Effect of drying methods on the reactivity of chitosan towards Maillard reaction

The effect of drying methods on chitosan reactivity towards Maillard reaction during storage of dried chitosan–lactose systems was investigated. Two different structural forms of chitosan, scaffold and microspheres, were prepared. Then they were dried by lyophilization or using supercritical fluid technology (SF-CO₂) and stored with lactose under controlled temperature conditions (60 °C) and water activity (a_w = 0.65). The drying method produced slight modifications on the chitosan structure especially in samples submitted to SF-CO₂ treatment. Differences were more evident in the reactivity of chitosan–lactose systems during storage. Maillard reaction development was assessed by quantification of a new compound which originated from the acid hydrolysis of Amadori compounds (NFMD) resulting from chitosan–lactose interactions, and not detected in the acid hydrolysates of freshly prepared chitosan-lactose systems. Maillard reaction was influenced by different factors such as the manner of lactose addition, structure of chitosan (microspheres and scaffolds) and drying method. Lyophilized chitosan in the form of microspheres with lactose, presented the highest values of NFMD (428.45 mg/100 g of sample). The determination of this compound could be used as an index of the progress of Maillard reaction.     

Hyperspectral Imaging-Based Classification and Wavebands Selection for Internal Defect Detection of Pickling Cucumbers

Hyperspectral imaging is useful for detecting internal defects of pickling cucumbers. The technique, however, is not yet suitable for high-speed online implementation due to the challenges in analyzing large-scale hyperspectral images. This research aimed to select the optimal wavebands from the hyperspectral image data, so that they can be deployed in either a hyperspectral or multispectral imaging-based inspection system for the automatic detection of internal defects of pickling cucumbers. Hyperspectral reflectance (400–700 nm) and transmittance (700–1,000 nm) images were acquired, using an in-house developed hyperspectral imaging system running at two conveyor speeds of 85 and 165 mm/s, for 300 “Journey” pickling cucumbers before and after internal damage was induced by mechanical load. Minimum redundancy–maximum relevance (MRMR) was used for optimal wavebands selection, and the loadings of principal component analysis (PCA) were also applied for qualitatively identifying the important wavebands that are related to the specific features. Discriminant analysis with Mahalanobis distance classifier was performed for the two-class (i.e., normal and defective) and three-class (i.e., normal, slightly defective, and severely defective) classifications using the mean spectra and textural features (energy and variance) from the regions of interest in the spectral images at selected waveband ratios. The classification results based on MRMR wavebands selection were generally better than those from PCA-based classifications. The two-band ratio of 887/837 nm from MRMR gave the best overall classification results, with the accuracy of 95.1 and 94.2 % at the conveyor speeds of 85 and 165 mm/s, respectively, for the two-class classification. The highest classification accuracies for the three-class classification based on the optimal two-band ratio of 887/837 nm were 82.8 and 81.3 % at the conveyor speeds of 85 and 165 mm/s, respectively. The mean spectra-based classification achieved better results than the textural feature-based classification, except in the three-class classification for the higher conveyor speed. The overall classification accuracies for all selected waveband ratios at the low conveyor speed were slightly higher than those at the higher conveyor speed, since the low speed resulted in more scan lines, thus higher spatial resolution hyperspectral images. The identified two-band ratio of 887/837 nm in transmittance mode could be applied for fast real-time internal defect detection of pickling cucumbers.     

Antimicrobial packaging based on ɛ‐polylysine bioactive film for the control of mycotoxigenic fungi in vitro and in bread

?‐Poly‐l‐ lysine (?‐PL) is a cationic peptide with a broad‐spectrum antimicrobial activity. This study investigates the use of ?‐PL as natural antimicrobial to inhibit fungal growth and to reduce aflatoxins (AFs) production. Antifungal activity of starch biofilms with different concentrations of ?‐Poly‐l‐ lysine (?‐PL) was determined in solid medium against Aspergillus parasiticus (AFs producer) and Penicillium expansum. Then, biofilms were tested as antimicrobial devices for the preservation of bread loaf inoculated with A. parasiticus CECT 2681 and P. expansum CECT 2278. Shelf life and AFs content were examined. Biofilms with concentrations of ?‐PL less than 1.6 mg/cm² showed no fungal growth inhibition in solid medium, while the antifungal activity of the films with greater than 1.6 mg/cm² of ?‐PL was dose dependent. The shelf life of bread inoculated with A. parasiticus was increased by 1 day with the use of films containing 1.6–6.5 mg ?‐PL/cm², while shelf life of bread tainted with P. expansum was increased by 3 day with 6.5 mg ?‐PL/cm². AFs production was greatly inhibited by ?‐PL biofilms (93–100%). Thus, ?‐PL biofilms could be potentially used as antimicrobial device during bread storage as a natural alternative to the synthetic preservatives.

