To develop a navel Citrus sinensis peel tea with suitable taste and unique flavor by inoculating the peels of Gan Nan navel Citrus sinensis with the Eurotium cristatum and conducting solid-state fermentation.

The single-factor experiment and response surface analysis method were adopted to optimize the fermentation process parameters of Gannan navel Citrus sinensis peel tea, and the sensory quality of the obtained product was comprehensively evaluated. Meanwhile, the in vitro antioxidant activity was evaluated by measuring the scavenging effects on 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and 2, 2’-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) positive ion free radicals.

The optimal fermentation process parameters of Gannan navel Citrus sinensis peel tea were determined as follows: Inoculation Eurotium cristatum amount of 2.7%, fermentation temperature of 27 ℃, and fermentation time of 7 days. Under these conditions, the sensory score of the Gannan navel Citrus sinensis peel tea reached 91.29. The in vitro antioxidant results showed that the in vitro antioxidant results showed that, with vitamin C (VC) as the reference, the fermented Gannan navel Citrus sinensis peels inoculated with Trichosporon cutaneum and the unfermented Gannan navel Citrus sinensis peels both before and after fermentation had the ability to scavenge free radicals DPPH and ABTS⁺. When the concentration was lower than 5 mg/mL, the scavenging ability of the fermented Gannan navel Citrus sinensis peels inoculated with Trichosporon cutaneum and the unfermented Gannan navel Citrus sinensis peels on DPPH and ABTS⁺ free radicals was lower than that of VC; when the concentration was 5 mg/mL, the scavenging ability of the fermented Gannan navel Citrus sinensis peels inoculated with Trichosporon cutaneum and the unfermented Gannan navel Citrus sinensis peels on DPPH and ABTS⁺free radicals was comparable to that of VC; the half scavenging rates of these three for DPPH free radicals before and after fermentation were (2.1892±0.0583), (0.7345±0.0052), (0.0024±0.0002) mg/mL, respectively, and for ABTS⁺ free radicals were (2.2372±0.0672), (0.7461±0.0048), (0.0026±0.0002) mg/mL, respectively. The numerical differences were significant, indicating that the Gannan navel Citrus sinensis peels after Trichosporon cutaneum fermentation have stronger antioxidant activity, but their antioxidant activity is still lower than that of VC.

This study successfully develop a navel Citrus sinensis peel fermented tea with excellent quality, good taste and strong antioxidant function. The process formula is stable and feasible, which can provide theoretical and methodological technical support for the market industrialization promotion of navel Citrus sinensis peels.