High-yield Pulp Research Articles

Jaboticaba genotypes: analysis of fruits, seeds, and artisanal wine

Jaboticaba is a fruit species native to Brazil that is appreciated for its sweet fruits, which are rich in chemical compounds. Despite the remarkable potential of this species, only few studies have explored fruit trees native to Brazil. This study aimed to evaluate the physical and chemical characteristics of fruits, the physiological quality of seeds, the production of artisanal fermented beverages, and the molecular characteristics of eight jaboticaba genotypes. The experiment was carried out in a completely randomized design and the following features were analyzed: the physical and chemical characteristics of fruits using four replicates of 25 ripe fruits; the physiological quality of seeds using four replicates of 50 seeds, with four replicates of 25 seedlings employed for growth evaluation; the production and quality of the artisanal fermented jabuticaba, including an analysis of the alcohol content (WAC - %), pH, and total acidity of the fermented jabuticaba (WTA - meq L-1), and molecular diversity, with 50 SSRs evaluated for transferability in eight jabuticaba genotypes. Of these, 12 SSR were selected to produce clear bands that indicated specificity. Genotype 4 presented one of the largest values for fruit mass (15.25 g) and SS/TA ratio (51.92), which are ideal values for in natura consumption and are associated with higher contents of antioxidant compounds, such as anthocyanins and total phenolics. The genotypes had no statistical difference in seedling emergence, with a mean of 97.6%, despite genotype 5 presenting the highest emergence speed (2.75) and the lowest mean emergence time (18.10 days). Genotype 5 was found to be more vigorous. Further, genotypes 2 and 4 were considered ideal for in natura consumption, with fruits presenting high pulp yield, balanced SS/TA ratio, and high contents of antioxidant compounds. Genotypes 6, 3, and 8 displayed great potential for use in industrial processes. The groups of genotypes reflect the detected genotypes with different purposes and may guide divergent crosses for traits of interest in breeding programs.

Production of High Yield Pulp and Paper from Jute Fibre in Bangladesh: A Comparison with Other Crop Residues

As the allocated forestland for pulp and paper production in Bangladesh is very limited and a substantial amount of crops residues are generated each year, the latter can substitute for pulp and paper production. In this context, eight residues of crops produced in Bangladesh were evaluated. Final pulp yields were 40 -65% with the kappa number of 11-32% depending on crops residues. The experimental processes are outlined. The physico-mechanical properties of handmade papers are estimated by standard procedure. Gram per Square Metre (GSM), brightness percentage, thickness and tearing strength of different handmade paper sheets shows acceptable papermaking properties. FT-IR analysis were carried out for identifying types of chemicals bonds (functional groups).The study indicates that these hand-made papers can be used for making eco-friendly paper bags, packaging material which will be suitable alternative to the non-biodegradable plastic, a cause of ecological and environmental pollution.

Utilization of Waste Banana Pseudostem for Paper Production via Organosolv Pulping

Banana (Musa sapientum) is a predominant fruit crop grown in Sri Lanka which occupies nearly 60,000 ha of land, accounting for 54% of the total fruit cultivation land utilization in the country. The banana tree has a ten months cycle to bear fruits and after its harvesting, the stems are thrown away and left to decay and rot. The waste produced by a single banana plant can make up to 80% of the total plant mass and it is estimated that 220 tons of post-harvest biomass wastes are produced per hectare annually. This has led to waste disposal problems and serious environmental issues. Management of such a vast amount of agricultural waste promotes the use of this biomass for value addition processes. In this research work, an organosolv process based on a mixture of formic acid, acetic acid, and water was adapted and optimized to pulp banana pseudostem fiber and investigate its potential, as a raw material for pulp and paper production through chemical, morphological and mechanical characterization. The global consumption of paper totals more than 400 million tons, cutting down about 7.2 billion trees each year to meet its demand for printing, packaging, and writing purposes. Therefore, the initiative in utilizing available banana waste as an alternative raw material for paper production could further offer a great potential in reducing the dependence on natural timbers, which in turn reduces the demand for global deforestation in the long run. Banana pseudostem fiber is characterized by a high cellulose content and a low lignin content, which is desirable for better pulp yield and papermaking properties. However, it has a high ash content and its interference in the recovery of black liquor was overcome with the selected pulping method. It resulted in a high pulp yield (48.2%) with a kappa number of 32.4. A shorter fiber length (1.12 mm) contributed to a highly uniform paper structure with a smooth surface. Furthermore, the pulp fibers showed an increased crystallinity and a higher slenderness ratio, which is favorable for paper making. The papers produced were heavier weight boards with a grammage of 272 g/m2 and showed higher tensile index (43.16 Nm/g) and tear index (2.08 mNm2/g) compared to other published non-wood fibers.
 Keywords: Banana pseudostem, Organosolv, Cellulose, Pulp, Lignin

