Abstract
Total determination of cinnamic acids (CA), including hydroxycinnamic acid derivatives is generally not accurate since, during hydrolysis, a possible degradation of dihydroxy CA such as caffeic acid could occur. Evaluations of CA (ferulic, p-coumaric, sinapic, cinnamic and caffeic acids) before and after hydrolysis have been undertaken using standards and either with or without addition of ascorbic acid and EDTA. The method was then applied to the determination of free and bound CA in five blond cultivars (Navelina, Washington navel, Pera, Salustiana and Valencia late) of sweet oranges [Citrus sinensis (L.) Osb.]. Four parts of the fruits (peel juice, flavedo, albedo and juice) have been investigated. Results show that CA are mainly bound (86% up to 92%) in the four fruit parts. The mean of total CA contents was found to be higher in peel juice (1.5 g kg−1) in comparison with flavedo (0.7 g kg−1), albedo (0.1 g kg−1) and juice (0.6 g kg−1). Free and bound ferulic acid represented 55-70% of CA in juices, followed by p-coumaric acid (20%), sinapic acid (10%) and caffeic acid (9%). Total contents of each CA in the four fruit parts are discussed and show the potential interest in orange peel wastes.