“Frattura a Scaglie” in Parmigiano Reggiano Cheese with Industrial Tomographic system

“Frattura a Scaglie” in Parmigiano Reggiano Cheese with Industrial Tomographic system


INTRODUCTION
The basic idea was to provide a clear definition of the “Frattura a Scaglie”, a structure-related property of the Parmigiano Reggiano (PR) cheese indicated by the PDO disciplinary as typical quality requirement, as well as some objective methods for quantitative determination of fracture toughness.
 

 
ACTIVITIES
Based on empirical evidences and fracture mechanic theory, we propose an engineering definition of the “Frattura a scaglie” property: “Unstable Fracture Under a Crack-Driving Critical Stress”. With this in mind, PR cheeses at different ripening ages (i.e. 12, 30, 37 and 72 months) were firstly investigated for their microstructure using a multi-level approach based mainly on non-destructive methods, with the aim to virtualize the inner structure and understand some key structure-mechanics relationships. Therefore, cheese samples with different structures were objectively characterized for both crack initiation and crack growth toughness under three-point bending tests with and without notch. The greater the fracture toughness, the lower the “Frattura a scaglie”. Finally, isothermal creep were carried out to evaluate the effect of temperature on fracture toughness.
 


 

OUR CONTRIBUTION
In order to explore the inner structure of PR cheese, TEC Eurolab engineers investigated the samples using the two Industrial Tomographic systems at our disposal.
Tomographic images put on evidence the presence of both micropores and microcracks in
the cheese at 72 months.
According to the fracture mechanics theory, it is reasonable to hypothesize a key role of such structure discontinuities on the fracture toughness of PR cheese. The shape and size of preexisting microcrack may be the main factors driving crack initiation and crack growth. On the other hand, little composition differences detected among the investigated cheeses, cannot be used to fully explain the major differences measured in toughness properties. 
 
 
CONCLUSIONS
According to the fracture mechanics theory, it is reasonable to hypothesize a key role of such structure discontinuities on the fracture toughness of PR cheese. The shape and size of preexisting microcrack may be the main factors driving crack initiation and crack growth. On the other hand, little composition differences detected among the investigated cheeses, cannot be used to fully explain the major differences measured in toughness properties. 
 
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