Occurence (sic) of a pink color in cooked turkey breast

• Main Author: Girard, Benoît
• Language: English
• Published: University of British Columbia 2010
• Subjects: Cookery (Turkey)
• Online Access: http://hdl.handle.net/2429/26262

A peculiar problem involving cooked turkey products is the appearance of a pink color which consumers often associate with undercooking. Measurements of redness over a period of 4 days of storage were taken on 2 mm thick breast slices from 12 or 18 week old turkeys cooked at selected temperatures of 65, 75, 85 and 95 °C. An analysis of variance indicated that, unlike the age effect, temperature, storage time and their interaction were statistically significant at p<0.01 level. Proper cooking, achieved when an end-point temperature of 85 °C was reached, did not only produce a white to golden-brown color. A tinge of redness was detected by Hunter aL measurement immediately after cooking and disappeared after 3 to 4 days. A simple method developed for the evaluation of pigments in situ, using transmission spectrophotometry, revealed that the residual pink color could be caused by cytochrome c. Visible spectra and electrophoretograms of extracts from cooked breast slices supported the involvement of this pigment. The concentration of cytochrome c in these extracts was 7.9x10⁻² and 5.4x10⁻² mg/g tissue in samples from 12 and 18 week old birds respectively. However the total hemoprotein content in these same breast samples increased from 0.60 to 0.77 mg/g tissue. The method for the evaluation of pigments in situ also was modified in order to investigate the effect of air contact on color immediately after cooking. Additional absorption bands were present when meat slices were kept under anaerobic conditions. The rapid disappearance of these peaks once the meat surface was exposed to air indicated the susceptibility of other hemochromes to oxidation and therefore underlined their relative unimportance in the pinkening phenomenon. Since the above hemoproteins and hemochromes involved in the pinkening phenomenon need to be in a reduced form to give the obtained difference spectra, procedures using ultrafiltration and chromatography were established to search for reducing compounds. The reducing capacity of 1 mL fraction during the first minute of contact with a solution of hemoprotein was called hemoprotein initial reducing activity (IRA). Two groups, one above (higher molecular weight compounds or HMW) and one below (lower molecular weight compounds or LMW) 3000 daltons, were separated. The LMW had a low IRA for both myoglobin and cytochrome c. On the other hand, HMW were produced after heating at 85 °C for 10 min and strongly reduced only cytochrome c. It is postulated that the isolated material may be Maillard reaction products. === Land and Food Systems, Faculty of === Graduate