Low Water Vapor Research Articles

Evaluation and Adjustment of Precipitable Water Vapor Products from FY-4A Using Radiosonde and GNSS Data from China

The geostationary meteorological satellite Fengyun-4A (FY-4A) has rapidly advanced, generating abundant high spatiotemporal resolution atmospheric precipitable water vapor (PWV) products. However, remote sensing satellites are vulnerable to weather conditions, and these latest operational PWV products still require systematic validation. This study presents a comprehensive evaluation of FY-4A PWV products by separately using PWV data retrieved from radiosondes (RS) and the Global Navigation Satellite System (GNSS) from 2019 to 2022 in China and the surrounding regions. The overall results indicate a significant consistency between FY-4A PWV and RS PWV as well as GNSS PWV, with mean biases of 7.21 mm and −8.85 mm, and root mean square errors (RMSEs) of 7.03 mm and 3.76 mm, respectively. In terms of spatial variability, the significant differences in mean bias and RMSE were 6.50 mm and 2.60 mm between FY-4A PWV and RS PWV in the northern and southern subregions, respectively, and 5.36 mm and 1.73 mm between FY-4A PWV and GNSS PWV in the northwestern and southern subregions, respectively. The RMSE of FY-4A PWV generally increases with decreasing latitude, and the bias is predominantly negative, indicating an underestimation of water vapor. Regarding temporal differences, both the monthly and daily biases and RMSEs of FY-4A PWV are significantly higher in summer than in winter, with daily precision metrics in summer displaying pronounced peaks and irregular fluctuations. The classic seasonal, regional adjustment model effectively reduced FY-4A PWV deviations across all regions, especially in the NWC subregion with low water vapor distribution. In summary, the accuracy metrics of FY-4A PWV show distinct spatiotemporal variations compared to RS PWV and GNSS PWV, and these variations should be considered to fully realize the potential of multi-source water vapor applications.

Enhanced wound healing with biogenic zinc oxide nanoparticle-incorporated carboxymethyl cellulose/polyvinylpyrrolidone nanocomposite hydrogels.

Contemporary wound dressings lack antibacterial properties, exhibit a low water vapour transmission rate, and demonstrate inadequate porosity. In order to overcome these limitations, scientists have employed water hyacinth to produce carboxymethyl cellulose (CMC). CMC/PVP nanocomposite films containing biogenic zinc oxide nanoparticles (nZnOs) were synthesised using cost effective solution-casting technique. As the proportion of nZnOs in the film increased, swelling and water permeability decreased, whereas mechanical stability improved. Dynamic light scattering testing and transmission electron microscopy confirmed that the particle size was around 50.7 nm. Field emission scanning electron microscopy (FESEM) images showed that nZnOs were distributed uniformly in the polymer matrix. Cell viability against Vero cells was greater than 94%, and a substantial zone of inhibition against S. aureus and E. coli bacteria was observed. Wounds of albino mice were treated with CMC/PVP and CMC/PVP/nZnO (6%) nanocomposite hydrogels and healed in 20 and 12 days, respectively, as demonstrated by wound healing assay and histological staining. In vitro and in vivo studies revealed that the novel nanocomposite hydrogels exhibit improved cell viability and wound healing features. Therefore, they could be exploited as promising skin wound dressing materials.

A Full Green, Sustainable Paper-Based Packaging Material with High-Strength, Water Resistance, and Thermal Insulation.

