Bioactive compounds and enzymatic browning inhibition in cloudy apple juice by a new magnetic UVM-7-SH mesoporous material

Abstract

Fruits and vegetables juices present a high supply of polyphenols, making them highly exposed to enzymatic browning. In this work, we report a novel magnetized mesoporous silica material (Fe₃O₄NPs-UVM-7) functionalised with thiol and amine groups and evaluate their effect on the enzymatic browning as well as the physicochemical properties (pH and °Brix), bioactive compounds (ascorbic acid, total phenolics, flavonoids, and flavonols) and the antioxidant capacity of cloudy apple juice. From the obtained results, the mesoporous silica material magnetized by 11 % (w/w) with magnetite and functionalized with thiol groups reduce by 70 % the enzymatic browning in apple juice. It did not affect the physicochemical parameters such as pH or total soluble solids with respect to freshly squeezed juice. In addition, the content of flavonoids, vitamin C, and the antioxidant capacity measured by ABTS are also not affected by oxidation. However, the total content of polyphenols in the treated juice drops by 15 % compared to freshly squeezed juice, nonetheless, the loss is 20 % less than the control untreated. Thus, the material mitigates the loss of total polyphenols and also the antioxidant capacity.

Keywords: Antioxidant capacity; Apple juice; Ascorbic acid; Enzymatic browning; Flavonoids; Flavonols; Inhibition; Magnetic UVM-7; Thiols; Total phenolics.