Effect of Theaflavins-Soy Protein Isolate Complex Coating on the Quality of Lentinus edodes

In order to clarify the preservation effect of theaflavins-soy protein isolate complex coating on Lentinus edodes, a TFs-SPI complex coating agent was prepared by mixing theaflavins and soy protein isolate as subjects, and its structure was characterized by ultraviolet spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry and X-ray power diffractometry. Meanwhile, the effect of TFs-SPI complex coating on sensory quality, nutrition indicators and total plate count of fresh Lentinus edodes stored at 4 ℃for 20 d were evaluated. The results showed that TFs and SPI could spontaneously form a stable complex through non-covalent interactions. Ultraviolet spectra demonstrated that the interaction between TFs and SPI caused a red shift in the maximum absorption wavelength of SPI and changed the conformation of SPI. Differential scanning calorimetry and X-ray diffraction analysis indicated that TFs-SPI complex was in the amorphous state. Fourier transform infrared spectra revealed that secondary structure of SPI was changed by TFs. Compared with the control, TFs-coated and SPI-coated groups, Lentinus edodes in the TFs-SPI complex coating group showed significant improvement in several qualities during storage, including slowed down the variations of sensory scores and pH values, reduced weight loss and soluble solids content, improved soluble protein and reducing sugar content, as well as inhibited the growth of bacteria. In conclusion, TFs-SPI complex coating treatment could futher maintain the quality of Lentinus edodes, and prolong their shelf life.