Paper-based packaging materials have gained attention from academia and industry for their outstanding environmental sustainability advantages. However, they still encounter major challenges, such as low mechanical strength and inadequate functionality, hindering the replacement of unsustainable packaging materials. Inspired by the remarkable strength of trees provided by cellulose fibers and the water and heat protection of trees provided by bark, this study developed a new biomass-based packaging material (SNC-C) that combines strength, thermal insulation, and water resistance. The material was created by simply blending straw nanocellulose (SNC) with oak bark (i.e., cork), which naturally provides water-resistant, thermal insulation, and unique regenerative properties. The dense layered structure formed entirely by SNC generates a tensile strength reaching up to 60.93 MPa. With the cork cavity structure, the heat transfer rate of the obtained material is reduced to 2.90-3.01 °C/(cm·min). The combining of the closed-cell structure and the suberin component of the cork results in a low water vapor transmission rate (WVTR) of the material of 400.30 g/(m2·24 h). This all-biomass material with excellent performance and low environmental footprint offers a promising solution for the development of sustainable multifunctional packaging materials.

Recent Wintertime Cooling in the Upper Troposphere and Lower Stratosphere of the Arctic

AbstractAs Arctic surface temperatures exhibit amplified warming, a warming center in the upper troposphere and lower stratosphere (UTLS) is also notable, which potentially plays a crucial role in polar‐to‐mid‐latitude interactions. While the surface warming has accelerated recently, UTLS temperatures, however, have declined since 2001, as demonstrated by multiple reanalysis data sets. This shift in trends provides a unique opportunity to understand the factors influencing Arctic UTLS temperature changes. Further analysis indicates that the descending component of the Brewer‐Dobson (BD) circulation over the Arctic was strengthened before 2000 but weakened thereafter. Simultaneously, Arctic lower stratospheric water vapor showed a decreasing trend before 2000, followed by an increasing trend. The weakening of the BD circulation led to reduced dynamical heating, and the increased water vapor resulted in enhanced radiative cooling, which together contributed to the cooling of the Arctic UTLS after 2000.

The elusive nature of Martian liquid brines

The possible presence of brines on Mars adds an intriguing dimension to the exploration of Martian environments. Their potential involvement in the formation of recurring slope lineae has sparked debates on the existence of liquid water versus alternative dry processes. In situ instrumentation on rovers and landers has been instrumental in providing valuable data for comprehending the dynamics of brines. Laboratory experiments and thermodynamic simulations conducted under Martian conditions offer insights into the formation and persistence of brines, shedding light on the planet’s current hydrological processes. Despite these findings, the prevailing surface conditions on Mars, characterized by a combination of low temperature, pressure, and water vapor pressure, generally hinder the stability of most brines. In such environments, only a few select salts, notably calcium perchlorate, could play a pivotal role in potentially forming brines through deliquescence or melting. These environmental factors emerge as critical contributors influencing the stability of brines, but such limitations generally restrict the locations, timescales, and amounts of brine formed. However, the exploration of brines extends beyond geochemical considerations, serving as a lens through which we can examine potential habitability and gain a broader understanding of the Martian climate. Therefore, observing brines on Mars would offer valuable insights into the dynamic interplay of various factors that influence their stability, contributing to our overall comprehension of Mars’ unique environmental conditions.

Cellulose Nanoworm Coatings for Enhancing the Water Resistance of Nanocellulose Film Substrates in Printed Electronics.

Cellulose-nanomaterial-derived films are promising platforms for engineering advanced substrates for printed electronics. However, they are highly susceptible to water and humidity, which limit their wide application. To overcome these drawbacks, cellulose nanoworms (distinct hydrophobized cellulose nanomaterials) were introduced in this study as sustainable coatings to enhance the water resistance of cellulose nanofiber (CNF) films. Alcogels of nanoworms, produced via ethanol-induced swelling and ultrasonication of a cellulose pulp esterified in a deep eutectic solvent, form a dense and transparent coating on the CNF films, significantly inhibiting their water absorption and improving their surface smoothness. Furthermore, the resulting coated CNF films exhibited enhanced hydrophobicity with improved wet mechanical properties and lower water vapor permeability. In addition, the results of the ink-printing tests revealed that the coated films partially or completely inhibited ink removal. Thus, this study demonstrated that cellulose nanoworm coatings provide a promising approach to overcome the moisture sensitivity of CNF films.

