Vibrational microspectroscopy of food. Raman vs. FT-IR

Advances, limitations, and considerations on the use of vibrational spectroscopy towards the development of management decision tools in food safety

Food safety and food security are two of the main concerns for the modern food manufacturing industry. Disruptions in the food supply and value chains have created the need to develop agile screening tools that will allow the detection of food pathogens, spoilage microorganisms, microbial contaminants, toxins, herbicides, and pesticides in agricultural commodities, natural products, and food ingredients. Most of the current routine analytical methods used to detect and identify microorganisms, herbicides, and pesticides in food ingredients and products are based on the use of reliable and robust immunological, microbiological, and biochemical techniques (e.g. antigen-antibody interactions, extraction and analysis of DNA) and chemical methods (e.g. chromatography). However, the food manufacturing industries are demanding agile and affordable analytical methods. The objective of this review is to highlight the advantages and limitations of the use of vibrational spectroscopy combined with chemometrics as proxy to evaluate and quantify herbicides, pesticides, and toxins in foods.

Microencapsulation of Bacillus thuringiensis strains for the control of Aedes aegypti

In this study, we investigated the microencapsulation of two strains of the entomopathogenic bacteria Bacillus thuringiensis (B. thuringiensis) (BtMA-750 and BtMA-1114), which are biopesticides of high toxicity for the mosquito vector Aedes aegypti. The encapsulation of different concentrations of microorganisms in starch microparticles was evaluated, and the inverse suspension polymerization technique was explored. It was possible to observe that the higher amounts of the biopesticide caused a slight decrease in the diameter of the particles; however, even when encapsulated, the biopesticide still presents an average diameter that is able to be consumed by the larvae of Aedes aegypti. Furthermore, it was noticed that the presence of both of the B. thuringiensis strains did not affect the thermal stability of the particles. The microencapsulated bacterial strains presented a high number of viable spores and preserved the expression of proteins with molecular masses corresponding to the insecticidal toxins Cry and Cyt, indicating that the encapsulation process was conducted satisfactorily. Finally, the encapsulated strains were tested against Ae. aegypti larvae and maintained 100% larval mortality even after 35 days. Therefore, microencapsulation of B. thuringiensis not only guarantees the bacterial activity, but also prolongs the action of the biopesticide. Collectively, such findings highlight the great potential of the new biopesticides, which may help to reduce the population indices of the mosquito vector Ae. aegypti via a sustainable and environment-friendly route.

Raman spectroscopy: Principles and recent applications in food safety

Food contaminant is a significant issue because of the adverse effects on human health and economy. Traditional detection methods such as liquid chromatography-mass spectroscopy for detecting food contaminants are expensive and time-consuming, and require highly-trained personnel and complicated sample pretreatment. Raman spectroscopy is an advanced analytical technique in a manner of non-destructive, rapid, cost-effective, and ultrasensitive sensing various hazards in agri-foods. In this chapter, we summarized the principle of Raman spectroscopy and surface enhanced Raman spectroscopy, the methods to process Raman spectra, the recent applications of Raman/SERS (surface-enhanced Raman spectroscopy) in detecting chemical contaminants (e.g., pesticides, antibiotics, mycotoxins, heavy metals, and food adulterants) and microbiological hazards (e.g., Salmonella, Campylobacter, Shiga toxigenic E. coli, Listeria, and Staphylococcus aureus) in foods.

Wide distribution of extracellular electron transfer functionality in natural proteinaceous organic materials for microbial reductive dehalogenation

Extracellular electron transfer materials (EETMs) in the environment, such as humic substances and biochar, are formed from the humification/heating of natural organic materials. However, the distribution of extracellular electron transfer (EET) functionality in fresh natural organic materials has not yet been explored. In the present study, we reveal the wide distribution of EET functionality in proteinaceous materials for the first time using an anaerobic pentachlorophenol dechlorinating consortium, whose activity depends on EETM. Out of 11 natural organic materials and 13 reference compounds, seven proteinaceous organic materials (albumin, beef, milk, pork, soybean, yolk, and bovine serum albumin) functioned as EETMs. Carbohydrates and lipids did not function as EETMs. Comparative spectroscopic analyses suggested that a β-sheet secondary structure was essential for proteins to function as EETMs, regardless of water solubility. A high content of reduced sulfur was potentially involved in EET functionality. Although proteinaceous materials have thus far been considered simply as nutrients, the wide distribution of EET functionality in these materials provides new insights into their impact on biogeochemical cycles. In addition, structural information on EET functionality can provide a scientific basis for the development of eco-friendly EETMs.

