###### Abstract  
In creating sustainable food systems, alternative uses of food waste and by-products as a source of phenolic compounds or dietary fiber in food formulations should be evaluated to reduce food losses and waste. In this study, wheat bread was fortified with agro-industrial by-products, namely, fresh pistachio hull (FPH), pistachio hull powder (PHP), fresh grape seeds (FGS), and grape seed powder (GSP), at different levels (0.5-4%). The effects of this enrichment on moisture content, crust and crumb color, specific volume, baking loss, total phenolic content, antioxidant activity, and textural properties were evaluated and compared with control bread. Fortification with pistachio hulls and grape seeds, especially in powdered form, improved the total phenolic content and antioxidant activity of the bread compared with the control bread. With the increase in the amount of PHP from 0 to 4.0%, the total phenolic content of the bread initially increased from 0.89 to 14.66 mg GAE/g dry weight and the specific volume decreased from 3.59 cm\({}^{3}\)/g to 2.91 cm\({}^{3}\)/g. Bread containing PHP showed a significant reduction in baking loss and specific volume, while the addition of FGS and GSP at a low level (0.5%) improved the specific volume. The brightness (\(L^{*}\)) of the crumb and crust gradually decreased with increasing levels of all additives. The crumbs of the breads with PHP and FPH were characterized by lower hardness, while GSP and especially FGS had higher hardness. All enriched breads (except those with FGS) were more elastic and easier to chew. pistachio hull; grape seeds; by-products; wheat bread; total phenolic content; antioxidant activity; texture +
Footnote †: journal: Applied Sciences  
mango peel [6], dry onion skin [7; 8], and pomegranate peel powder [9], which are often cheap, functional, and an excellent source of nutraceuticals and bioactive compounds [10]. The amount of waste generated in the food industry is significant, and it is critical to consider alternative recycling options. Grapes are the most widely produced fruit in the world and generate the most waste or by-products (pulp, peel, seeds, and stems). Grape seeds are rich in phenolic compounds, dietary fiber, proteins, vitamins, and organic acids [11]. Pistachio hulls are a major agro-industrial by-product of the pistachio industry and are accumulated in large quantities during industrial postharvest processing. Pistachio hulls are the soft mesocarp and epicarp of the pistachio, which are firmly attached to the hard inner shell. During ripening, it has a pinkish-yellow color that changes to a reddish-light yellow as it matures [12]. Researchers reported that pistachio hulls have antioxidant, antimicrobial, and antimutagenic effects [13; 14; 15; 16]. [PERSON] et al. [15] found that aqueous and methanolic extracts of pistachio hulls are rich in phenols, which effectively retard the deterioration of soybean oil at 60 \({}^{\circ}\)C, with efficacy comparable to that of the synthetic antioxidant BHA (butylated hydroxyanisole). Furthermore, pistachio hulls also contain polysaccharides, dietary fibers, essential oils, unsaturated fatty acids, phytosterols, carotenoids, chlorophylls, tocopherols, and triterpene acids [16; 17; 18]. Due to its antioxidant polyphenic compounds (phloroglucinol, gallic acid, protocatechuic acid, galloyl-shikimic acid, 4-hydroxybenzoic acid, catechin, vanillic acid, eriodictylo-7-O-glucose, naringin, and cinnamic acid) [19] and phytochemical contents, such as fatty acids (1500 mg/100 g dried hull), anacardic acids (355 mg/100 g dried hull), phytosterols (21.36 mg/100 g dried hull), carotenoids (0.55 mg/100 g dried hull), chlorophylls (1.14 mg/100 g dried hull), andtocopherol (0.98 mg/100 g dried hull) [16], pistachio hull can be used in bread formulation to improve bread quality. Due to their strong antioxidant activity, pistachio hulls might be an interesting additive to fortify cereal products.