Enhanced Barrier and Optical Properties of Inorganic Nano-Multilayers on PEN Substrate Through Hybrid Deposition.

In this study, an inorganic multilayer barrier film was fabricated on the polyethylene naphthalate (PEN) substrate, which was composed of a SiO2 layer prepared by inductively coupled plasma chemical vapor deposition (ICP-CVD) and a Al2O3/ZnO nanolaminate produced by plasma-enhanced atomic layer deposition (PEALD). The multilayer composite film with a structure of 50 nm SiO2 + (4.5 nm Al2O3/6 nm ZnO) × 4 has excellent optical transmittance (88.1%) and extremely low water vapor permeability (3.3 × 10-5 g/m2/day, 38 °C, 90% RH), indicating the cooperation of the two advanced film growth methods. The results suggest that the defects of the SiO2 layer prepared by ICP-CVD were effectively repaired by the PEALD layer, which has excellent defect coverage. And Al2O3/ZnO nanolaminates have advantages over single-layer Al2O3 due to their complex diffusion pathways. The multilayer barrier film offers potential for encapsulating organic electronic devices that require a longer lifespan.

Reversible Photo-Responsive Hydrophobic Coating Synthesized from Lignin-Derivable Molecules on Nanocellulose Films for Packaging Applications.

Paper-based packaging can offer a sustainable replacement for plastics. However, paper provides a poor barrier to water, oxygen and moisture. This study presents a novel renewable lignocellulosic composite made from a hydrophobic photo-reversible coating deposited onto a cellulose nanofiber film that has improved barrier properties and can be reprocessed. Diglycerol and lignin-derivable aldehyde were reacted to form a tetra-functional monomer with photo-responsive unsaturated double bonds that can be converted to covalent cyclobutane rings to create reversibly crosslinkable network upon UV-irradiation. The photo-responsive compound was applied as a thin coating of thickness 2.7±0.4 μm over cellulose nanofiber (CNF) films of thickness 80±19 μm. The surface of the coated films became hydrophobic with a contact angle (CA) of 93.1±1.7° and displayed a low water vapour transmission rate (WVTR) of 16±2 g/m2/day vs. 30.7±1.5° CA and 81±11 g/m2/day WVTR for uncoated CNF films. The coated film is also oleophobic, an attractive feature for food packaging applications. The reversible photo-reaction enables the crosslinked covalent network to be broken down to unsaturated double bonds once exposed to a higher-energy UV irradiation, allowing reprocessing and recycling. The novel coating was developed using a sustainable green synthesis method (process simple E factor 0.9).

Development of antioxidant films based on anthocyanin microcapsules extracted from purple corn cob and incorporated into a chitosan matrix

Biodegradable food packaging films were prepared from chitosan incorporated with microencapsulated anthocyanins powder (MAP) that was extracted from purple corn cob using the casting method. Anthocyanins extracts were microencapsulated with maltodextrin, gum arabic, and soy protein using a spray-drying method. The film based on chitosan and MAP (CHt@MAP) was prepared through citric acid cross-linking and plasticization with glycerol. The structural analysis of the CHt@MAP film revealed a semicrystalline structure by X-ray diffraction. The interactions were mainly via electrostatic and hydrogen bonding, as confirmed by Fourier-transform infrared. Based on scanning electron microscopy, the morphology of the films revealed evidence of the presence of MAP on the surface and cross-section. The microcapsules inside the films produced an increase in thickness (0.18–0.21 mm), lower water vapor permeability (12.4–8.5 × 10−10 g m−1s−1Pa−1), and reduced elongation at break (217 % to 165 %), as well as tensile strength (1.3 to 0.45 MPa) compared to the chitosan film. Furthermore, the antioxidant activity of CHt@MAP film was high, with a radical scavenging activity of 56 %. It also exhibited a strong barrier to UV and visible light. The results indicate that the CHt@MAP film preserves the shelf life of blueberries at room temperature and could be used as an active packaging film for foods.

