Abstract: Bitterness affects consumer acceptance of foods as a taste sensation generally considered undesirable. The bitter taste of plant foods originates from compounds such as phenolics, terpenoids, alkaloids, and amino acids. Most bitter compounds are biologically active, contributing to disease prevention and having human health benefits. Citrus is a typical class of fruits with bitter taste. The degree of bitterness and functional activity of citrus fruits varies greatly among different varieties due to the different types and contents of bitter substances. In recent years, as the functionality of bitter substances has been widely recognized, an extensive literature has developed on citrus bitter substances. This article reviews the types, structures, biochemical properties, synthesis and metabolism pathways, and functional activities of bitter substances in citrus fruits. In addition, we summarize the main debittering techniques for citrus fruit processing, and envision future research directions toward bitter substances and their synergistic effects, rational processing pathways and breeding, aiming to provide theoretical references for the effective utilization of bitter substances in citrus fruits.

Key words: citrus; bitter substances; naringin; limonin; synthesis pathway; debittering techniques