Effect of octenyl succinic anhydride modified starch on soy protein-polyphenol binary covalently linked complexes

The present study aimed to investigate the effects of octenyl succinic anhydride modified starch (OSAS) on soy protein (SP)-(-)-epigallocatechin-3-gallate (EGCG) binary covalently linked complexes. Mean diameters of OSAS-SP-EGCG complexes decreased from 379.6 ± 54.9 nm to 272.7 ± 47.7 nm as the OSAS-to-SP-EGCG ratio changed from 1:2 to 4:1, while ζ-potential decreased from -19.1 ± 0.8 mV to -13.7 ± 1.2 mV. Fourier transform infrared spectroscopy results revealed that the characteristic peaks at 1725 cm^-1 and 1569 cm^-1 for OSAS disappeared in the OSAS-SP-EGCG complexes, indicating an interaction between OSAS and SP-EGCG complexes. X-ray diffraction analysis showed that with the increase of OSAS content, the diffraction peak at approximately 8.0° decreased from 8.22° to 7.74°, implying that the structures of OSAS and SP-EGCG complexes were rearranged after forming into OSAS-SP-EGCG complexes. The contact angle of the OSAS-SP-EGCG complexes significantly increased from 59.1° to 72.1° with the addition of OSAS increased, revealing that the addition of OSAS improved hydrophobicity of the SP-EGCG complexes. Transmission electron microscopy images revealed that the individual OSAS-SP-EGCG complexes became smaller but stuck together to form large fragments, which was different from the morphology of OSAS and SP-EGCG complexes. Thus, the OSAS-SP-EGCG complexes developed in this study may be effective emulsifiers for improving the stability of emulsion systems in the food industry.

Quantitative Determination of Polyphenols and Flavonoids in Cistus × incanus on the Basis of IR, NIR and Raman Spectra

Cistus is a plant that has been used in natural medicine for hundreds of years; it works primarily as an antioxidant and cleansing agent. Cistus × incanus leaves or herb can be an attractive source of polyphenols and flavonoids. The official protocols of active compound analysis relies on the extraction of compounds of interest from plant matter, which makes their determination long and costly. An analysis of plant material in its native state can be performed using vibrational spectroscopy. This paper presents a comparison of Raman spectroscopy, attenuated total reflection in mid-infrared and diffuse reflectance technique in the near-infrared region for the simultaneous quantification of total polyphenols (TPC) and flavonoids (TF) content, as well as the determination of FRAP antioxidant activity of C. incanus material. Utilizing vibrational spectra and using partial least squares algorithm, TPC and TF were quantified with the RSEP_VAL errors in the 2.7-5.4% range, while FRAP antioxidant activity for validation sets was determined with relative errors ranged from 5.2 to 9.3%. For the analyzed parameters, the lowest errors of predictions were computed for models constructed using Raman data. The developed models allow for fast and precise quantification of the studied active compounds in C. incanus material without any chemical sample treatment.

Cold-modulated leaf compounds in winter triticale DH lines tolerant to freezing and Microdochium nivale infection: LC-MS and Raman study

Tolerance to freezing and seedling diseases caused by Microdochium spp. is an essential trait for the wintering of triticale (×Triticosecale Wittmack) and other cereals. Preceding multi-year studies indicate that after long-term exposure to the low temperature, cereal seedlings acquire a genotype-dependent cross-tolerance to other subsequent stresses. This paper presents the first non-gel protein profiling performed via high performance liquid chromatography coupled with Mass Spectrometry as well as Fourier Transform-Raman spectroscopy measurements performed directly on leaves of triticale seedlings growing under different conditions. The research used doubled haploid lines selected from the mapping population, with extreme tolerance/susceptibility to freezing and M. nivale infection. These non-targeted methods led to the detection of twenty two proteins cold-accumulated in the most tolerant seedlings in relation to susceptible ones, classified as involved in protein biosynthesis, response to different stimuli, energy balancing, oxidative stress response, protein modification, membrane structure and anthocyanin synthesis. Additionally, in seedlings of the most freezing- and M. nivale -tolerant line, cold-hardening caused decrease of the carotenoid and chlorophyll content. Moreover, a decrease in the band intensity typical for carbohydrates as well as an increase in the band intensity characteristic for protein compounds were detected. Both studied lines revealed a different answer to stress in the characteristics of phenolic components.

