Thickness (4 cm diameter × 1.5 cm) samples were analysed. Six measurements were made per sample.
An integration sphere was used.
A calcium sulphate tablet was used for calibration.
Samples were illuminated at 90° ± 10° angle.
Light reflection was measured at 45° ± 5° angle.
Samples were scanned for 40 s using a 400–760 nm wavelength.
The metmyoglobin relative percentage was calculated as follows: % MM = [1.395 − (A572 − A730)/(A525 − A730)]100.
Lipid oxidation was expressed as thiobarbituric acid reactive substances (TBARS) (mg malonaldehyde/kg sample), as determined by Botsoglou et al. (1994), using a UV2 spectrophotometer
The pH was measured using a micropH 2001 pHmeter , and a combined electrode Cat. No. 52-22, to remove the possible contribution to microbiological or colour changes caused by to variations in the pH of the patties.