A computational and experimental study of cis-trans isomeric pesticides based on collision-induced dissociation of high-resolution mass spectrometry

RATIONALE

Pesticide isomers are widely available in agricultural production and may vary widely in biological activity, potency, and toxicity. Chromatographic and mass spectrometric analysis of pesticide isomers is challenging due to structural similarities.

METHODS

Based on liquid chromatography time-of-flight mass spectrometry, identification of cis-trans isomeric pesticides was achieved through retention time, characteristic fragment ions, and relative abundance ratio. Furthermore, theoretical and basic research has been conducted on the differences in characteristic fragment ions and their relative abundance ratios of cis-trans isomers. On the one hand, the cleavage pathways of six cis-trans isomers were elucidated through collision-induced dissociation to explain different fragment ions of the isomers. On the other hand, for those with the same fragment ions but different abundance ratios, energy-resolved mass spectrometry combined with computational chemical density functional theory in terms of kinetics, thermodynamics, and bond lengths was employed to explain the reasons for the differences in characteristic fragment ions and their abundance ratios.

RESULTS

A high-resolution mass spectrometry method was developed for the separation and analysis of cis-trans isomers of pesticides in traditional Chinese medicine Radix Codonopsis, and six pesticide isomers were distinguished by retention time, product ions, and relative abundance ratios. The limits of quantification of the six pesticides were up to 10 μg/kg, and the linear ranges of them were 10-200 μg/kg, with coefficients of determination (R2) > 0.99, which demonstrated the good linearity of the six pesticides. The recoveries of the pesticides at spiked concentrations of 10, 20, and 100 μg/kg reached 70-120% with relative standard deviations ≤20%.

CONCLUSIONS

It was demonstrated that the application of the method was well suited for accurate qualitative and quantitative analysis for isomers with different structures, which could avoid false-negative results caused by ignoring other isomers effectively.

Stability of high internal-phase emulsions prepared from phycocyanin and small-molecule sugars

BACKGROUND

The use of high internal-phase Pickering emulsions in the food industry is widespread due to their excellent stability and special rheological properties. Proteins are often used as food-grade Pickering stabilizers due to their safety and nutritious properties. Nowadays, the development and efficient utilization of novel proteins as Pickering stabilizers has become a new challenge.

RESULTS

Phycocyanin complexes with small-molecule sugars (SMS), formed as a result of non-thermal interactions, can serve as stabilizers for high internal-phase Pickering emulsions. The addition of SMS-enabled gel-like emulsions significantly reduced the amount of emulsifier used. When the SMS was sorbitol, the emulsion had excellent elastic properties and self-supporting ability and was stable during long-term storage, when subjected to centrifugation, and under different temperature conditions. The fluorescent property of phycocyanin was utilized to investigate the formation mechanism of the emulsion. Small-molecule sugars were able to form 'sugar-shell' structures on the surface of proteins to enhance the structural stability of proteins. Phycocyanin-SMS-stabilized emulsions provided superior protection for photosensitive and volatile substances. The retention rates of trans-resveratrol and n-hexane increased by 384.75% and 30.55%, respectively.

CONCLUSION

These findings will encourage the development of proteins that stabilize Pickering emulsions. They will also provide new ideas for protecting photosensitive and volatile substances. © 2023 Society of Chemical Industry.

Impact of Whey Protein Isolate and Xanthan Gum on the Functionality and in vitro Digestibility of Raw and Cooked Chestnut Flours

Due to the limitations of the properties of chestnut flour, its applications have been restricted. The objective of this study is to investigate the impact of whey protein isolate (WPI) and xanthan gum (XG) on the functional and digestive properties of chestnut flour, specifically focusing on gel texture, solubility and swelling power, water absorption capacity, freeze-thaw stability and starch digestibility. The addition of both WPI and XG reduced the gel hardness, gumminess and chewiness of the co-gelatinized and physically mixed samples. Furthermore, the inclusion of physically mixed WPI and XG led to an increase in the solubility (from 58.2 to 75.0%) and water absorption capacity (from 3.11 to 5.45 g/g) of chestnut flour. The swelling power of the chestnut flour was inhibited by both additives. WPI was superior to XG at maintaining freeze-thaw stability, by reducing the syneresis from 71.9 to 68.1%. Additionally, WPI and XG contributed to the inhibition of starch hydrolysis in the early stage of digestion, resulting in a lower starch digestibility of chestnut flours. This research provides insights into the interaction mechanisms between WPI, XG, and chestnut flour, offering valuable information for the development of chestnut flour products with enhanced properties.