Curing produces a characteristic pink color during meat processing through the production of nitrosyl myoglobin (NOMb), which requires nitric oxide (NO). Nitrites and nitrates in coloring agents are crucial NO sources; however, a reducing agent is necessary to facilitate their chemical conversion to NO. This study aimed to investigate the effect of the reducing properties of whey protein hydrolysate (WPH) on the reddening of cured meat products. Cured and cooked sausage models were treated with WPH, which enhanced the reddening of the meat color and increased the a* value in the models compared with that of the controls. Additionally, ethanol-extracted WPH induced Fe3⁺ reduction, lowered oxidation-reduction potential, and decreased nitrite (NO2-) levels. Moreover, ethanol-extracted WPH promoted the formation of NOMb in myoglobin solution. This effect was also observed when ethanol-extracted WPH treated with maleimide was used, implying that certain peptides rather than the thiol group of WPH are involved in promoting NOMb formation. Furthermore, the peptides that decreased NO2- levels were isolated from ethanol-extracted WPH, identified, and synthesized. These synthesized peptides, particularly the FFVAPFPEVFGK peptide, showed NO2--reducing activity. Hence, WPH may promote the coloration of cured meat products through the reducing potential of the peptides contained within.
Keywords: nitrite; nitrosyl myoglobin; redness; reduction; sausage; whey protein hydrolysate.