Phytochemical composition of onion during long-term storage

Abstract

Onion cultivar "Sunpower" has growing popularity in Korea due to high storability. The present study considers changes in flavonols, sugars, and two amino acids in onion bulbs during a long-term storage in the ambient dark storage room and in glasshouse equipped with a climate control system. Flavonol and sugar contents were found to fluctuate noticeably during the storage period. Amino acid content remained relatively unchanged till the onset of inner sprouting, increasing afterward. Visible sprouts appeared at week 22 in the dark storage room and for four weeks later in the glasshouse. The bulbs lost 20-30% of their weight depending on storage conditions at the end of the storage trials. At the same time, the content of nutraceutics in study expressed on the dry weight basis remained of the same order of magnitude. The nature of observed variations in chemical composition of onions as well as relation of this phenomenon to physiological development of stored onion bulbs is discussed. A conclusion is made that the "Sunpower" onion cannot sustain overwinter storage.

Long-term storage effect on chemical composition, nutritional value and quality of Greek onion landrace “Vatikiotiko”

“…Abayomi and Terry (2008) reported significant differences in glucose and pyruvate content of dry onion bulbs under controlled atmosphere storage, which were dependent on both the analysed cultivar and bulb section (top, middle and bottom section or outer, middle or central part). Sharma et al (2014) reported significant changes in flavonols and sugars content during long-term storage at different light regimes (dark room and glasshouse storage), whereas amino acids content remained unaffected (Hansen, 2001). Similarly, pungency, flavor and sugar content of dry onion bulbs remained unaffected when they were stored under controlled atmospheres, whereas storage at 5 °C, controlled atmospheres or field conditions increased pungency, pH and flavonols, and decreased soluble solids content and bulb firmness (Chope et al, 2006;Rodrigues et al, 2010a;Yoo et al, 2012).…”

“…and 60-80% RH) bySharma et al (2015).In addition, Benkbelia et al (2005a,b) have reported an increase in reducing sugars after a long-term storage due to hydrolysis of fructooligosaccharides prior to sprouting initiation, whereas Abayomi and Terry (2009), Yoo et al(2012) andSharma et al (2014) reported fluctuations in sucrose, fructose and glucose content…”

Reducing and Total Sugar Content in Onion During Storage in the Republic of Macedonia

“…Reducing sugar content in our research showed amplitude and periods of fluctuations having no regular pattern. According to Sharma et al (2015) this behavior can hardly be attributed to a known physiological process and suggests the existence of unrecognized, non-controlled but important influencing factors. It can be a function of temperature as in the study of Hurst et al (1985), the sugar percentage monotonously decreased with time at 1°C but fluctuated at 4°C and 21°C.…”

“…Also, sugar content could be correlated with the other physiological factors such as dormancy break and sprouting (Sharma & Lee, 2016). According to Sharma et al (2015) there are two types of sugar content behavior. According to the first one, the concentration of sugar changes with storage time following a regular pattern such as a monotonous increase, decrease, or a stable behavior.…”

Effect of storage on quality features of local onion landrace ‘Vatikiotiko’

“…Significant differences in glucose and pyruvate content of dry onion bulbs under controlled atmosphere storage, depending on both the cultivar and the bulb section (top, middle and bottom section), have been reported (Abayomi and Terry, 2009). Sharma et al (2014) reported significant changes in flavonol and sugar contents during long-term storage at different light regimes (dark room and glasshouse storage). Pungency, flavor and sugar content of dry onion bulbs were not affected when stored under controlled atmospheres, whereas storage at 5°C or under field conditions decreased soluble solids content and bulb firmness, and increased pungency, pH and flavonols (Coolong et al, 2008;Rodrigues et al, 2010a, b).…”