| The low-sodium salinization of flour food is of great significance in promoting the construction of Healthy China and improving People’s health level.How to ensure the quality of flour products while effectively reducing the content of sodium salt in the products is a major problem to be solved in the flour food industry in China and even the world.In this study,wheat flour dough in flour food processing as the research object,the effects of lowsodium salt(70% Na Cl and 30% KCl)on the formation and properties of dough were studied in order to lay a theoretical foundation for the application of low-sodium salt in flour food.The effects of low-sodium salt on the macroscopic rheological properties of wheat dough were discussed.The results showed that the addition of low-sodium salt reduced water absorption and weakening degree of flour,and increased stability time,development time,extensional area and the resistance to extension of dough.The stress relaxation results showed that low-sodium salt improved the compressive properties of the dough,and the test dough presented a typical viscoelastic solid material.In conclusion,the addition of low sodium salt effectively improved the macroscopic rheological properties of dough,where effect of lowsodium salt on the rheological properties of dough was equal to or less than that of Na Cl dough,but higher than that of KCl dough,indicating that reducing sodium content had little effect on dough quality under the same salt concentration.The effects of low-sodium salt on the characteristics of gluten in dough were discussed.The results showed that low-sodium salt significantly reduced the extractability of gluten,acid soluble glutenin and SDS soluble glutenin in dough(P<0.05),and the free SH content in dough markedly decreased(P<0.05)and S-S content markedly increased(P<0.05)with the increase of low-sodium salt addition,indicating that low-sodium salt promoted the aggregation of gluten and increased the degree of covalent cross-linked aggregation of gluten.SDS-PAGE and particle size distribution analysis showed that low-sodium salt mediated gluten aggregation.In addition,the charge distribution results indicated that low-sodium salt promoted protein aggregation by reducing the non-covalent bond(electrostatic repulsion)of gluten.Therefore,the aggregation of dough gluten induced by low-sodium salt is the main reason for the improvement of dough rheological properties.The effects of low-sodium salt on gluten aggregation behavior in dough were discussed.Gluto Peak analysis showed that low-sodium salt enhanced gluten strength and prolonged gluten aggregation time,and the dynamic rheological properties and creep–creep recovery characteristics of low-sodium salt gluten were improved to some extent,which in turn affected the aggregation of low-sodium salt and dough gluten.Atomic force microscopy(AFM)analysis showed that low-sodium salt promoted the folding of small molecular weight proteins to form larger protein clusters.Size exclusion phase-high performance liquid chromatography(SE-HPLC),reversed phase-high performance liquid chromatography(RP-HPLC)profiles and correlation analysis suggested that low-sodium salt induced the aggregation of gluten,and this aggregation was highly correlated with the content changes of gliadin and glutenin fractions.Fluorescence spectra and Fourier transform infrared spectra showed that lowsodium salt changed the molecular conformation of gluten and increased the polarity of tryptophan microenvironment.In addition,low-sodium salt promoted the aggregation of gluten and made the gluten network structure denser,which may be the reason for the improvement of dough rheology and dough physical properties.The effects of low-sodium salt on the aggregation behavior of different fractions of dough gluten were discussed.The dynamic rheological properties and creep-creep recovery characteristics indicated that low-sodium salt improved the dynamic modulus of glutenin and gliadin,and enhanced the elasticity,tensile resistance and strain hardening ability of glutenin fractions,making them more inclined to solid elastic characteristics.AFM and SE-HPLC spectra showed that low-sodium salt induced glutenin to form larger molecular weight glutenin polymers,and increased the molecular chain size of glutenin and gliadin to a certain extent,but the increase was lower than that of gluten,indicating that the interaction between glutenin and gliadin was more important for the aggregation of gluten.In summary,low-sodium salt promoted the aggregation of gliadin and glutenin molecules mainly through covalent(SH/SH)and non-covalent forces(hydrogen bonding,hydrophobic interaction),where the effect of lowsodium salt on the aggregation degree of gluten and its components was lower than that of Na Cl,but higher than that of KCl.All of the above are the reasons for the changes of glutenin and gliadin/gluten/dough macroscopic rheological properties and dough physical properties.The effects of low-sodium salt on the mechanism of gluten aggregation in fresh noodles were discussed.The addition of low-sodium salt significantly improved(P<0.05)the chewiness,tensile strength,tensile fracture distance and internal texture structure of noodles,where the effect of low-sodium salt on the chewiness,hardness and tensile strength of noodles was not significantly different from that of Na Cl noodles,but higher than that of KCl noodles,indicating that reducing sodium content had little effect on the quality of noodles under the same salt concentration.Low-field nuclear magnetic resonance(LF-NMR)analysis indicated that low-sodium salt changed water migration state of noodles from free water to weakly bound water,limited water mobility,and increased the interaction between water and nonaqueous matrix.In addition,low-sodium salt cross-linked with gluten in noodles through covalent bonds(SH/SS)and non-covalent bonds(hydrophobic interaction),and further promoted the aggregation of gluten to make gluten network structure denser,thereby improving the quality of fresh noodles.The effects of low-sodium salt on the shelf life of fresh noodles were discussed.The results showed that total plate count,mold and yeast in fresh noodles increased with the extension of storage time,and the texture and cooking characteristics of noodles deteriorated and the color became darker;the p H was stable in the early stage of storage and decreased markedly in the late stage of storage.Compared with unsalted noodles,the addition of lowsodium salt effectively prolonged the shelf life of fresh noodles. |
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