# Innovations in Wheat Bread: Using Food Industry By-Products for Better Quality and Nutrition
## 6 Nutritional Value of Bread
A similar trend was observed for antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothazoline-6-sulfonic acid) (ABTS), and Ferric Reducing Antioxidant Power (FRAP), increasing from 0.32-0.77 mg Trolox Equivalent Antioxidant Capacity (TEAC)/g in white bread to 1.24-2.64 mg GAE/g in bread supplemented with a 20% addition of olive raw materials. The highest values for both TPC and antioxidant activity were recorded for the supplementation of white bread with refrigerated pomace, although these differences were not statistically significant compared to other raw materials. [PERSON] et al. [25] observed a 7-fold increase in total phenol content with the supplementation of 10% dried olive paste flour, from 0.28 mg GAE/g dry matter (d.m.) for the control to 1.96 mg GAE/g d.m. for the supplemented sample. Flavonoid content for the control was 0.06 mg Quercetin Equivalent (QE)/g d.m., while for the fortified bread, it was 0.85 mg QE/g d.m. A significant increase, by 56-fold, was also noted for antioxidant activity (from 0.02 mg Trolox equivalent/g d.m. for the control to 1.12 mg Trolox equivalent/g d.m.). The research also aimed to determine the impact on the bioactive properties of bread with the addition of olive mill wastewater (OMWW), olive paste (OP), or both. The total polyphenol content of bread with OMWW instead of water was 6 mg GAE per g d.m., while with a 10% addition of OP, it was 4.3 mg GAE per g d.m. Combining both additives resulted in a total of 10.2 mg GAE per g d.m. The total phenol content increased from 0.14 mg GAE per g d.m. to 0.49 mg GAE per g d.m. for OMWW addition, 1.33 mg GAE per g d.m. for OP addition, and 1.8 mg GAE per g d.m. for both,representing a 950% increase compared to the control. Antioxidant activity (measured by Trolox and FRAP) also significantly increased with supplementation, particularly with OP addition, up to three times more for FRAP and over five times more for Trolox compared to OMWW. While the total polyphenol and phenol content showed a summation effect in bread with both additives, there was a synergy observed for antioxidant activity, which increased from 12% for FRAP to 34% for Trolox with both additives compared to the sum of this activity for supplementation with individual raw materials [25]. When evaluating the bioactivity of food products, it's crucial to consider not only the content of bioactive compounds but also their bioavailability. [PERSON] et al. [25] demonstrated that the stability of total polyphenols during in vitro digestion indicated their higher bio-accessibility in enriched bread compared to the control. This stability, attributed to milk proteins forming polyphenol-protein complexes, enhances antioxidant activity. Moreover, the food matrix influences compound release during digestion. Studies suggest that polyphenols from olive oil by-products are more bio-accessible when in the matrix, such as table olives. The glycemic index (GI) ranks carbohydrate-containing foods from 0 to 100 based on their effect on blood glucose levels compared to a reference food, usually white wheat bread [159]. Bread enriched with olive paste exhibited a significantly lower GI compared to the control, likely due to its high fiber content. Dietary fibers, such as those found in olive paste, can reduce the glycemic response of carbohydrate-rich foods like bread. Additionally, the increased polyphenol content, particularly cyanidin-3-glucose present in olive paste, may also modulate glucose absorption. Studies on other anthocyanin-rich foods like blueberries and pomergnates have reported similar effects on glucose metabolism, suggesting a potential role for anthocyanins in reducing blood sugar levels [25; 160]. Similarly to other plant sources, waste from flaxseed oil pressing is a valuable source of dietary fiber. These by-products contain various components such as cellulose, hemicellulose, and lignin, contributing to the nutritional value of food products.