Enhancing Gluten-Free Muffins with Milk Thistle Seed Proteins: Evaluation of Physicochemical, Rheological, Textural, and Sensory Characteristics

This study investigated the potential utilization of milk thistle seed protein (MTP) isolates in gluten-free muffins to enhance the protein quantity and technological attributes. MTP was employed to partially substitute a blend including equal amounts of rice flour and corn starch (RCS) at 3%, 6%, 9%, and 12%. The study encompassed a rheological assessment of muffin batters and physicochemical, textural, and sensory analyses of the muffins. The consistency coefficient (K) of muffin batters exhibited an increase with the incorporation of MTP, with all batters demonstrating shear-thinning behavior (n < 1). The dough samples exhibited solid-like characteristics attributed to G' > G″, indicative of their viscoelastic nature. The storage modulus (G') and loss modulus (G″) escalated with higher levels of MTP, suggesting an overall enhancement in dough viscoelasticity. The muffin containing wheat flour displayed the lowest hardness value, followed by MTP-added muffins at ratios of 12% and 9%. Additionally, MTP-added muffins exhibited greater springiness values than control samples without MTP (C2). However, the oxidative stability of MTP-added muffins was lower than the wheat control muffin (C1) and gluten-free control muffin. The protein content in muffins increased with MTP addition, reaching parity with wheat flour muffins at 6% MTP replacement. Sensory analysis revealed that substituting RCS with up to 6% MTP did not significantly alter the overall quality (<i>p</i> > 0.05), whereas higher MTP levels (9% and 12%) led to a decline in sensory attributes. Incorporating MTP at up to 6% yielded protein-enriched muffins with sensory characteristics comparable to the wheat flour muffin (C1). Furthermore, higher MTP additions (9% and 12%) conferred more favorable textural properties than the C2 muffin. However, the oxidative stability of the control muffins was found to be higher than that of MTP-added muffins. This study suggested that MTP could be a potential ingredient to increase the protein amount and specific volume of gluten-free muffins and to improve textural attributes such as springiness and hardness.