# Innovations in Wheat Bread: Using Food Industry By-Products for Better Quality and Nutrition
## 2 Chemistry of Selected By-Products
Understanding their metabolism in various health conditions is crucial [66, 67]. [PERSON] et al. [68] found that flavanols have specific hypotensive effects on hypertension, with microbial metabolism influencing differences between healthy and hypertensive rats. These findings underscore the importance of tailored metabolic studies to fully grasp the health benefits of grape phenols. The FAOSTAT data indicates that global olive (_Olea europaea_ L.) production in 2022 exceeded 23 million tons, with approximately 5.3 million tons designated for table olives, while the remaining portion is allocated for olive oil production, yielding around 3.5 million tons annually [69]. During olive oil production, the quantity of olive pomace generated varies from 2.75 to 4 tons per ton of oil, influenced by fruit quality and extraction technology [13, 70]. Olive pomace stands as a significant by-product in the olive oil industry, making up roughly 65% of the initial weight of pressed olives in a three-phased pressing system or 80% in a two-phased decanter [71, 72]. Olive pomace encompasses pulp, skin, seeds, and stone fragments and has a high moisture content ranging from 65-75% [13]. Specifically, olive pomace is commonly repurposed as fuel and utilized as an ingredient for compost production or as fertilizer for agricultural soils [25]. Olive pomace contains between 4.5 to 9% residual oil, with cis-oleic acid being the predominant fatty acid [73, 74, 75]. The main component of olive pomace is dietary fiber (69.6-80.1 g/100 g d.m.). According to literature, the majority of the fiber consists of insoluble fiber (56.7-76.1 g/100 g d.m. ), with soluble fiber accounting for only 3.5-12.9 g/100 g d.m. The main fractions of fiber include lignin (25.5-42.6 g/100 g d.m. ), hemicellulose (10-28.9 g/100 g d.m. ), and cellulose (6.2-27 g/100 g d.m.) [16, 76]. Sugars present in the pomace are mainly glucose (23.6-23.9 g/100 g d.m. ), xylose (13 g/100 g d.m. ), and arabinose (2 g/100 g d.m.) [16]. Olive pomace also contains 0.88-4.44 g/100 g d.m. of protein and 9.93-16.68 g of ash /100 g d.m., including minerals such as potassium (up to 2843 mg/100 g d.m. ), calcium (up to 450 mg/100 g d.m. ), iron (up to 61 mg/100 g d.m. ), and copper (2.1 mg/100 g d.m.) [77, 78, 79, 80]. They also contain certain amounts of vitamin E (0.87-2.25 mg/100 g) [13, 75]. Olive oil byproducts, rich in polyphenols (to 98% of the polyphenols found in olives; to 14.1 g/100 g d.m. ), offer potential health benefits [81]. Main compounds include hydroxytyrosol, tyrosol, caffe acid, p-coumaric acid, vanillic acid, syringic acid, gallic acid, luteolin, quercetin, cyanidin, and verbascoside [82, 83], and fatty acids such as oleic, palmitic, and linoleic acids [84]. These by-products are cost-effective sources for extracting antioxidants used in various applications [25, 85]. Phenolic compounds in olive pomace, particularly hydroxytyrosol derivatives, act as powerful antioxidants, offering various health benefits. These dietary antioxidants are essential for counteracting free radicals, which are implicated in oxidative stress and diseases such as cancer, cardiovascular issues, and diabetes. Olive-derived polyphenols also influence signaling pathways related to inflammation, oxidative stress, and insulin resistance. Moreover, they serve as natural food additives, prolonging shelf life and minimizing nutrient loss [86, 87]. On the other hand, due to the presence of antimutrients like condensed tannins and insoluble fibers in dietary olive pomace, it was theorized that incorporating olive pomace into the diet would negatively impact serum biochemical parameters [88]. Flux, also known as linesed (_Linum usitatissimum_ L.), is one of the most popular oil and fibrous crops worldwide. Data indicates that in 2022, global flaxseed production reached3.64 million tons [89]. Historically, flaxseed has been primarily valued for its oil, which serves various purposes such as in paints, coatings, printing inks, soap making, core oils, brake linings, and herbicide adjuvants.