Textural stability of intermediate-moisture extrudates: Effects of formulation

Effects of formulation on the textural stability of intermediate-moisture, flour-based, "jerky"-type extrudates were assessed. Potato-based extrudates containing various particulate-meat concentrations and different plasticiz ers (sucrose, fructose, glycerol, and glucose) were produced and subjected to accelerated storage for three weeks. The elastic modulus of the samples was measured before storage and then weekly. The relative fluidity and mois ture mobility of the specimens were assessed by dynamic mechanical spectrom etry (DMS), electron spin resonance (ESR), and nuclear magnetic resonance ( NMR). Samples were also evaluated by fluorometry and X-ray diffraction to d etermine the extent of browning reaction and degree of molecular ordering, respectively. While elastic modulus increased appreciably during storage, f irming was progressively reduced by entrained meat content and also by plas ticizers, especially glycerol; plasticized and meat-containing samples had correspondingly lower tan delta peak temperatures as measured by DMS. Textu ral results were also in keeping with fluidity and local viscosity as asses sed by ESR measurements. NMR Tl relaxation values, reflecting moisture mobi lity, increased during storage. Diffraction spectra were consistent with pu blished observations of hydrated starch, suggesting that water may have bee n released due to increased association of proteinaceous constituents. Fluo rescence measurements confirmed moderate Maillard browning in all samples a nd significant chlorogenic browning in glucose-containing samples, although these effects were unrelated to degree of firming. It was concluded that t extural stability was optimized by interruption of the matrix by dispersed meat or by plasticization by low molecular weight constituents.