Sensory profile of hemicellulose-rich wood extracts in yogurt models

Wood is an abundant and sustainable source of emerging food ingredients, namely hemicelluloses that fulfil a number of requirements for functional hydrocolloids. Hemicelluloses, especially spruce galactoglucomannans (GGM) and birch glucuronoxylans (GX), have potential to be used as stabilizers in various foods such as yogurts, beverages, dressings, and desserts. However, in addition to good technological functionality, safety, and low price, the applicability and market potential of new hydrocolloids is determined by their sensory properties. The present study reports, for the first time, the sensory profile of spruce GGM and birch GX in food. Sensory profiles from generic descriptive analysis of GGM- and GX-rich extracts, processed by spray drying or ethanol precipitation, were compared in three types of model food systems: water solutions, yogurt with solutions, and yogurt with emulsions stabilized by GGM or GX. Gum Arabic was included for comparison with a commercial ingredient known to have a mild flavor. The results showed that GGM and GX have a woody flavor, which can be reduced by ethanol precipitation and, in yogurt, masked by other food ingredients.Peer reviewe

Addressing criticalities in the INFOGEST static in vitro digestion protocol for oleogel analysis

The interest on the digestive fate of oleogels, i.e., substitutes for solid fats rich in liquid oil, have pushed re-searchers to use the widely adopted INFOGEST protocol for static in vitro digestion. However, this protocol was originally designed to simulate the digestibility of conventional foods and to accommodate the large fraction of oil in oleogels, researchers have deliberately modified the INFOGEST protocol, inadvertently leading to results difficult to be compared. In this study, we highlighted possible problems that may arise during oleogel simulated digestion such as under-or overestimation of oleogel lipolysis. The effect of oleogel amount, oleogelator type and concentration, and shear applied during digestion on the rate and extent of oleogel digestion was studied. The release of fatty acids during the application of INFOGEST protocol was monitored using the pH-stat method and compared to those analyzed by HPLC-ELSD. Oleogels' structural information was obtained using brightfield, polarized, and fluorescence microscopy, and DSC. We determined that lipolysis of ethylcellulose oleogels follow the "interaction with enzymes and bile salts " pattern, whereas that of wax oleogels follow the "disintegration of oleogel and interaction with enzymes and bile salts ". We also observed that the chemical composition of wax, crystal morphology, and crystal distribution do not alter the lipolysis of oil entrapped inside the wax crystals. We finally recommended a few minimal but fundamental modifications to the INFOGEST protocol to achieve more reliable results from the static in vitro digestion of oleogels and possibly other lipid-based systems.Peer reviewe

Environmentally-compatible alkyd paints stabilized by wood hemicelluloses

Wood biorefining currently involves large-scale industrial processes where a notable portion of raw materials, namely hemicelluloses and lignin, are either lost with the process water, degraded, or burnt for energy. Value added utilization of polymeric hemicelluloses is challenging due to their intermediate molar mass and the presence of other wood components, such as phenolic residues or wood extractives. Oil-in-water (O/W) emulsions represent a diverse and abundant class of applications in which the natural properties of wood hemicelluloses are beneficial. In the current work, we present highly promising new technical alkyd paint emulsion systems stabilized with hardwood glucuronoxylans (GX) and softwood galactoglucomannans (GGM). Samples from three isolation methods and their further fractionation by ethanol precipitation were systematically compared with regard to hemicellulose composition, interfacial activity, and functionality in emulsions. Emulsification of alkyd resins was successful with both GX and GGM obtained by various biorefining strategies. The highest emulsion stability over storage was achieved using crude non-purified GX and GGM fractions, and was correlated with the presence of phenolic compounds and extractives, interfacial activity, and small droplet size. Hardwood GX and softwood GGM are envisioned as natural emulsifiers of alkyd O/W emulsions, which are examples of diverse and abundantly-used technical dispersions. This study can be utilized as a guideline for targeted extraction of hemicelluloses with desired functionality, and as a protocol for developing environmentally-compatible industrial dispersions.Peer reviewe

Centrifugal fractionation of softwood extracts improves the biorefinery workflow and yields functional emulsifiers

With the emerging bio-based technologies, the fractionation of complex biomass is essential to obtain value-added functional molecules for material, chemical, and energy production. The refining process of biomasses often requires the use of solvents and hazardous chemicals, whose removal after fractionation decreases the eco-compatibility of the process and increases the cost and time of the refinement. Softwood extracts obtained through the environmentally friendly pressurized hot water extraction are heterogeneous mixtures rich in hemicelluloses and lignin. Here we developed a simple, fast, organic solvent-free, and sustainable method to fractionate softwood extracts using centrifugal forces. The characteristics of each obtained fraction in terms of composition, macromolecular properties (particle size, molar mass, charge), interfacial activity, and stabilization capacity were highly dependent on the centrifugal force and time applied. The hemicellulose and lignin contents in the fractions were balanced by centrifugal forces to obtain functional emulsifiers that efficiently stabilized the oil/water interface. Through fractionation of softwood extracts, we also found that both the hemicelluloses and lignin particles are involved in emulsion interface formation and stabilization. Centrifugation is a scalable concept that can be feasibly and easily introduced into the biorefinery system and used to optimize the composition of biomass fractions for targeted purposes.Peer reviewe

Use of amaranth, quinoa and kañiwa in extruded corn-based snacks

Amaranth (Amaranthus caudatus), quinoa (Chenopodium quinoa) and kañiwa (Chenopodium pallidicaule) are pseudocereals regarded as good gluten-free sources of protein and fiber. A co-rotating twin screw extruder was used to obtain corn-based extrudates containing amaranth/quinoa/kañiwa (20% of solids). Box–Behnken experimental design with three independent variables was used: water content of mass (WCM, 15–19%), screw speed (SS, 200–500 rpm) and temperature of the die (TEM, 150–170 °C). Milled and whole samples were stored in open headspace vials at 11 and 76% relative humidity (RH) for a week before being sealed and stored for 9 weeks in the dark. Hexanal content was determined by using headspace gas chromatography. Extrudates containing amaranth presented the highest sectional expansion index (SEI) (p < 0.01) while pure corn extrudates (control) presented the lowest SEI and greatest hardness (p < 0.01). SEI increased with increasing SS and decreasing WCM. In storage, whole extrudates exposed to 76% RH presented the lowest formation of hexanal. This study proved that it was possible to increase SEI by adding amaranth, quinoa and kañiwa to pure corn flour. The evaluation of lipid oxidation suggested a remarkable stability of whole extrudates after exposure to high RH.Peer reviewe

Runsaasti kuitua ja proteiinia sisältävien kiinteiden vaahtojen valmistaminen keittoekstruusiolla

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

Valorization of urban street tree pruning residues in biorefineries by steam refining: conversion into fibers, emulsifiers and biogas

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-0 = 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.Peer reviewe

Sensory profile of spruce galactoglucomannans and birch glucuronoxylans in food

201

Clustering of oleogel production methods reveals pitfalls and advantages for sustainable, upscalable, and oxidative stable oleogels

Peer reviewe