Study on the structure and physicochemical properties of fenugreek galactomannan modified via octenyl succinic anhydride

To improve the mechanical strength of borax-crosslinked fenugreek galactomannan hydrogels and broaden the application field of galactomannan-based hydrogels, fenugreek galactomannan (FG) was esterified via octenyl succinic anhydride (OSA), and the parameters affecting the esterification reaction were systematically studied. The optimum process for OSA-modified FG (OFG) was as follows: FG concentration 1.5 wt%, n (OSA): n (FG) = 2, n (4-dimethylamino-pyridine, DMAP): n (FG) = 4, and reaction time 12 h. Under this condition, the degree of substitution (DS) was 0.31, and the product yield was 115.05 %. Characterization of FT-IR, H¹ NMR, and HPLC confirmed that the OSA group was successfully introduced into the FG skeleton. The mechanical strength of borax crosslinked OFG hydrogel (OFGH) is 18 times higher than that of FG hydrogel. OFGH shows excellent self-healing, injectable properties and electrical conductivity. This will further expand the application of borax crosslinked galactomannan-based hydrogels in the fields of sensors, drug delivery, and wound dressing.

Contemporary Developments and Emerging Trends in the Application of Spectroscopy Techniques: A Particular Reference to Coconut (Cocos nucifera L.)

The number of food frauds in coconut-based products is increasing due to higher consumer demands for these products. Rising health consciousness, public awareness and increased concerns about food safety and quality have made authorities and various other certifying agencies focus more on the authentication of coconut products. As the conventional techniques for determining the quality attributes of coconut are destructive and time-consuming, non-destructive testing methods which are accurate, rapid, and easy to perform with no detrimental sampling methods are currently gaining importance. Spectroscopic methods such as nuclear magnetic resonance (NMR), infrared (IR)spectroscopy, mid-infrared (MIR)spectroscopy, near-infrared (NIR) spectroscopy, ultraviolet-visible (UV-VIS) spectroscopy, fluorescence spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy (RS) are gaining in importance for determining the oxidative stability of coconut oil, the adulteration of oils, and the detection of harmful additives, pathogens, and toxins in coconut products and are also employed in deducing the interactions in food constituents, and microbial contaminations. The objective of this review is to provide a comprehensive analysis on the various spectroscopic techniques along with different chemometric approaches for the successful authentication and quality determination of coconut products. The manuscript was prepared by analyzing and compiling the articles that were collected from various databases such as PubMed, Google Scholar, Scopus and ScienceDirect. The spectroscopic techniques in combination with chemometrics were shown to be successful in the authentication of coconut products. RS and NMR spectroscopy techniques proved their utility and accuracy in assessing the changes in coconut oil’s chemical and viscosity profile. FTIR spectroscopy was successfully utilized to analyze the oxidation levels and determine the authenticity of coconut oils. An FT-NIR-based analysis of various coconut samples confirmed the acceptable levels of accuracy in prediction. These non-destructive methods of spectroscopy offer a broad spectrum of applications in food processing industries to detect adulterants. Moreover, the combined chemometrics and spectroscopy detection method is a versatile and accurate measurement for adulterant identification.

The Spectral Compositions of Light Changes Physiological Response of Chinese Cabbage to Elevated Ozone Concentration

The effects of ozone combined with other environmental factors remain an important topic of the research, both in connection with climate change and the possibility of using modern solutions in horticulture. In our experiment, we compared the influence of ozone (100 ppb) on photosynthesis and changes in the pigment composition of Chinese cabbage (Brassica rapa subsp. pekinensis) leaves depending on the spectral composition of light. We used white LED light (WL), a combination of red + green + blue (RGBL) with a dominant red component and white +blue (WBL) with a dominant blue component in comparison with the classic sodium lamp lighting (yellow light—YL). The values of the parameters describing the light-dependent phase of photosynthesis and the parameters of the gas exchange, as well as non-photosynthesis pigment contents, show that the spectral composition strongly differentiates the response of Chinese cabbage leaves to ozone. In general, the efficiency of photochemical reactions was the highest in YL, but after O₃ fumigation, it decreased. In plants growing in WL and WBL, the increase of O₃ concentration stimulated light photosynthesis reactions and led to the enhancement of transpiration, stomatal conductance and intracellular CO₂ concentration. Changes in photosynthetic activity were accompanied by an increase in the content of anthocyanins and flavonols.

Increasing the pH value during thermal processing suppresses the starch digestion of the resulting starch-protein-lipid complexes

To date, how the pH conditions of thermal processing tailor the structure and digestibility of resulting starch-based complexes remains largely unclear. Here, indica rice starch (IRS), stearic acid (SA), and a whey protein isolate (WPI) were used as materials. Increasing the pH value from 4 to 8 during thermal processing (pasting) mainly suppressed the starch digestion of starch-WPI-SA complexes rather than starch-SA counterparts. The starch-SA complexes showed moderate structural changes as the pH value rose, and there was less rapidly digestible starch (RDS) only at pH 8. For the starch-WPI-SA complexes, an increased pH value allowed larger nonperiodic structures and more V-type starch crystallites, with almost unchanged short-range orders but apparently collapsed networks at pH 8. Such ternary complexes displayed more resistant starch (RS) as the pH value rose. The ternary sample at pH 8 contained ca. 29.87% of the RS fractions.

