Effects of temperature and time on polyphenolic content and antioxidant activity in the pressurized hot water extraction of deodorized thyme (Thymus vulgaris).
The effects of temperature (50-200 °C) and contact time (5-30 min) on the pressurized hot water extraction of deodorized thyme were explored for antioxidant activity, polyphenol profiles, and total antioxidants. Six not previously reported polyphenolic compounds were identified in thyme. An inverse correlation was found between the antioxidant activity and total antioxidants with the amount and diversity of polyphenols. The highest total extract yield and antioxidant activity were obtained at 200 °C, although maximum polyphenol extraction yields of hydroxycinnamic acids, flavones, flavonols/flavanones, and total polyphenols were detected at 100 °C and 5 min. Higher temperatures and longer exposure times reduced extract polyphenol diversity. Dihydroxyphenyllactic acid was the only phenolic compound for which extraction yield increased with temperature, probably as a product of the thermal degradation of rosmarinic acid. Consequently, for extracting phenolics from thyme, 100 °C and 5 min would be appropriate operating conditions, whereas antioxidant-active nonphenolic compounds were favored at higher temperatures and exposure times.
Department of Chemical and Bioprocesses Engineering, Pontificia Universidad Católica de Chile, Avenida Vicuña Mackenna 4860, Santiago, Chile.
José R
JR
Vergara-Salinas
Jara
J
Pérez-Jiménez
Josep Lluís
JL
Torres
Eduardo
E
Agosin
José R
JR
Pérez-Correa
D000975:Antioxidants / Q000032:analysis* / Q000302:isolation & purification; D006358:Hot Temperature; D009812:Odorants; D010936:Plant Extracts / Q000737:chemistry*; D059808:Polyphenols / Q000032:analysis* / Q000302:isolation & purification; D011312:Pressure; D013696:Temperature; D046930:Thymus Plant / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D000975:Antioxidants; D010936:Plant Extracts; D059808:Polyphenols; D014867:Water