Study on the formation mechanism of color and flavor during the processing of Polygonatum cyrtonema Hua (PCH)

This study elucidated the formation mechanism of color and flavor in Polygonatum cyrtonema Hua (PCH) processing, corrected the traditional view that the Maillard reaction dominated, and verified the effects of processing on PCH's pharmacological activity and safety. Key parameters were monitored through colorimetric reactions and HPLC analysis during processing. Metabolic variations were analyzed by LC-MS, and volatile flavor compounds were examined via HS-SPME-GCMS. Antioxidant activity was assessed using DPPH and ABTS methods, and anti - aging efficacy was evaluated with a UVB-induced senescence model of HaCaT cells. The relationship between components and color/flavor profiles was explored through correlation analysis. The correlation coefficient between caramelization marker 5 - HMF and browning degree reached 0.96, much higher than that of Maillard marker CML (0.50). 5 - HMF accumulated significantly in the later processing stages (fourth and fifth drying cycles) up to 5.13 ± 0.39 mg/L, while CML increased only in the earlier phases. LC-MS analysis showed that fructose content significantly accumulated during processing, suggesting PCH's sweetness mainly comes from fructose. Fructose, a ketose, undergoes less enolization than aldose sugars like glucose, making it hard to bind with amino compounds for Maillard reaction. After the fourth and fifth drying cycles, amino acid content decreased by 30.70%, favoring caramelization over Maillard reaction in later stages. HS-SPME-GCMS revealed that PCH's primary aromatic compounds are oxygen - containing heterocyclics, which form during drying stages with content changes consistent with 5 - HMF accumulation. Maillard - related nitrogen - containing heterocyclic compounds have low content and minimal flavor contribution. Moreover, PCH antioxidant activity increased after processing, and its anti-aging effect was retained. In conclusion, contrary to traditional assumptions, the caramelization reaction in PCH processing is the primary process for color formation and contributes significantly to flavor development along with the Maillard reaction. This study analyzed the color and flavor formation mechanism and provided a theoretical basis for subsequent food development quality optimization.