Significant Color Change Research Articles

Effect of olive leaf extract on the quality of Cantal cheese

This study aimed to evaluate the impact of olive leaf extract (OLE) on the quality of Cantal cheese. The cheeses were fortified with different concentrations (Control, 1, 2, and 3 %) of OLE and analysed for quality during storage. The cheeses were evaluated on days 1, 28, and 63 for physicochemical, compositional, textural, rheological parameters, colour, microbiological analysis, and antioxidant activity. The MIR and fluorescence spectroscopies were used to study the changes in the cheese structure. A positive impact of OLE was observed on the antioxidant capacity. A mild inhibitory effect was observed against some beneficial bacteria (such as Lactococcus and Lactobacillus), while a strong inhibitory effect was found against pathogen microorganisms. No negative impact was found on the texture and chemical composition. Significant colour and structural changes were observed. The results indicate the potential of OLE to be used as bioactive ingredient to improve the quality of cheese.

Stability of antibiotics for use in the testing of immediate drug allergy reactions

BackgroundLimited information is available regarding the physicochemical stability of penicillins-based preparations for skin testing purposes and no information is currently available for other classes of antibiotics. ObjectiveTo perform chemical and physical stability studies on 16 parenteral antibiotics for skin testing purposes, with an overall aim to provide practical recommendations to clinicians on suitable components, storage, and optimal shelf-life of such preparations. MethodsChemical stability was assessed via validated stability-indicating high performance liquid chromatography with ultraviolet detection assays, while absence of precipitations or haziness, significant pH shift and colour change were used to determine physical stability. ResultsOther than amoxicillin/clavulanic acid, all of the parenteral antibiotics were found to have adequate physicochemical stability between 2 to 7 days. Amoxicillin in Water for Injection BP retained >90% stability, while amoxicillin/clavulanic acid dropped to <80%. Ampicillin remained >90% stable for 2 days, and benzylpenicillin, flucloxacillin, and piperacillin/tazobactam were stable for ≥2 days at ∼95%. Cephalosporins were stable for 2 days, except ceftazidime, which increased to >110%. Aztreonam, ciprofloxacin, and vancomycin retained >95% stability for 7 days, while meropenem was stable for 2 days. Sulfamethoxazole/trimethoprim lost 15% but stabilized at ∼85% for 7 days. No precipitation occurred, but amoxicillin/clavulanic acid changed colour by day 7. pH decreases of ≤1.0 unit were observed in penicillins, while cefepime dropped below acceptable pH limits by day 7. Absorbance shifts >100 units were seen in several antibiotics by day 7. ConclusionsThis study has generated practical stability information for clinicians, allowing 15 parenteral antibiotics from 7 different classes to be aseptically prepared in advance for use in the testing of drug allergy reactions.

Dual "Turn-On" Fluorescent and Colorimetric Sensing of Permanganate Based on Yellow Carbon Dots.

Existing permanganates (MnO4 -) sensing methods suffered from the poor selectivity, restricted solubility, and/or less desirable signaling mechanisms (e.g., "turn-off" processes), resulting in the false positive result. In this work, an effective "turn-on" fluorescence method for MnO4 - detection in aqueous media was proposed via yellow fluorescence carbon dots (Y-CDs) with the maximum emission peak of 553 nm. Upon the introduction of MnO4 -, the fluorescence of Y-CDs increased significantly due to the enhanced surface passivation degree and intramolecular charge transfer. In the range of 0.1-10 μM, the fluorescence ratio (F/F0) is proportional to the MnO4 - ions concentration, realizing the "turn-on" fluorescence sensing of MnO4 -. On the other hand, utilizing the significant color change of Y-CDs by MnO4 - ions, the colorimetric analysis can also be established for MnO4 - assay. Compared with other probes, the analysis results obtained by bimodal sensing tactics of fluorescent and colorimetric can be mutually verified to improve the reliability and meet the sensing needs of targets in complex environments.

Strategic Design of Anion-Responsive Triarylboranes Exhibiting Colorimetric and Fluorometric Red-Shift for Sensing and Optoelectronic Applications.

