Influence of Cultivar and Harvest Stage on Growth and Phytochemical Composition of Amaranth Microgreens

Jatuporn Hongthongkham and Surachai Rattanasuk

Background and Objective: Amaranth microgreens are increasingly recognized as valuable functional foods due to their rapid growth, short cultivation cycle, high nutritional density and rich phytochemical content. This study investigated how cultivar and harvest stage affect growth performance and the accumulation of key phytochemical compounds in amaranth microgreens grown under greenhouse conditions. Materials and Methods: Two amaranth cultivars, red amaranth and small red-centered amaranth, were grown under greenhouse conditions and harvested at 7, 10 and 14 days after sowing. Growth parameters, including plant height, fresh weight and dry weight, were measured. Chlorophyll content, dietary fiber, vitamin C, total phenolic content and antioxidant activity were also determined. Data was analyzed using analysis of variance and treatment means were compared at p<0.05. Results: Harvest stage significantly affected most growth and biochemical traits. In both cultivars, plant height, dry weight, chlorophyll content, total phenolic content and antioxidant activity increased with plant age. At 14 days after sowing, red amaranth showed the highest chlorophyll content (0.49 mg/g fresh weight), total phenolic content (4.51 mg GAE/g fresh weight) and antioxidant activity (52.27%). Small red-centered amaranth showed slightly higher dietary fiber (3.18%) and vitamin C content (94.44 mg/g fresh weight) at the same harvest stage. Conclusion: Both cultivar and harvest stage influenced the nutritional and phytochemical quality of amaranth microgreens. Harvesting at 14 days after sowing provided the most favorable balance between growth and bioactive compound accumulation, with red amaranth showing superior overall phytochemical performance.

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