Citrus essential oils (CEOs) are a mixture of volatile compounds consisting mainly of monoterpene hydrocarbons and are widely used in the food and pharmaceutical industries because of their antifungal activities. To face the challenge of growing public awareness and concern about food and health safety, studies concerning natural biopreservatives have become the focus of multidisciplinary research efforts. In the past decades, a large amount of literature has been published on the antifungal activity of CEOs. This paper reviews the advances of research on CEOs and focuses on their in vitro and food antifungal activities, chemical compositions of CEOs, and the methods used in antifungal assessment. Furthermore, the antifungal bioactive components in CEOs and their potential mechanism of action are summarized. Finally, the applications of CEOs in the food industry are discussed in an attempt to provide new information for future utilization of CEOs in modern industries.

In this study, the volatile compounds in the flowers of nine Citrus species/varieties, seven of which are native to China, were analyzed using headspace-solid phase microextraction (HS-SPME) coupled with gas chromatography mass spectrometry (GC-MS). A total of 94 compounds were identified, including various terpenes, such as monoterpenes, sesquiterpenes, terpene alcohols and aldehydes, which together accounted for 80.4% to 92.4% of the total compounds analyzed. Limonene, linalool and γ-terpinene were the dominant terpenes. Different species/varieties were characterized by their volatile compounds. Papeda was characterized by a high level of βocimene, linalyl acetate, myrcene and neo-alloocimene; Citrophorum was characterized by a high level of limonene and caryophyllene, and Cephelocitrus by a high level of limonene, β-pinene and linolool. Sinocitrus had the highest amount of linolool. Sweet orange had the highest level of limonene, while sour orange was distinct from others with the highest level of γ-terpinene. The four basic types of the genus Citrus L., Papeda, Cephalocitrus, Citrophorum and Sinocitrus, can be clearly classified based on a cluster analysis of their volatile compounds. All of the presumed hybrid species, including Jinchengbeibei 447 (C. sinensis Osb.), Goutoucheng (C. aurantium L.), Ningmeng 4 (C. limon Burm.f.), and Changshanhuyou (C. paradisi cv. Changshanhuyou), were grouped closely together with a suggested parent species in the constructed dendrogram. Our study clearly demonstrates that Citrus flower volatile compounds and their variation patterns can be used for Citrus species identification and taxonomic study.