Triarylboranes (TABs) have been employed as colorimetric and/or fluorometric anion sensors. The majority of TAB-based anion sensors exhibit blue-shift modes of absorption and photoluminescence (PL) or turn off of PL, attributed to the intrinsic electronic polarity of the trivalent boron unit in their molecular designs. In this Concept article, we introduce a novel approach to modulating the photophysical properties of TABs toward a red-shift mode by balancing the dual, opposing roles of the amine-bridged TAB (phenazaborine). This molecular design strategy enables significant changes in color and emission response to anions, shifting to the lower energy regime in solution. Additionally, this approach is applicable to the solid-state modulation of PL in films and organic light-emitting diodes (OLEDs).

A Highly CO2-Sensitive Wood-Based Smart Tag for Strawberry Freshness Monitoring.

Smart tags are used for monitoring the freshness of foods. However, they often lack significant color changes, and their accuracy needs to be improved. In this study, a poplar veneer with a natural pore structure was selected as a matrix to prepare a smart tag with high pH sensitivity for tracking the freshness of strawberries. The delignified veneer was modified using 2,3-epoxypropyltrimethylammonium chloride (EPTAC) to be given positive charges to adsorb bromothymol blue (BTB) through electrostatic interactions. The adsorption capacity of the veneer reached 7.0 mg/g at 50 °C for 4 h, and the veneer showed an obvious blue color. The smart tags exhibited distinct color changes at different pHs and showed quick color changes in response to acetic acid. As the freshness of strawberries decreased, the color of the smart tags changed from blue to yellow-green, which indicated that the accuracy was high. In this study, an effective method was fabricated to prepare a highly sensitive tag, promoting popular application to ensure food quality.

Rational Design of Regenerable Amino-Functionalized Fluorescent Covalent Organic Framework for the Exclusive Detection of Mercury(II).

Goal-oriented development of novel covalent organic frameworks (COFs) to construct a sensing platform for highly toxic mercury (II, Hg2+) is of tremendous significance. Recently, numerous COFs with sulfur-based ligands were developed for Hg2+ monitoring; however, strong binding of Hg2+ by sulfur makes their regeneration very tough. Herein, we designed and developed an amino-functionalized fluorescent COF (COF-NH2) through facile postmodification for Hg2+ detection in which the π-conjugation skeleton is the signal reader and the nitrogen-based side is the highly selective Hg2+ receptor. More importantly, this nitrogen-based receptor permits the reversible binding of Hg2+. As a sensing platform, the outstanding performance of COF-NH2 for Hg2+ detection was reached with respect to high sensitivity with an ultralow detection of 15.3 nM, real-time response with rapid signal change of 10 s, and facile visualization with significant fluorescence color change. Expectedly, COF-NH2 obtained facile recycling which still shows excellent response performance toward Hg2+ after six cycles based on the reversible interaction between amino groups and Hg2+. Our work not only shows an attractive foreground of fluorescent COF for Hg2+ detection but also emphasizes the easy construction of novel COF materials via the rational introduction of metal ligands for the recognition of other metal ions.

Effect of micro-oxygenation on color of wines made with toasted vine-shoots.

Toasted vine-shoots (SEGs) are an enological tool to improve wines, to differentiate them, and to encourage sustainable wine production. Micro-oxygenation (MOX) is typically combined with the use of alternative oak products to simulate the oxygen transmission rate of traditional barrel aging, affecting wine color. Its use alongside SEGs has been studied. Tempranillo wines were treated with SEGs at two doses (12 and 24 g L-1) after malolactic fermentation at two fixed micro-oxygenation levels: (a) low, which received 6.24 ± 0.87 mg L-1·month-1 of oxygen; and, (b) high, which received 11.91 ± 0.71 mg L-1·month-1 of oxygen. The wines were bottled and stored for 6 months. At the end of the treatment, MOX affected the anthocyanins and color parameters, but not the enological characteristics. At this time, the anthocyanins content reduction presented a negatively significant correlation with oxygenfor wines treated with 12 g L-1. The factors that most influenced the development of color parameters during the time after bottling were the period for which the wine evolved in the bottle and SEG dose. The visual sensorial descriptors showed an evolution according to aged red wines, but without differences according to the SEG-MOX treatments. The SEG-MOX treatments caused significant changes in wine color. It would be advisable to adjust SEG-MOX techniques to increase their effectiveness. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Visual colorimetric label for real-time monitoring of SO2 concentration change in grape and mango during storage

