Protonation Equilibria of Carminic Acid and Stability Constants of Its Complexes with Some Divalent Metal Ions in Aqueous Solution

Extraction pathways and purification strategies towards carminic acid as natural-based food colorant: A comprehensive review

As a current trend of fabricating healthier products, food manufacturing companies seek for natural-based food colorant aiming to replace the synthetic ones, which apart from meeting sensorial and organoleptic aspects, they can also act as health promoters offering additional added value. Carminic acid is a natural based food colorant typically found in several insect taxa. However, there are current approaches which pursue the production of this natural pigment via biotechnological synthesis. To date, this colorant has been intensively applied in the manufacture of several food items. Unfortunately, one of the main limitations deals with the establishment of the right protocol of extraction and purification of this component since there is no report analyzing the main extraction techniques for obtaining carminic acid. Therefore, this review, for the first time, comprehensively analyzes the ongoing strategies and protocols proposed by scientists towards either extraction or purification of carminic acid from its origin source, and from biotechnological systems. Emphasis has been focused on the main findings dealing with extraction techniques and the relevant insights in the field. A detailed discussion is provided on the advantages and drawbacks of the reported extraction and purification methods, main solvents used and their key interactions with target molecules.

Interaction of barley β-glucan with food dye molecules - An insight from pulse dipolar EPR spectroscopy

The interactions between dietary fibers (DFs) and small molecules are of great interest to food chemistry and nutrition science. However, the corresponding interaction mechanisms and structural rearrangements of DFs at the molecular level are still opaque due to the usually weak binding and the lack of appropriate techniques to determine details of conformational distributions in such weakly organized systems. By combining our previously established methodology on stochastic spin-labelling of DFs with the appropriately revised set of pulse electron paramagnetic resonance techniques, we present here a toolkit to determine the interactions between DFs and small molecules, using barley β-glucan as an example for neutral DF and a selection of food dye molecules as examples for small molecules. The proposed here methodology allowed us to observe subtle conformational changes of β-glucan by detecting multiple details of the local environment of the spin labels. Substantial variations of binding propensities were detected for different food dyes.

A review on colorimetric indicators for monitoring product freshness in intelligent food packaging: Indicator dyes, preparation methods, and applications

Intelligent food packaging system exhibits enhanced communication function by providing dynamic product information to various stakeholders (e.g., consumers, retailers, distributors) in the supply chain. One example of intelligent packaging involves the use of colorimetric indicators, which when subjected to external stimuli (e.g., moisture, gas/vapor, electromagnetic radiation, temperature), display discernable color changes that can be correlated with real-time changes in product quality. This type of interactive packaging system allows continuous monitoring of product freshness during transportation, distribution, storage, and marketing phases. This review summarizes the colorimetric indicator technologies for intelligent packaging systems, emphasizing on the types of indicator dyes, preparation methods, applications in different food products, and future considerations. Both food and nonfood indicator materials integrated into various carriers (e.g., paper-based substrates, polymer films, electrospun fibers, and nanoparticles) with material properties optimized for specific applications are discussed, targeting perishable products, such as fresh meat and fishery products. Colorimetric indicators can supplement the traditional "Best Before" date label by providing real-time product quality information to the consumers and retailers, thereby not only ensuring product safety, but also promising in reducing food waste. Successful scale-up of these intelligent packaging technologies to the industrial level must consider issues related to regulatory approval, consumer acceptance, cost-effectiveness, and product compatibility.

A Simple Distance Paper-Based Analytical Device for the Screening of Lead in Food Matrices

A simple and rapid distance paper-based analytical device (dPAD) for the detection of lead (Pb) in foods is proposed herein. The assay principle is based on competitive binding between carminic acid (CA) and polyethyleneimine (PEI) to Pb in a food sample. The paper channels were pre-immobilized with PEI, before reacting with a mixture of the sample and CA. Pb can strongly bind to the CA; hence, the length of the red color deposition on the flow channel decreased as a lower amount of free CA bound to PEI. The dPAD exhibited good linear correlation, with ranges of 5-100 µg·mL-1 (R2 = 0.974) of Pb. Although, the limit of detection (LOD) of this platform was rather high, at 12.3 µg·mL-1, a series of standard additions (8.0, 9.0, and 10.0 µg·mL-1) can be used to interpret the cutoff of Pb concentrations at higher or lower than 2 µg·mL-1. The presence of common metal ions such as calcium, magnesium, nickel, and zinc did not interfere with the color distance readout. The validity of the developed dPAD was demonstrated by its applicability to screen the contamination of Pb in century egg samples. The results obtained from the dPAD are in accordance with the concentration measured by atomic absorption spectroscopy (AAS) (n = 9). In conclusion, this proposed dPAD, combined with the standard addition method, could be applied for screening Pb contamination in food matrices. This platform is, therefore, potentially applicable for field measurements of Pb in developing countries, because it is cheap and rapid, and it requires no significant laborious instruments.

Effects of different food ingredients on the color and absorption spectrum of carminic acid and carminic aluminum lake

In this study, three foodstuffs (surimi, minced meat, and milk) were dyed with carminic acid and carminic aluminum lake. The effects of protein, metal ions, and food additives on the color of carminic acid and carminic aluminum lake were investigated. After being dyed by carminic acid, the colors of surimi, minced meat, and milk were light purple, red, and gray-green, respectively. When using carminic aluminum lake, surimi and milk were magenta, and minced meat was red. Regarding the carminic acid solution, the presence of myofibrillar protein (MFP), whey protein isolate (WPI), and soy protein isolate (SPI) turned it red by changing the pH, while the presence of casein made it orange. The carminic aluminum lake solution turned magenta in all four cases, which were not affected by protein. The color of carminic acid and carminic aluminum lake was significantly affected by 0.001-0.1 mol/L Fe3+, 0.001-0.1 mol/L Fe2+, 0.001-0.1 mol/L Cu2+, and 0.1 mol/L Ca2+, limiting their application in iron-, copper-, and high-calcium foods. The color of carminic acid was changed to yellow by 0.01%-1% sodium nitrite, but 0.01%-1% ascorbic acid and 0.01%-0.1% monascus color did not significantly affect the color of either carminic acid or carminic aluminum lake. This paper provides a reference for the application of carminic acid and carminic aluminum lake in food science.

Characterization of Dye Extracts from Historical Cultural-Heritage Objects Using State-of-the-Art Comprehensive Two-Dimensional Liquid Chromatography and Mass Spectrometry with Active Modulation and Optimized Shifting Gradients

Unbiased characterization of dyes and their degradation products in cultural-heritage objects requires an analytical method which provides universal separation power regardless of dye classes. Dyes are small molecules that vary widely in chemical structure and properties, which renders their characterization by a single method challenging. We have developed a comprehensive two-dimensional liquid chromatography method hyphenated with mass spectrometry and UV–vis detection. We use stationary-phase-assisted modulation to enhance the method in terms of detection limits and solvent compatibility and to reduce the analysis time. The PIOTR program was used to optimize an assembly of shifting second-dimension gradients, which resulted in a high degree of orthogonality (80% in terms of the asterisk concept). The resulting method is universally applicable to all classes of dyes extracted from cultural-heritage objects. Thanks to the high peak capacity and orthogonality, dye components can be separated from chemically similar impurities and degradation products, providing a detailed fingerprint of the dyes mixture in a specific sample. The method was applied to a number of challenging dye extracts from 17th- and 19th-century cultural-heritage objects.