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The structure of a common cereal-based crispy snack product can be defined as solid foam. Consumption of such snack products has become popular especially among teenagers and young adults. At the same time obesity has become a common problem. Conventional snack products consist mainly of starch and fat and they have very low protein and dietary fiber content. It is known that dietary fiber and protein have many health effects and they can help in losing weight by avoiding the feeling of hunger. It is therefore important to develop products with high protein and fiber content which can be used instead of common low nutritional value snack products. The aims of this academic research were to utilize several fiber and protein sources in order to produce snack products using extrusion cooking technology which is a common way to produce foods. Special attention was paid to using by-products from the food industry and ingredients which are not commonly used in snacks. Snack products were prepared with extrusion cooking technology in several trials with various mixtures of ingredients. Studied ingredients were: whole grain barley flour, defatted whole grain and endosperm oat flour, corn flour, differently treated oat bran concentrate fractions (OBC), brewer´s spent grain from barley (BSG), polydextrose (PD), whey protein isolate (WPI), Peruvian pseudocereals (amaranth, quinoa, kañiwa), barley starch and waxy corn starch. Snack products were prepared by varying several extrusion parameters: water content of the mass, screw speed and temperature of section 6 and die. Effects of extrusion parameters on the process (torque, specific mechanical energy and pressure at the die) and on the properties (water content, expansion, hardness) of the snacks were studied using response surface methodology. Properties of the most expanded products were studied in more detail. Several fiber sources could be used in the production of snacks, but high fiber content made snacks hard and poorly expanded. However, expanded and crispy barley-based snacks with high fiber and protein content were obtained by adding starch or WPI. Extrusion cooking was also found to increase the extractability and viscosity of barley β-glucan. Furthermore, water-soluble OBC increased the expansion of extrudates made of defatted endosperm oat flour. Expanded, crispy gluten free snack products could be prepared using defatted oat endosperm flour with water-soluble OBC or corn flour enriched with Peruvian pseudocereals at content of 20% of solids. Even though ingredients had a great effect on the properties of the snacks, structure could be modified by extrusion variables: increasing screw speed and decreasing water content of the extruded mass increased expansion and decreased hardness of the snack products. This research gave information how fiber and protein rich ingredients for example by-products could be utilized in the production of healthy snacks made by extrusion cooking. Viljaperäiset rapeat snack-tuotteet ovat rakenteeltaan kiinteitä vaahtoja. Kiinteä vaahto muodostuu ilmatäytteisistä huokosista, joita ympäröi kiinteä materiaali aikaansaaden tuotteelle pienen tiheyden. Tällaisten snack-tuotteiden kulutus on yleistä erityisesti nuorilla. Tavanomaiset snack-tuotteet sisältävät pääasiassa tärkkelystä ja rasvaa, ja niiden ravintokuitu- ja proteiinipitoisuus on hyvin pieni. Niiden kulutus voi osaltaan aiheuttaa erilaisia terveysongelmia kuten ylipainoa. Runsaasti ravintokuitua ja proteiinia sisältävät elintarvikkeet voivat auttaa painonhallinnassa vähentämällä tuotteen energiasisältöä mutta myös lisäämällä kylläisyyden tunnetta. Tämän väitöskirjatutkimuksen tavoitteena oli tutkia erilaisia kuidun ja proteiinin lähteitä keittoekstruusiolla valmistettavien syötävien kiinteiden vaahtojen raaka-aineina. Pääraaka-aineina käytettiin täysjyväohrajauhoa, rasvatonta kaurajauhoa ja maissijauhoa. Kiinteän vaahdon kuitu- ja proteiinipitoisuutta nostettiin lisäämällä pääraaka-aineen joukkoon erilaisia kuidun ja proteiinin lähteitä kuten polydekstroosia, heraproteiini-isolaattia, ohramäskiä, kauralesekonsentraattia ja perulaisia pseudoviljoja (amaranttia, kvinoaa ja kañiwaa). Tutkimuksessa selvitettiin myös ekstruusioprosessimuuttujien (massan vesipitoisuus, syöttönopeus, ruuvien pyörimisnopeus, lämpötilaprofiili) vaikutusta kiinteän vaahdon rakenteeseen ja ominaisuuksiin. Rapeita ja huokoisia kiinteitä vaahtoja saatiin aikaan, kun ohrajauhon sekaan lisättiin heraproteiini-isolaattia ja kun maissijauhoon lisättiin perulaisia pseudoviljoja. Runsaasti beetaglukaania sisältäviä huokoisia kiinteitä vaahtoja saatiin aikaan lisäämällä rasvattomaan kaurajauhoon kauraleseen vesiliukoista jaetta. Ohramäskiä voitiin hyödyntää lisäämällä tärkkelystä ja heraproteiini-isolaattia. Suuren kuitupitoisuuden havaittiin kuitenkin vähentävän kiinteiden vaahtojen huokoisuutta ja lisäävän kovuutta. Tätä negatiivista vaikutusta voitiin vähentää reseptimuutoksilla sekä ekstruusioprosessimuuttujien valinnalla. Yleisesti massan vesipitoisuuden alentaminen ja ruuvien kierrosnopeuden nostaminen lisäsi kiinteiden vaahtojen huokoisuutta ja vähensi niiden kovuutta. Saatua tietoa erilaisten kuidun ja proteiinin lähteiden soveltuvuudesta kiinteiden vaahtojen valmistamiseen ekstruusiolla voidaan hyödyntää snack-tuotteiden kehittelyssä.

Street tree pruning residues are a widely available and currently undervalorized bioresource. Their utilization could help alleviate an increasing biomass shortage and offset costs of the pruning process for the municipalities. In this work, a holistic valorization pathway of pruning residues leading to fibers, oligosaccharides, biogas, and compost is presented. For this, representative mixtures of tree pruning materials from the most prevalent street tree genera (oak, linden, maple) found in Hamburg (Germany) were prepared by shredding and cleaning procedures. Collection of sample material was performed in summer and winter to account for seasonality. A steam-based fractionation was conducted using treatment severities ranging from log R��� = 2.5 to 4.0. At the highest severity, a fiber yield of around 66%, and liquor yield of 26���30% was determined. The fibers were evaluated with respect to their properties for paper product applications, with higher treatment severities leading to higher paper strengths. From the oligosaccharide-rich liquor, emulsions were created, which showed promising stability properties over 8 weeks of storage. The liquors and the rejects from the material preparation also displayed good potential for biomethane production. Overall, the differences between material collected in summer and winter were found to be small, indicating the possibility for a year-round utilization of pruning residues. For the presented utilization pathway, high severity treatments were the most promising, featuring a high liquor yield, good biomethane potential, and the highest paper strengths.