0000000000116173
AUTHOR
Jarkko Hellström
showing 7 related works from this author
Applicability of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) bark extract as a precursor of rigid carbon foam and activated carbon
2023
Hybrid aspens have long attracted scientific interest, but the research on their use as feedstocks for chemical applications are still very limited. The bark biomass of the poplar species contains many valuable extractives that can be utilized as value-added products. This paper examines the applicability of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) bark extract as a precursor of rigid carbon foam and activated carbon. To explore this, the study considers 1) the basic chemical composition of the bark in terms of added value potential, 2) the basic chemical composition of the bark extract and the effect of its pretreatment on the extract composition, 3) the production of rigi…
Enzyme-assisted extraction of anthocyanins and other phenolic compounds from blackcurrant (Ribes nigrum L.) press cake: From processing to bioactivit…
2022
The effects of commercial enzymes (pectinases, cellulases, beta-1-3-glucanases, and pectin lyases) on the recovery of anthocyanins and polyphenols from blackcurrant press cake were studied considering two solid:solvent ratios (1:10 and 1:4 w/v). β-glucanase enabled the recovery of the highest total phenolic content – 1142 mg/100 g, and the extraction of anthocyanins was similar using all enzymes (∼400 mg/100 g). The use of cellulases and pectinases enhanced the extraction of antioxidants (DPPH − 1080 mg/100 g; CUPRAC – 3697 mg/100 g). The freeze-dried extracts presented antioxidant potential (CUPRAC, DPPH), which was associated with their biological effects in different systems: antiviral a…
The effect of thermal drying on the contents of condensed tannins and stilbenes in Norway spruce (Picea abies [L.] Karst.) sawmill bark
2021
Norway spruce (Picea abies (L.) Karst.) bark contains marked amounts of polyphenolic compounds. Condensed tannins (CTs) and stilbenes show commercial potential as antioxidants, antimicrobials, preservatives in food and cosmetic applications, technochemical products, and pharmaceuticals. Storing of bark before the conversion process leads to substantial losses of extractives compounds. In the present study, the potential of thermal drying for maintaining extractives content was assessed based on an experiment in which bark samples were dried in convection kilns at 40, 50, 60, and 70 °C temperatures. The development of CTs and stilbene contents and CT degradation were followed for 28–34 h. CT…
Toxicological and bioactivity evaluation of blackcurrant press cake, sea buckthorn leaves and bark from Scots pine and Norway spruce extracts under a…
2021
Aqueous extracts from blackcurrant press cake (BC), Norway spruce bark (NS), Scots pine bark (SP), and sea buckthorn leaves (SB) were obtained using maceration and pressurized hot water and tested for their bioactivities. Maceration provided the extraction of higher dry matter contents, including total phenolics (TPC), anthocyanins, and condensed tannins, which also impacted higher antioxidant activity. NS and SB extracts presented the highest mean values of TPC and antioxidant activity. Individually, NS extract presented high contents of proanthocyanidins, resveratrol, and some phenolic acids. In contrast, SB contained a high concentration of ellagitannins, ellagic acid, and quercetin, exp…
From Norway Spruce Bark to Carbon Foams : Characterization, and Applications
2020
Fresh bark from spruce Picea abies was milled and extracted with hot water. The extracts were purified in a number of steps in order to get tannin-extracts pure enough to prepare tannin-based carbon foams. The chemical composition of the extracts were analyzed. The foams were maturated and thermally treated to obtain desired properties, such as specific surface area, porosity, and compressive strength. It was possible to produce carbon foams even if they contained carbohydrate impurities. Differences in the properties of the carbon foams such as compressive strength, specific surface areas, and pore size distributions might be related to the compositions of the extracts. The foams were fina…
Behaviour of Extractives in Norway Spruce (Picea abies) Bark during Pile Storage
2022
The current practices regarding the procurement chain of forest industry sidestreams, such as conifer bark, do not always lead to optimal conditions for preserving individual chemical compounds. This study investigates the standard way of storing bark in large piles in an open area. We mainly focus on the degradation of the most essential hydrophilic and hydrophobic extractives and carbohydrates. First, two large 450 m3 piles of bark from Norway spruce (Picea abies) were formed, one of which was covered with snow. The degradation of the bark extractives was monitored for 24 weeks. Samples were taken from the middle, side and top of the pile. Each sample was extracted at 120 °C with both n-h…
Inspired by nature: Fiber networks functionalized with tannic acid and condensed tannin-rich extracts of Norway spruce bark show antimicrobial effica…
2023
This study demonstrated the antibacterial and antiviral potential of condensed tannins and tannic acid when incorporated into fiber networks tested for functional material purposes. Condensed tannins were extracted from industrial bark of Norway spruce by using pressurized hot water extraction (PHWE), followed by purification of extracts by using XADHP7 treatment to obtain sugar-free extract. The chemical composition of the extracts was analyzed by using HPLC, GC‒MS and UHPLC after thiolytic degradation. The test matrices, i.e., lignocellulosic handsheets, were produced and impregnated with tannin-rich extracts, and tannic acid was used as a commercial reference. The antibacterial and antiv…