Techno-economic and environmental evaluation of a market pulp reinforced with micro-/nanofibers as a strengthening agent in packaging paper

Partly inspired by the concept of masterbatch in plastics manufacturing, we developed a strategy to improve the technical viability, the economic feasibility, and the environmental performance of lignocellulosic micro-/nanofibers. Instead of investing strenuous efforts in dewatering and/or drying nanocellulose suspensions to maximize their consistency without significantly hampering redispersion, which still stands as an unresolved challenge, we used them in high proportions (up to 50 wt%) to reinforce a high-yield pulp. The suspension can be dewatered-pressed (0.70–1.75 MPa) to obtain wet laps of never-dried reinforced pulps, or dried to consistencies over 90% to produce dry boards, but at the cost of lower strengthening capability. In any case, both wet and dry reinforced boards succeeded in enhancing the breaking length of a recycled pulp by up to 62% and 56%, respectively. In light of these results, we proposed a tentative upscaling and subsequent assessment of the process, evaluating different scenarios. From the technical point of view, reinforced pulp boards are much easier to handle and to deliver than dilute aqueous suspensions. In economic terms, savings in transportation costs are worth remarking. Last but not least, this strategy fulfills at least three goals associated with the concept of cleaner production: water recovery (internal recycling), lower CO2 emissions (especially if transportation takes place by road), and avoiding hazardous chemicals such as hypochlorite.

Furnishing autohydrolyzed poplar weakly alkaline P-RC APMP to make lightweight coated base paper

This work investigated the effects of autohydrolysis pretreatment severity on poplar (Populus tomentosa Carr.) woodchips used to make a type of high-yield pulp (HYP) known as preconditioning followed by refiner chemical treatment, alkaline peroxide mechanical pulp (P-RC APMP). It also investigated the ratios for partial-ly replacing sodium hydroxide (NaOH) with magnesium oxide (MgO) in the high-consistency (HC) retention stage of the P-RC APMP process on the obtained HYP’s properties. The results show that the pretreatment severity of autohydrolysis at combined hydrolysis factor (CHF) = 10.77 and the 50 wt% ratio for partially substituting NaOH with MgO were the optimum conditions for making light-weight coated (LWC) base paper. Compared to the conventional P-RC APMP, the optimized P-RC APMP had similar bulk and higher tensile, burst, and tear indices, as well as opacity, but a slightly lower ISO brightness. When the optimized P-RC APMP and commercial softwood bleached sulfate pulp (SBKP) were blended to make LWC base paper, the most favorable pulp furnish was comprised of 50% optimized P-RC APMP and 50% commercial SBKP. The obtained LWC base paper handsheet had better bulk, and its other properties could also meet the require-ments of LWC base paper.

Growth attributes and wood properties of lesser-grown agroforestry tree species in the semi-arid zone for quality pulp and paper production

