6647
200200.2200.4200.6200.8
201201.2201.4201.6
0.0000 2.0000 4.0000 6.0000 8.0000
Median Time (hr)
Med
ian
milk
out
let (
F)
9) BLG AA (Test3)
y = -0.341x + 200.5R2 = 0.6373
198
198.5199
199.5
200
200.5201
201.5
202
0.0000 2.0000 4.0000 6.0000 8.0000
Median Time (hr)
Med
ian
milk
out
let (
F)
Figure B.7,8,9 Linear regression plot of milk outlet temperature versus time
81
APPENDIX C
“Data for heat transfer rates as a function of operating time”
82
1) Control BLG AB (Test 1)
y = -0.0353x + 10269R2 = 0.8782
9200.009400.009600.009800.00
10000.0010200.0010400.0010600.0010800.0011000.00
0 5000 10000 15000 20000 25000
Time (sec)
Q (
W)
2) Control BLG AB (Test 2)
y = -0.0277x + 10074R2 = 0.8018
9200.09400.09600.09800.0
10000.010200.010400.010600.010800.0
0 5000 10000 15000 20000 25000
Time (sec)
Q (
W)
3) Control BLG AB (Test 3)
y = -0.1076x + 10381R2 = 0.9815
0.0
2000.0
4000.0
6000.0
8000.0
10000.0
12000.0
0 5000 10000 15000 20000 25000
Time (sec)
Q W
Figure C.1,2,3 Linear regression plot of heat transfer rate (Q) versus time
83
4) BLG BB (Test 1)
y = -0.0707x + 11110R2 = 0.9653
0.00
2000.00
4000.00
6000.00
8000.00
10000.00
12000.00
14000.00
0 5000 10000 15000 20000 25000
Time (sec)
Q
(W)
5) BLG BB (Test 2)
y = -0.0411x + 10170R2 = 0.7944
9000.09200.09400.09600.09800.0
10000.010200.010400.010600.010800.011000.0
0 5000 10000 15000 20000 25000Time (sec)
Q (
W)
Figure C.4,5,6 Linear regression plot of heat transfer rate (Q) versus time
6) BLG BB (Test 3)
y = -0.0709x + 10692R2 = 0.9657
0
2000
4000
6000
8000
10000
12000
0 5000 10000 15000 20000 25000
Time (sec)
Q
(W)
84
7) BLG AA (Test 1)
y = -0.1037x + 10276R2 = 0.9763
0
2000
4000
6000
8000
10000
12000
0 5000 10000 15000 20000 25000
Time (sec)
Q
(W)
8) BLG AA (Test 2)
y = -0.1401x + 10735R2 = 0.9883
0
2000
4000
6000
8000
10000
12000
0 5000 10000 15000 20000 25000Time (sec)
Q
(W)
9) BLG AA (Test 3)
y = -0.0418x + 10664R2 = 0.842
940096009800
1000010200104001060010800110001120011400
0 5000 10000 15000 20000 25000Time (sec)
Q (
W)
Figure C.7,8,9 Linear regression plot of heat transfer rate (Q) versus time
85
APPENDIX D
“Milk types used in biofouling experiments”
86
Genetic Variant Cow ID KCN BLG Breed 361 AB BB Jersey 568 AB BB Jersey AB-BB 643 AB BB Jersey 514 BB BB Jersey 550 BB BB Jersey 606 BB BB Jersey 609 BB BB Jersey 633 BB BB Jersey 672 BB BB Jersey 673 BB BB Jersey 674 BB BB Jersey 679 BB BB Jersey
9013 BB BB Jersey
BB-BB
1806 BB BB Holstein 1812 AA BB Holstein 1832 AA BB Holstein 1844 AA BB Holstein 1846 AA BB Holstein 1848 AA BB Holstein 1849 AA BB Holstein 1867 AA BB Holstein 1874 AA BB Holstein
AA-BB
1897 AA BB Holstein
Figure D 1. Milk type used for biofouling experiment based on the cow’s classification.
87
Genetic Variant Cow ID KCN BLG Breed
527 AB AA Jersey 561 AB AA Jersey AB-AA 642 AB AA Jersey 503 BB AA Jersey 515 BB AA Jersey 517 BB AA Jersey 525 BB AA Jersey 535 BB AA Jersey 566 BB AA Jersey 573 BB AA Jersey 593 BB AA Jersey 646 BB AA Jersey 678 BB AA Jersey
BB-AA
687 BB AA Jersey 1754 AA AA Holstein 1763 AA AA Holstein 1784 AA AA Holstein 1787 AA AA Holstein 1788 AA AA Holstein 1794 AA AA Holstein 1801 AA AA Holstein 1821 AA AA Holstein 1823 AA AA Holstein 1835 AA AA Holstein 1853 AA AA Holstein 1898 AA AA Holstein 1900 AA AA Holstein
AA-AA
1912 AA AA Holstein Figure D 2. Milk type used for biofouling experiment based on the cow’s classification.