Second Harmonic Generation Microscopy: A Tool for Spatially and Temporally Resolved Studies of Heat Induced Structural Changes in Meat

Abstract

Myofibers and collagen show non-linear optical properties enabling imaging using second harmonic generation (SHG) microscopy. The technique is evaluated for use as a tool for real-time studies of thermally induced changes in thin samples of unfixed and unstained pork. The forward and the backward scattered SHG light reveal complementary features of the structures of myofibers and collagen fibers. Upon heating the myofibers show no structural changes before reaching a temperature of 53°C. At this temperature the SHG signal becomes extinct. The extinction of the SHG at 53°C coincides with a low-temperature endotherm peak observable in the differential scanning calorimetry (DSC) thermograms. DSC analysis of epimysium, the connective tissue layer that enfold skeletal muscles, produces one large endotherm starting at 57°C and peaking at 59.5°C. SHG microscopy of collagen fibers reveals a variability of thermal stability. Some fibers show severe shrinkage at 57°C, before the signal for most of them vanishes between 59°C and 61°C and thus coinciding with the endotherm of the thermograms. However, in some areas, strong SHG signals from collagen can be visualized even after prolonged heating to 67°C and thus indicating regions of much higher thermal stability. It is seen that the benefits of the structural and temporal information available from SHG microscopy reveals complementary information to a traditional DSC measurement and enables a more complete understanding of the thermal denaturation process.

Effect of typical starch on the rheological properties and NMR characterization of myofibrillar protein gel

“…indicated that the first decrease in G ′ was mainly because of rising temperature, which destroyed the hydrogen bonds. Brüggemann et al . showed that the characteristic peak of myosin almost disappeared at 53 °C, which was indicative of protein denaturation.…”

Validation of feasibility and quality of chicken breast meat cooked under various water‐cooking conditions

“…According to the DSC results, Kijowski and Mast () observed that there was one major peak temperature of thermal shrinkage of connective tissue at 65.3°C and some minor thermal transitions at temperatures lower than 65.3°C. Using Second Harmonic Generation microscopy, Bruggemann et al () reported that the structural changes in collagen mainly occurred at 57−61°C. Accordingly, most of the collagens in this study were denatured at 80°C, thus leading to the non‐significant difference in collagen solubility between the treatments.…”

Low temperature, long time treatment of porcine M. longissimus thoracis et lumborum in a combi steamer under commercial conditions

“…At 58 °C the tenderization could be achieved at a clearly lower heating time. This is probably due to the fact that collagen alteration mainly occurs at this temperature (Brüggemann, Brewer, Risbo, & Bagatolli, 2010;Christensen et al, 2011b;Christensen et al, 2013). Christensen et al (2013) is only marginal.…”