Changes in the molecular structures of water-soluble pectin from cloud precipitation of not-from-concentrate (NFC) orange juice during refrigerated storage.

Cloud stability is critical for NFC orange juice, and water-soluble pectin (WSP) is a key component of the cloud. This study investigated the physicochemical properties and nanostructure of WSP from cloud sediment during refrigerated storage to clarify its impact on cloud stability. Results showed that WSP content in cloud sediment increased after storage, indicating continuous aggregation in juice. Chemical analysis revealed a decrease in neutral sugar and an increase in uronic acid content, suggesting that RG-I-rich WSP aggregates readily during early storage stages. SAXS analysis demonstrated that WSP-0d exhibited larger and more compact structures compared to WSP-14d and WSP-21d, supporting the progressive aggregation tendency of RG-I-enriched WSP. These findings suggested that WSP in NFC orange juice aggregated over time, forming insoluble states, with RG-I-rich WSP aggregating faster and HG-enriched WSP taking longer. This study highlights the dynamic behavior of WSP and its critical role in maintaining cloud stability during storage.