Sulfur dioxide (SO2) is widely utilized as a preservative in food transportation and storage, but excessive consumption poses health risks. This study presents a novel and efficient method for the real-time detection of SO2 using a sensor named TK, synthesized from triphenylamine and 2-cyanomethyl-1-methyl-quinolinium. The core mechanism involves the Michael addition reaction of the CC bond in TK with SO2, which disrupts the intramolecular charge transfer process, resulting in a significant color change and a blue shift in fluorescence emission. Methodologically, the sensor's response was quantified by the change in fluorescence intensity ratio (I425/I647) within a SO2 concentration range of 0–180 μM. The sensor exhibited high sensitivity and selectivity. For practical application, TK was incorporated into hydrophilic polyvinyl alcohol to create a smart label capable of visual colorimetry and fluorescence analysis. SO2 concentration changes were monitored by using this label, demonstrated by the color transition from burgundy red to colorless, yielding a maximum color difference (ΔE) of 73.6. The smart label was successfully used to monitor the quality of various grapes and mangoes during long-term storage, providing a reliable, equipment-independent method suitable for household use. The study offers a new tool for enhancing food safety and mitigating health risks associated with SO2 exposure.

Colorimetric detection of pyrophosphate using gold nanorods and Fe3+ based on anti-etching mechanism

Pyrophosphate (PPi), as a derivative of inorganic phosphate, has important applications in the fields of food and environment, it also plays an important role in biological metabolism and serves as a biomarker for clinical diagnosis of certain diseases. Thus, the development of a simple and convenient method to quantify PPi is of great significance for environmental protection, food safety and disease diagnosis. In this study, visual colorimetric detection of PPi was achieved by inhibiting the morphological change of gold nanorods (Au NRs). In the presence of SCN-, Fe3+ with low concentration can oxidatively etch Au NRs due to the potential difference, leading to significant color change of Au NRs solutions and blue shift in longitudinal local surface plasmon resonance (LSPR) absorption peak of Au NRs solutions. Due to the strong complexation between PPi and Fe3+, the etching of Au NRs by Fe3+ was restrained, while the morphology of Au NRs, the color and UV–vis absorption spectrum of Au NRs solution remained uninfluenced. Under optimal conditions, this colorimetric detection method exhibited exceptional selectivity, anti-interference, and sensitivity towards PPi, with a linear detection range of 0.8–24 μM. Moreover, practical application results suggest that this colorimetric method holds significant potential for swiftly detecting PPi in intricate samples.

Structure development and photoluminescence properties of high-purity greenish-yellow emitting LaGaO3:Dy3+ phosphors

This study investigates the structure development and photoluminescence properties of high-purity greenish-yellow emitting LaGaO3 phosphors doped with dysprosium ions Dy3+. The phosphors were synthesized using a high-temperature solid-state reaction method. X-ray diffraction (XRD) confirmed the formation of a single-phase LaGaO3:Dy3+ structure and scanning electron microscopy (SEM) revealed uniform particle size and morphology. The phosphor exhibits the capability of being efficiently excited by ultraviolet 350 nm exhibiting the characteristic greenish-yellow emission with two strong peaks at 478 nm (cyan) and 572 nm (yellow), ascribing to the transitions of 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2, respectively. The electronic transition mechanism is direct exchange interaction between activators, contributing to the concentration quenching. The phosphor was able to retain 67 % of its intensity without significant color change at an elevated temperature up to 25 °C to 150 °C. The CIE chromaticity coordinates of the emitted light were calculated and found in the desired greenish-yellow region. The electroluminescence performance of the LaGaO3:0.06Dy3+ phosphor was investigated using 365 nm LED chips to check their applicability in the field of white light-emitting diodes (WLEDs). The synthesized phosphors demonstrated high thermal stability, making them suitable for white-LED applications. The study highlights the potential of LaGaO3:Dy3+ phosphors in enhancing white-LEDs' color quality and efficiency.

Effects of different drying methods on drying characteristics and quality of silage Broussonetia papyrifera L.

