Effects of pH and muscle type on the viscoelastic and water-holding properties during heat-induced gelation of porcine myofibrillar proteins
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The gelation characteristics of myofibrillar protein have impact on the final texture of meat products. Understanding the gelation mechanism of meat gel systems is beneficial for the development of processed meat products as well as maintaining quality and consistency in meat processing. The aim of this study was to investigate the impact of pH (5.6, 6.0, 6.5, and 7.0) and muscle type (psoas major (predominately glycolytic), semimembranosus (less glycolytic) and longissimus dorsi (less glycolytic) all at pH 6.0 and 6.5) on the heat-induced gelation properties of myofibrillar proteins from porcine muscle. Dynamic rheological properties were measured while heating at 10C/min from 20-850C, followed by a holding phase at 850C for 3 minutes and a cooling phase from 850C to 50C at a rate of 50C/min. Storage modulus (G)́ increased as gel formation occurred, but decreased after reaching the temperature of myosin denaturation (520C) until approximately 600C when the gel strength increased again. This resulted in a peak and subsequent depression in the thermogram. This depression in the curve was more pronounced with increasing pH. Results indicate protein denaturation and gel formation are pH dependent. Testing muscle type at 2 pH values showed that semimembranosus produces the strongest gels at temperatures greater than 600C. Stronger gels formed in samples of pH 6.0 than the sample of pH 6.5 from the same muscle. Strong correlations were identified between storage modulus from muscle type treatments at 57, 72, 85 and 50C. It is clear the variation in gel strength is determined prior to reaching 570C. Muscle type and pH were found to influence water-holding capacity. It was determined that muscle type influenced water-holding capacity to a greater degree than varying pH from 6.0 to 6.5.