Ulla Holopainen-Mantila

Impact of hydrothermal pre-treatment to chemical composition, enzymatic digestibility and spatial distribution of cell wall polymers

The effect of hydrothermal pretreatment on chemical composition, microscopic structure and enzymatic digestibility of wheat straw was studied. Wheat straw was pretreated with increasing severity to obtain series of samples with altered chemistry and structure. The hydrothermal pretreatment caused solubilisation of arabinoxylan and phenolic acids and their dimers in a temperature dependent manner with minor effects on the cellulose and Klason lignin content. In the cell wall level, the pretreatment intensified staining of cellulose and relocalised xylan in the cell walls. The distribution, properties and content of the cell wall phenolic compounds was altered as observed with phloroglucinol and autofluorescence imaging. In the enzymatic hydrolysis, the highest yields were obtained from the samples with a low xylan and diferulate content. On the cell wall structural level, the sample with the highest digestibility was observed to have intensified cellulose staining, possibly reflecting the increased accessibility of cellulose.

Characterization of Lipids and Lignans in Brewer's Spent Grain and Its Enzymatically Extracted Fraction

Brewers spent grain (BSG), the major side stream of brewing, consists of the husks and the residual parts of malts after the mashing process. BSG was enzymatically fractionated by a two-step treatment with carbohydrate- and protein-degrading enzymes, which solubilized 66% of BSG. BSG contained 11% lipids, which were mostly triglycerides, but also a notable amount of free fatty acids was present. Lipids were mostly solubilized due to the alkaline pH applied in the protease treatment. The main fatty acids were linoleic, palmitic, and oleic acids. Several lignans were identified in BSG, syringaresinol and secoisolariciresinol being the most abundant, many associated with the cell wall matrix and released by the alkaline-protease treatment.

Effects of Disintegration on in Vitro Fermentation and Conversion Patterns of Wheat Aleurone in a Metabolical Colon Model

This work aimed to elucidate the effect of wheat aleurone integrity on its fermentability, i.e., the formation of short-chain fatty acids (SCFA) and microbial phenolic metabolites, in an in vitro model using human faecal microbiota as an inoculum. The structure of aleurone was modified by mechanical (dry grinding) or enzymatic (xylanase with or without feruloyl esterase) treatments in order to increase its physical accessibility and degrade its complex cell-wall network. The ground aleurone (smaller particle size) produced slightly more SCFA than the native aleurone during the first 8 h but a similar amount at 24 h (102.5 and 101 mmol/L, respectively). Similar colonic metabolism of ferulic acid (FA) was observed for native and ground aleurone. The enzymatic treatments of aleurone allowed a high solubilization of arabinoxylan (up to 82%) and a high release of FA in its conjugated and free forms (up to 87%). The enzymatic disintegration of aleurones structure led to a higher concentration and formation rate of the colonic metabolites of FA (especially phenylpropionic acids) but did not change significantly the formation of SCFA (81 mmol/L for enzyme treated versus 101 mmol/L for the native aleurone).

Traditional and New Food Uses of Pulses

The global production of pulses, such as various peas, beans, lupines, and lentils, is about 77 million metric tons. Pulses are diverse in their traditional food uses in Asia, Africa, and America, where they have been used, for example, in soups, spreads, meal components, snacks, and breakfast items. Having high protein content (about 20–40%), pulses have recently gained interest when alternative sustainable protein sources are considered. Pulses have been used for protein enrichment in pasta and bread, and they also are suitable ingredients in gluten-free foods. Wet and dry fractionation methods as well as bioprocessing such as germination and fermentation provide useful tools for development of new functional pulse ingredients. The use of pulses is bound to increase in the future, and especially in combination with cereal raw materials they may find new applications meeting both sensory and nutritional needs of consumers on all continents.

Bilberry and bilberry press cake as sources of dietary fibre

Background Dietary recommendations for Nordic countries urge the use of plant foods as a basis for healthy nutrition. Currently, the level of dietary fibre (DF) intake is not adequate. Berries are an elementary part of the recommended Nordic healthy diet and could be consumed in higher amounts. Materials and methods Finnish bilberries and a bilberry press cake from juice processing were studied for DF content, carbohydrate composition, and non-carbohydrate fibre content, which was analysed as sulphuric acid insoluble and soluble material. The microstructure of all samples was also studied using light microscopy and toluidine blue O, calcofluor, and acid fuchsin staining. Results The total DF contents of fresh and freeze-dried bilberries and the press cake were 3.0, 24.1, and 58.9%, respectively. Most of the DF was insoluble. Only about half of it was carbohydrate, the rest being mostly sulphuric acid–insoluble material, waxy cutin from skins, and resilient seeds. Bilberry seeds represented over half of the press cake fraction, and in addition to skin, they were the major DF sources. Microscopy revealed that skins in the press cake were intact and the surface of the seeds had thick-walled cells. Conclusions Bilberry press cake is thus a good source of insoluble non-carbohydrate DF, and could be used to provide DF-rich foods to contribute to versatile intake of DF.