The effects of hot air drying (HAD), vacuum drying (VD) and pulsed vacuum drying (PVD) on moisture ratio, drying rate, effective diffusion coefficient, activation energy, color, ash, protein, acid detergent fiber, neutral detergent, fiber total digestible nutrients (TDN) and relative feeding value (RFV) of silage paper mulberry were investigated, and optimal drying processes were developed using entropy weight method. Results show that the drying characteristics of silage paper mulberry, which can be seen as particle packed porous media, undergoing different drying methods exhibit similarities to those of conventional hygroscopic porous media. In terms of quality, noticeable browning occurs when the silage paper mulberry is subjected to HAD at 70 °C or higher, whereas no significant color change is observed under VD at temperatures of 80 °C or lower. Increasing the material thickness leads to higher TDN and RFV after HAD, but higher pressures and drying temperatures resulting in reducing in RFV after VD or PVD. The optimal drying process for HAD is 3 cm, 70 °C, 20%, 1 m/s and it is recommended to use 3 cm, 7 kPa and 70 °C for VD. As for PVD, the conditions are same as VD and using pulsation ratio of 50:5 min.

A pH visual sensing platform based on dual-emission chiral carbon dots for discrimination of normal/cancer cells and monitoring food freshness

Accurate detection of pH is important in pathological processes and food freshness. Developing sensors of sensitive response and visualization for pH is highly demanded. In this work, Chiral carbon dots(CCDs) was synthesized via one-pot hydrothermal process using o-phenylenediamine and L-Tryptophan, which displayed circular dichroism (CD) signals at 200–255 nm and 255–300 nm. The CCDs exhibited dual-emission peaks with blue and red emission bands when excited at 360 nm. The ratiometric signals of UV–vis absorption and fluorescence intensity of L-CDs were responsive over the pH range of 2.0 to 11.0 with significant color changes in solution. Fluorescence imaging of live cells displayed different signals related to pH in both the blue and red channels, allowing accurate measurement of the pH of the cellular environment. Furthermore, the pH test paper based on L-CDs enabled monitoring the freshness of shrimp and pork under 365 nm UV light. Therefore, L-CDs provided a multifunctional visual pH sensing platform for environmental monitoring and biosensing.

Improving ready-to-eat meat safety: Evaluating the bacterial-inactivation efficacy of microplasma-based far-UVC light treatment of food-contact surfaces and deli turkey breast

The safety of ready-to-eat (RTE) deli meats, especially those sliced in retail establishments, may be improved by light-based surface decontamination. Conventional 254 nm ultraviolet-C (UVC) systems have strong germicidal effects but pose human-health hazards that make them unsuitable for retail use. This study therefore explores the efficacy of microplasma-based 222 nm far-UVC lamps as a safer alternative for decontaminating liquid buffer, two common food-contact surfaces (polyethylene terephthalate and stainless steel), and RTE turkey breast. In all three non-meat cases, the system achieved approximately 5-log reductions of both Listeria monocytogenes and Salmonella Typhimurium. The system also caused a 1.3-log reduction of L. monocytogenes and a 1-log reduction of S. Typhimurium on turkey breast at the highest tested dose of 786.3 mJ/cm2. Color is a key quality indicator for RTE meat consumers, and treatment caused no significant change in L*, a*, or b* color values (p > 0.05) until doses reached 224.7 mJ/cm2. However, higher doses could lead to statistically significant color changes. Given that far-UVC light has been deemed human-safe by other studies, the proposed system has considerable potential to improve RTE food-related safety in retail establishments, even when consumers and workers are present.

Preserving snake fruit (Salacca zalacca) Voss) quality: Effective control of Peniophora salaccae SKRU002 with fungicides and biological agents