Growth traits, wood properties, fibre dimensions and fibre derived indices of five lesser-grown agroforestry tree species viz., Ailanthus excelsa, Eucalyptus tereticornis, Leucaena leucocephala, Melia dubia and Neolamarckia cadamba were studied to evaluate the suitability of these species for pulp and paper production in the semi-arid zone of Bundelkhand, India. The result showed that there was a significant variation for all the studied traits. The range of all the studied growth and wood traits among five pulpwood trees were recorded for tree height (5.2-5.9 m), GBH (20-24 cm), volume (0.017-0.027 m3), biomass (8.50-15.28 kg), wood basic density (509.6-584.4 kg/m3), fibre length (819.8-1416.0 μm), fibre diameter (14.6-37.9 μm), fibre lumen diameter (7.5-29.8 μm), fibre double cell wall thickness (4.8-9.7 μm), Runkel ratio (0.23-0.94), Rigidity coefficient (0.19-0.49), Flexibility coefficient (51.54-81.44), Slenderness ratio (31.68-62.74) and Luce’s shape factor (0.20-0.58). Kadamb performed better, however all five species were found to be suitable for making good quality pulp and paper on the basis of wood properties and fibre derived indices grown in such hot and dry conditions. Tree height and GBH traits were positively influenced on the wood physical and anatomical properties, therefore these traits can be used as indirect selection for further improvement of the species which shown high potentiality for promising pulpwood tree species under agroforestry. Further, tree improvement research work required to test the suitable harvesting period for high pulp yield and better paper quality to fulfil the fastest growing demand of pulpwood for paper industries in India.

Variability of Fruit Quality among 103 Acerola (Malpighia emarginata D. C.) Phenotypes from the Subtropical Region of Brazil

Acerola fruit is one of the richest natural sources of ascorbic acid. As a consequence, acerola fruit and its products are in demand worldwide for the production of health supplements and for the development of functional products. Acerola phenotypes (103) were screened in Western Paraná State, in the Southern region of Brazil, and evaluated to obtain information on fruit quality characteristics with the aim of using them in future breeding programs. Principal Component and Hierarchical Cluster analysis were performed on all datasets to explore the variability among samples and to identify the main clusters. A great variability among phenotypes was observed, with potential for use in breeding programs. Seven phenotypes were selected as candidates in the next breeding program, characterized by high vitamin C content and yield, or higher values of fruit size and color parameters. Four belong to cluster 1 and three to cluster 2. Specifically, two phenotypes, belonging to cluster 2, showed the best performance in terms of vitamin C (2150 mg 100 g−1 pulp and 2625 mg 100 g−1 pulp respectively) and pulp yield (74.8% and 82.3% respectively), and one phenotype, belonging to cluster 1, for high pulp yield, fruit size and vitamin C content (80.3% 6.43 g and 2490 mg 100 g−1 pulp).

Comparative assessment of the pulping potentials of soda and mea processes for the development of paper-pulp from sugarcane bagasse

Pulping trials were carried out using MEA and the soda process comparing their pulping potentials. The operating conditions such as the concentration of the cooking liquor (50%, 75%, 100%) for MEA and (10%, 15%, 20%) for NaOH, the maximum cooking temperature (150oC, 160oC, 170oC) and cooking time (60, 90, 120minutes) for both processes were investigated systematically to establish optimal pulping conditions. The agro-biomass used in this investigation is Sugarcane Bagasse viewed as alternative raw material for pulp and paper production. The lignin content of Bagasse (19.5%) was low; indicating that Bagasse should be easier to pulp. The optimum cooking conditions (independent variables) for MEA pulping were 75% MEA concentration, 150oC cooking temperature and 90 minutes cooking time. Excel 2013 was used to analyze the effect of independent variables on yield of bagasse pulp and properties of furnished paper from MEA process in comparison with the Soda process which include tear index, tensile index, burst index and folding endurance with errors less than 15% in all cases. The Kappa number range (12.7-16.9), viscosity (270-870 ml/g) and brightness (62.1-93.2%) of bagasse pulp are appropriate for high-brightness printing and writing papers. The physical properties of furnished paper, tear index (13.4 mN.m2/g), tensile index (71Nm/g), Burst index (4.8 KN/g) and folding endurance (82) recommend the cellulosic pulp from Sugarcane Bagasse obtained from the MEA process for strengthening the virgin fiber in recycled papers and also for developing certain types of printing and packaging papers. Due to the awareness towards the negative impact of kraft mill’s effluent to the environment recently, soda pulping started to regain its popularity among the pulp mills especially non-wood based pulp mills. MEA process is more economically attractive given its high pulp yield, despite the significant increase in chemical demand for bleaching. MEA pulping is a good alternative to soda pulping furnishing high pulp yield with less cooking temperature, i.e. 150oC, thereby saving a considerable amount of energy with less odoriferous pollutants and pollution load associated with the soda process.