Agricultural Potentials of Molecular Spectroscopy and Advances for Food Authentication: An Overview

Meat, fish, coffee, tea, mushroom, and spices are foods that have been acknowledged for their nutritional benefits but are also reportedly targets of fraud and tampering due to their economic value. Conventional methods often take precedence for monitoring these foods, but rapid advanced instruments employing molecular spectroscopic techniques are gradually claiming dominance due to their numerous advantages such as low cost, little to no sample preparation, and, above all, their ability to fingerprint and detect a deviation from quality. This review aims to provide a detailed overview of common molecular spectroscopic techniques and their use for agricultural and food quality management. Using multiple databases including ScienceDirect, Scopus, Web of Science, and Google Scholar, 171 research publications including research articles, review papers, and book chapters were thoroughly reviewed and discussed to highlight new trends, accomplishments, challenges, and benefits of using molecular spectroscopic methods for studying food matrices. It was observed that Near infrared spectroscopy (NIRS), Infrared spectroscopy (IR), Hyperspectral imaging (his), and Nuclear magnetic resonance spectroscopy (NMR) stand out in particular for the identification of geographical origin, compositional analysis, authentication, and the detection of adulteration of meat, fish, coffee, tea, mushroom, and spices; however, the potential of UV/Vis, 1H-NMR, and Raman spectroscopy (RS) for similar purposes is not negligible. The methods rely heavily on preprocessing and chemometric methods, but their reliance on conventional reference data which can sometimes be unreliable, for quantitative analysis, is perhaps one of their dominant challenges. Nonetheless, the emergence of handheld versions of these techniques is an area that is continuously being explored for digitalized remote analysis.

Fabrication and characterization of gum arabic- and maltodextrin-based microcapsules containing polyunsaturated oils

BACKGROUND

Polyunsaturated oils have various health-promoting effects, however, they are highly prone to oxidation. Encapsulation using biopolymers is one of the most effective strategies to enhance oil stability. This research examined the potential of gum arabic and maltodextrin for microencapsulation of omega-3 rich oils, aiming to enhance encapsulation efficiency and stability of encapsulated oil.

RESULTS

We encapsulated fish and flaxseed oils by emulsification-spray drying. Spray-dried microcapsules were prepared by oil-in-water emulsions consisting of 10 wt% oil and 30 wt% biopolymer (gum arabic, maltodextrin, or their mixture). Results showed that both microcapsules were spherical in shape with surface shrinkage, and exhibited amorphous structures. Gum arabic-based microcapsules had higher encapsulation efficiency as well as better storage stability for both types of oil. Flaxseed oil microcapsules generally had higher oxidative stability regardless of the type of wall material.

CONCLUSIONS

Through a comprehensive characterization of the physical and chemical properties of the emulsions and resulting microcapsules, we proved gum arabic to be a more effective wall material for polyunsaturated oil microencapsulation, especially flaxseed oil. This study provides a promising approach to stabilize oils which are susceptible to deterioration, and facilitates their wider uses as food and nutraceutical products. © 2021 Society of Chemical Industry.

Amygdalin: Toxicity, Anticancer Activity and Analytical Procedures for Its Determination in Plant Seeds

Amygdalin (d-Mandelonitrile 6-O-β-d-glucosido-β-d-glucoside) is a natural cyanogenic glycoside occurring in the seeds of some edible plants, such as bitter almonds and peaches. It is a medically interesting but controversial compound as it has anticancer activity on one hand and can be toxic via enzymatic degradation and production of hydrogen cyanide on the other hand. Despite numerous contributions on cancer cell lines, the clinical evidence for the anticancer activity of amygdalin is not fully confirmed. Moreover, high dose exposures to amygdalin can produce cyanide toxicity. The aim of this review is to present the current state of knowledge on the sources, toxicity and anticancer properties of amygdalin, and analytical methods for its determination in plant seeds.

