Sensory evaluation, gas chromatography-ion mobility spectrometry (GC-IMS) and multivariate statistical methods such as principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used to analyze the changes of volatile flavor compounds in sea duck egg white during salting. A total of 43 volatile organic compounds (VOCs) were identified, including esters, ketones, aldehydes, acids and alcohols, ranked in decreasing order of their numbers. A total of 20 characteristic compounds were identified throughout the salting process, including ethyl acetate, 3-hydroxy-2-butanone, n-propanol, isobutyric acid, isopropyl acetate, 2,3-butanedione, propionic acid, 3-methyl-3-butene-1-alcohol, 2-methylbutyraldehyde, propyl acetate, n-butyraldehyde, 2-butanone, isopropanol, isovaleraldehyde, ethyl isobutyrate, tetrahydrofuran, 2-pentanone, n-butanol isoamyl alcohol and trans-2-pentenoaldehyde. Isobutyric acid and propionic acid were the major fishy odor compounds of salted egg white. The content of 2-butanone in fresh duck eggs was the highest. After five days of salting, ethyl acetate became the most abundant volatile compound. After 25 days of salting, the relative proportions of isobutyric acid and propionic acid gradually increased. The relative contents of n-butyraldehyde and isovaleraldehyde increased gradually during salting. The characteristic flavor substances clearly differed among salting stages. GC-IMS identification of flavor substances in sea duck egg white can provide a theoretical basis for identifying the unique flavor and judging the quality change of sea duck eggs during salting.

In order to study the interaction between Tremella fuciformis polysaccharide (TFP) and soybean protein isolate (SPI), the complex coacervation process between them was characterized by turbidity measurement as well as using a nano particle size analyzer, a laser confocal scanning microscope, a rheometer and Fourier transform infrared (FTIR) spectroscopy. The results showed that pH, the ratio of SPI to TFP and salt concentration had great influence on the formation of coacervates. When the SPI/TFP ratio was larger than 1, the critical pH associated with complex formation (pH_c and pH_φ1) shifted to higher pH. When the SPI/TFP ratio was less than 1, pH_φ1 shifted to a lower level. The maximum absorption peak for turbidity gradually decreased (pH_opt gradually decreased) with increasing level of TFP. When the SPI/TFP ratio was 1, the interaction between them was the strongest at pH 3.0, and the viscosity of the system was the largest (1.30 Pa·s). In addition, the largest amount of coacervates was formed with the largest particle size. The formation of SPI-TFP coacervates was promoted by low salt concentrations (c(NaCl) < 20 mmol/L) but inhibited by high salt concentrations (c(NaCl) ≥ 20 mmol/L) due to shielding. When the shear frequency was 10 Hz, the NaCl concentration was 20 mmol/L, and the SPI/TFP ratio of 1:1, the highest viscoelastic modulus was obtained, along with storage modulus of 9.24 Pa and loss modulus of 3.40 Pa. This study may provide a theoretical basis for the application of TFP in plant protein based beverage.

Odor compounds produced in salted egg yolk during thermal processing were identify by sensory evaluation and gas chromatography-mass spectrometry (GC-MS) combined with multivariate statistical analysis such as hierarchical cluster analysis (HCA), orthogonal partial least squares-discriminant analysis (OPLS-DA) and principal component analysis (PCA). By using quantitative descriptive sensory analysis, it was found that there was a significant difference in the flavor profile between egg yolk samples with and without unpleasant odor, and it was determined that some egg yolks had obvious off-flavor during hot processing. Cluster analysis showed that the six groups of salted egg yolk samples were clearly divided into two categories, which was consistent with the sensory evaluation results. Furthermore, OPLS-DA identified 33 major differential components with variable importance in the projection (VIP) scores greater than one between samples with and without unpleasant odor, and aldehydes and alcohols were the most significant differential components. Finally, the volatile compounds showing a positive correlation with sour odor were screened by PCA, and n-hexanal, n-valeraldehyde, 1-octen-3-ol, trans,trans-2,4-decadienal, styrene, dimethyl disulfide and 2-nonone were identified due to their odor activity values (OAV) greater than one as the major odor compounds of salted egg yolk during thermal processing. The results provide a reference for analysis of the flavor characteristics and possible off-flavor components of salted egg yolk after thermal processing and provide a scientific basis for accessing the quality of salted egg yolk.