To investigate the distribution of carboxymethyllysine (CML) in plant-based meat products and its toxic effects on zebrafish larvae, five representative commercially available plant-based meat products were selected. Liquid chromatography-mass spectrometry (LC-MS) was employed to analyze the CML content in these products and compare it with those of other product types. Zebrafish were used as a biological model to evaluate the acute embryonic toxicity and developmental toxicity of exogenous CML on zebrafish larvae. Results indicated CML concentrations in plant-based meat products ranged from 0.39 (prepared products and smoked and cooked products) to 35.36 mg/kg (deep-fried products), comparable to those of instant noodles, cereal products, and certain meat products. The median lethal concentration (LC₅₀) of CML at 96 hours post-fertilization (hpf) was 864.521 mg/L; it did not affect the survival of zebrafish embryos at concentrations ≤ 250 mg/L nor the hatching rate at concentrations ≤ 62.5 mg/L. CML concentrations ≥ 125 mg/L induced developmental malformations in zebrafish larvae. The estimated daily intake (EDI) of CML via plant-based meat consumption was assessed, indicating that CML levels were far below the threshold for causing developmental toxicity to zebrafish. These findings provide support for assessing the potential food safety of CML in plant-based meat and evaluating dietary exposure to this compound.

To investigate the effects of constant high-temperature sterilization (HTS) and gradient heating sterilization (GHS) on the volatile flavor compounds of braised beef under the same sterilization intensity, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS), electronic nose analysis and sensory evaluation were used to analyze the unsterilized (US), HTS (121 ℃ for 15 min), GHS1 (115 ℃ for 25 min, followed by 118 ℃ for 30 min), and GHS2 (115 ℃ for 30 min, followed by 121 ℃ for 6 min) samples. The results showed that GHS had a significant impact on the content of volatile flavor compounds. A total of 59 volatile flavor compounds were detected in the four groups of samples. The total contents of volatile flavor compounds in the US, HTS, GHS1, and GHS2 samples were 639.53, 897.83, 1223.46, and 1953.93 μg/kg, respectively, with phenols, aldehydes, alcohols, and other compounds being relatively more abundant. Moreover, the content of volatile flavor compounds was significantly higher in group GHS2 than in the other groups (P < 0.05). Based on odor activity values (OAVs), eugenol, eucalyptol, geraniol, 1-octen-3-ol, nonanal, n-octanal, 4-allylanisole, and anethole were the major characteristic flavor compounds of the product. From the results of electronic nose and sensory evaluation, it was found that GHS2 had a better effect on the generation and retention of characteristic flavor compounds. In conclusion, GHS2 was more effective in maintaining the flavor characteristics and overall sensory properties of braised beef.

In order to study the oxidative stability of mutton oxymyoglobin (OxyMb), OxyMb was prepared from mutton myoglobin (Mb). The effects of NaCl, pH value, temperature and plant extracts on the stability of OxyMb were investigated under conditions simulating auto-oxidation of OxyMb. Results showed that the relative content of OxyMb increased at first and then decreased with increasing NaCl concentration, reaching the highest value of 67.07% at 1.5 g/100 mL. The stability of OxyMb in alkaline environment was higher than that in acidic environment. OxyMb could remain relatively stable in the temperature range of 4–30 ℃. The relative content of OxyMb decreased significantly when the temperature were higher than 35 ℃, while the relative content of metmyoglobin increased. Magnolia extract and bamboo leaf extract could improve the stability of mutton OxyMb.

In order to understand the changes of protein structure during the processing of spiced beef, protein turbidity, intermolecular interactions, microstructure, secondary structure and water distribution of samples collected at different stages of processing (raw meat, tumble marination, cooking, and secondary sterilization at 90, 100, 110 or 120 ℃) were detected by a microplate reader, a scanning electron microscope, a Fourier transform infrared spectrometer, and a nuclear magnetic resonance analyzer. Results showed that the turbidity of myofibrillar protein extracted from spiced beef was higher than that of sarcoplasmic protein. Tumble marination reduced the turbidity of sarcoplasmic and myofibrillar protein (P < 0.05), whereas heat treatment had the opposite effect. Tumble marination increased the protein-protein interactions, while heat treatment reduced the electrostatic interaction between protein molecules. Hydrogen bond, hydrophobic interaction and disulfide bond were the main intermolecular interaction forces. Different treatments destroyed the structures of sarcoplasmic and myofibrillar protein, and the degree of damage increased with increasing number of processing steps and increasing secondary sterilization temperature. Tumble marination, cooking and secondary sterilization had significant effects on the secondary structure of proteins, the free water content and total water content were the highest after sterilization at 100 ℃ among the four temperatures, and the effect of different sterilization temperatures on the bound water content was not significant (P > 0.05).