The total antioxidant capacity of fruit was determined by TAMzyme pseudo-peroxidase activity colorimetry.

The total antioxidant capacity (TAC) of fruits is a key indicator for measuring their quality and nutritional value. Traditional detection methods are time-consuming and cumbersome, failing to meet the requirements for rapid detection. In this study, a novel triple metal organic framework nanozyme (TAMzyme) with superior peroxidase-like (POD-like) activity is constructed for colorimetric detection of TAC. Owing to the Fe, Co, Ni doping and unique long spindle structures, the TAMzyme possesses more surface active oxygen species, negative surface charges and rapid mass transport, thus resulting in higher catalytic activity and reaction rate. Thanks to the remarkable peroxidase-like activity, the antioxidant capacity of ascorbic acid (AA), cysteine (Cys), glutathione (Glu), and gallic acid (GA) was evaluated with a detection limit between 0.54 and 1.58 μM. Antioxidant capacity was quantified in μM Trolox Equivalent (TE), with Trolox as the standard reference compound. The sensor accurately determined the TAC in kiwi fruit (194.97 ± 2.73 μM TE) and oranges (205.10 ± 3.85 μM TE), aligning with results from a standardized ABTS kit. This study presents a rapid, cost-effective, and straightforward method for quantifying TAC in complex food matrices.