Using advanced microscopy techniques to guide Cheddar cheese manufacture

Transcription

1 Using advanced microscopy techniques to guide Cheddar cheese manufacture L. Ong 1, K. Soodam 1, I.B. Powell 2, S. E. Kentish 1, S. L. Gras 1 1 Department of Chemical and Biomolecular Engineering, The University of Melbourne, Australia. 2 Dairy Innovation Australia Limited, Werribee, Australia. 10 µm * Project funded by ARC and DIAL

2 Cheddar cheese production in Australia In 2012/2013 (Dairy Australia, 2014) Milk Milk production: 9,200 million litres Milk usage: Cheese (33 %) Cheese sales Domestic sales : AUD $ 1.8 billion ~1.2 billion Export sales : AUD $ 787 million ~550 million Mould, 2% Fresh, 30% Hard Grating, 4% Semi Hard, 17% Cheddar, 47% Cheddar, 47% Any improvement in yield, improvement in quality and consistency of dairy product economic benefit for the dairy industry

3 Microstructure approach key techniques What is cheese microstructure? Spatial arrangement of protein and fat in the cheese matrix at micron levels. Key techniques CLSM Protein Fat 20 µm Rheology, texture, chemical analysis Cryo SEM Fat Protein Control structure Tailor texture Improve consistency & yield TEM Casein micelles MFGM Fat

4 CLSM and cryo SEM are complementary techniques Protein Fat Fat Protein 10 µm Image analysis: porosity Number of fat globules, size, sphericity

5 How does cheese microstructure develop during cheese-making? How do process changes alter microstructure? CaCl 2 Rennet Starter culture Pre-treatment of milk: pasteurization standardization Coagulation Protein concentration 10 µm Gel Whey Cutting Heating and stirring Draining Draining ph 10 µm Cooked curd Cheddaring Milling Cheddared curd Salt Salting and mellowing 10 µm Salty whey Pressing Curd junction Packaging and ripening Cheese 50 µm Ong et al. : FOODS (2013) 2: ; IDJ (2013) 33:

6 Protein concentration Murray Goulburn Pilot Plant 250 L vat Cheddaring Raw milk Raw LC UF retentate Standardize Pasteurize Pasteurize 3.7% 4%, 4.8%, 5.8% Potential changes from UF addition in cheese making? productivity whey production bank/interface/vic/murray/cobram.html

7 Porosity = 0.36 ± 0.02 CLSM & cryo SEM microstructure of the gel 3.7% milk protein Fat globules pool together at higher protein concentration. Porosity = 0.26 ± % milk protein Protein Fat Scale bar = 20 µm Denser gel network Increased colloidal calcium phosphate (CCP). Lower volume fraction of the aqueous phase, lowers distance between casein micelles increases CM aggregation.

8 Cryo-SEM of cooked curd Cooking 3.7% 4% 4.8% 5.8% Starter bacteria Fat globules Protein network More porous structure in cooked curd with no UF

9 Fat lost to sweet whey is minimum at ~4-5% protein Cooked curd without UF Gel with 5.8 % protein More porous structure Denser gel microstructure Fat globules pool together CLSM and cryo SEM can be used to observe the impact of processing parameters. Give insights as to how fat may be lost during processing. Changes in protein network structures affect cheese texture. Ong et al. (2013) FOODS 2:

10 Texture profile analysis and composition of cheese Cohesiveness Hardness 3.7% 4% 4.8% 5.8% Differences in texture become less significant after ripening.

11 The effect of protein concentration: MICROSTRUCTURE: Microstructure of the gel (5.8% protein) was dense, fat pooled together. Cooked curd without UF retentate (3.7% protein) was more porous. Both resulted in higher fat loss during cooking. COMPOSITION: Higher yield and YDM (as expected) increase productivity. Lower moisture content in cheeses with higher protein. TEXTURE: Harder texture as protein increases less differences with ripening. Standardization of milk protein with UF retentate has positive effect up to 5% w/w. Link between microstructure and texture properties.

12 Calcium chloride addition and draining ph Cheese milk CaCl (mg/kg milk) Draining ph 6.2 Draining ph ol%20cheese%20and%20butter%20bidding%20war%20continu es.aspx Cheese Ripening (8 o C) 20 L vats Press

13 Fat loss and protein loss (% w/w) Calcium chloride addition (mg kg -1 ) PL, ph 6.0 PL, ph 6.2 FL, ph 6.2 FL, ph 6.0 Addition of CaCl 2 lower fat loss denser structure of gel possibly retain more fat Draining ph no significant effect

14 Calcium in cheese (mg kg -1 ) 8000 Drain ph Drain ph Calcium chloride addition (mg kg -1 ) Total calcium: cheese with 300 mg/kg CaCl 2 -drain ph 6.0 = cheese without added CaCl 2 -drain ph 6.2 The combination of calcium addition and lower draining ph could be used to increase network formation at the early stages of cheese making to improve fat retention while maintaining a similar level of total calcium in the final cheese.

15 Summary CLSM and cryo SEM can be used to observe the impact of processing parameters on the microstructure of fat and protein. Give insights as to how fat may be lost during processing. Shows how changes in protein network structures correlate with texture and functionality. This knowledge may help manufacturers to further optimize the cheese-making process, increase yield and productivity.

16 Acknowledgements Thanks