Effect of static magnetic fields on the quality of frozen bread dough.
The magnetic field is an emerging physical method used for food preservation, characterized by high penetrability in food materials. In this context, the objective of a recent study, carried out by a group of Chinese researchers (Zhou et al., 2022), was to assess the effect of this technology (field density of 2 mT) on the quality of frozen bread dough, during several freeze-thaw cycles of the product (from 3 up to 10 cycles).
Results showed that the magnetic field ensured the baked bread made from dough a 17.6% larger specific volume and a 30.9% smaller crumb hardness compared to the control sample. Furthermore, it was noted that with the proposed technology even the yeast viability and activity were better maintained, as highlighted bu a significant increase (by about 42.2%) in its survival and gassing power (carbon dioxide) compared to the conventional product.
Finally, a reduction of 24.3% in glutenin macropolymer depolymerization was achieved, indicating a more stable gluten structure under the magnetic field. In summary, the study leads to the conclusion that the proposed technology is a promising effective method to improve the quality of frozen bread dough. Further studies are, however, desirable to analyse the effects of magnetic fields also on other qualitative parameters of bread, in particular on sensorial ones.
Influence of freezing conditions on the protein profile of steamed bread.
The aim of a recent study, carried out by a group of Chinese researchers (Zhang et al., 2022), was to investigate the effect of frozen storage on the quality of steamed bread. In particular, the samples were analysed in terms of: Water holding capacity, oil holding capacity, emulsifying capacity, soluble protein content, surface hydrophobicity, secondary structure and molecular weights of gluten proteins. The bread was stored for a maximum period of 4 weeks at -6, -12, -18, -24 or -30°C.
The results showed that with an extension of frozen storage time, the disulfide bond (S‒S) and total content of sulfydryl (-SH) decreased as a whole. Furthermore, with a decrease in frozen storage temperature, the soluble protein contents and protein water holding capacities of steamed bread first increased and then decreased, and the trend of the surface hydrophobicity was opposite.
According to the study, the frozen storage temperature had a significant effect on the protein properties of bread, whose molecular weights were mainly distributed between 22 and 31 kDa.
Finally, during the storage of the product at -24°C, the changes in oil holding capacity, protein emulsification and soluble protein content were stable. Consequently, the authors indicate this temperature is suitable for long-term frozen storage of steamed bread.
References: Zhou et al., LWT – Food Science and Technology, 154, 2022, 112670, Zhang et al., Food Science and Technology, 42, 2022, e68622.
