气介式超声强化西兰花热风干燥过程中硫苷分解代谢途径相关物质的变化

Evolutions of Components Involved in the Catabolic Pathway of Glucosinolates in Broccoli Florets during Air Drying Coupled with Air-borne Ultrasound

为探究气介式超声对西兰花热风干燥过程中硫苷分解代谢的影响,本文研究了西兰花小花球在气介式超声联合热风干燥(20 kHz,60℃,125.2和180.1 W/dm^(2))过程中的干燥特性以及硫苷、萝卜硫素、抗坏血酸、Fe^(2+)和酚酸含量以及黑芥子酶、体外抗氧化活性的变化规律。结果表明:相比于单独热风干燥,超声处理不仅可以加快干燥进程(125.2和180.1 W/dm^(2)超声处理下干燥时间分别比单独热风干燥缩短11.1%和17.8%),同时,超声联合热风干燥过程中3-吲哚甲基硫苷含量增加且黑芥子酶活力增强。180.1 W/dm^(2)气介式超声联合热风干燥终点样品中3-吲哚甲基硫苷、萝卜硫素含量和黑芥子酶活力分别比单独热风干燥终点的样品高出10.7%、26.0%和15.2%,Fe^(2+)含量比单独热风干燥终点的样品低8.1%,表明超声处理减少了Fe^(2+)对硫苷酶促降解的干扰,能够促进4-甲基硫氧丁基硫苷降解形成萝卜硫素,但超声处理对西兰花干燥过程中抗坏血酸含量、游离酚酸含量和体外抗氧化活性变化影响不明显。本研究表明气介式超声联合热风干燥既能加快西兰花干燥进程,又能促进4-甲基硫氧丁基硫苷的转化,并对生物活性成分具有一定的保护作用。

In order to understand the effect of air-borne ultrasound on the catabolic pathway of glucosinolates in broccoli florets during air drying,the drying property,contents of key components(glucosinolates,sulforaphane,ascorbic acid,Fe^(2+)and phenolic acids),myrosinase activity and antioxidant capacity in vitro in broccoli florets during air drying at 60℃ coupled with air-borne ultrasound(20 kHz,125.2 and 180.1 W/dm^(2))were analyzed.The results showed that air-borne sonication accelerated the drying process.The drying times were shortened by 11.1% and 17.8% under sonication at 125.2 and 180.1 W/dm^(2),respectively.Meanwhile,glucobrassicin content and myrosinase activity increased during ultrasound-intensified air drying.In the end of drying,the contents of glucobrassicin and sulforaphane as well as myrosinase activity in ultrasound-treated samples at 180.1 W/dm^(2) were 10.7%,26.0%and 15.2% higher than those in samples dried without sonication,respectively.Reversely,sonicated samples at 180.1 W/dm^(2) possessed 8.1%less amount of Fe^(2+)than only air-dried samples after drying.The results implied that ultrasound treatment alleviated the interference of Fe^(2+)on the enzymatic degradation of glucosinolates,as well as promoted the degradation of glucoraphanin to sulforaphane.Besides,air-borne sonication had no significant influence on the contents of ascorbic acid and phenolic acids,and antioxidant capacity in vitro of broccoli under air drying.This study demonstrated that air-borne ultrasound assisted-air drying could not only speed up the drying process of broccoli florets,but also promote the conversion of glucoraphanin and preserve the bioactive components in certain aspects.