Preparation and Characterization of Lithraea molleoides Gum Flour and Its Blend Films

Lithraea molleoides fruit gum (LMFG) is a valuable product obtained from the total hydrolysis of the fruit. The hydrolysis process involves three methods: thermal (LMFGT), alkaline (LMFGB), and acid (LMFGA). Through these methods, the aim is to break bonds and de-esterify polysaccharides, resulting in increased solubility and decreased molecular weight. The resulting hydrolysates are then combined with pectins in a 1:2 ratio to form films. In this study, the focus is on utilizing the hydrolysates of Lithraea molleoides gums for film applications, with an evaluation of their structural and physicochemical characteristics. The films produced exhibit excellent mechanical properties and low water vapor permeability, as well as exceptional thermal stability. These properties make them highly suitable for industrial films in pharmaceutical and food applications. This research highlights the potential of LMFG-based films as a viable solution for various industrial needs due to their outstanding performance across multiple parameters.

Water Vapor-Impermeable AlON/HfOx Bilayer Films Deposited by Hybrid High-Power Impulse Magnetron Sputtering/Radio-Frequency Magnetron Sputtering Processes.

Water vapor-impermeable AlON/HfOx bilayer films were constructed through a hybrid high-power impulse magnetron sputtering (HiPIMS) and radio-frequency magnetron sputtering process (RFMS), applied as an encapsulation of flexible electronics such as organic photovoltaics. The deposition of monolithic and amorphous AlON films through HiPIMS was investigated by varying the duty cycles from 5% to 20%. At an accelerated test condition, 60 °C, and 90% relative humidity, a 100 nm thick monolithic AlON film prepared using a duty cycle of 20% exhibited a low water vapor transmission rate (WVTR) of 0.0903 g m-2 day-1 after testing for 336 h. Furthermore, after introducing a nanocrystalline HfOx film through RFMS, a 214 nm thick AlON/HfOx bilayer film reached the lowest WVTR of 0.0126 g m-2 day-1.

Role of Tropical Disturbances along the South Asian Monsoon Trough in the 2022 Pakistan Floods and the Implications for Interannual Variability

Abstract This study examined the atmospheric circulation patterns that were responsible for the severe flooding that occurred in Pakistan in 2022. It focused on the role of westward-propagating tropical disturbances (TDs) along the South Asian monsoon trough, which are associated with flood-related precipitation events. The study also investigated the interannual precipitation variation in Pakistan over 23 years from 2000 to 2022, using satellite-derived precipitation and atmospheric reanalysis. The results showed high precipitation in southern and central Pakistan, implying tropical influences. The precipitation was the highest in the past 23 years. The massive rainfall was brought by several TDs under the highest water vapor conditions, although a TD of South Asia climatologically tends to weaken before affecting Pakistan. Enhanced easterlies along the Indo-Gangetic Plain, part of the enhanced monsoon trough, supported high water vapor conditions over Pakistan. The high water vapor was also partly supported by the long-lasting active phase of the South Asian monsoon intraseasonal oscillation in 2022. Moreover, the La Niña condition increased moisture transport as a background. On an interannual time scale, the enhanced moisture flux over the Indo-Gangetic Plain resulted in higher precipitation over Pakistan, as occurred in 2022. These high (low) water vapor and precipitation can be partly explained by La Niña (El Niño). However, La Niña and El Niño may not control the TD activity over South Asia. Thus, for 2022, the high water vapor is somewhat empirically predictable, but the active TD activity can be coincidental. Significance Statement In 2022, Pakistan was hit by catastrophic flooding that affected 15% of the population. The analysis of the atmospheric circulation associated with the flooding indicates that weak but rain-bearing tropical disturbances played a significant role in flooding. Several tropical disturbances stayed or moved into Pakistan, bringing massive rainfall although, usually, they tend to weaken before hitting Pakistan. In the past 23 years, La Niña–related weather patterns have partly explained the year-to-year precipitation variation in Pakistan. However, in 2022, the unusually heavy flooding was due to the combined La Niña effect and tropical disturbance activity. Because it is still difficult to predict the seasonal tropical disturbance activity from La Niña, El Niño, and other climatic conditions, seasonal prediction of these floods remains challenging.

