Temporal dynamics of the microbiome, metabolite profiles, enzyme activities, and quality deterioration in postharvest Malus asiatica Nakai “Shaguo”

• Quality, microbes & key enzyme activities of Shaguo were monitored during storage. • Nutrients (sugars, organic acids, phenolics) of Shaguo degrade after 4 days. • Microbes & cell wall-degrading enzymes jointly drive postharvest spoilage. • 4. Key spoilage bacteria/fungi of Shaguo: Gluconobacter & Penicillium . Malus asiatica Nakai, commonly known as Shaguo, is a nutrient-rich fruit with significant economic value. However, its short postharvest shelf life and high susceptibility to spoilage severely limit commercial application. This study aimed to elucidate the deterioration mechanisms of Shaguo by analyzing dynamic changes in appearance, physicochemical properties, microbial community structure, and enzyme activities during room-temperature storage. Results showed that Shaguo maintained good appearance quality within the first 4 days of storage. After 4 days, key nutrients, including soluble sugars, organic acids, and phenolics, decreased sharply, accompanied by intensified browning, skin cracking, and spoilage. Polygalacturonase and hemicellulase activities increased continuously throughout storage, with 44-fold and 13-fold increments, respectively, by day 12. High-throughput sequencing revealed that microbial community richness and diversity gradually declined with storage time; Gluconobacter and Penicillium were significantly enriched in rotten samples. Correlation analysis confirmed that Gluconobacter and Penicillium were positively correlated with decay indices and enzyme activities, but negatively correlated with nutrient contents. Collectively, Polygalacturonase, hemicellulase, Gluconobacter , and Penicillium are key drivers of Shaguo postharvest deterioration. This study provides understandings of the physiological and microbiological mechanisms underlying Shaguo spoilage, offering a theoretical basis for developing targeted preservation technologies.