Sugar and Organic Acid Changes in Stored Onion Bulbs Treated with Maleic Hydrazide

Maleic hydrazide (MH)-treated and untreated (control) onion (Allium cepa L.) bulbs were stored for up to 20 weeks at 0, 15, or 30C with relative humidities (RH) of 40% or 60%. MH and RH had minimal effect on sugars and organic acids in inner or outer scale leaves that were analyzed at S-week intervals. Concentrations of fructose, glucose, and total sugars were higher in inner than outer leaves of the bulb, while the reverse was true for sucrose. Total sugars, glucose, and fructose decreased and sucrose increased with higher storage temperature. Total sugars and glucose decreased with increased storage duration. Malic acid concentration was greater in the outer leaves while citric acid levels were higher in inner leaves. Malic acid increased in onion bulbs during storage while citric acid levels were not influenced by storage duration. Total acids showed little difference across temperatures, due to the concurrent increase in citric acid and decrease in malic acid at 30C.