Extending The Calendar Life of Fiber Lithium-Ion Batteries to 200 Days with Ultra-High Barrier Polymer Tubes.

Scalable fiber lithium-ion batteries (FLIBs) have garnered significant attention due to huge potential applications in wearable technology. However, their widespread applications have been limited by inadequate cycle and calendar life, primarily due to the high permeability of the encapsulation layer to water vapor in ambient air. To address this challenge, an ultra-high barrier composite tube is developed by blending polytrifluorochloroethylene (PCTFE) with organically modified montmorillonite (OMMT) for the continuous packaging of FLIBs. Due to the high crystallinity (≈40.21%) and small free volume (103.443 Å3), the PCTFE tube exhibited a low water vapor transmission rate (WVTR) of 0.123 mgday-1pkg-1. Furthermore, through the melt extrusion, OMMT with its plate-like morphology are fully exfoliated and dispersed within the PCTFE matrix. This created more complex pathways for water, increasing the diffusion path length and thereby reducing WVTR to 0.006 mgday-1pkg-1. This innovation enabled an ultra-long calendar life of 200 days and cycle life of 870 cycles for FLIBs, with over 80% capacity retention in ambient air. Additionally, 2%OMMT-PCTFE-FLIBs exhibited excellent flexibility, retaining an impressive 85.31% capacity after 10000 bending cycles. This research presents a simple yet effective approach to enhance the lifetime and practicality of FLIBs through building a high-performance polymer-based encapsulation layer.

Physicochemical characterization of bioactive polysaccharides from three seaweed and application of functional fruit packaging films

Seaweed polysaccharides show tremendous research and application value because of their significant and unique biological activities. However, reports on seaweed polysaccharides usually focus on in-depth studies of a specific biological activity, which severely limits their further development. Herein, three seaweed polysaccharides were isolated from Undaria pinnatifida (UPPS), Sargassum pallidum (SPPS), and Ulva lactuca (ULPS), respectively. The physicochemical properties, structure, rheological properties, antioxidant activities, antibacterial activities, and anti-glycation activities of UPPS, ULPS, and SPPS were comprehensively studied. It was first demonstrated that SPPS and UPPS had triple prominent biological activities. SPPS exhibited the best biological activities in antioxidation (IC50 in the ABTS test: 0.4616 ± 0.0134 mg/mL), antibacterial effect, and anti-glycation activity (inhibitory rate: 84.74 ± 0.07 %). Additionally, UPPS films (UPPSF) demonstrated superior ultraviolet shielding performance, lower water vapor permeability (1.78 ± 0.01 g/m·s·Pa × 10−11), higher hydrophobicity (water contact angle: 96.91 ± 2.52°), and higher antioxidant activity compared to ULPS films (ULPSF). UPPSF and ULPSF effectively prolonged the shelf life of strawberries to six days, and UPPSF showed better preservation properties. This work provides novel theoretical insights into the use of polysaccharides as medicinal nutraceuticals, bioactive agents, and food packaging films.