NH<sub>4</sub>OH- KOH Pulping and Single-Stage Bleaching Processes of Banana Pseudostem Waste: A Feasibility Study for Molded Pulp Packaging Use

The NH4OH-KOH pulping was a highly efficient process for extracting banana pseudostem waste (BNW) pulp. Besides, this greener pulping process allowed NH4OH recovery and KOH can be later used as fertilizer, reducing the environmental impact. It was found that the optimal BNW pulping condition was using 8.3 wt% NH4OH and 3.3 wt% KOH at a cooking temperature of 155°C for 1 h, and liquid to solid ratio 6:1. From the results, this process allowed low chemical usage and provided high pulp yield (44%) with a high delignification degree (80%) and low Kappa no. (22). After pulping, the single-stage bleaching of BNW pulp using 8 wt% H2O2 and 1.5 wt% NaOH at 90°C for 1 h was shown to improve the whiteness and brightness of the BNW molded pulp samples to 69.7% and 28.7%ISO (3-fold increase), respectively. As compared to commercial molded pulp food packaging, the present BNW molded pulp exhibited a superior tensile index of 54.3 Nm/g and Young’s modulus of 4.8 GPa.

MEA-conversion of agro-wastes to paper-pulp: Optimization of pulping conditions

This paper investigates the potentials of a novel environmental friendly pulping (Monoethanoleamine-MEA) process in comparison with conventional Soda and Kraft pulping processes in furnishing high yield pulp from agro-biomass for the formation Papers and other paper products. The pulping investigation had three (3) factors at three (3) different levels each: Factor 1, MEA concentration (50, 75 and 100%); Factor 2, cooking time (60, 90 and 120minutes); Factor 3, liquor-biomass ratio (4, 6 and 8) at a fixed temperature of 123±5oC. Consequently, the experimental design had 27 treatments (3×3×3) and 2 replicates. By using a central composite factorial design, equations relating the dependent variable (pulp yield) to the different independent variables (cooking temperature, cooking time and liquor concentration) were derived; reproducing the experimental result for the dependent variable with errors less than 15%. Models were evaluated to analyze the effect of experimental pulping conditions on pulp properties and evaluate the effect of these properties on furnished paper samples. Pulp Screened Yields was in the range of 42.45 to 49.18% calculated on oven dry (O.D) basis. The resultant pulps obtained from the cooking operation had very good appearance, exhibiting fairly bright color, with slow tendency to felt, thereby making drainage and consequent paper making time short. It is recommended that the cellulosic pulp obtained from MEA pulping of EFB is appropriate as virgin fiber for strengthening secondary fibers in recycled papers and also for developing certain types of writing, printing and packaging paper materials. Conclusive investigation on EFB fiber in this research study asserts that it has a promising future (when used in blend with certain long fiber plant i.e. kenaf) in substituting wood in the pulp, paper and fiber- board industry. Conclusive investigation also asserts from over-all parameter achieved that monoethanolamine-MEA when used as the main de-lignifying agent furnished pulp and subsequent paper with good strength properties that can adequately match those from conventional (i.e. kraft and soda) processes and because it works without the use of sulphur compounds, it attributes a particular benefit of simple MEA recovery by distillation, allowing black liquor combustion to be dispensed and the dissolved lignin recovered without negative impact on the environment.

Chemical-free production of lignocellulosic micro- and nanofibers from high-yield pulps: Synergies, performance, and feasibility

