Citral deterioration

Lemon peel oil is much more valuable than its juice therefore, extensive research efforts have been expended to determine its natural composition as a way to detect adulteration as well as to determine quality factors [6, 31, 32]. However, a few studies on lemon juice volatiles can be found [33-35]. Lemon oils are notable for possessing relatively low levels of limonene (more than 70%) and relatively high levels of a-pinene (1-2%), -pinene (6-13%), sabinene (1-2%) and y-terpinene (8-10%) [32]. The relatively high concentration of -pinene is thought to instil the green peely odour of lemon oil. The concentrations of aliphatic and monoterpenic aldehydes, (especially citral) as well as those of esters and alcohols are critical components in the perceived quality of the oil. As lemon oil is unstable, quality can deteriorate with improper storage, resulting in... 

Citral is well-known as the most characteristic component of lemon flavor. The value of citrus drinks containing lemon flavor is dependent on the stability of citral (/). However, citral is deteriorated through acid-catalyzed or oxidation mechanisms (2-7). The potent off-flavor components formed from citral under acidic and heated conditions have been clarified by aroma extract dilution analysis (AEDA) (8). In recent years, longer storage times and displays using transparent containers under fluorescent lamps in stores have significantly increased and citral is easily deteriorated by UV light from fluorescent lamps. 

Taking into account the instability of cih, it is important for many flavor and food companies to use food additives which inhibit the deterioration of citral. However, the relationship between the stability of citral and die kinds of additive compounds inhibiting its deterioration has scarcely been reported (ISIS). In addition, in spite of the wide use of ascorbic acid, the degraded components derived from it can lower the value of a citrus drink (19-21). Therefore, it was necessary to find effective additive compounds that inhibit the deterioration of citral. 

Kimura K., Nishimura H., Iwata L, Mizutani J. Deterioration mechanism oflemon flavor. 2. Formation mechanism of off-flavor substances arising from citral. Journal of Agricultural and Food Chemistry, 31 801-804 (1983). 

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