Effects of structural and textural properties of brittle cereal foams on mechanisms of oral breakdown and in vitro starch digestibility

Structural and textural properties as well as the dietary fibre content of solid cereal foams influence the oral breakdown of structure, bolus formation and digestibility. The aim of this study was to investigate how structural differences of solid cereal foams (puffs vs. flakes) affect in vivo chewing and in vitro starch digestion. Four extruded puffs and flakes were produced from endosperm rye flour by extrusion processing without or with 10% rye bran (RB) addition. Extruded puffs and flakes were masticated by fifteen healthy females and the process was monitored using electromyography. Extruded puffs were more porous than flakes (97% vs 35%). The two products were also significantly different (p<0.05) in their structural and textural properties such as expansion, hardness, density and crispiness. A negative correlation was observed between hardness and crispiness index (p<0.05, r=-0.950) and density and porosity (p<0.05, r=-0.964). Addition of 10% RB had a significant effect on structural, textural and mastication properties both for puffs and flakes. Mastication of puffs required less total work than flakes (204 vs. 456%) and they were degraded to smaller particles than flakes during mastication. Irrespectively of the considerable differences in structure, texture and oral disintegration process, no significant (p<0.05) differences were observed between puffs and flakes (86.4 vs. 85.1) in terms of starch hydrolysis index. RB addition increased the hydrolysis index of puffs and flakes to 89.7 and 94.5, respectively, which was probably attributable to the increased number of particles in the bolus.

Keratin-reinforced cellulose filaments from ionic liquid solutions

Cellulose-based filaments produced with ionic liquid-based processes have high application potential in textiles and composites to replace cotton fibres. These filaments already have unique properties that could be further improved with the addition of proteins. Keratin from poultry feathers is currently a low-value material that has potential as a renewable feedstock in material applications. In this study, cellulose filaments with chicken feather keratin were prepared by wet-spinning from an ionic liquid solution. Both keratin and cellulose were dissolved in [EMIM]AcO and spun into ethanol to regenerate cellulose and keratin and wash out the ionic liquid. The effect of keratin addition on the filament properties was investigated by microscopic, spectroscopic and strength analyses. It was observed that a small keratin addition into the cellulosic filaments improved the mechanical properties remarkably, whereas high keratin additions resulted in reduced mechanical performance. Keratin accumulation on the surface of the prepared filaments was observed. In addition, based on FTIR spectroscopy, it is likely that the morphology of cellulose changed from cellulose I to II and the β-sheets in feather keratin unfolded to unordered keratin upon dissolution and regeneration. The cellulose–protein filaments may find applications from areas where good biocompatibility and easy modifiability are required characteristics.

Effect of Hydrolyzing Enzymes on Wheat Bran Cell Wall Integrity and Protein Solubility

Wheat bran contains good quality protein, but given its location inside aleurone cells, this protein has restricted digestibility. The aim of this work was to liberate and solubilize wheat bran proteins via cell wall degradation by using carbohydrate-hydrolyzing and proteolytic enzymes without causing extensive protein hydrolysis. Bran incubated with water (without added enzymes) for 16 h increased the solubilized organic nitrogen content from 14.0 to 42.8%. Enzymes with solely carbohydrate-hydrolyzing activity increased the water-soluble pentosan and reducing sugar contents but did not significantly increase protein solubilization or protein release from the aleurone cells. Enzymes with proteolytic activity significantly increased the solubilization of protein to 58.2% already at 4 h. Significant protein hydrolysis was detected with a high dosage of protease. However, based on light microscopy, the enzymatic treatment mainly modified the proteins in the subaleurone layer, and it was less effective on pro...

Biochemical and sensory characteristics of the cricket and mealworm fractions from supercritical carbon dioxide extraction and air classification

Insects represent a sustainable but under-exploited food resource partly due to the chitin-containing exoskeleton and also the high lipid content that hamper the production of food ingredients. Here we present dry fractionation technology for upgrading house crickets (Acheta domesticus) and yellow mealworm larvae (Tenebrio molitor) by extraction with supercritical carbon dioxide followed by separation to fine and coarse fractions by air classification. The defatted insects contained 73–79% crude protein that was partially fractionated by air classification to protein-enriched fractions containing less chitin. In addition to the significant difference in the coarse mouthfeel between the fine and coarse fractions, the fine fraction of crickets was perceived saltier and more intense in flavour, and the fine fraction of mealworms having more meat-like flavour than the coarse fraction. Thus, it seems that the fractionation process has a clear impact on the texture (coarseness), but the flavour characteristics could be varied according to the insect variety. Overall, the dry fractionation technology holds promising prospects for the production of insect-based food ingredients that are modified in their chitin content and flavour intensity, does not contain identifiable anatomical parts, and thus, could better meet consumer acceptance.

Impact of in situ produced exopolysaccharides on rheology and texture of fava bean protein concentrate

The aim of this study was to investigate the impact of in situ produced exopolysaccharides (EPS) on the rheological and textural properties of fava bean protein concentrate (FPC). EPS (dextrans) were produced from sucrose by two lactic acid bacteria (LAB). The acidification, rheology, and texture of FPC pastes fermented with Leuconostoc pseudomesenteroides DSM 20193 and Weissella confusa VTT E-143403 (E3403) were compared. A clear improvement in rheological and textural parameters was observed in sucrose-added pastes after fermentation, especially with W. confusa VTT E3403. Only moderate proteolysis of fava bean protein during fermentation was observed. The microstructure of the protein in FPC pastes, as observed by confocal laser scanning microscopy, revealed a less continuous and denser structure in EPS-abundant pastes. The beneficial structure formed during EPS-producing fermentation could not be mimicked by simply mixing FPC, isolated dextran, lactic acid, and acetic acid with water. These results emphasize the benefits of in situ produced EPS in connection with the LAB fermentation of legume protein-rich foods. Fermentation with EPS-producing LAB is a cost-effective and clean-labeled technology to obtain tailored textures, and it can further enhance the usability of legumes in novel foods.