In this study, we investigated the effects of different frying conditions on the quality characteristics of fried Spanish mackerel (Scaberulous niphonius) to address the food quality degradation of self-heating fish products after frying, sterilization, and reheating. Furthermore, the effect of different moisture contents (65%, 60%, 55%, and 50%) of fried Spanish mackerel on texture, color, and microstructure after sterilization and self-heating were examined. The flavor fingerprints of different frying temperatures (140 °C, 160 °C, 180 °C, and 200 °C) coupled with the optimal moisture content were identified; furthermore, volatile organic compounds (VOCs) were studied using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) with principal component analysis (PCA). The results indicated that the shear force value significantly increased, while the hardness and chewiness significantly decreased simultaneously with decreasing moisture content. Samples containing 65% moisture content showed the highest L*, a*, and W values, while their b* value was the lowest, and the most clearly visible fibrous veins with tiny cracks could be observed in them. Samples fried at 160 °C and 65% moisture content exhibited the richest VOCs, with a greasy or fried aroma. Based on the PCA, there were significant differences in the sample VOCs under different frying conditions. In summary, among all treatments, frying at 160 °C with 65% moisture content resulted in the highest food quality of fish filets. The results of this study could provide a theoretical basis for improving the food quality of self-heated fish products.

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BACKGROUND Recently, there is a growing interest in developing protein‐fortified liquid systems, which are formulated to provide special nutrient combinations to those with special dietary needs. The fabrication of heat‐stable protein for protein‐fortified liquid systems relies heavily on precise control of the edible protein‐building process. RESULTS Results suggested that heat‐stable 7S protein particles (7SPPs) could be obtained by preheating at 100 °C for an extended time, whereas 7S proteins with better gelling properties were discovered after preheating at lower temperatures. According to the findings of the protein conformational and morphological characterization, the 7SPPs showed rather stable tertiary and secondary structures as well as size distributions, which might be responsible for their heat stability. Additionally, during the reheating test, suspensions of 7SPPs showed no signs of gelation and had a low viscosity even though the protein content was as high as 120 mg mL−1. However, 7S proteins with improved gelling properties were found to show rising aggregate size, higher susceptibility and larger conformational structure changing rates upon reheating treatment. CONCLUSION Soy β‐conglycinin (7S) proteins with tunable heat stability were successfully prepared by preheating 10 mg mL−1 protein dispersions at various temperatures (80–120 °C) and durations (15–120 min). These findings provide fundamental insights for developing 7S‐based protein‐fortified systems. © 2023 Society of Chemical Industry.

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Recently, the pursuit of having a healthy diet has heightened the superiority of protein‐enriched beverages; however, this is challenged by the heat‐induced aggregation and gelation of proteins at high concentration. In this study, a facile and efficient strategy of combined preheating and microfluidic homogenisation treatment (CPMHT) was tested to enhance the heat stability of soy proteins (SPs). Results revealed that the CPMHT promoted the denaturation and unfolding of SPs, evidenced by the reduction of β‐sheet content and a slight red shift of fluorescence intensity. Increasing the number of CPMHT cycle led to an apparent decrease in the surface hydrophobicity and total sulfhydryl groups of soy proteins. In addition, when the suspensions (10% (w/v)) of modified soy proteins at higher CPMHT cycle were reheated at 100 °C for 30 min, no gelation was found, along with lower viscosities and higher flow behaviour index. The present study provides an approaching to enhance the heat stability of soy proteins by CPMHT, which might expand the application of soy proteins in protein‐enriched beverages.