The effect of thermal processing on the content and antioxidant capacity of free and bound phenolics of cookies enriched by nettle (Urtica dioica L.) seed flour and extract

Abstract

The content of free and bound phenolics and their antioxidant capacity in cookies enriched by nettle seed flour and a nettle seed phenolic extract, before, during and after thermal processing (baking at 180°C for 25 min) were examined. The results compare these properties to a cookie obtained only from wheat flour, as the control. Better results were obtained by incorporating nettle seed flour than nettle seed extract. During thermal processing, different changes of phenolic content and antioxidant capacity (increase, decrease or retention) occurred, depending on the form of the phenolics (free or bound), thermal processing time, the cookie and applied antioxidant assays. The free and bound phenolics in the cookie with seed flour were more stable than in the other cookies. At the end of the thermal processing, the cookie with nettle seed flour had a higher content of free and bound phenolics (2.1 and 2.5 times, respectively), and greater antioxidant capacity (the DPPH RSC of free and bound phenolics 9.2 and 4.6 times, and of reducing power 1.6 and 3.4 times, respectively) than the control. There are great possibilities of using nettle seeds in the food industry with the aim of obtaining a functional product with powerful health benefits.

Functional biscuits enriched with potato peel powder: Physical, chemical, rheological, and antioxidants properties

“…Whole grain products should be considered good sources of phenolic antioxidants, despite the fact that the effect of baking seems to depend on a type of baked product, type of phenolic, recipe, and baking conditions [43]. The dissociation of the bound phenolic moiety, which is followed by polymerization and oxidation reactions, as well as the formation of new phenolic compounds that were not present prior to thermal processing, can be the cause of an increase in the content of free phenolics during the process [44,45,46,47]. The development of Maillard reaction products (MRPs) can also be responsible for an increase in the content of phenolic compounds [47].…”

“…The dissociation of the bound phenolic moiety, which is followed by polymerization and oxidation reactions, as well as the formation of new phenolic compounds that were not present prior to thermal processing, can be the cause of an increase in the content of free phenolics during the process [44,45,46,47]. The development of Maillard reaction products (MRPs) can also be responsible for an increase in the content of phenolic compounds [47]. It is necessary to note that certain products of the Maillard reaction have the reductone structures and the formation of MRPs can contribute to an increase in the total phenolic compounds in the Folin-Ciocalteu assay [48].…”

“…Bressa et al [49] found that MRPs produced within the first 20 to 30 minutes of cooking had the high antioxidant capacity. An improvement in the antioxidant properties of naturally occurring compounds and formation of Maillard reaction products are probably responsible for an increase in the antioxidant capacity [47].…”

Preparation, characterization, and bioactivities of polysaccharides fractions from sugarcane leaves

“…The reducing power was measured following a previously reported method (Mitrović et al, 2022). The samples (1 mL) at various concentrations (1.0-3.5 mg/mL) were combined with 2.5 mL of 0.2 M PBS (pH 6.6) and 2.5 mL of K 3 [Fe (CN) 6 ] solution (1%, w/v).…”

Effect of air drying temperature on the phenolics and antioxidant activity of Xuan-Mugua fruit

“…Phenolics are typical phytochemicals that are widely distributed in the different parts of plants such as roots (Wang et al, 2022), stems, leaves (Mazahir et al, 2022), fruits and seeds, showing dominant antioxidant (Mitrović et al, 2021), anti-wrinkling (Byun et al, 2021) and antidiabetic activity (Shafay et al, 2021). According to their structural characteristics, phenolic phytochemicals are generally divided into two main groups such as phenolic acids and flavonoids (Vargas-Madriz et al, 2021).…”