Peniophora salaccae (Russulales, Basidiomycota), a newly identified pathogen of Salacca zalacca, is a major cause of snake fruit rot, resulting in significant agricultural losses. This study evaluates the efficacy of chemical fungicides and biological controls against P. salaccae SKRU002, focusing on disease suppression and fruit quality preservation. Commercial fungicides (propiconazole®, prochloraz®, metalaxyl®, azoxystrobin®, thiram®) and Streptomyces philanthi strains RM-1-138 and RL-1-178 were tested. In vitro, prochloraz® (1000 μL mL−1) fully inhibited P. salaccae growth, outperforming other fungicides. Both S. philanthi strains exhibited strong antifungal activity through volatile and non-volatile compounds. Additionally, autoclaved (at 121 °C for 15 min) and diluted (1/1000) bacterial culture filtrates (BCF) from both strains achieved over 55 % inhibition of P. salaccae. In liquid culture, RM-1-138 (86.80 %) and RL-1-178 (80.86 %) demonstrated greater inhibition than metalaxyl® (9.34 %) and azoxystrobin® (56.84 %), though prochloraz® and propiconazole® remained the most effective (100 %). In vivo, untreated fruits inoculated with P. salaccae showed 100 % disease incidence, significant weight loss (13.28 %), color changes (L∗, a∗, and b∗), and reductions in total soluble solids, total phenolic content, and antioxidant activity, while titratable acidity remained unchanged. Both biological and chemical treatments effectively controlled the pathogen and preserved fruit quality. These findings highlight the potential of S. philanthi strains and fungicides in managing P. salaccae, offering promising strategies for snake fruit cultivation.

Preparation and characterization of porous corn starch-based antibacterial sustained-release intelligent film

A novel porous corn starch-based antibacterial sustained-release intelligent film was prepared with the porous corn starch as the substrate, purple corn cob anthocyanin (PCA) as the indicator, and tangerine peel essential oil as the antibacterial agent, and its properties were studied. The results showed that the porous corn starch-based antimicrobial sustained-release indicator film had good mechanical strength, surface hydrophobicity and light transmittance. The tensile strength of the sustained-release indicator film (PLSt-12) prepared by porous corn starch with an enzymatic hydrolysis time of 12 h was 14.35 MPa and the elongation at break was 6.55 %. The water contact angle was 89.10°, and the water vapor transmittance was 6.62 × 10−4 g·mm2·s−1·Pa−1. The PLSt-12 was brown at pH 10 and had a sensitive color response. The PLSt-12 reduced the release rate of anthocyanins by 25.01 %, and the sustained-release mechanism was non-Fick diffusion. It showed a significant color change when the pork quality deteriorated, which can be used to monitor the freshness of the pork. This type of antibacterial sustained-release intelligent film had considerable application potential in indicating food freshness.

Novel Pink Pigments Produced by Thermal Interaction of Theaflavins, Theanine, and Glucose: Color Formation, Isolation, and Structural Characterization.

A color-deepening effect of theaflavins on the theanine-glucose thermal reaction model was revealed. Generated chromogenic intermediates in the initial stage and an accelerated browning rate through the promoted degradation of theanine-glucose Amadori rearrangement product in the intermediate and final stages are responsible for the color-deepening effect. Four pink-to-red theaflavin-theanine intermediates were verified as theaflavinies referencing the nuclear magnetic resonance and liquid chromatography-mass spectrometry information on theaflavins and l-theanine, including one accurately identified as theaflavinie 4. Theaflavinie 4 showed two maximum absorption peaks at 401 and 506 nm with parallel intensities, which resulted in a significant dichromic color change from pale pink to orange and red. Theaflavinies also could undergo further thermal reactions to yield brown polymers under higher temperatures (130 and 140 °C). This research provided new insight into realizing thermally formed polymers during black tea processing, which may be formed by oxidation products and amino acids or proteins through non-enzymatic thermal reactions.

Drone-Based Localization of Hazardous Chemicals by Passive Smart Dust

The distribution of tiny sensors over a specific area was first proposed in the late 1990s as a concept known as smart dust. Several efforts focused primarily on computing and networking capabilities, but quickly ran into problems related to power supply, cost, data transmission, and environmental pollution. To overcome these limitations, we propose using paper-based (confetti-like) chemosensors that exploit the inherent selectivity of chemical reagents, such as colorimetric indicators. In this work, cheap and biodegradable passive sensors made from cellulose could successfully indicate the presence of hazardous chemicals, e.g., strong acids, by a significant color change. A conventional color digital camera attached to a drone could easily detect this from a safe distance. The collected data were processed to define the hazardous area. Our work presents a combination of the smart dust concept, chemosensing, paper-based sensor technology, and low-cost drones for flexible, sensitive, economical, and rapid detection of hazardous chemicals in high-risk scenarios.

