Insight into the mechanism of myofibrillar protein gel stability: Influencing texture and microstructure using a model hydrophilic filler

Abstract

In the present study we have characterized the influence of incorporating micron-sized glass particles into a comminuted protein matrix at increasing filler volume fractions (ϕf). Liquid expulsion during gelation was rapidly reduced in an approximately linear fashion from ∼20 wt% in unfilled gels to no expulsion at ϕf = 0.03. Similarly, large deformation mechanical attributes improved with increasing filler addition, reaching a plateau at when water expulsion was eliminated. Hardness increased from 4.3 N in unfilled gels to ∼11.3 N at ϕf ≥ 0.03. Similarly, Resilience increased 2-fold from 0.18 in unfilled gels, reaching a plateau of ∼0.34 at ϕf ≥ 0.03. SEM micrographs indicated the glass beads weakly interact with the protein network, leaving their hydrophilic surface exposed and available to interact with free/mobile water. Light micrographs showed that in the absence of filler particles the myofibrillar gels contain an integrated network of water channels which deteriorate the integrity of the gel matrix. By incorporating the ∼4 μm glass beads, these channels decreased in size, and were no longer apparent when water expulsion was arrested. Low-field NMR T2 relaxation measurements confirmed that incorporating the glass beads restricted the mobility of the aqueous phase prior to gelation. The dominant relaxation peak was centered around 130 ms prior to gelation, and shifted to ∼70 ms after thermal treatment. Filled gels which exhibited no liquid expulsion during gelation had relaxation times <70 ms even prior to gelation. This work provides insight into the mechanism of myofibrillar protein gel stabilization during gelation and suggests that food-grade, hydrophilic colloidal particles may be of use in improving the textural properties of comminuted meat products.