Chinese Academy of Agricultural Sciences Reveals Pectin's Crucial Role in Fruit and Vegetable Browning Phenomenon

In a groundbreaking revelation, the Fruit and Vegetable Processing and Quality Control Innovation Team at the Chinese Academy of Agricultural Sciences has deciphered the intricate mechanism through which pectin influences polyphenol oxidation, leading to the browning of fruits and vegetables during thermal processing and storage.

Employing a comprehensive approach, the study utilized various pectin structures, including apple, citrus, and sugar beet pectin, alongside primary polyphenols found in apples, such as chlorogenic acid and catechins. The team incorporated polyphenol oxidase to construct a simulation system, delving into the nuanced effects of pectin on the oxidative browning of polyphenols throughout the thermal processing and storage of fruits and vegetables.

Browning stands as a significant factor contributing to the diminished sensory quality and nutritional value during fruit processing and storage. This phenomenon involves the accumulation of brown substances and alterations in optical properties. While fruit browning traditionally results from polyphenol oxidation, the study highlights the pivotal role of pectin during food processing, with a close correlation to optical changes induced by microstructural transformations. Moreover, the release of pectin macromolecules due to pulp cell ruptures further influences the occurrence of browning in the system. The study underscores the necessity for additional exploration into the correlation between pectin structures and the browning phenomenon.

Utilizing pectins with distinct structures—apple, citrus, and sugar beet pectin—alongside primary polyphenols in apples, the study constructed a simulation system to unravel the impact of pectin on polyphenol oxidation-induced browning during the thermal processing and storage of fruits and vegetables. Results demonstrated a pronounced dependency of polyphenol oxidation systems containing different pectin structures on both pectin concentration and structure. Further analysis revealed that the cross-linking of aromatic rings in pectin and polyphenols influenced the system's fluorescence characteristics and pectin-related chemical bond vibrations, ultimately contributing to browning.

Moreover, correlation analysis pinpointed the monosaccharide composition, chain conformation (Ratio 1, Ratio 2, and Ratio 3), methyl esterification degree, ζ-potential, and polydispersity index of pectin as intricately connected to polyphenol oxidation systems containing pectin. These factors were found to be significantly correlated with the observed browning phenomenon.

The research findings, authored by Hu Jiaxing, a 2022 doctoral candidate in the Fruit and Vegetable Processing and Quality Control Innovation Team, were published in the esteemed journal "Carbohydrate Polymers" (JCR Area 1, IF=11.2). Researcher Bi Jinfeng and Assistant Researcher Li Xuan served as corresponding authors for this study, which received support from the National Natural Science Foundation of China (31901714). This groundbreaking exploration sheds light on the previously obscured intricacies of pectin's role in the browning process, paving the way for enhanced control and preservation of fruit and vegetable quality during processing and storage.