Impact of Carnauba Wax–Structured Olive Oil Oleogels Enriched with Thyme Essential Oil on the Physicochemical, Rheological, and Textural Properties of Biscuits

Abstract

This study investigated the effects of using olive oil-based oleogels as an alternative to traditional solid fats in biscuit formulations on their physicochemical, rheological and textural properties. The fat content in the biscuit formulations was standardised to 24 per cent, and all production conditions were kept constant to ensure comparability between samples. The oleogels developed were characterised using oscillatory rheological measurements; the textural properties of the biscuit doughs were determined by Texture Profile Analysis (TPA); and the relationships between the variables were evaluated using Principal Component Analysis (PCA). Furthermore, the baked biscuits were evaluated using Principal Component Analysis (PCA) in terms of physicochemical and textural change parameters, such as water activity (aw) and moisture content, over a 14-day storage period. In the rheological analyses, it was determined that the storage modulus (G′) was higher than the loss modulus (G″) across the entire frequency range under investigation, thereby demonstrating that solid-like viscoelastic behaviour predominated in all structured systems. An increase in CW concentration systematically raised the values of G′, G″ and complex viscosity, leading to the formation of denser, mechanically stronger and more deformation-resistant lipid networks. In all samples, the decrease in complex viscosity with increasing angular frequency demonstrated the shear-thinning behaviour characteristic of structured lipid systems. TPA results revealed that all textural parameters examined were significantly influenced by the formulation. The CW10K05 sample stood out with the highest values for hardness, gumminess and chewability, whilst VOO-based samples exhibited the lowest structural strength. PCA results, the first two principal components explained 87.8 per cent of the total variance. PC1 explained 70.1 per cent of the total variance and was found to be primarily related to hardness, gumminess, chewability, cohesion and resilience, whilst PC2 explained 17.7 per cent of the variance and was mainly related to the flexibility parameter. During storage, water activity increased from a range of approximately 0.12–0.159 on day 1 to a range of 0.411–0.438 on day 14, indicating a significant gain in moisture. Changes in moisture content were also observed, depending on the formulation. Although the hardness of the biscuits generally decreased with storage, CW10K05 retained the highest hardness value on day 14. The brittleness values, which initially differed between formulations, became statistically similar by the end of storage. Whilst oleogels formulated with CW improve dough strength and product texture, the control of moisture transfer during storage is of critical importance for maintaining product quality.