A simple method to quantify azo dyes in spices based on flow injection chromatography combined with chemometric tools.

Para Red (PR) and Sudan dyes have been illegally used as colorants to adulterate certain foods by enhancing their red/orange colour. In addition, they are toxic and carcinogenic. This work presents the development of a simple flow injection chromatographic method combined with chemometric tools to perform the determination of PR, Sudan I (SI) and Sudan II (SII) in food samples. The flow chromatographic system consisted of a low-pressure manifold coupled to a reverse phase monolithic column. A Partial Least Square (PLS) model was applied to resolve overlapped absorption spectra registered for each dye at the corresponding retention time. The relative errors of calibration (RMSECV, %) were 0.49, 0.85 and 0.23, and the relative errors of prediction (RMSEP, %) were 1.12, 0.75 and 0.33 for PR, SI and SII, respectively. The residual predictive deviation (RPD) values obtained were higher than 3.00 for all analytes. The method was successfully applied to quantify the dyes in six different commercial spices samples. The results were compared with the HPLC reference method concluding that there were no significant differences at the studied confidence level (α = 0.05). The proposed method can be used to rapidly determine the analytes in a simple, reliable, low-cost and environmentally-friendly manner. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-021-05299-8.

The Water-Soluble Chitosan Derivative, N-Methylene Phosphonic Chitosan, Is an Effective Fungicide against the Phytopathogen Fusarium eumartii.

Chitosan has been considered an environmental-friendly polymer. However, its use in agriculture has not been extended yet due to its relatively low solubility in water. N-Methylene phosphonic chitosan (NMPC) is a water-soluble derivative prepared by adding a phosphonic group to chitosan. This study demonstrates that NMPC has a fungicidal effect on the phytopathogenic fungus Fusarium solani f. sp. eumartii (F. eumartii) judged by the inhibition of F. eumartti mycelial growth and spore germination. NMPC affected fungal membrane permeability, reactive oxygen species production, and cell death. Also, this chitosan-derivative exerted antifungal effects against two other phytopathogens, Botrytis cinerea, and Phytophthora infestans. NMPC did not affect tomato cell viability at the same doses applied to these phytopathogens to exert fungicide action. In addition to water solubility, the selective biological cytotoxicity of NMPC adds value in its application as an antimicrobial agent in agriculture.

Qualitative and quantitative analysis based on digital images to determine the adulteration of ketchup samples with Sudan I dye.

Sudan I is a synthetic-azo dye commonly used to adulterate foods to increase sensory appearance. However, it is banned due to its carcinogenic, mutagenic and genotoxic properties, which represent a serious risk to human health. Thus, this paper proposes a feasibility study to identify and quantify Sudan I dye in ketchup samples using colour histograms (obtained from digital images) and multivariate analysis. The successive projections algorithm coupled with linear discriminant analysis (SPA-LDA) classified correctly all samples, while the partial least squares coupled with SPA for interval selection (iSPA-PLS) quantified adequately the adulterant, attaining values of RMSEP of 11.64 mg kg-1, R2 of 0.96, RPD of 5.28, REP of 13.63% and LOD of 39.45 mg kg-1. Therefore, the proposed methodology provides a simple, fast, inexpensive, promising analytical tool for the screening of both the quality and safety of ketchup samples. As a consequence, it can help to protect the consumer's health.

NIR-based Sudan I to IV and Para-Red food adulterants screening.

Spices are added in order to enhance the organoleptic characteristics of food and culinary dishes, making them more attractive for consumers. The use of illicit cheap colourants might be profitable along the food supply chain, posing undue risks to human health. This work evaluates the feasibility of NIR spectroscopy with chemometrics as a rapid, simple, non-destructive and affordable screening tool to determine the presence of Sudan I, II, III, IV and Para-red dyes in paprika. The dataset comprised unadulterated and adulterated samples with the five studied dyes at different concentration levels. Several multivariate classification models were built with Linear Discriminant Analysis (LDA) and different machine learning techniques. Preliminary results show that a classifier based on only six wavenumbers is able to determine the presence of some of these dyes in food samples in levels that may represent risk to human health. Sensitivities and specificities above 90% were obtained in almost all cases. These results show the feasibility of inexpensive and portable devices that can be useful for screening out adulterated stock along the food chain supply.

Synthesis, characterization and evaluation of reactional parameters on substitution degree of N-hexyl-N-methylene phosphonic chitosan.

