Effect of NaCl and Whey Protein Concentrate on Desmin Structure of Semitendinosus Beef Muscle

PAZOS ADRIANA A.; PIGHIN DARIO; SZERMAN NATALIA; VAUDAGNA SERGIO R.; GONZALEZ CLAUDIA B.

Ljubljana, Slovenia

Congreso; First European Food Congress (EFFoST 2008); 2008

European Federation of Food Science and Technology (EFFoST)

Desmin is the main protein of intermediate filaments, which are responsible of maintaining the structural integrity of the Z disc and link the adjacent myofibrils at the Z line (1). Previous studies of our group were successful in increasing water holding capacity (WHC) and reducing shear force values of cooked beef muscle by the addition of NaCl and whey protein concentrate (WPC) (2). Therefore, the aim of the present study was to investigate the potential modification of desmin structure exerted by the presence of the added ingredients. At 72h post-mortem, 10 Semitendinosus muscles were obtained from a commercial slaughterhouse (pH: 5.57±0.07). Previous to injection procedure, the muscles were submitted to a continuous tumbling treatment (8.5rpm for 0.5h). Then, muscles were injected (30% w/w) using an automatic multi-needle injector. Brines were formulated to obtain the concentrations of WPC and NaCl shown in Table I. Subsequently, muscles were vacuum packed and tumbled during 8.5h at 5rpm (1.5±0.5ºC). Muscle samples were then stored at -80ºC until assays were performed. Desmin was extracted from isolated myofibrils according to O´Shea et al. (3). Protein content was tested by the Lowry technique (4). Protein profile in the extracts was analyzed through SDS/PAGE. Protein thermal behavior was studied by differential scanning calorimetry (DSC). Warming range was from 25 to 100°C, at a heating rate of 10°C/min. Analysis of electrophoretic patterns showed no significant differences among treatments. Thermograms depicted a decrease in desmin melting temperature (Tm), when compared treated muscles to non-treated ones. No significant differences were found between treatments. Electrophoretic analysis suggests that the addition of NaCl in combination with WPC does not induce desmin degradation. Instead, desmin thermal analysis shows protein destabilization, probably as a consequence of the addition of NaCl (5).