Effects of pork collagen on thermal and viscoelastic properties of purified porcine myofibrillar protein gels

The objectives of this study were to examine the thermal, water-binding and viscoelastic properties of mixed protein systems containing purified myofibrils from porcine semimembranosus (MP) and pork collagen (PC) during gelation and subsequent cooling. MP:PC mixtures (100:0, 90:10, 80:20, 70:30, 60:40, 50:50) normalized to 4% protein were evaluated. No significant differences in thermal characteristics of these mixtures could be detected using differential scanning calorimetry. A primary peak was observed near 66 °C. Using small-strain oscillatory testing, the rheological properties during gelling and cooling were quantified. Storage modulus (G′) increased upon heating for all treatments, but the rate of gel firming and the G′ value at 85 °C were significantly lower (P<0.05) as PC was added to the mixed protein system. Upon cooling, gels revealed a significantly lower (P<0.05) rate of gel firming and significantly lower (P<0.05) G′ value at 5 °C in samples with 20% inclusion of PC and higher. Addition of PC yielded a significant linear (R²=0.65; P<0.01) increase in the water-holding capacity (WHC) of the gels, indicating that the matrix formed in MP:PC gels had a greater ability to entrap water than that of the control MP gels. The inclusion of 10% PC resulted in gels with significantly higher (P<0.05) WHC and similar firmness when compared with gels comprised of MP as the only protein source.