Abstract: This study investigated the effects of kiwifruit juice addition (with volume ratios of orange juice to kiwifruit juice at 5:1 and 1:1) combined with high-pressure homogenization (HPH) on the cloud stability of not-from-concentrate (NFC) orange juice. The results showed that in addition to improving the nutritional quality, the treatment significantly increased the turbidity of the orange juice, and the uniformity of cloud particle size distribution, decreased the pectin methylesterase activity to below 14%, and maintained the cloud stability above 85% after 16 days of storage. Kiwifruit juice addition improved the composition and structure of water-soluble pectin (WSP) in the orange juice: the proportion of homogalacturonan (HG), a polymer of α-1,4 glycosidically linked D-galacturonic acid (GalA) residues, increased, while that of rhamnogalacturonan-I (RG-I) decreased, resulting in fewer WSP side chains, a smoother structure, higher esterification degree, and lower hydrophobicity. These modifications enhanced WSP stability and minimized intermolecular interactions and aggregation, thereby markedly improving juice cloud stability. In conclusion, the combined treatment increased juice turbidity and improved nutritional quality. It had significantly reduced structural damage to pectin, resulting in relatively intact pectin structure with better hydrophilicity, thereby contributing to long-term stability.

Key words: not-from-concentrate orange juice; kiwifruit; high pressure homogenization; cloud stability; water-soluble pectin; pectin structure