Effect of Heat Treatment on the Phenolic Compounds and Antioxidant Capacity of Citrus Peel Extract

Abstract

This paper reports the effects of heat treatment on huyou (Citrus paradisi Changshanhuyou) peel in terms of phenolic compounds and antioxidant capacity. High-performance liquid chromatography (HPLC) coupled with a photodiode array (PDA) detector was used in this study for the analysis of phenolic acids (divided into four fractions: free, ester, glycoside, and ester-bound) and flavanone glycosides (FGs) in huyou peel (HP) before and after heat treatment. The results showed that after heat treatment, the free fraction of phenolic acids increased, whereas ester, glycoside, and ester-bound fractions decreased and the content of total FGs declined (P < 0.05). Furthermore, the antioxidant activity of methanol extract of HP increased (P < 0.05), which was evaluated by total phenolics contents (TPC) assay, 2,2‘-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS•+) method, and ferric reducing antioxidant power (FRAP) assay. The correlation coefficients among TPC, ABTS, FRAP assay, and total cinnamics and benzoics (TCB) in the free fraction were significantly high (P < 0.05), which meant that the increase of total antioxidant capacity (TAC) of HP extract was due at least in part to the increase of TCB in free fraction. In addition, FGs may be destroyed when heated at higher temperature for a long time (for example, 120 °C for 90 min or 150 °C for 30 min). Therefore, it is suggested that a proper and reasonable heat treatment could be used to enhance the antioxidant capacity of citrus peel. Keywords: Citrus peel; phenolic acids; flavanone glycosides; HPLC-PDA; total antioxidant capacity

Nutritional Profile, Mineral Content and in Vitro Antioxidant Potency of Capsicum Annum L. Cultivated in 24 Parganas [South], West Bengal, India

“…Moreover, the temperature for polyphenol extraction, as well as the incubation time, also contributes to the efficacy of the antioxidant activity [42][43][44]. However, contradicting the above results, few studies also suggested that the total amount of phenolic acids and flavonoids decreased after heat treatment [45,46]. This indicated that some phenolic acids probably are heat labile, whereas others are converted from insoluble phenolic compounds to soluble phenolics after heat treatment.…”

Bioactive compounds and quality parameters of natural cloudy lemon juices

“…But, the differences among the production stages were not significant, statistically. Xu et al (2007) reported that free fraction of phenolics increased, whereas ester, glycoside, and ester-bound fractions decreased after heating. Moreover, there was a decrease of total phenolic acid content after heat treatment and the content of four flavanone glycosides (narirutin, naringin, hesperidin, and neohesperidin) declined with heating time and temperature.…”

“…For example, polyphenols at an intermediate oxidation state can exhibit higher radical scavenging activity than the completely nonoxidized ones (Nicoli et al 1999;Polydera et al 2004). Xu et al (2007) assumed that many antioxidant phenolic compounds in plants are usually presented as the covalently-bound form; therefore, some processing methods were employed to liberate them in order to enhance their antioxidant capacity. Seok-Moon et al (2004) reported that heat treatment may liberate some low molecular weight in phenolic compounds and increase the antioxidant capacity of citrus peel as a result.…”

Effect of sulfation on the antioxidant properties and in vitro cell proliferation characteristics of polysaccharides isolated from corn bran

“…These conditions resulted in the highest values for DS and phenolic content (4.65 and 119.1 mg GAE/g, respectively) at 2.5 h. This indicated that the esterification time extension contributed to an improvement in the esterification effect as well as the DS and phenolic content of the polysaccharides. However, flavonoids might be damaged due to partial degradation-induced ester bond and glycosidic bond rupture, as a result of a decrease in solvent amount caused by a peracid condition and an excessive esterification time (Xu, Ye, Chen, & Liu, 2007). Thus, phenolic acid distribution was altered, leading to decreases in the esterification degree and phenolic concentration.…”