The glass transition has attracted great interest from food scientists in recent years, because many phenomena related to food manufacturing and preservation could be systematically explained with a concept of glass transition: for example, food materials maintain their physical and chemical stability better in a glassy state than in a rubbery state. However, it is often difficult to apply the methodology in polymer science to the analysis of glass transition for foods. In this review, the availability of the concept of glass transition in food science and engineering was explained. Such phenomena as reaction rate of non-enzymatic browning, powder caking, and in freeze drying can be described by glass transition.
In addition, the analysis of the glass transition of foods by electrical methods in our research was also reviewed. The dielectric relaxation, i.e., the peak of the dielectric loss, ε”, was observed for glassy gelatin of low moisture contents and ascribed to the local motion of molecules. However, when the ionic conductivity dominated the electrical properties, the ε” peak was masked. For analyzing such a system, the electric modulus, M* was an effective tool.

View full abstract

Thermally induced gelation of white croaker myosin solutions was studied by means of circular dichroism (CD) and viscoelasticity measurements both in heating and cooling processes at different KCl concentrations of the medium. In the heating process, the α-helix content decreased steeply around 30°C, irrespective of KCl concentration. In the cooling process for the heated sample, it increased around the same temperature but did not return to the initial value at low temperatures, especially at low KCl concentration. In the first heating process, around 32°C, G and η increased at high KCl concentrations of 0.3M and 0.6M, whereas they decreased sharply at 0.2M KCl. This characteristic temperature effect shifts to the higher side at 0.12M KCl. In the second cooling process, G and η increased with larger slopes from 40°C at 0.3M and 0.6M KCl, whereas no clear change in the slope was found at 0.2M and 0.12M KCl because of data fluctuations due to the inhomogeneity of the sample. From these experimental results, it was suggested that the gelation of myosin solutions at the physiological KC1 concentration occurs by refolding myosin molecules once heated, but the network structure is inhomogeneous because of restricted unfolding in the heating process..

View full abstract

We compared the anticoagulant and fibrinolytic effects of the major functional food products generated by Bacillus subtilis natto. We analyzed NSK-SD^R and NKCP^R powders that consist mainly of nattokinase and bacillopeptidase F, respectively. The specific activity of the plasmin-like activity of NKCP^R H was about 2.5-fold higher than that of NSK-SD^R. Although both NSK-SD^R and NKCP^R reduced fibrin monomer levels in human blood, the anticoagulant effect of NKCP^R was over 100-fold higher than that of NSK-SD^R. Dietary supplements with anticoagulant and fibrinolytic effects might play an important role in preventing thrombotic diseases.

View full abstract