In this study, pulsed electric fields (PEF) treatments and their effects on the structure of vitamin C (VIT-C) were estimated by fluorescence and Fourier transform infrared (FT-IR) spectroscopy, the relative content of VIT-C was measured by HPLC and the antioxidant properties of treated VIT-C by DPPH radical scavenging as well as reducing power tests. The fluorescence intensity of treated VIT-C increased slightly compared to the untreated VIT-C. Moreover, the effect of PEF on the structure of VIT-C was observed using the FT-IR spectra. These phenomena indicated that the PEF affected the conformation of VIT-C, which promoted the VIT-C isomer transformed enol-form into keto-form. In addition, the PEF treatments did not suffer the damage to VIT-C and could slow down the oxidation process in involving of experimental conditions by HPLC. The antioxidant properties of the treated VIT-C were enhanced, which was proved by radical scavenging and also the reducing power tests.

Using high hydrostatic pressure (HHP) to treat liquid foods can improve their aroma; however, no information about the effects of HHP on soy sauce aroma has yet been reported. The effects of HHP on the aroma of soy sauce fermented for 30 d were investigated using quantitative descriptive analysis (QDA), SPME–GC–olfactometry/MS, hierarchical cluster analysis (HCA) and principal component analysis (PCA). Results showed that the pressure used during HHP treatment had a greater influence on soy sauce aroma than the duration of HHP. Compared to the control, soy sauce that was treated with HHP at 400 MPa for 30 min (HHP400–30) obtained the highest sensory score (33% higher) by increasing its sour (7%), malty (9%), floral (27%) and caramel-like (47%) aromas, while decreasing its alcoholic (6%), fruity (6%) and smoky (12%) aromas; moreover, the aroma of HHP400–30 soy sauce was comparable with that of soy sauce fermented for 180 d. Further investigation demonstrated that HHP (400 MPa/30 min) enhanced the OAVs of compounds with sour (19%), malty (37%), floral (37%), caramel-like (49%) and other aromas (118%), and lowered the OAVs of compounds with alcoholic (5%), fruity (12%) and smoky (17%) aromas. These results were consistent with the results of the QDA. HHP treatment positively regulated the Maillard, oxidation and hydrolysis reactions in raw soy sauce, which resulted in the improvement and accelerated formation of raw soy sauce aroma. HHP was capable of simultaneously improving raw soy sauce aroma while accelerating its aroma formation, and this could treatment become a new alternative process involved in the production of high-quality soy sauce.

A synergetic method integrating both pulsed electric field (PEF) and ozone treatment was developed as a novel approach to investigate the degradation of high molecular weight chitosan ( M _w =4.5×10 ⁵ Da). A device integrating both components was designed and assembled for the experiments. Results showed that the highest degradation percentage of chitosan was achieved with PEF/ozone co-treatment generated at experimental conditions of 1.2 L/min of ozone flow rate, 100 mL/min of 0.6% (w/v) chitosan solution flow rate, and 26.7 kV/cm of PEF intensity. The degradation percentage after 60 min PEF treatment was 24.89%, whereas it was improved to 94.89% by ozone treatment for 60 min. Combining the two treatments resulted in enhanced degradation percentage of 99.56%, with low molecular weights sample ( M _w <2,500 Da) obtained. FTIR analysis demonstrated that the amide structure of the degradation products was minimally affected by the co-treatment. XRD pattern indicated that the crystallinity of the degradation products decreased. In addition, it could complete dissolve in water after 60 min PEF/ozone co-treatment. These results demonstrated the synergetic PEF/ozone co-treatment as an effective method for degradation of high molecular weight chitosan.

Beef potentiator is an important flavor enhancer in food industry, while it is prone to generating insufficient taste compounds and off-odor compounds during enzymatic hydrolysis of beef, resulting in poor flavor of beef potentiator. It has been extensively reported that sonication is capable of improving food flavor. However, the effect of sonication on the flavor of enzymatically hydrolyzed beef liquid (EHBL) was scarcely reported. Herein, we investigated the effect of sonication on the flavor of EHBL using quantitative descriptive analysis (QDA), physicochemical analysis and SPME-GC-olfactometry/MS. QDA showed that sonication had a significant effect on taste improvement and off-odor removal of EHBL. Compared with the control, sonication (40 kHz, 80 W/L) increased the contents of total nitrogen, formaldehyde nitrogen, total sugar, reducing sugar, free amino acids (FAAs) and hydrolysis degree of EHBL by 19.25%, 19.80%, 11.83%, 9.52%, 14.37% and 20.45%. Notably, sonication markedly enhanced the contents of sweet FAAs, umami FAAs and bitter FAAs of EHBL by 19.66%, 14.04% and 9.18%, respectively, which contributed to the taste improvement of EHBL. SPME-GC-olfactometry/MS analysis showed that aldehydes and alcohols were the main contributors to aroma compounds of EHBL, sonication significantly increased the contents of key aroma compounds and 115.88% of alcohols content in EHBL. Notably, sonication decreased contents of the fishy odorants, hexanoic acid and nonanal, markedly by 35.29% and 26.03%, which was responsible for the aroma improvement of EHBL. Therefore, sonication could become a new potential tool to improve the flavor of EHBL.