Allium cepa (onion) and Allium sativum (garlic) are widely used for their nutritional and medicinal properties, but their high perishability leads to post-harvest losses and seasonal scarcity. This study investigated preservation techniques to extend shelf life while retaining nutritional quality. Fresh onion and garlic bulbs were purchased from Wadata market, Makurdi, Nigeria and taxonomically authenticated. It was then taken to the laboratory for preparation and analyses. Forty bulbs each were sliced and divided into four parts: one fresh (meshed and stored), and three processed via sun drying, freeze drying, and microwave irradiation. Samples underwent phytochemical screening and quantification, antioxidant assays and allicin quantification. All samples contained tannins, flavonoids, glycosides, phenols, alkaloids, saponins, phytate, and steroids. Oxalate was undetected in freeze-dried samples, minimizing potential health risks like kidney stones. High flavonoid (3.75±0.01-4.89±0.01 mg/100 g) and phenol (4.89±0.01-96.97±1.27 mg/100 g) contents suggested strong antioxidant capacity. Freeze-dried samples showed the highest antioxidant activity, particularly in the DPPH assay (40.67±0.11 % at 1000 µg/mL), and similar trends were seen in other assays. Freeze-dried onion and garlic also had the highest allicin content (93.63±0.01 µg/100 g in onion, 95.60±0.06 µg/100 g in garlic), contributing to enhanced bioactivity. While all methods retained key compounds, freeze drying proved most effective in preserving antioxidants and eliminating oxalate. Therefore, freeze-dried onion and garlic offer superior nutritional and medicinal benefits.
Iortile et al. (Sat,) studied this question.