Effect of nettle (Urtica dioica L.) seed powder supplementation on some important quality characteristics of cakes

The nutritional adjustment of food products has gained popularity in recent years as consumer interest in healthy eating has increased. Cake is a widely consumed cereal-based product containing such key nutrients as carbohydrate, fat, protein, fiber, vitamins, and minerals. In the present study, crust and crumb color, specific volume, microstructure, antimicrobial activity, total phenolic content, antioxidant activity, and sensory analyses were evaluated in four cake groups: a control cake (IT0) and cakes supplemented with 1% (IT1), 3% (IT2), and 5% (IT3) nettle seed powder. The addition of nettle seed powder to the cakes significantly reduced the crust (L*, a* and b*) and crumb color (L* and b*) parameters, with darker coloration due to the natural pigments and phenolic compounds in nettle seeds. The total phenolic content (TPC) in the cake samples ranged from 3.58 to 4.80 mg gallic acid equivalent (GAE)/g, and addition of nettle seed powder significantly increased TPC, which was attributed to the phenolic-rich composition of nettle seeds. The elimination rates of superoxide (O2•–), hydroxyl (OH•), nitric oxide (NO•), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radicals, as well as the iron-reducing potential, increased as the nettle seed concentration was increased, confirming the strong antioxidant capacity of nettle bioactives. The majority of sensory analysis parameters were found to be statistically significant. Although enrichment improved chemical and functional quality, it led to lower sensory scores, particularly in the 5% (IT3) group, which can be attributed to the darker color and distinct herbal flavor from the nettle seed powder. Considering all parameters, the 3% nettle seed cake (IT2) had the most balanced profile, successfully combining enhanced nutritional and antioxidant properties with acceptable sensory characteristics. IT2 can thus be recommended as the optimal, functional and most innovative cake formulation among the tested concentrations.