Preparation and characterization of intelligent packaging labels based on pea starch, κ-carrageenan and black raspberry extract for monitoring freshness of pork

Intelligent biodegradable packaging has gained significant attention recently due to its great potential for food freshness monitoring. In this study, we developed intelligent labels using pea starch (PS), κ-carrageenan (KC) and black raspberry extract (BRE) and evaluated their physicochemical properties and effectiveness in pork freshness monitoring. Incorporation of KC significantly decreased tensile strength (TS) (33.43 to 19.84 MPa) and increased elongation at break (EAB) (6.26 to 7.41 %) and water vapor permeability (WVP) (2.11 to 2.48 × 10−9 g m−1 s−1 Pa−1) of PS label. Incorporation of BRE significantly decreased WVP (2.48 to 1.96 × 10−9 g m−1 s−1 Pa−1) and increased TS (19.84 to 29.68 MPa) and EAB (7.41 to 11.09 %) of PS-KC label. PS-KC-BRE labels showed increased light barrier performance, thermal stability, antioxidant activity, pH and ammonia sensitivities, and significant visible color change as pH indicators. Findings suggest PS-KC-BRE labels can be used as intelligent packaging in food industry.

A facile synthesis of a novel polymer-based nanocomposite as colorimetric response sensor for fluoride ion detection in real-life complex mediums

The surface modification of Poly (acrylamide-co-methylenbisacrylamide-co-N-(4-(2-(phenylcarbamothioyl)hydrazineyl)phenyl)methacrylamide) as a sensor (AR) via titanium dioxide as a novel colorimetric nanocomposite sensor with high sensitivity and selectivity for determination of fluoride anion was described. The colorimetric response of the AR has been screened in dimethyl sulfoxide /Water with a volumetric ratio of 7:3 and acetonitrile in separate media with equal amounts of various anions. In the presence of the mentioned anionic solutions, only the solutions containing fluoride ions, made a significant change in color from pale yellow to orange-red via the –NH deprotonation mechanism, which could be detected with the naked eye. The Box-Behnken design, response surface methodology through UV-Vis spectroscopy techniques in various pH and temperatures and reaction times were tested to optimize the AR conditions. Also, a lateral flow assay test of the synthesized AR detected fluoride ions in real-life samples, including water, contrary to different sources such as toothpaste and mouthwash. Furthermore, according to the World Health Organization report on fluoride ion toxicity in water, the detection limit of the AR was lower than of the declared level.

Effect of Packaging Material and Storage Period on Popping Behaviour of Roasted Makhana Seeds

The effect of storage period and type of packaging material on the popping behaviour of roasted makhana seeds was studied. Raw makhana seeds with a diameter of 9-10 mm were roasted using a batch-type primary roasting machine and tempered for 48 hours to bring the roasted seed moisture content to about 16% dry basis (d.b.). The roasted seeds were stored in 15, 25, and 80 µm Low-Density Polyethylene (LDPE), 110 µm Polypropylene (PP), 140 µm Biaxially Oriented Polypropylene (BOPP), and 60 μm Silver Laminate (SL) packets for six months. Popping of the stored seeds was conducted at 15-day intervals, and observations were made on popped makhana recovery, popping efficiency, colour of popped makhana, and expansion characteristics. The expansion ratio, expansion index, popped makhana recovery and popping efficiencies prior to storage were 2.37±0.22, 13.64±4.04, 48.53±0.50, and 82.89±0.78%, respectively. Duncan’s multiple range tests showed that the seeds packed in 15 µm LDPE packages maintained the quality and recovery up to 60 days only. The 80 μm LDPE packets, BOPP, PP, and SL packets were found effective in maintaining popping efficiency, recovery of popped makhana, and expansion ratio more than 81.44±0.70%, 47.95±0.43%, and 2.14±0.14, respectively with no significant colour change up to 135 days storage of the roasted seeds. Significant changes in colour values of popped makhana were observed after 135 days of storage and a* value increased whereas L* and b* values decreased. This study showed that makhana seeds may be popped effectively with &gt;47% popped makhana recovery, &gt;16 mm average diameter and acceptable colour values up to 120 days when the roasted seeds are stored at 15.53±0.49% (d.b.) in airtight packaging material, which was not possible until now.