Mashitoa Florence M, Shoko Tinotenda, Shai Jerry L, Slabbert Retha M, Sultanbawa Yasmina, Sivakumar Dharini
Phytochemical Food Network Research Group, Department of Crop Sciences, Tshwane University of Technology, Pretoria West Campus, Pretoria, South Africa.
Department of Horticulture, Tshwane University of Technology, Pretoria West Campus, Pretoria, South Africa.
Front Nutr. 2021 Jun 29;8:694649. doi: 10.3389/fnut.2021.694649. eCollection 2021.
Leaves of pumpkin species var. Butternut squash ( Duchesne ex Poir) is a popularly consumed leafy vegetable in the Southern African region. Traditional vegetables are commonly sun-dried as a method of postharvest preservation during the off-season. However, different drying methods affect the superior quality, functional properties, and bioactivities of the final product. Therefore, in this study, var. Butternut squash () underwent different drying methods, such as freeze-, oven, sun-, solar, and microwave drying to evaluate the color properties, pigments, phenolic metabolites, antioxidants, and antidiabetic activities. Results indicate that freeze-drying retained the total chlorophyll content with green color by reducing the color difference Δ), improved the concentration of different phenolic metabolites and the content of ascorbic acid, and enhanced the FRAP, ABTS activities and the inhibitory effects of α-glucosidase, and α-amylase. Freeze-dried leaves contained the highest concentrations of quercetin 3-glucoside 7-rhamnoside (rutin), quercetin 3-galactoside, isorhamnetin-3-galactoside-6″-rhamnoside, isorhamnetin-3-O-rutinoside compared with the leaves that underwent four other drying treatments and raw leaves. The OPLS-DA and the UPLC-QTOF/MS and chemometric approach showed that the peak at /z 609, 1441 (quercetin 3-galactoside 7-rhamnoside) separated the freeze-dried leaves of var. Butternut squash () from the other four drying treatments. Therefore, freeze-drying is highly recommended to obtain good quality leaf powders that are rich in functional compounds and bioactive properties for use as functional ingredients.
南瓜品种笋瓜(Duchesne ex Poir)的叶子是南部非洲地区一种广受欢迎的叶菜类蔬菜。传统蔬菜通常在淡季进行晒干,作为一种收获后保存的方法。然而,不同的干燥方法会影响最终产品的优质品质、功能特性和生物活性。因此,在本研究中,笋瓜品种()采用了不同的干燥方法,如冷冻干燥、烘箱干燥、日晒干燥、太阳能干燥和微波干燥,以评估其颜色特性、色素、酚类代谢产物、抗氧化剂和抗糖尿病活性。结果表明,冷冻干燥通过降低色差Δ保留了总叶绿素含量并保持绿色,提高了不同酚类代谢产物的浓度和抗坏血酸含量,增强了铁离子还原抗氧化能力(FRAP)、2,2'-联氮-双-3-乙基苯并噻唑啉-6-磺酸(ABTS)活性以及α-葡萄糖苷酶和α-淀粉酶的抑制作用。与经过其他四种干燥处理的叶子和新鲜叶子相比,冷冻干燥的叶子中槲皮素3-葡萄糖苷7-鼠李糖苷(芦丁)、槲皮素3-半乳糖苷、异鼠李素-3-半乳糖苷-6″-鼠李糖苷、异鼠李素-3-O-芸香糖苷的浓度最高。正交偏最小二乘法判别分析(OPLS-DA)以及超高效液相色谱-四极杆飞行时间质谱联用(UPLC-QTOF/MS)和化学计量学方法表明,质荷比为609、1441处的峰(槲皮素3-半乳糖苷7-鼠李糖苷)将笋瓜品种()的冷冻干燥叶与其他四种干燥处理区分开来。因此,强烈推荐采用冷冻干燥来获得富含功能化合物和生物活性的优质叶粉,用作功能成分。