Characterization of Collagen Structure in Normal, Wooden Breast and Spaghetti Meat Chicken Fillets by FTIR Microspectroscopy and Histology

Recently, two chicken breast fillet abnormalities, termed Wooden Breast (WB) and Spaghetti Meat (SM), have become a challenge for the chicken meat industry. The two abnormalities share some overlapping morphological features, including myofiber necrosis, intramuscular fat deposition, and collagen fibrosis, but display very different textural properties. WB has a hard, rigid surface, while the SM has a soft and stringy surface. Connective tissue is affected in both WB and SM, and accordingly, this study's objective was to investigate the major component of connective tissue, collagen. The collagen structure was compared with normal (NO) fillets using histological methods and Fourier transform infrared (FTIR) microspectroscopy and imaging. The histology analysis demonstrated an increase in the amount of connective tissue in the chicken abnormalities, particularly in the perimysium. The WB displayed a mixture of thin and thick collagen fibers, whereas the collagen fibers in SM were thinner, fewer, and shorter. For both, the collagen fibers were oriented in multiple directions. The FTIR data showed that WB contained more β-sheets than the NO and the SM fillets, whereas SM fillets expressed the lowest mature collagen fibers. This insight into the molecular changes can help to explain the underlying causes of the abnormalities.

Excellent Fire Retardant Properties of CNF/VMT Based LBL Coatings Deposited on Polypropylene and Wood-Ply

In this report, layer by layer (LBL) fire retardant coatings were produced on wood ply and Polypropylene Homopolymer/Flax fiber composites. FE-SEM and EDAX analysis was carried out to analyze the surface morphology, thickness, growth rate and elemental composition of the samples. Coatings with a high degree of uniformity were formed on Polypropylene composite (PP/flax), while coatings with highest thickness were obtained on wood ply (wood). FTIR and Raman spectroscopy were further used for the molecular identifications of the coatings, which confirmed the maximum deposition of the solution components on the wood substrate. A physiochemical analysis and model was proposed to explain the forces of adhesion between the substrate and solution molecules. Fire protection and thermal properties were studied using TGA and UL-94 tests. It was explored, that the degradation of the coated substrates was highly protected by the coatings as follows: wood > PP/flax > PP. From the UL-94 test, it was further discovered that more than 83% of the coated wood substrate was protected from burning, compared to the 0% of the uncoated substrate. The flammability resistance of the samples was ranked as wood > PP/flax > PP.

Graphene oxide nanofilm and chicken embryo extract decrease the invasiveness of HepG2 liver cancer cells

Background

The extracellular matrix (ECM) is a mosaic of various structural and functional proteins that cooperate with the cell, regulate adhesion, and consequently manage its further fate. Liver destruction is accompanied by a disruption of the physicochemical properties of the ECM which deregulates the cell–ECM interaction and can lead to uncontrolled proliferation and neoplastic transformation of cells. Therefore, it can be assumed that ECM modification and restoration of its characteristics for healthy tissue may counteract uncontrolled cell proliferation. The purpose of the presented research model was to optimise the physical characteristics of ECM by introducing a graphene oxide plane/nanofilm (nfGO) and enriching the cell environment with potentially missing proteins by adding a functional protein cocktail (chicken embryo liver extract) and determine the impact of these factors on cell–ECM cooperation and its consequences on adhesion, proliferation, and cell phase, which are factors of the invasiveness of cancer cells.

Results

Experiments were performed with non-cancer HS-5 cells and liver cancer cells HepG2 and C3A. The cells were divided into four groups: (1) control, (2) cultured on nfGO, (3) cultured with the addition of chicken embryo liver extract (CELE) and (4) cultured on the nfGO with the addition of CELE. CELE contained 1735 proteins; the top 57 of these proteins have been presented. The use of nfGO as well as CELE and nfGO + CELE reduced the proliferation of HepG2 cancer cells to the greatest extent; this is in contrast to non-cancer cells and also to C3A cancer cells. Furthermore, the combined use of the CELE protein cocktail and GO substrate effectively resulted in a decrease in the population of HepG2 cells in the G0/G1 phase and an increase of the population in G2/M. Molecular analysis of HepG2 cancer cells also showed an increase in the expression of genes responsible for adhesion such as focal adhesion kinase (fak), e-cadherin, and n-cadherin and a decrease in β-catenin, which is considered a proto-oncogene.

Conclusions

Studies have shown that both the GO surface structure on which the cells are grown as well as the presence of a multi-component natural cocktail of regulatory proteins, can modify the expression of integrins, increase adhesion and, as a consequence, proliferation and the cell cycle—entering the resting phase. For the first time, it has been documented that hepatic cancer cells of the HepG2 line under the influence of stimuli derived from mimic ECM (graphene oxide) in interaction with a unique protein complex derived from chicken liver embryo decreased of the invasiveness of cancer cells.

