长叶莴苣外叶,与更普遍销售的心脏相反,通常被丢弃,并提供了作为干粉进行更新的机会。对DuquesneRomaine莴苣进行了评估,以量化和比较新鲜外叶和心叶的质量属性,热空气干燥后的干粉,和干燥的粉末在干燥前经过红外(IR)烫漂预处理。为新鲜叶子测量的属性包括水分,水活度(Aw),颜色,总可溶性酚类物质(TSP),和抗氧化能力(AC)。评估了通过IR烫漂的干燥动力学和时间/能量节省。干燥粉末测量的属性包括水分,啊,颜色,真实密度,水蒸气等温线,TSP,AC,镉(Cd)含量,和农药残留。TSP,AC,Cd,农药残留更高,而新鲜的外部叶片和心脏叶片中的水分含量和Aw较低。热风干燥将TSP和AC降低到新鲜值的63.6%和35.2%,分别,而红外烫漂进一步将外叶粉末中的TSP和AC降低至37.3%和25.4%。另一方面,TSP和AC分别增加了237%和151%,分别,用于未漂白的心脏粉末。心叶粉末中TSP的增加高于AC的增加可能表明在初始干燥阶段由非生物胁迫如切割和高温激活的酚类化合物的合成。IR烫漂导致用于干燥外叶的显著时间/能量节省。微生物负荷在干燥过程中大大降低,尽管外叶上的微生物种群更具抗性。可以安全食用外叶长叶莴苣粉,采取适当的农业做法。
Romaine lettuce outer leaves, as opposed to the more commonly marketed heart, are typically discarded and present an opportunity for upcycling as dried powders. Duquesne Romaine lettuce was evaluated to quantify and compare quality attributes of fresh outer and heart leaves, dried powders following hot air drying, and dried powders following an infrared (IR) blanching pretreatment before drying. Attributes measured for fresh leaves included moisture, water activity (Aw), color, total soluble phenolics (TSP), and antioxidant capacity (AC). Drying kinetics and time/energy saving through IR blanching were evaluated. Attributes measured for dried powders included moisture, Aw, color, true density, water vapor isotherms, TSP, AC, cadmium (Cd) content, and pesticide residues. TSP, AC, Cd, and pesticide residues were higher, whereas moisture content and Aw were lower in fresh outer versus heart leaves. Hot air drying reduced TSP and AC to 63.6% and 35.2% of fresh values, respectively, whereas IR blanching further reduced TSP and AC to 37.3% and 25.4% in outer leave powders. On the other hand, TSP and AC increased 237% and 151%, respectively, for unblanched heart powders. Higher increase of TSP than AC in heart leaf powder may indicate synthesis of phenolic compounds activated by abiotic stresses such as cutting and high temperatures at the initial drying stage. IR blanching resulted in significant time/energy savings for drying of outer leaves. Microbial loads were substantially reduced during drying, although microbial population on outer leaves were more resistant. Safe to eat outer leaf Romaine lettuce powders can be produced, assuming appropriate agricultural practices.