Microgreens are emerging as a culinary novelty ingredient, with rich nutritional content and fresh taste. It can be produced within just a few weeks and is becoming popular among chefs and health-conscious consumers. Cold stress is one of the abiotic stresses, it may induce the accumulation of phytochemical properties in plants. This study investigated the effects of short-term, pre-harvest cold treatment on the nutritional contents of microgreens. Four microgreens including buckwheat, pea, sunflower and watercress, were grown in a growth chamber maintained at a constant temperature of 25°C. The photoperiod was set for a 15-hour light cycle. We treated these four microgreens with a short-term treatment including control and cold treatment at 4°C for 24h before harvesting. The results showed that shoot length, stem diameter, and shoot dry weight in four microgreen species were not affected by cold treatment compared to the control. But cold treatment increased the fresh weight of watercress and the SPAD values in pea and sunflower. Cold treatment significantly affected soluble sugar content. Specifically, it increased fructose, glucose, and sucrose contents in pea microgreen compared to the control. In sunflower microgreen, it improved fructose and glucose content by 65% and 78%, respectively, but had no effect on sucrose levels. Buckwheat microgreen under short-term cold treatment showed increased sucrose content, while fructose and glucose levels remained unchanged. In watercress microgreen, short-term cold treatment increased fructose content by 39% but decreased glucose content by 29%. These findings suggest that buckwheat, pea, sunflower, and watercress microgreens have different responses to a 24h short-term cold treatment regarding plant growth and specific phytochemical contents. While this treatment did not have a negative effect on the yield of the four microgreens, it influenced their flavor by significantly increasing fructose, glucose, and sucrose levels. Given the small space required for a microgreen tray, a short-term 4°C cold treatment is easily achievable in refrigerators. This innovative pre-harvest cold treatment presents an accessible method for enhancing the flavor and nutritional quality of microgreens. Future research will explore the impact of short-term cold treatment on other phytochemicals in microgreens.
