Muffin Enriched with Bioactive Compounds from Milk Thistle By-Product: Baking and Physico–Chemical Properties and Sensory Characteristics

Muffins are sweet, high-calorie baked products with a typical porous structure and high volume, which confer a spongy texture. Because of this texture and good taste, these products are highly valued by consumers. However, muffins have low nutritional value. The aim of this study was to develop a technology of muffins as a functional product with hepatoprotective activity using defatted milk thistle powder (DMTP). The incorporation of this dietary supplement was carried out by the partial replacement of flour in the classic formulation. Physico-chemical and sensory analyses were performed to evaluate muffins with and without defatted milk thistle seed powder. The moisture sorption isotherms of the porous structure were determined by the gravimetric method with a MacBen microbalance over a 0.05–1.0 water activity range, and the data were fitted to Brunauer–Emmet–Teller (BET) and Guggenheim–Anderson–de Boer (GAB) models. It was established that the addition of milk thistle powder reduces baking, increases the drying out of products and the water-holding capacity, and increases the volume and crumb density of muffins. The microstructure of the muffins was examined using a moisture sorption isotherm. The moisture sorption isotherms of muffin samples presented a sigmoid shape and belong to type II of classification. The hysteresis loops of the samples are almost the same, which indicates similar structural data. The capacity of the monolayer according to the BET models varied in the range of 1.63–2.15 mmol/g of the dried sample, showing a slightly decreasing trend for muffins with DMTP. The GAB model accurately fits the adsorption isotherms in the water activity range from 0.05 to 0.88. The sensory results from a consumer evaluation indicate that both samples were characterized by the traditional pleasant appearance of the muffin, without visible flaws and with a pleasant taste and a good flour aroma. The result is a muffin with the same texture and sensory characteristics but as a potential functional food.