The impact of fruit size on internal browning in pineapples

A typical symptom of post-harvest pineapple (Ananas comosus L.) internal browning is influenced by multiple factors. However, the precise mechanism through which fruit size influences the occurrence of browning remains unclear. Therefore, this study aimed to investigate the impacts of fruit size in browning and its possible mechanisms in harvested pineapple fruit using physical and biochemical analysis and RNA-seq. Disease incidence was assessed in four groups of fruits (1, 1.5, 2, and 2.5 ± 0.2 kg), with the two most significant groups (1 and 2.5 ± 0.2 kg) selected for detailed analysis. The results showed that the large pineapple fruits had faster browning senescence and membrane lipid peroxidation, higher respiration intensity, more reactive oxygen species accumulation, and higher malondialdehyde content. Likewise, lower antioxidant capacity such as ascorbic acid, ascorbate peroxidase, catalase, and superoxide dismutase and higher polyphenol oxidase activity, peroxidase activity, phenylalanine ammonia-lyase activity, and lipoxygenase activity. It can be concluded that the large pineapple fruits were severely subjected to oxygen stress and membrane lipid peroxidation during storage. Gene ontology enrichment reveals that this relates mainly to oxidoreductase and glutathione metabolism. The large pineapple fruits accelerated AsA-GSH cycle pathway metabolism. Real-time quantitative PCR shows downregulated expression of AcAPX1, AcAPX6, AcAPX6 × 1, AcCAT2, AcSOD[Fe]2, and AcSODX2 in large pineapple fruits, whereas AcPPO and AcLOX upregulated expression. This study offers insights into fruit size and browning. Future molecular techniques may reduce fruit browning.