Far from being devoid of improvement, mechanical fibrillation benefits from high-yield pulping and refining to produce lignocellulosic micro- and nanofibers (LCMNFs). Spruce thermomechanical pulp was pretreated in a PFI mill to 10,000–30,000 revolutions and then passed, from 3 to 12 times and at 300–900 bar, through a high-pressure homogenizer. Mainly depending on those variables, the yield of nanofibrillation (in weight) ranged from 3% to 23%. The successive passes in the homogenizer significantly increased the specific surface area of the LCMNFs, hereby determined by Congo Red (from 115 to 164 m2/g) and poly(diallyldimethylammonium chloride) (from 54 to 89 m2/g) adsorption and contributed to higher cationic demands and water retention values, reaching values up to 229 μeq/g and 2.53 g/g, respectively. The performance of LCMNFs as a strengthening additive in papermaking was assessed, addressing the feasibility of the process. For instance, LCMNFs that had undergone 20,000 PFI revolutions and 6 passes through the homogenizer produced a 73% relative increase in breaking length of a virgin pulp, with an energy input of 19.2 kWh/kg (implying ~1.3 $/kg). Considering the synergic effects between mechanical treatments, a high fines content and the presence of lignin and hemicellulose, this can be a step towards waste minimization and reduction of hazardous chemicals, including sulfur and chlorine compounds.

H2O2 bleaching in mixed triploid poplar and acacia woodchips high-yield pulping process with substitution of 50 wt% NaOH by MgO and its kinetics study

In the present work, the H2O2 bleaching with the substitution of 50 wt% NaOH by MgO as the alkali source in the high-consistency (HC) retention stage of mixed triploid poplar (Populus tomentosa Carr.) and acacia (Acacia confusa Merr.) woodchips P-RC APMP (preconditioning followed by refiner chemical treatment, alkaline peroxide mechanical pulp) was conducted. Meanwhile, the related bleaching reaction kinetics was well established. The obtained high-yield pulp presented a higher bleaching yield, improved bulk, favorable brightness and physical properties in comparison with the obtained pulp using 100 % NaOH as the alkali source. Most importantly, the chemical oxygen demand (COD) of the bleaching effluent was greatly decreased. The established bleaching kinetic equation is as following: dwdt=K[H2O2]3.63[NaOH]1.08[MgO]0.57[Na2SiO3]0.05w−1.89K= A·e–E/RT where the activation energy E =57.2 kJ/mol. It demonstrates that the bleaching reaction rate greatly depends on the concentration of primary bleaching reagents. The magnitude of the dependent extent is [H2O2] > [NaOH] > [MgO] > [Na2SiO3]. The rapid rise of the pulp brightness increment occurred in the first 35 min in the bleaching reaction.

Effect of sodium borohydride and hydrogen peroxide pretreatments on soda pulping of sugar maple (Acer saccharum)

For recovering value-added wood-based organic material prior to delignification, sodium borohydride (NaBH4) and hydrogen peroxide (H2O2) pretreatments under alkaline conditions were performed before soda pulping of sugar maple (Acer saccharum) chips with sodium hydroxide (NaOH). In this investigation, it was determined whether the pulp yield could be increased by partly stabilizing the hemicelluloses by these pretreatments, and simultaneously obtains lower pulp kappa numbers. The results indicated that when aiming to the same kappa numbers (i.e., kappa numbers 14.3-20.5), roughly 3% higher pulp yield could be achieved if the chips were pretreated with alkaline 0.5% NaBH4 solutions, compared to those produced without such pretreatment or pretreated only with NaOH (i.e., without NaBH4). In contrast, pretreatments conducted with alkaline 2.5% H2O2 did clearly lower pulp yields at the same kappa number range (14.0-22.7) when compared to the reference cooks conducted with NaOH pretreated materials. However, an increase in the H2O2 charge of the pretreatment from 2.5% to 5.0% had a clearly beneficial effect, as the pulp yield and kappa numbers after pulping of 5.0% H2O2 pretreated pulps were comparable to the reference cooks.

Damping‐off, root rot and wilting caused by Pythium myriotylum on Acacia crassicarpa in Sumatra, Indonesia

