Free and Bound Volatile Compounds in Juice and Peel of Eureka Lemon

Abstract

Free and glycosidically bound volatile compounds in different parts of Eureka lemon were studied. Free volatile compounds were extracted by solid phase microextraction (SPME). Bound volatile compounds were isolated from juice by adsorption onto an Amberlite XAD-2 column, and then hydrolyzed by almond β-glucosidase. Both the free volatile compounds and the released aglycones were analyzed by using gas chromatography-mass spectromerty (GC-MS). Gas chromatography-olfactometry (GC-O) was also used to determine the aroma-active compounds in juice and peel. Totally 29 and 34 free volatiles were found in juice and peel, respectively. Terpenes and aldehydes were the most abundant compounds in free fractions. Four and six bound volatile compounds were found in juice and peel with a total concentration of 127.8 and 1161.52 μg/L. Benzenic and terpenic compounds were the main bound volatiles found in Eureka lemon fruit. Mannose and glucose were found as sugar moiety in juice, and glucose was found the only sugar linked to bound volatiles in peel.Keywords: eureka lemon, volatile compounds, glycosides, enzymatic hydrolysis, aroma active compounds IntroductionEureka lemon originated in America and grew widely under tropical and sub-tropical climatic conditions, including many countries such as Australia, Israel and southern China. It is a common lemon species in the world (Ford, 1942). It is called "the true 'better' lemon" and has large quantity of juice and acid content.Eureka lemon has not been got much attention. The fruit is elliptic in shape, bright yellow and medium thickness of the skin.It is more acidic than Meyer lemon, its peel is thicker, and also the juice is less than Lisbon lemon, a lemon similar to Eureka lemon.Generally speaking, Meyer lemon and Lisbon lemon are more used as juice production, cooking and eating. But the characters of Eureka lemon make it better to be a good material to produce essential oil and other aroma products. The luxuriant aroma compounds of lemon are applied in many fields. d-Limonene plays a potential role in preventing breast cancer (Miller et al., 2011), and the antioxidant activity of lemon essential oils has been confirmed (Di et al., 2010). Lemon products are also important for food industry and health care (González-Molina et al., 2010).Volatile compounds in Meyer lemon (Moshonas et al., 1972), Italian lemon (Allegrone et al., 2006) and petitgrain Eureka lemon essential oil (Baaliouamer et al., 1985) have been reported, except Eureka lemon. Many studies showed the common volatile compounds in lemon. Several studies showed that the main volatile compounds in lemon essential oil were monoterpenes, such as limonene, γ-terpinene and β-myrcene (Fan et al., 2009a;Verzera et al., 2004). Limonene was the most abundant compound in lemon. Additionally, aldehydes, ketones and esters were the other important volatile compounds in lemon (Lota et al., 2004;Moufida et al., 2003). The free volatile compounds and particular character compounds of Eureka lemon have not been reported yet. The boun...

Characteristics of β‐glucosidase from oranges during maturation and its relationship with changes in bound volatile compounds

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“…8‐Hydroxylinalool is generated from the hydroxylation of linalool and is a precursor of lilac aldehydes and alcohols . It was reported that benzoic acid, p ‐vinylguaiacol, 8‐hydroxylinalool, isoeugenol and vanillin were also found as bound forms in peel of citrus fruits, while large differences in the concentrations of these compounds were observed.…”

Optimization of process conditions for vacuum microwave drying of lemon peel by response surface methodology: Quality characteristics and volatile compounds

“…Thirty‐five compounds (except limonene) were identified and quantified including six aldehydes, five alcohols, one aromatic hydrocarbons, one oxide, three esters, and 19 monoterpene hydrocarbons (Table ). In a previous study, totally 34 volatile compounds were found in Eureka lemon peel (Zhong et al, ). The main compounds were limonene followed by alpha pinene, beta pinene, gamma terpinene, and myrcene.…”

Determination of the Volatile Profile of Lemon Peel Oils as Affected by Rootstock

“…For this, many citrus cultivars have been analyzed to identify their volatile profile [20]. Several authors have studied the volatile profile of the oil from the lemon peel [22][23][24], but information on how the rootstock influences the odorous compounds is very limited.…”