Quality Preservation of Fresh-Cut Amaranth (Amaranthus crispus) by Combined Use of Blue Light and Fennel Essential Oil

The effect and mechanism of light-emitting diodes (LED) blue light with different photosynthetic photon flux densities (10, 20 and 30 μmol/(m²·s)) combined with fennel essential oil (0.35 μL/mL) on the quality preservation of fresh-cut amaranth was studied. Four treatment groups: T1 (fennel essential oil alone), T2 (10 μmol/(m²·s) blue light + fennel essential oil), T3(20 μmol/(m²·s) blue light + fennel essential oil) and T4 (30 μmol/(m²·s) blue light + fennel essential oil) were designed as well as a control group without any treatment. The total bacterial count, physicochemical properties, antioxidant enzyme activity and sensory properties of each group were evaluated. The results showed that combined treatment with blue light (30 μmol/(m²·s)) and fennel essential oil (0.35 μL/mL) could maintain the contents of chlorophyll, ascorbic acid and soluble solids in amaranth well. The bacteriostatic effects of the four treatments could be ranked as follows: T4 > T3 > T2 > T1.Superoxide dismutase (SOD) and peroxidase (POD) activity of fresh-cut amaranth treated by 460 nm blue light and fennel essential oil were significantly higher than those in amaranth treated with fennel essential oil alone. The combined treatment effectively inhibited the accumulation of malondialdehyde (MDA) and nitrite in fresh-cut amaranth, significantly increased the sensory score, and extended the shelf life up to 10 days. Therefore, the combined treatment with LED blue light and fennel essential oil is an effective way to delay the senescence and preserve the quality of fresh-cut amaranth.