AbstractAcacia crassicarpa is a legume tree of rapid growth and high pulp yield and fibre quality, making this species the basis of large commercial plantations for pulpwood production in Southeast Asian countries. Since a disease has caused significant economic losses in a nursery in the province of Riau, Sumatra, Indonesia, this study aimed to identify the causal agent of the root rot, damping‐off and wilting symptoms of A. crasicarpa seedlings. Isolations were made from infested soil by baiting with young leaves of native Quercus spp. from northern Sumatra. Classical identification using colony growth patterns and morphological characters, molecular identification based on ITS sequence analysis and direct PCR with specific primers, and pathogenicity tests were performed. All isolates formed typical Pythium structures and had fast growth, with optimum and maximum temperatures of 35 and 42°C, respectively. ITS sequence analysis of seven selected isolates showed 99.7–99.9% homology with Pythium myriotylum, the causal agent of nursery diseases on many crops. In addition, species‐specific primers Pmy5/ITS2 successfully yielded an expected amplicon of approximately 144 bp. A soil infestation trial under controlled conditions confirmed the pathogenicity of P. myriotylum to A. crassicarpa, with typical symptoms starting six days after inoculation. The pathogen was re‐isolated only from diseased inoculated plants fulfilling Koch's postulates. This is the first report of P. myriotylum as a pathogen on A. crassicarpa.

Unique steel belt press technology for high strength papers from high yield pulp

The dry strength properties of hot-pressed moist paper improved as stiff high-yield pulp fibers soften and the sheet density increased. Very high wet strength was also achieved without adding strengthening agents. This research focuses on a new hot-pressing methodology based on a steel belt-based pilot cylinder press with infrared heating. The heated steel belt transports the moist paper into the cylinder nip with two adjacent steel rollers with adjustable nip pressure. The temperature ranges up to 300 °C, maximum speed is 5 m/min, maximum pulling force from the steel belt is 70 kN and the line load in the two press nips is 15 kN/m each. High peak pressures are possible due to the hard press nip between steel rolls and steel belt, allowing a good heat transfer to the paper. The long dwell time allows strained drying of the paper which results to high density and high wet strength. Paper samples from high-yield pulps were tested at different nip pressures, temperatures and machine speeds while the dry content was kept constant at about 63%. High nip pressure showed the largest effect on densification and dry strength. While high temperature and long dwell time seem to be most important in achieving high wet strength.

Biorefining of Pinus pinaster Stump Wood for Ethanol Production and Lignin Recovery

AbstractStump wood is a forest residue having significant valorization potential. The aims of this work were to exploit pine stumps as a carbohydrate and lignin feedstock, and to convert the carbohydrate fraction to bioethanol by simultaneous saccharification and fermentation (SSF). Pinus pinaster stump wood (PPSW) was delignified by the alkaline organosolv (AOS) process. Soda (SA) cooking was used as benchmark process. Higher pulp yields were obtained in AOS treatments, whilst SA pulp showed the highest cellulose content. In the SSF of PPSW pulps, high ethanol concentrations were obtained with high productivity and yield. AOS lignins were purer and had lower molar mass and dispersity index, which are important parameters in high‐value co‐product applications.

Pulping and bleaching potential of banana pseudo stem, banana leaf and banana peduncle

The chemical, morphological and anatomical characteristics of banana pseudo stem, banana leaf (midrib) and banana peduncle were determined. Banana wastes were characterized with good amount of α-cellulose (40–45%), moderate amount of lignin (20–24%) and medium to long fiber length (1.22–1.92 mm). Alkaline nitrobenzene oxidation (ANO) showed that the main lignin unit of banana stem and leaf was p-hydroxybenzaldehyde and that of banana peduncle was syringaldehyde. The yield of ANO was very low (17–24%). Soda-anthraquinone (AQ) and formic acid/peroxyformic (FA/PFA) acid pulping processes of these banana wastes were evaluated. In soda-AQ process, pulping at 20% alkali charge, pulp yields were 30.0%, 34.55% and 39.12%, for banana stem, leaf and peduncle, respectively, with kappa number below 20. Higher pulp yield was found in FA/PFA process than soda-AQ process due to very high ash content in the samples. The banana waste pulps showed excellent papermaking properties.

