Determination of gallic acid, ρ-hydroxybenzoic acid,

ρ-coumaric acid, ferulic acid, caffeic acid, (+)-catechin, (−)-epicatechin, quercetin and kaempferol was performed according to Hakkinen, Karenlampi, Heinonen, Mykkanen, and Torronen (1998). Phenolic compounds were extracted and hydrolysed from 5 g of ground fruit using acidified methanol (35 ml). The extract was stirred in the dark at 35 °C for 24 h, then filtered (Millipore membrane 0.22 μm) and analysed by reverse-phase HPLC in the same system described earlier (for the AA analysis). The mobile phase was composed of A – acidified water (1% acetic acid v/v) and B – 100% methanol. The elution gradient learn more started at 100% A; then linearly went to 60% A at 25 min; held for 2 min; then 95% A at 37 minutes; held for 5 min; and back to the initial conditions. Flow rate was 0.9 ml min−1, and column temperature was kept at 25 °C. Quantification was based on external standard calibration curves for gallic acid, ρ-hydroxybenzoic acid, ρ-coumaric acid, ferulic acid, caffeic selleck compound library acid, (+)-catechin, (−)-epicatechin, quercetin and kaempferol (Sigma–Aldrich) and results were expressed as mg 100 g−1 of fruit fw. The antioxidant capacity was determined using the ABTS assay based on the method described by Re et al. (1999). ABTS radical cation (ABTS +) was produced by reacting 7 mM ABTS solution with 2.45 mM potassium persulphate and allowing the mixture to stand in the

dark at room temperature for 16 h. The ABTS + solution was then diluted with ethanol until absorbance measured at 734 nm was 0.70 ± 0.02. After addition of 10 μl of sample or Trolox (0–1.5 mM) standard to 990 μl of diluted ABTS + solution, absorbance at 734 nm was measured at exactly 7 min. Results were expressed as trolox equivalent antioxidant capacity (TEAC). Six major ester volatiles typical of strawberry flavour were identified by GC–MS (Shimadzu QP-5000) and quantified by GC (Varian 3800; Palo Alto, CA, USA) equipped with flame ionisation detector (FID). All extractions were performed manually using 0.75 μm carboxen-PDMS SPME fibers (Supelco, Bellefonte, PA, USA). A Oxalosuccinic acid two gram fruit sample, spiked with 2 μl of an internal standard solution, was placed in a 16 ml vial

and volatiles were collected using a headspace collection mode (with a distance from the liquid surface of 20 mm) at 30 °C for 15 min (equilibrium) and 45 min under stirring. After extraction, the SPME device was introduced in a splitless mode and was thermally desorbed for one minute. The capillary column was a DB-5 (30 m × 0.25 mm i.d. × 0.25 μm; J&W Scientific, Folson California, USA). Helium was used as a carrier gas at a flow rate of 1.0 ml min−1. The injector and detector temperatures were both set at 280 °C. The temperature program started at 35 °C (held for 10 min) and ramped to 210 °C at 1 °C min−1, then held for 10 min. Volatile compounds were identified using a quadrupole mass selective detector. Mass spectral ionisation was set at 180 °C.