N-methylene phosphonic chitosan (NMPC) is treated with hexyl aldehyde to give an imine, which is easily converted into N-hexyl-N-methylene phosphonic chitosan (HNMPC) under mild conditions. The structure of this new chitosan derivative is characterized by FT- IR, 1H, 13C, 31P, 1H13C-HSQC NMR, SEM and XRD. The influence of reactional parameters on the substitution degree (DS), evidenced that a mol ratio 1.50:1.00 (hexyl aldehyde: free amino groups); a reaction time of 1 h. and 45 °C of temperature afford the best DS. HNMPC molecular weight is 12,768.62 Da. It shows good emulsifying properties giving o/w emulsions with high stability in time. Microscopic observation as well as particle size distribution show an unimodal droplet size distribution with low droplet diameters. Preliminary tests lead us to believe that this new polymer has good film forming properties.

Nitric-oxide-mediated cell death is triggered by chitosan in Fusarium eumartii spores.

BACKGROUND: The genus Fusarium comprises a heterogeneous group of fungi important for agriculture. Fusarium solani f. sp. eumartii (F. eumartii), historically considered to be a fungal pathogen of potato, has also been associated with tomato disease. Currently, chitosan and its derivatives have been receiving more attention as environmentally friendly antimicrobial compounds in sustainable practices. The aim of the present work was to characterize downstream events associated with the mode of action of chitosan, including nitrosative reactive species, in order to identify new biomarkers of its cytotoxic action. RESULTS: Data indicated that chitosan-mediated nitric oxide (NO) production might lead to conidial death, concomitant with the strong reduction in fungal pathogenicity in tomato plants. Following chitosan applications, a notably dose-dependent reduction in conidial viability was demonstrated in F. eumartii. Thereafter, the infectivity of chitosan-treated spores was tested by a bioassay using tomato seedlings. CONCLUSION: All these data highlight NO valuable properties as a quantitative and qualitative biomarker of cytotoxic action of chitosan in conidial cells. In addition, these findings place the chitosan assayed here as a fungicide with a high potential of application in sustainable horticultural practices.

Physico-chemical studies and emulsifying properties of N-propyl-N-methylene phosphonic chitosan.

Chitosan is a modified, natural carbohydrate polymer derived by deacetylation of chitin. Due to the presence of two functional groups can undergo many chemical modifications. In a previous work we described the synthetic strategy and characterization of a novel soluble derivative: N-propyl-N-methylene phosphonic chitosan (PNMPC). In the study of some physicochemical properties, results showed that this modified chitosan aggregates in several steps when the concentration is increased. By addition of NaOH the initially coiled molecules stretch exposing more phosphonic acid groups to neutralization and finally give a cooperative reaction with OH((). PNMPC has emulsifying properties and gives O/W emulsions with quasi-monodisperse small droplets. Emulsions with 0.18% PNMPC and 30:70 o:w ratio exhibited the best emulsifying properties within the test range. This emulsion ratio showed high stability to long time storage and several successive freeze/thaw and heating/cooling cycles.

Chitosan interaction with iron from yoghurt using an in vitro digestive model: comparative study with plant dietary fibers.

The objective of this work was to investigate the interaction of chitosan with iron from yoghurt by an in vitro gastrointestinal tract model. Taking into account that chitosan is a polysaccharide included in fiber definition by Codex Alimentarius; chitosan behavior was studied and compared with different plant fiber (wheat, bamboo, apple, psyllium and inulin) behaviors, in the same in vitro conditions. Ferrous sulfate was added to yoghurts with each type of fiber. The gastric environment was simulated with HCl (pH 1.0-2.0). The duodenal environment was simulated with NaHCO(3) (pH 6.8-7.2) and a dialysis tubing cellulose membrane. Results showed that chitosan had the highest iron retention percentages (53.2% at 30 min; 56.8% at 60 min) interacting in a more pronounced manner with iron than the plant fibers used in this work.

Interaction between chitosan and oil under stomach and duodenal digestive chemical conditions.

Chitosan, the N acetylated derivative of chitin, has an effect on the absorption of dietary lipids, but there is not enough scientific knowledge about the mechanism. To study the interaction between chitosan and oil, the action of this biopolymer has been evaluated through an experimental model of the stomach and duodenum tract, although the enzimatic activity had not been evaluated. We microscopically confirmed that chitosan in a hychloridic acid medium (pH 1.0-2.0) emulsified lipids and the emulsion was a water in oil in water type (w/o/w). When the pH value and speed of agitation were increased to mirror the duodenum medium conditions under which lipids are absorbed, the emulsion capacity was better with an increased number of droplets and the emulsion continued as the w/o/w type. At pH 6.2, chitosan precipitated and lipids were entrapped in the formed flocculus. The binding oil was quantitatively determined, and we also demonstrate that a larger oil quantity induced less retention, while the chitosan characteristics had no influence. These observations allow us to postulate that the interaction between chitosan and oil inhibited duodenal absorption and enhanced lipid excretion.