The various ecotypes differ mainly for their ripening and harvesting period, which goes from February to June, and which they are named after - Febbrarese, Marzatica, Aprilatica, Maggiaiola and Giugnese. This way, growers can provide the market with fresh produce for a long time avoiding storage problems and costs.
Researchers from the University of Salerno, CRA-ORT Pontecagnano and CNR-IMM Naples have characterised 5 ecotypes of Bianca di Pompei onions according to their chemical composition and antioxidant properties. The volatile compound, organic acid, sugar and polyphenol content was analysed as well as their anitoxidant activity and pungency value.
Onions were harvested at the end of their growth cycle, corresponding to their ripening stage and therefore to their harvesting time, i.e. February, March, April, May and June.
The total content of volatile compounds, mainly those containing sulphur, in Aprilatica onions was significantly higher than that in other varieties. The nutraceutical feature, assessed by analysing the phenol profile and antioxidant activity, was higher in the onions harvested in spring. Pungency values, expressed as pyruvate produced by alliinase, was high for all ecotypes, with an interval between 9 and 14 mmol of pyruvate per gram of fresh weight.
The organic acid profile (malic, citric, succinic, pyruvic, oxalic, ascorbic and tartaric) showed that malic acid (between 58 and 79 mg/100 FW) and citric acid (between 20 and 63 mg/100g FW) levels are high in all ecotypes. As regards soluble sugars (fructose, glucose and sucrose), fructose was the most abundant, ranging from 1.74 to 2.26 g/100g FW.
In general, results showed the effect of the increasing temperatures on the quality parameters measured. Aprilatica, Maggiaiola and Giugnese onions, which are cultivated during the milder period, showed in fact higher levels of sulphur compounts compared to Febbrarese and Marzatica onions. The phenol profile and antioxidant activity were also higher in the onions harvested in spring.
Source: Loredana Liguori, Rosa Califano, Donatella Albanese, Francesco Raimo, Alessio Crescitelli, Marisa Di Matteo, 'Chemical Composition and Antioxidant Properties of Five White Onion (Allium cepa L.) Landraces', 2017, Journal of Food Quality, Article ID 6873651, 9 pages, doi.org/10.1155/2017/6873651
The total content of volatile compounds, mainly those containing sulphur, in Aprilatica onions was significantly higher than that in other varieties. The nutraceutical feature, assessed by analysing the phenol profile and antioxidant activity, was higher in the onions harvested in spring. Pungency values, expressed as pyruvate produced by alliinase, was high for all ecotypes, with an interval between 9 and 14 mmol of pyruvate per gram of fresh weight.
The organic acid profile (malic, citric, succinic, pyruvic, oxalic, ascorbic and tartaric) showed that malic acid (between 58 and 79 mg/100 FW) and citric acid (between 20 and 63 mg/100g FW) levels are high in all ecotypes. As regards soluble sugars (fructose, glucose and sucrose), fructose was the most abundant, ranging from 1.74 to 2.26 g/100g FW.
In general, results showed the effect of the increasing temperatures on the quality parameters measured. Aprilatica, Maggiaiola and Giugnese onions, which are cultivated during the milder period, showed in fact higher levels of sulphur compounts compared to Febbrarese and Marzatica onions. The phenol profile and antioxidant activity were also higher in the onions harvested in spring.
Source: Loredana Liguori, Rosa Califano, Donatella Albanese, Francesco Raimo, Alessio Crescitelli, Marisa Di Matteo, 'Chemical Composition and Antioxidant Properties of Five White Onion (Allium cepa L.) Landraces', 2017, Journal of Food Quality, Article ID 6873651, 9 pages, doi.org/10.1155/2017/6873651