(P19-016-24) Effect of Drying Temperatures on Postharvest Nutritional and Chemical Composition of Broccoli and Radish Microgreens

Objectives: Microgreens are small seedlings of edible plants. They are well-known for their rapid growth cycle, and high concentration of phenolic compounds and essential micronutrients. However, they have a short shelf-life due to their high moisture content. The objective of this study is to analyze the effects of hot air drying as a means of food preservation on the chemical and nutritional content of microgreens in order to support the development of shelf-stable products.

Methods: Fresh radish and broccoli microgreens were dried at 45°C, 65°C, and 95°C in a convection oven. Freeze-dried samples (-50°C) were used as a control. The drying time at these temperatures was determined using drying curves. Color, water activity, total anthocyanin (TA), phenolic (TP), and digestible protein (DP) contents were measured. In addition to these studies, high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC- MS) were used to identify and compare the vitamin, glucosinolate, and amino acid profiles of the samples.

Results: Results showed that temperature had a significant effect on several physical and chemical properties of the final products. Darkening in the samples was observed in the samples dried at 95°C. 45°C was shown to be the optimal temperature to maintain the anthocyanin levels (11% loss), whereas drying at 95°C better maintained TP content (6% loss). HPLC and LC-MS analysis indicate that drying temperature had an adverse effect on the glucosinolate, amino acid, and vitamin content of radish and broccoli microgreens. However, drying at 45°C was less deleterious with powders retaining 50% - 100% of the content of the evaluated compounds.

Conclusions: The findings in this study indicate that micronutrients and phytochemicals found in microgreens are sensitive to deterioration when dried at high temperatures. However, the exposure to lower drying temperatures better maintains the nutritional qualities of the resultant product. Dry powders obtained from radish and broccoli microgreens may be a useful approach to supplementing formulated foods with various nutritive and non-nutritive phytochemicals and protein.

Funding Sources: Open Philanthropy