Preliminary Assessment of Parmigiano Reggiano Authenticity by Handheld Raman Spectroscopy

Raman spectroscopy, and handheld spectrometers in particular, are gaining increasing attention in food quality control as a fast, portable, non-destructive technique. Furthermore, this technology also allows for measuring the intact sample through the packaging and, with respect to near infrared spectroscopy, it is not affected by the water content of the samples. In this work, we evaluate the potential of the methodology to model, by multivariate data analysis, the authenticity of Parmigiano Reggiano cheese, which is one of the most well-known and appreciated hard cheeses worldwide, with protected denomination of origin (PDO). On the other hand, it is also highly subject to counterfeiting. In particular, it is critical to assess the authenticity of grated cheese, to which, under strictly specified conditions, the PDO is extended. To this aim, it would be highly valuable to develop an authenticity model based on a fast, non-destructive technique. In this work, we present preliminary results obtained by a handheld Raman spectrometer and class-modeling (Soft Independent Modeling of Class Analogy, SIMCA), which are extremely promising, showing sensitivity and specificity of 100% for the test set. Moreover, another salient issue, namely the percentage of rind in grated cheese, was addressed by developing a multivariate calibration model based on Raman spectra. It was possible to obtain a prediction error around 5%, with 18% being the maximum content allowed by the production protocol.

Peak Fitting Applied to Fourier Transform Infrared and Raman Spectroscopic Analysis of Proteins

FTIR and Raman spectroscopy are often used to investigate the secondary structure of proteins. Focus is then often laid on the different features that can be distinguished in the Amide I band (1600–1700 cm−1) and, to a lesser extent, the Amide II band (1510–1580 cm−1), signature regions for C=O stretching/N-H bending, and N-H bending/C-N stretching vibrations, respectively. Proper investigation of all hidden and overlapping features/peaks is a necessary step to achieve reliable analysis of FTIR and FT-Raman spectra of proteins. This paper discusses a method to identify, separate, and quantify the hidden peaks in the amide I band region of infrared and Raman spectra of four globular proteins in aqueous solution as well as hydrated zein and gluten proteins. The globular proteins studied, which differ widely in terms of their secondary structures, include immunoglobulin G, concanavalin A, lysozyme, and trypsin. Peak finding was done by analysis of the second derivative of the original spectra. Peak separation and quantification was achieved by curve fitting using the Voigt function. Structural data derived from the FT-Raman and FTIR analyses were compared to literature reports on protein structure. This manuscript proposes an accurate method to analyze protein secondary structure based on the amide I band in vibrational spectra.

Applicability of Confocal Raman Microscopy to Observe Microstructural Modifications of Cream Cheeses as Influenced by Freezing

Confocal Raman microscopy is a promising technique to derive information about microstructure, with minimal sample disruption. Raman emission bands are highly specific to molecular structure and with Raman spectroscopy it is thus possible to observe different classes of molecules in situ, in complex food matrices, without employing fluorescent dyes. In this work confocal Raman microscopy was employed to observe microstructural changes occurring after freezing and thawing in high-moisture cheeses, and the observations were compared to those obtained with confocal laser scanning microscopy. Two commercially available cream cheese products were imaged with both microscopy techniques. The lower resolution (1 µm/pixel) of confocal Raman microscopy prevented the observation of particles smaller than 1 µm that may be part of the structure (e.g., sugars). With confocal Raman microscopy it was possible to identify and map the large water domains formed during freezing and thawing in high-moisture cream cheese. The results were supported also by low resolution NMR analysis. NMR and Raman microscopy are complementary techniques that can be employed to distinguish between the two different commercial formulations, and different destabilization levels.

Latest advances in imaging techniques for characterizing soft, multiphasic food materials

Over the last two decades, the development and production of innovative, customer-tailored food products with enhanced health benefits have seen major advances. However, the manufacture of edible materials with tuned physical and organoleptic properties requires a good knowledge of food microstructure and its relationship to the macroscopic properties of the final food product. Food products are complex materials, often consisting of multiple phases. Furthermore, each phase usually contains a variety of biological macromolecules, such as carbohydrates, proteins and lipids, as well as water droplets and gas bubbles. Micronutrients, such as vitamins and minerals, might also play an important role in determining and engineering food microstructure. Considering this complexity, highly advanced physio-chemical techniques are required for characterizing the microstructure of food systems prior to, during and after processing. Fast, in situ techniques are also essential for industrial applications. Due to the wide variety of instruments and methods, the scope of this paper is focused only on the latest advances of selected food characterization techniques, with emphasis on soft, multi-phasic food materials.

