烹饪方式对桑叶生物碱类和酚类物质的影响

研究微波、蒸、煮和油炸等烹饪方式对桑叶酚类物质组成变化和1-脱氧野尻霉素(1-deoxynojirimycin,DNJ)含量的影响。采用福林-酚比色法测定桑叶总酚含量,高效液相色谱-质谱法测定桑叶DNJ和酚类单体含量。结果表明:除了蒸3 min的桑叶总酚含量增加,所有烹饪处理后的桑叶DNJ和总酚含量均显著降低。蒸制处理后桑叶的总酚和DNJ含量最高,油炸处理DNJ含量最低,而微波(70 W)5 min桑叶酚类物质含量最低。不同烹饪方式对酚类组成影响显著,蒸3 min和微波(700 W)3 min的桑叶异槲皮素和紫云英苷含量增加,油炸的桑叶增加了山柰酚-乙酰基-葡萄糖苷、槲皮素和山柰酚等成分。综上,蒸制处理能保留桑叶中较多的活性成分,是适宜桑叶的烹饪方式。

Effect of Cooking Methods on the Contents of Alkaloids and Phenolics in Mulberry (Morus alba L.) Leaves

The present study aimed to investigate the effects of different cooking methods (microwaving, steaming, boiling, and deep-frying) on the contents of 1-deoxynojirimycin (DNJ) and phenolic compounds in leaves of mulberry (Morus alba L.). The total phenolic contents were determined by the Folin-Ciocalteu method. The contents of DNJ and phenol monomers were measured by high performance liquid chromatography (HPLC). The results showed that all the cooking methods except steaming for 5 min, increasing the total phenolic content, significantly reduced the levels of DNJ and phenolics. The highest contents of DNJ and phenolics were detected in steamed mulberry leaves, while the lowest contents of DNJ and phenolics were obtained by deep-frying and microwaving at 70 W for 3 min, respectively. All the cooking methods had significant effects on the composition of phenolics. Steaming for 3 min and microwaving at 700 W for 3 min increased the contents of isoquercitrin and astragalin. Notably, certain amounts of kaempferol-acetyl-glucoside (KAG), quercetin and kaempferol were found in the deep-fried mulberry leaves, but not in the other samples. In conclusion, steaming can be considered as a suitable cooking method for mulberry leaves to ensure the maximum retention of bioactive components.