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The microstructure of Australian cheddar cheese
and other dairy products
L. Ong, H. Nguyen, K. Soodam, S.E. Kentish, S.L. ...
How can we:
• Control structure?
• Improve consistency and yield?
• Tailor textures?
How does the microstructure of Chedda...
How does microstructure develop during Cheddar cheese
making?
How do process changes alter microstructure?
• Coagulation t...
25 L4 L 250 L
Laboratory scale
Pilot scale
Industrial scale
~60,000L
Conditions relevant to Australian manufacturing:
• fu...
Cheese press
Microscopy capabilities
CLSM
Cryo SEM
TEM
= fat globules
= protein
FG
MFGM
C
M
FG
Pr
10 µm
Volume rendering
3D image analysis process
Protein
Number of
vertices
Total volume (P
vol)
Fat globules
Number of
globules...
Pilot scale
at MG
3.7% 4% 5% 6% (w/w)
Pasteurise Pasteurise
Standardise
The effect of milk protein concentration
0
50
100
...
Texture profile analysis and composition of cheese
3.5% 4% 5% 6%
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0
3000
6000
9000
12...
3.7% 4% 5% 6%
Denser gel network
Fat globules Protein network
↑ casein micelles
↑ colloidal calcium phosphate
↓ volume fra...
3.7%
6%
Scale bar = 20 µm
Fat =
Protein =
Heterogeneous pooled fat
Porosity
0.36 ± 0.02
Porosity
0.26 ± 0.02
Starter bacteria
3.7% 4% 5% 6%
Denser cooked curd
3.7% 4% 5% 6%
More compact milled curd
curd junction
Cheese
Pooling of fatHigher porosity
Intermediate protein concentrations are optimal
0
50
100
150
200
250
5
10
15
20
25
3 4 5 6
W...
3.7%
Week 1
Week 39
Maturation of the pressed cheese
6.0 %
Changes in the protein network with
maturation
Protein
strands
Fat Protein
junctions
0
0.5
1
1.5
2
0 20 40
Number of prote...
3.7% 6%
10 µm
Week 1
Week 26
0
5
10
15
20
25
30
0 10 20 30 40 50
(TCA‐SN/TN) %
Ripening Period (weeks)
0
20
40
60
80
100
120
0 10 20 30 40 50
Hardness ...
Summary
• Changes in the composition of the sweet whey (fat loss) and
cheese hardness correlate with changes in curd micro...
Buffalo and bovine cheese and yoghurt
Cheese
Yoghurt
Buffalo  Bovine 
Lactobacilli Streptococci
Microstructure of yoghurt and cream cheese
10 µm
Fat agglomeratesFree fatFat globules
Dairy Innovation Hub: 
Transformational Research to Underpin the Future of the 
Australian Dairy Manufacturing Industry
9 ...
Microstructure within the Dairy innovation Hub:
Crystal structures and morphologies of 
fractionated milk fat in nanoemuls...
Acknowledgements
Ong L. et al. (2010), Journal of Food Science, 75(3): E135‐E145.
Ong L. et al. (2010), Australian Journal...
Abstract submitted
• Confocal microscopy and Cryo‐Scanning Electron Microscopy can be used to assess the 
microstructure o...
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The Microstructure of Australian Cheddar Cheese and other Dairy Products

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This is Assoc Prof Sally Gras presentation to the IDF Symposium on Microstructure in Melbourne, March 2014

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The Microstructure of Australian Cheddar Cheese and other Dairy Products