Preparation of active films with antioxidant and antimicrobial properties by combining ginger essential oil nanoemulsion with xylan and polyvinyl alcohol

Due to the environmental challenges of petroleum-based packaging, new biodegradable and active food packaging has garnered significant attention. In this work, active films were generated with xylan/polyvinyl alcohol (PVA) as the film-forming matrix, combined with ginger essential oil nanoemulsions (GEO-NEs) at varying concentrations (2.0 %, 4.0 %, 6.0 %, and 8.0 % w/w). The GEO-NEs, produced via ultrasound, had a mean particle size measuring 176.4 ± 1.2 nm and demonstrated excellent stability for up to 28 d. FTIR and XRD analyses revealed that interactions between GEO-NEs and the film matrix occurred through hydrogen bonding, indicating good compatibility between the components. Incorporating GEO-NEs significantly enhanced the UV shielding performance and mechanical characteristics of the composite films, achieving mechanical characteristics comparable to those of commercial packaging materials such as high-density polyethylene (HDPE). Additionally, composite films with 2 % and 4 % GEO-NEs exhibited lower water vapor permeability (WVP) than the control film, indicating improved water barrier performance. GEO-NEs also significantly improved the antioxidant activity of the composite films and imparted certain antimicrobial properties. As a result, these films hold promise for applications in active food packaging.

Properties of Guar Gum/Pullulan/Loquat Leaf Extract Green Composite Packaging in Enhancing the Preservation of Chinese Water Chestnut Fresh-Cut Fruit.

Loquat leaf extract (LLE) was added to guar gum and pullulan as an environmentally friendly packaging film (GPE) to preserve Chinese water chestnuts (CWCs). The effect of the amount of LLE on the guar gum/pullulan composite film was investigated. The optimal amount of LLE was 4% (GPE4), with lower water vapor permeability (WVP) and greater mechanical strength, antioxidant, and comparable antibacterial performance than many pullulan-based films. Upon packing the CWCs for 4 days, the weight loss rate of GPE4 was only 1.80 ± 0.05%. For GPE4, the POD activity, the soluble solid content, and the vitamin C (Vc) content of the CWCs were 21.61%, 36.16%, and 26.22% higher than those of the control sample, respectively. More importantly, GPE4 was effective in preserving the quality of CWCs after 4 days of storage, better or at least comparable to non-biodegradable plastic wrapping (PE). Therefore, it can be concluded that GPE films hold significant promise as a sustainable alternative packaging material for preserving fruit-based foods like CWCs, potentially replacing PE in the future.

Multifunctional electrospun nanofibrous film integrated with cinnamon essential oil emulsion stabilized by dealkali lignin for active packaging material

Cinnamon essential oil (CEO) has good antibacterial properties, but its volatility, hydrophobicity and bad odor limit its use in food preservation. In this study, a dealkali lignin (DAL) stabilized emulsion loaded with CEO was encapsulated into poly (vinyl alcohol) (PVA) and zein using an emulsion electrospinning technique. With the existence of DAL, the PVA/zein/DAL/CEO nanofibrous film (PVA/zein/DAL/CEO NF) exhibited good antioxidant properties. Moreover, higher antibacterial activity was achieved owing to the nanosized structure and enhanced stability compared to DAL/CEO emulsion and pure CEO. Scanning electron microscopy (SEM) revealed uniformly produced PVA/zein/DAL/CEO NF with an average diameter of 295 nm. The interactions among the nanofibrous film's components were confirmed using attenuated total internal reflectance fourier transform infrared spectroscopy (ATR-FTIR). The nanofibrous film demonstrated a low water vapor permeability (WVP) of 5.07 mm∙g/(m2∙h∙kPa), which was beneficial for reducing moisture transfer from the external environment to the interior of the packaging. Additionally, the PVA/zein/DAL/CEO NF also exhibited a marked enhancement in antioxidant activity, neutralizing 94.54 % of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. The nanofibrous film also demonstrated potent antibacterial effects, with inhibition zones measuring 19.47 mm for Escherichia coli (E. coli) and 30.37 mm for Staphylococcus aureus (S. aureus), respectively. This study provided a reference for preparing a multifunctional electrospun nanofibrous film integrated with CEO as an active packaging material.