A reversible, switchable pH-driven quaternary ammonium pillar[5]arene nanogate for mesoporous silica nanoparticles

Here we describe the assembly and pH-driven operation of two nanocarriers based on non-functionalized (MCM-41) and carboxylate-functionalized (MCM-41-COOH) containers loaded with the anticancer drug doxorubicin (DOX) and capped by quaternary ammonium pillar[5]arene (P[5]A) nanogates. MCM-41 and MCM-41-COOH containers were synthesized and transmission and scanning electron microscopies showed nanoparticles with spherical morphology and dimensions of 85 ± 13 nm. The nanochannels of MCM-41 loaded with DOX were gated through the electrostatic interactions between P[5]A and the silanolate groups formed at the silica-water interface, yielding the MCM-41-DOX-P[5]A nanocarrier. The second nanocarrier was gated through the electrostatic interactions between the carboxylate groups mounted on the surface of MCM-41 and P[5]A, resulting in the MCM-41-COO-DOX-P[5]A nanocarrier. The DOX release profiles from both nanocarriers were investigated by UV-vis spectroscopy at different pH values (2.0, 5.5 and 7.4) and also in the presence of ions, such as citrate^3- (19 mmol L^-1) and Zn²⁺ (1.2 and 50 mmol L^-1) at 37 °C. MCM-41-COO-DOX-P[5]A can be turned on and off eight times through the formation and breaking of electrostatic interactions. In vitro studies show that MCM-41-COO-DOX-P[5]A can penetrate and release DOX in the nucleus of human breast adenocarcinoma MCF-7 cancer cells leading to a pronounced cytotoxic effect. Therefore, the fabricated nanocarrier based on a water-soluble cationic pillar[5]arene nanogate, which is reversibly opened and closed by electrostatic interactions, can be considered as a promising drug transport and delivery technique for future cancer therapy.

Preparation and Characterization of a Modified-β-Cyclodextrin/β-Carotene Inclusion Complex and Its Application in Pickering Emulsions

β-Cyclodextrin (β-CD) was modified using octenyl succinic anhydride (OSA) to introduce amphiphilic groups (hydrophilic carboxyl and lipophilic octenyl chains) by esterification under alkaline conditions. The FT-IR results indicated that the OSA-modified β-CD (OCD) showed new absorption peaks of an ester bond and a carboxylate (RCOO^-) at 1724 and 1570 cm^-1, respectively, confirming the successful preparation of OCD. Then the embedding effects of β-CD and OCD on β-carotene and the emulsifying and antioxidant properties of their inclusion complexes were evaluated. The results of XRD showed that the β-CD (or OCD)/β-carotene inclusion complexes were converted from a cage-type structure to a channel-type structure. AFM and SEM showed that the crystal characteristics and surface morphologies of the inclusion complexes were different from those of the physical mixture. The emulsion stabilized by OCD exhibited smaller droplet sizes and larger zeta-potentials than that stabilized by β-CD. In addition, the inclusion complexes-prepared emulsion exhibited lower POV values and TBARS contents than did the physical mixture. OCD/β-carotene inclusion complexes can improve the physical and oxidative stability of the emulsion, which is of great significance to the food industry.

Glycerin-Grafted Starch as Corrosion Inhibitor of C-Mn Steel in 1 M HCl solution

C-Mn steels, commonly employed in structural applications, are often exposed to near-neutral aerated environments and hence subjected to general corrosion. In broader contexts, for example during pickling, acidizing treatments, or acid-releasing processes, where steel comes in contact with more aggressive solutions, the use of corrosion inhibitors is a supplementary strategy to cathodic protection and/or coating. This work focuses on the C-Mn steel corrosion protection in the presence of HCl, either as process fluid or by product. In order to avoid the toxicological issues related to conventional synthetic products, a bio-copolymer containing glycerin-grafted starch, synthesized by modification of maize starch, was studied as a “green” corrosion inhibitor by the weight loss method and electrochemical techniques (open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy). Corrosion-related parameters, such as inhibitor concentration and temperature, were varied and optimized to characterize the corrosion process. Results showed that inhibition efficiency increases with increasing bio-copolymer concentration, reaching a maximum of 94%at the concentration of 300 mg L−1. The kinetic and thermodynamic parameters were determined and discussed. The obtained values of corrosion potential and corrosion current density, Ecorr and icorr, obtained by potentiodynamic polarization, are in agreement with the weight loss method. The corrosion current densities decrease when the concentration of the inhibitor increases.