Effect of the storage period on physical-chemical characteristics, microbiological composition and sensory acceptance of two varieties of frozen sweet cassava

Abstract Sweet cassava can be sold frozen, i.e., frozen food, to facilitate preparation and consumption. This study aimed to evaluate physical-chemical characteristics, cooking time, microbiological quality and sensory attributes regarding the varieties BRS Aipim Brasil and Eucalipto in frozen storage. The roots were washed in water, sanitized, cut into cylinders, peeled, sanitized, drained, packed in nylon/ low density polyethylene packages and stored at -18 °C, being evaluated every 30 days, approximately. The Eucalipto variety showed the lowest moisture (61.98%) and the highest pulp yield (71.41%) and starch content (33.45%). However, the BRS Aipim Brasil variety had lower color intensity (11.48) and greater color angle (97.45°) than Eucalipto. The two cassava genotypes showed no difference in terms of acidity, luminosity, soluble solids, total sugar content and pH. The Eucalipto variety showed the shortest cooking time (25 minutes) and moisture (62.92%) concerning the five storage times that were evaluated. This variety also had the highest starch content during storage, except at 31 days. The Eucalipto variety was more accepted for the color, aroma and overall impression attributes. Regarding flavor and texture, the two varieties were considered similar and were classified between the hedonic terms “like slightly” and “like moderately”. The sensory acceptance of the roots was not altered during storage and the grades attributed were above 6.0, which represents the minimum acceptance limit, for all evaluated attributes. Cassava frozen at -18 °C can be marketed for 120 days without microbiological risk, and without significant changes in its physical-chemical and sensory characteristics.

Improving paper wet strength via increased lignin content and hot-pressing temperature

It is known that the strength properties of wood-based paper materials can be enhanced via hot-pressing techniques. Today, there is a desire not only for a change from fossil-based packaging materials to new sustainable bio-based materials, but also for more effective and eco-friendly solutions for improving the dry and wet strength of paper and board. Against this background, hot pressing of paper made from high yield pulp (HYP), rich in lignin, becomes highly interesting. This study investigated the influence of pressing temperature and native lignin content on the properties of paper produced by means of hot pressing. Kraft pulps of varied lignin content (kappa numbers: 25, 50, 80) were produced at pilot scale from the same batch by varying the cooking time. We then studied the effect of lignin content by evaluating the physical properties of Rapid Köthen sheets after hot pressing in the temperature range of 20°C–200°C with a constant nip pressure of 7 MPa. The pilot-scale cooked pulps were compared with reference samples of mill-produced northern bleached soft-wood kraft (NBSK) pulp and mill-produced chemithermomechanical pulp (CTMP). Generally, the results demonstrated that lignin content had a significant effect on both dry and wet tensile index. All of the pilot cooked pulps with increased lignin content had a higher tensile index than the reference NBSK pulp. To obtain high tensile index, both dry and wet, the pressing temperature should be set high, preferably at least 200°C; that is, well above the glass transition temperature (Tg) for lignin. Moreover, the lignin content should preferably also be high. All kraft pulps investigated in this study showed a linear relationship between wet strength and lignin content.

Preparation of performance of nanosilica-loaded fluorescent yellowing inhibitor in paper made from high-yield pulp

3-Aminopropyl-trimethoxysilane was introduced into bis-triazinyl amino-stilbene through the condensation reaction to obtain fluorescent whitening agents (FWAs) having excellent photo-stability. Tetraethoxysilane was hydrolyzed and combined with FWAs through in situ polymerization to obtain nanosilica-loaded yellowing inhibitors (SiO2–FWAs). Ultraviolet (UV) spectroscopy showed that the ratios of the trans-isomer structure in FWAs after 3 h of UV irradiation was 5.41 times higher than those of the cis-isomer. Moreover, the absorption intensity in the UV region was increased distinctly after nano-silica loading. Fluorescence spectroscopy revealed that the fluorescence of SiO2–FWAs was more intense than that of FWAs. In addition, the fluorescence quantum yield of SiO2–FWAs reached 0.416, whereas that of the default FWAs was only 0.279. UV-aging test results showed that SiO2–FWAs can improve the initial whiteness and anti-yellowing performance of paper made from high-yield pulp (HYP). These results indicated that the as-prepared SiO2–FWAs not only exhibited more excellent UV absorption and fluorescence emission properties, but it also exerted better whitening and anti-yellowing effects on high-yield pulp paper than the default FWAs. The enhanced performance of SiO2–FWAs can be ascribed to the synergy between the excellent UV-scattering effect of nanosilica and the fluorescent whitening property of FWAs.