In food industry,HPMC can improve the farinaceous and tensile properties of the dough. In addition, the addition of Hydroxypropyl Methyl cellulose ether HPMC reduces the increase of the freezable water content in the dough during freezing storage, thereby inhibiting the effect of ice crystallization on the dough network structure. The damage maintains the relative stability and integrity of its structure, thus providing a guarantee for the quality of the final product. On the other hand, the addition of HPMC also has a good quality control and improvement effect on steamed bread. For the unfrozen samples, the addition of HPMC increased the specific volume of the steamed bread and improved the texture properties of the steamed bread; while with the extension of the freezing time, the addition of HPMC inhibited the deterioration of the quality of the steamed bread made from the frozen dough degree. This shows that HPMC can be applied to the processing of frozen dough with steamed bread as the final product, and has a better effect on improving the quality of steamed bread.
(2) Experiments showed that the gluten structure without HPMC was destroyed due to the formation and growth of ice crystals, the elastic modulus decreased significantly, the free thiol content increased significantly, and the network microstructure was destroyed; however, the addition of HPMC can effectively inhibit the This change, especially when the addition amount is 2%, compared with the control group, the content of free sulfhydryl groups, the content of freezable water and the exposure of hydrophobic groups were reduced, while the secondary structure and microscopic network structure of gluten remained relatively Stablize. This is because HPMC can reduce the mobility of water and limit the increase of the freezable water content, thereby reducing the damage to the spatial conformation and network structure of gluten protein by ice crystals.
(3) The experiment found that after 60 days of frozen storage, the gelatinization characteristics of starch all increased, the gelatinization enthalpy increased significantly, while the gel strength of starch paste decreased, which indicated that the structure of starch was changed (relative crystallinity increased significantly). , the degree of starch damage increased); however, the starch suspension with HPMC added, the starch structure remained relatively stable after freezing, thus reducing the degree of changes in gelatinization characteristics, gelatinization enthalpy, gel strength, etc. It shows that the addition of HPMC can inhibit the effect of ice crystals on the structure and properties of native starch granules.
(4) The experiment shows that compared with the control group, the addition of HPMC can better maintain the fermentation activity of the yeast, inhibit the decline of the fermentation height of the dough and the survival number of the yeast after freezing for 60 days, thereby reducing the extracellular reduction type. The increase rate of glutathione content, and within a certain range, the protective effect of HPMC was positively correlated with its addition amount. This suggests that HPMC can protect yeast by inhibiting the formation and growth of ice crystals.
6.2 Outlook
(1) To further systematically study the effects of adding HPMC on the glass transition temperature (H) of frozen dough, the fermentation kinetics of yeast and the flavor of steamed bread, as well as the formation, growth, and redistribution of ice crystals in frozen dough, etc. Therefore, new strains with strong stress resistance suitable for frozen dough were selected, and a reference for the production and cold chain transportation of frozen dough and even other frozen foods was provided.
(2) Further study the improvement effect of HPMC on the quality of frozen dough and its products during longer freezing storage time, and explore the application of HPMC in other types of frozen dough.
(3) Further optimize the frozen dough recipe and process parameters that are in line with the actual production of steamed bread, so as to improve and enhance the quality of the frozen dough steamed bread product, and at the same time control and reduce the production cost. In addition, the application of HPMC in frozen dough Chinese-style pasta products can also be expanded, and more designs and types of products can be developed to meet the needs of consumers.