  1. 1. The microstructure of Australian cheddar cheese and other dairy products L. Ong, H. Nguyen, K. Soodam, S.E. Kentish, S.L. Gras Department of Chemical and Biomolecular Engineering, and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne.
  2. 2. How can we: • Control structure? • Improve consistency and yield? • Tailor textures? How does the microstructure of Cheddar cheese structure and texture? Water Casein Fat Minerals
  3. 3. How does microstructure develop during Cheddar cheese making? How do process changes alter microstructure? • Coagulation temperature; • Calcium addition; • pH at rennet addition; • Calcium addition and draining pH; • Protein concentration (including cheese maturation). Cutting CookingGel Cheddaring Milling Pressing Cheddar Cheese Whey Focus on curd and intermediate stages
  4. 4. 25 L4 L 250 L Laboratory scale Pilot scale Industrial scale ~60,000L Conditions relevant to Australian manufacturing: • full fat product, • fresh pasteurised and standardised milk, • Cheddar as a model system (protein to fat ratio of 0.84).
  5. 5. Cheese press Microscopy capabilities CLSM Cryo SEM TEM = fat globules = protein FG MFGM C M FG Pr 10 µm
  6. 6. Volume rendering 3D image analysis process Protein Number of vertices Total volume (P vol) Fat globules Number of globules Sphericity Total volume (F vol) Pore volume = total volume – (F vol + P vol) Porosity = Pore volume/ total volume in sampling area 40 layers of 2D images, total image depth of 10 µm. 10 µm
  7. 7. Pilot scale at MG 3.7% 4% 5% 6% (w/w) Pasteurise Pasteurise Standardise The effect of milk protein concentration 0 50 100 150 200 250 5 10 15 20 25 3 4 5 6 Weightofwhey(kg) Fatorproteinlosttosweet whey(%w/w) Protein in cheese-milk (% w/w) fatprotein sweet whey Raw milk Raw LC UF RetentateCream 0.0 0.5 1.0 1.5 2.0 2.5 3.0 20 25 30 35 40 3 4 5 6 Saltincheese(%w/w) Fat,proteinormoistureincheese (%w/w) Protein in cheese-milk (% w/w) saltmoisture
  8. 8. Texture profile analysis and composition of cheese 3.5% 4% 5% 6% 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 3000 6000 9000 12000 15000 3 4 5 6 Cohesiveness(g.s/g.s) Hardnessandgumminess(g) Protein in cheese-milk (% w/w) Hardness Gumminess Cohesiveness
  9. 9. 3.7% 4% 5% 6% Denser gel network Fat globules Protein network ↑ casein micelles ↑ colloidal calcium phosphate ↓ volume fraction of the aqueous phase ↓ distance between casein micelles ↑ aggregation
  10. 10. 3.7% 6% Scale bar = 20 µm Fat = Protein = Heterogeneous pooled fat Porosity 0.36 ± 0.02 Porosity 0.26 ± 0.02
  11. 11. Starter bacteria 3.7% 4% 5% 6% Denser cooked curd
  12. 12. 3.7% 4% 5% 6% More compact milled curd curd junction Cheese
  13. 13. Pooling of fatHigher porosity Intermediate protein concentrations are optimal 0 50 100 150 200 250 5 10 15 20 25 3 4 5 6 Weightofwhey(kg) Fatorproteinlosttosweetwhey (%w/w) Protein in cheese-milk (% w/w) fat protein weight of sweet whey 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 3000 6000 9000 12000 15000 3 4 5 6 Cohesiveness(g.s/g.s) Hardnessandgumminess(g) Protein in cheese-milk (% w/w) Hardness Gumminess Cohesiveness
  14. 14. 3.7% Week 1 Week 39 Maturation of the pressed cheese 6.0 %
  15. 15. Changes in the protein network with maturation Protein strands Fat Protein junctions 0 0.5 1 1.5 2 0 20 40 Number of protein  junctions (x 106) Ripening time (weeks) 4%3.50% 4% 5% 6% 0 0.5 1 1.5 2 0 20 40 Ripening time (weeks) P<0.01
  16. 16. 3.7% 6% 10 µm Week 1 Week 26
  17. 17. 0 5 10 15 20 25 30 0 10 20 30 40 50 (TCA‐SN/TN) % Ripening Period (weeks) 0 20 40 60 80 100 120 0 10 20 30 40 50 Hardness (N) Ripening Period (weeks) 3.7% 4% 5% 6% Changes in TCA-SN and cohesiveness consistent with decreasing protein junctions with time: r = - 0.66, P< 0.001 r = 0.70; P<0.001
  18. 18. Summary • Changes in the composition of the sweet whey (fat loss) and cheese hardness correlate with changes in curd microstructure. • A milk protein concentration of 4% or 5% reduces fat loss at intermediate stages; 4% produced a better texture. • The addition of UF assists cheese making. • The protein network in Cheddar changes during maturation as a result of proteolysis; a change observable by microscopy. • Cheddar hardness is similar for cheese made with higher protein concentrations after 40 weeks of maturation.
  19. 19. Buffalo and bovine cheese and yoghurt Cheese Yoghurt Buffalo  Bovine 
  20. 20. Lactobacilli Streptococci Microstructure of yoghurt and cream cheese 10 µm Fat agglomeratesFree fatFat globules
  21. 21. Dairy Innovation Hub:  Transformational Research to Underpin the Future of the  Australian Dairy Manufacturing Industry 9 academics across University of Melbourne and University of Queensland. 7 staff technical staff from Dairy Innovation Australia. 5 years. Aims to: • address technical challenges facing the Australian dairy manufacturing industry.  • develop transformational processing technologies and innovative products. • enhance productivity, growth and sustainability.
  22. 22. Microstructure within the Dairy innovation Hub: Crystal structures and morphologies of  fractionated milk fat in nanoemulsions Tuyen Truong (2:15 today) 
  23. 23. Acknowledgements Ong L. et al. (2010), Journal of Food Science, 75(3): E135‐E145. Ong L. et al. (2010), Australian Journal of Dairy Technology, 65(3): 222.  Ong L. et al. (2011), Food Science and Technology, 44(5): 1291‐1302. Ong et al. (2011), Dairy Sci Tech (2011) 91:739‐758; Ong et al. (2012), Food Res Inter 48:119‐130;  Ong et al. (2013), FOODS, 2013, 2(3), 310‐331; Ong et al. (2013), Inter Dairy J, 33(2), 135–141. Nguyen et al. (2013), Food Bioprocess Technology, in press.
  24. 24. Abstract submitted • Confocal microscopy and Cryo‐Scanning Electron Microscopy can be used to assess the  microstructure of dairy products during production; enabling the optimisation of manufacturing  processes and the reverse engineering of desired product properties. We have applied these tools  to study the microstructure of full fat Cheddar cheese produced at a laboratory and pilot scale  using conditions employed in Australian manufacturing.  • Process variables including temperature, calcium concentration, draining pH and protein  concentration have been systematically altered and the effect on the curd microstructure and  resulting product properties, such as cheese texture examined.  • These studies have shown a link between the curd microstructure and product functional  properties.  • The two microscopic techniques have been further applied to a range of dairy products including  yoghurt and cream cheese and used to assess structural changes as a function of Cheddar  maturation.  • Useful comparisons have also been drawn between the microstructure observed in yoghurt and  cheese made from bovine and buffalo milk, where differences in composition and product  processing lead to markedly different structures and properties.  • The further study of dairy microstructure forms a program within Dairy Innovation Hub, an  Australian Research Council Industrial Transformation Research Hub in collaboration with Dairy  Innovation Australia  Time allocated 20 minutes (including questions).

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