title: Changes in flavor precursors, pungency, and sugar content in short-day onion bulbs during 5-month storage at various temperatures or in controlled atmosphere.
abstract: Short-day onion bulbs (cv. TG 1015Y) were stored in 1% O(2,)  99% N(2)  air at 5 °C (controlled atmosphere [CA]), or in ambient air at 5, 24, or 30 °C, for 5 mo. Changes in flavor precursors, pungency, and sugar content were investigated. After 5 mo of storage, 1-propenyl-L-cysteine sulfoxide concentrations increased continuously at 5 °C, gradually decreased in CA, slightly increased for 3 mo, and returned to initial levels at 24 °C and decreased below initial levels at 34 °C. Methyl-L-cysteine sulfoxide concentrations remained unchanged in all storage conditions. Onion pungency levels significantly increased at 5 °C, and decreased at 30 °C. Storage in CA and at 24 °C resulted in some fluctuations in pungency but the levels remained similar to initial levels. The calculated pyruvic acid concentrations were approximately 1.0 μmole/mL higher than the measured concentrations, and showed an increase at 5 °C and a slight reduction at 30 °C, consistent with the pungency results. Storage at 5 °C and in CA resulted in slight increases in fructose and glucose concentrations for 3 to 4 mo with subsequent rapid decreases, while sucrose concentrations remained unchanged. However, at 24 and 30 °C, fructose and glucose concentrations continuously decreased, accompanied by a continuous increase in sucrose concentrations. Storage in CA maintained the quality of onions best, as evidenced by the smallest changes in flavor precursors, pungency, and sugar concentrations, while storage at 5 °C resulted in increased pungency. Storage at 24 and 30 °C was tested for the purpose of comparison only; these temperatures are not recommended for commercial storage.
authors.affiliation: Vegetable & Fruit Improvement Center, Dept of Horticultural Sciences, Texas A&M Univ, College Station, TX 77843, USA. k-yoo@tamu.edu
authors.forename: Kil S
authors.initials: KS
authors.lastname: Yoo
authors.forename: Eun J
authors.initials: EJ
authors.lastname: Lee
authors.forename: Bhimanagouda S
authors.initials: BS
authors.lastname: Patil
mesh_terms: D001272:Atmosphere; D003545:Cysteine / Q000031:analogs & derivatives / Q000032:analysis; D005519:Food Preservation / Q000379:methods; D061353:Food Storage / Q000379:methods*; D005632:Fructose / Q000032:analysis; D005947:Glucose / Q000032:analysis; D019697:Onions / Q000737:chemistry*; D018517:Plant Roots / Q000737:chemistry*; D019289:Pyruvic Acid / Q000032:analysis; D013395:Sucrose / Q000032:analysis; D013454:Sulfoxides / Q000032:analysis; D013649:Taste; D013696:Temperature
chemical_list: C467561:1-propenylcysteine sulfoxide; D013454:Sulfoxides; D005632:Fructose; D013395:Sucrose; D019289:Pyruvic Acid; D005947:Glucose; D003545:Cysteine; C017507:mecysteine