Promoting effect of whey protein hydrolysate on the color formation of meat products was investigated. Whey protein concentrate (80%, WPC80) as a substrate, was hydrolysed at 50°C for 16 hours using commercial protease and then freeze-dried. The sausages prepared with sodium chloride (2%), sodium nitrite (100ppm) and WPC 80 hydrolysate (5%) or sodium ascorbate (0.1%) had essentially the same color forming ratio (CFR). The main part of the powdered preparation was estimated to be peptides having molecular weight of below 1, 000 using HPLC with gel-filtration column. Of the ethanol soluble fractions in WPC80 hydrolysate, the component having lower molecular weight exhibited higher promoting effect on the color formation. In case of heated myoglobin (Mb) model solution, the CFR increased and residual nitrite level decreased with the concentration of WPC80 hydrolysate. Color accelerating effect of WPC80 hydrolysate was almost the same as the case of sodium erythorbate (NaEry, 0.1%). Using a ferricyanide method, the reducing ability (RA) of NaEry was shown to decrease during heating process, although the value was higher at the beginning of the heating. The RA of WPC80 hydrolysate was intially lower, but tended to increase during heating. The high level of nitrite decomposed with heating was found in the NaEry-added sample. WPC80 hydrolysates had an accelerating effect on the heat-denaturation of Mb, and the denatured Mb showed the high color forming ability. In this research, the possible action of the WPC80 hydrolysate, which contained mainly peptides appeared to accelerate heat denaturation of Mb during heating with increase in RA, thus enhancing the color formation of cooked cured meat products.

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