Development of functional foods and ingredients using by-products from plant foods

The aim of this PhD project was the valorization of by-products from some mediterranean plant foods through their re-utilization in new functional foods and ingredients having the ability to modulate the oxidative processes and nutrient metabolism in the gastrointestinal tract (GiT). Obesity is an urgent social problem and functional foods able to modulate oxidative stress and energy homeostasis are promising tools to control inflammatory status and body weight. Several evidence shows that polyphenols (PPs) and dietary fiber (DF) may control energy intake and appetite in humans through several mechanisms. PPs may quench free radicals forming in GiT, may counteract subclinical oxidative stress and high-fat diet induced inflammation, and may also influence the activity of key digestive enzymes thus modulating nutrients bioavailability and the related neuro-hormonal signals. In this way, PPs are hypothesized able to modulate appetite cues in the short term, and to control body weight in the long term. However, food processes as well as the physicochemical interconnections of PPs with DF and other food components, are crucial factors influencing their bioaccessibility and their functionality along the GiT. Plant foods by-products from agricultural and food industry are a natural and cheap source of PPs and DF. In this thesis the possible reutilization of pomegranate peels (PPe), artichoke leaves (ALe) and stems (AS), and olive leaves (OLe) was investigated by developing three studies. In a first study the bioaccessibility of PPs from PPe and a PPe-enriched cookie (PPeC), their potential total antioxidant capacity (TAC) along the GiT, as well as the ability of PPeC to modulate glucose and lipid metabolism was assessed. To this purpose PPeC were developed and in vitro sequential enzyme digestion coupled to LC/MS/MS and biochemical analyses of the soluble and insoluble fractions collected at each digestion steps were carried out. Data showed the chemical transformations induced by baking process on PPe PPs, the potential release of antioxidants along the GiT and their ability to inhibit α-glucosidase, α-amylase and lipase activities in the duodenal tract. In a second study the development of breads enriched with AS at 3%, 6% and 9% was performed and the intestinal fate of PPs and cynaropicrin was studied in vitro using a simulated human digestion model coupled to High Resolution Mass Spectrometry (HRMS) analysis of digestive extracts. The potential metabolic fate of PPs and cynaropicrin from AS-enriched breads and the ability of the extracts from the duodenal step to inhibit α-glucosidase activity was assessed. A third study was conducted in collaboration with Prof. Bruce Hamaker and Prof. Osvaldo Campanella at Purdue University, (Indiana, USA) and consisted in the development of new antioxidant DF by including PPs-rich extracts from PPe, OLe and ALe in starch-alginate based microspheres (MS). The physicochemical properties of the new ingredients were compared to those of 6 commercially available DF concentrates as well as to whole wheat bran and oat bran in order to position the new ingredients on the actual market of DF concentrates and dietary source of DF. All in all data obtained in this thesis demonstrated that plant foods by-products are promising source of PPs and DF to develop foods and ingredients that may control oxidation and nutrient metabolism along the GiT