Urban surface-emitted longwave radiation estimation from high spatial resolution thermal infrared images using a hybrid method

Accurate estimation of the surface-emitted longwave radiation (SELR) has important scientific value in understanding its spatiotemporal dynamics and surface thermal environment. Thermal infrared (TIR) images with high spatial resolution offer enhanced data support for studying SELR of complex surfaces, such as urban surface. This study proposes a new urban-oriented hybrid (UoHy) method, which considers multiple scattering and adjacent effects of urban pixel using the term sky view factor, to estimate urban SELR from the top-of-atmosphere radiance of TIR images with high spatial resolution, and performs sensitivity analysis and application. The experimental results for the thermal images of GF-5/VIMS as an example showed that the UoHy method has relatively high accuracy, and obtains SELR errors of less than 12.0 W/m2 under low atmospheric water vapor conditions and less than 17.0 W/m2 under high atmospheric water vapor conditions. The application of the method during daytime and nighttime also demonstrated the method's validity and effectiveness. Compared with the natural surface-oriented hybrid method, the UoHy method obtains an improvement of about 7.0–10.0 W/m2 in SELR estimation, which indicates that it has the potential for practical SELR estimation over urban surface with TIR images of high spatial resolution.

Functionalized cellulose nanofiber films as potential substitutes for Japanese paper

Japanese papers (JPs) are among the most common materials used for the restoration of historical papers. However, they have low transparency and may structure the paper surface. To overcome the limitations of JPs, in the present work films of cellulose nanofibers with and without lignin (LCNFs and CNFs, respectively) were explored. For this, chemically different LCNFs (carboxylated by TEMPO-mediated oxidation using variable oxidant amount and sulfated with deep eutectic solvent) and two reference CNFs were produced from Eucalyptus kraft pulps. Lignin slightly hindered the introduction of carboxyl groups into the cellulose structure, but did not affect the incorporation of sulfate groups. (L)CNFs gave films with better mechanical properties than those determined for three types of JP (tensile strength of 79–142 MPa (±11) vs 3.5–13.0 MPa (±0.4) and Young's modulus of 4900–5900 MPa (±300) vs 240–1800 MPa (±70)). Additionally, the (L)CNF films exhibited lower water vapor transmission rates (132–312 g.m−2.day−1) compared to the JPs (685–719 g.m−2.day−1), and a higher transparency (up to 89% and ≤82% for JPs). Except for the thermal stability, all properties studied favored (L)CNF films over JPs, indicating their strong potential for restoration/conservation applications. This systematic comparison between the properties of (L)CNF films and JPs has never been conducted before.

Characteristics and properties of co-precipitated protein and film based on Bambara groundnut protein isolate and fish skin acid-soluble collagen

Co-precipitated protein (CPP) from Bambara groundnut protein isolate (BGPI) and fish skin acid-soluble collagen (ASC) at different BGPI/ASC ratios (100:0, 75:25, 50:50, 25:75 and 0:100 (v/v)) were prepared and characterized. CPP of BGPI/ASC at ratio of 75:25 had higher solubility at acidic and alkaline pHs, compared to other CPP samples. All CPPs had good emulsifying properties. Based on protein patterns, the combination of major bands from BGPI and ASC in the resulting CPP sample was observed. CPP with BGPI/ASC at ratio of 75:25 showed higher surface hydrophobicity than those of other CPP samples. When the films from CPPs were fabricated, similar tensile strength (p > 0.05) was observed, regardless of BGPI/ASC ratios. Nevertheless, film from CPP with BGPI/ASC ratio of 25:75 had higher elongation at break along with lower water vapor permeability (p < 0.05), compared to other CPP films. All CPP films had bright-yellowish color. Increasing ASC ratio augmented (p < 0.05) light transmission of resulting CPP films. FTIR spectra revealed that all CPP films had the similar pattern and functional groups. Therefore, the co-precipitated BGPI and ASC at appropriate ratio could improve properties of resulting proteins, especially for film forming ability.