Effects of different molecular weight water-extractable arabinoxylans on the physicochemical properties and structure of wheat gluten

The effects of water-extractable arabinoxylans (WEAXs) with different molecular weights on the physicochemical properties and structure of wheat gluten were studied, a transition between β-turns in β-leaves in the structure of gluten has been demonstrated by Fourier transform infrared spectroscopy when WEAX samples were added. The ratio of weakly hydrogen-bonded β-sheets to strongly hydrogen-bonded β-sheets tended to decrease with increasing WEAX content. FT-Raman analysis demonstrated other changes in the structure of gluten concerning β-structures, the conformation of the disulfide bridges, and aromatic amino acid environments; these changes were dependent on the molecular weight of the WEAX. Native WEAXs of different molecular weights that are present as discrete fragments of the cell wall have had a negative effect on the properties of gluten. However, low molecular weight WEAX has helped gluten maintain the left-left conformation of its disulfide bonds. In addition, the gluten elasticity was reduced by the native WEAX to make it softer, but the WEAX low molecular weight impeded this process and improved the gluten network.

A review on the application of vibrational spectroscopy to the chemistry of nuts

Nuts are highly appreciated due to their nutritional relevance and flavour, being the source of many desirable and healthy compounds as polyunsaturated fatty acids and antioxidants. Their characterization became the target of many studies in the last years through conventional analytical techniques as chromatographic ones. Due to the limitations associated to these techniques, as time, cost and environmental concerns, spectroscopic techniques have been increasingly pointed as reliable alternatives. Either applied to raw materials quality control or to more complex process, as industrial in-line monitoring, spectroscopic techniques, namely vibrational spectroscopy, are gathering strong acceptance. This paper presents a review on the application of vibrational spectroscopy, infrared and Raman, to nuts characterization. Estimates of several qualitative and quantitative parameters, origin authentication and/or adulteration in almonds, peanuts, pine nuts, hazelnuts, walnuts, Brazil nuts, cashews, chestnuts and pistachios will be covered. Advantages and limitations of these techniques and future trends will also be discussed.

Research Progress of Raman Spectroscopy in Drug Analysis

Raman spectroscopy is a spectroscopic analysis technique that enables rapid qualitative and quantitative detection based on inelastic collision and Raman scattering intensity. This review detailed the generation principle, instrument composition, influencing factors, and common classifications of Raman spectrum. Furthermore, it summarized and forecast the research progress of Raman spectroscopy in the field of drug analysis simultaneously over the past decade, including the identification of active pharmaceutical ingredients (APIs), qualitative and quantitative studies of pharmaceutical preparations, detection of illicit drugs, the identification of Chinese herbal medicines, and the combination with other technologies. The development of Raman spectroscopy in other fields is additionally summarized.

Rapid Determination of Chlorophyll and Pheophytin in Green Tea Using Fourier Transform Infrared Spectroscopy

The chlorophyll, pheophytin, and their proportions are critical factors to evaluate the sensory quality of green tea. This research aims to establish an effective method to determine the quantification of chlorophyll and pheophytin in green tea, based on Fourier transform infrared (FT–IR) spectroscopy. First, five brands of tea were collected for spectral acquisition, and the chlorophyll and pheophytin were measured using the reference method. Then, a relation between these two pigments and FT–IR spectroscopy were developed based on chemometrics. Additionally, the characteristic IR wavenumbers of these pigments were extracted and proved to be effective for a quantitative determination. Successively, non-linear models were also built based on these characteristic wavenumbers, obtaining coefficients of determination of 0.87, 0.80, 0.85 and 0.89; and relative predictive deviations of 2.77, 2.62, 2.26 and 3.07 for the four pigments, respectively. These results demonstrate the feasibility of FT–IR spectroscopy for the determination of chlorophyll and pheophytin.

Effects of Chain Length and Degree of Unsaturation of Fatty Acids on Structure and in Vitro Digestibility of Starch-Protein-Fatty Acid Complexes

The effects of chain length and degree of unsaturation of fatty acids (FAs) on structure and in vitro digestibility of starch-protein-FA complexes were investigated in model systems. Studies with the rapid visco analyzer (RVA) showed that the formation of ternary complex resulted in higher viscosities than those of binary complex during the cooling and holding stages. The results of differential scanning calorimetry (DSC), Raman, and X-ray diffraction (XRD) showed that the structural differences for ternary complexes were much less than those for binary complexes. Starch-protein-FA complexes presented lower in vitro enzymatic digestibility compared with starch-FAs complexes. We conclude that shorter chain and lower unsaturation FAs favor the formation of ternary complexes but decrease the thermal stability of these complexes. FAs had a smaller effect on the ordered structures of ternary complexes than on those of binary complexes and little effect on enzymatic digestibility of both binary and ternary complexes.