Practical applications

?‐Polylysin is a natural substance from microbial metabolism. Polylysine has a function to prevent a microbe from proliferating by ionic adsorption in the microbe. ?‐polylysine has a wide antibacterial spectrum and has an obvious lethal effect on Gram‐positive and Gram‐negative bacteria, yeast, mold, viruses, etc. It has a good antibacterial effect on the Gram‐negative bacteria E. coli and Salmonellae, which are difficult to control with other natural preservatives. ?‐Polylysine has already been used generally as a food additive in Japan, Korea and other part of world. In the United States, FDA has recognized the polylysine as a GRAS material. Considered the positive results obtained in the study, this compound could be used for the production of antimicrobial biofilms, applied as separator slices in the loaf bread production, to prevent the growth of the mycotoxigenic fungi A. parasiticus and P. expansum, contributing to reduce the use of the synthetically preservatives in bakery industry and also of the negative impact that these compounds could generate on the health of the end users.     

Microencapsulation of Curcumin by a Spray-Drying Technique Using Gum Arabic as Encapsulating Agent and Release Studies

Curcumin is a natural yellow pigment extracted from dried roots of turmeric, used in food applications. Despite its applicability in food products, this phenolic compound is also used in the pharmaceutical field. It is reported to have health benefits such as anticancer, antitumor, and antiviral effects. However, curcumin is a very unstable compound. Therefore, this work proposes the microencapsulation of curcumin, in order to protect it and to improve its stability and solubility in water, by spray-drying, using the gum arabic as an encapsulating agent in three different concentrations 10, 15, and 20% (weight/volume (w/v)). Emulsions were prepared with coconut oil and used to prepare the curcumin microparticles. For this purpose, different analysis and studies were performed. A product yield ranging from 44 to 52% and from 29 to 42% was obtained for the production of microparticles without and with curcumin, respectively. The curcumin microcapsules and empty capsules were characterized and evaluated. All the microparticles presented a spherical form, had a diameter around 7–9 μm (considering a volume distribution), and had a rough surface. The efficiency of encapsulation was between 75 and 85%, being higher for the particles prepared with higher concentrations of encapsulating agents. Considering the controlled release studies, the microcapsules were prepared with different concentrations of gum arabic but showed similar release profiles. However, it was also concluded that increasing the amount of gum arabic used in the formulation of the microparticles, the amount of curcumin released in the first minutes decreases; therefore, the release tends to be slower (63.2% of the release varied between 25.5 and 69.0 min). Fitting the experimental results to a linearized equation of the Weibull model, it was possible to obtain a good correlation coefficient (R² varying from 0.94 to 0.97), indicating that this model adapts to the experimental data obtained.

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Graphical Abstract SEM images for the microparticles prepared with curcumin using gum arabic, as encapsulating agent and experimental and Weibull model release profiles

     

Yoghurt‐type beverage with partial substitution of milk by a chickpea extract: Effect on physicochemical and flow properties

The objective of this study was to determine the evolution of physicochemical and flow properties of a yoghurt‐type beverage partially replaced with a chickpea extract over a period of 22 days. From two chickpea extracts, Blanco Noroeste was selected for its higher protein content. Six yoghurt‐type formulations were prepared, stored at 4 °C and analysed on days 1, 8, 15 and 22. pH was 4.24–4.75, while brightness was 81.7–94.5. Flow properties of the yoghurt‐type exhibited a non‐Newtonian behaviour. From three formulations that underwent sensory evaluation, the 30:70 mix obtained the highest acceptation. This yoghurt‐type beverage exhibited characteristics similar to natural yoghurt.     

Cation/H+ antiporters mediate potassium and sodium fluxes in Pichia sorbitophila. Cloning of the PsNHA1 and PsNHA2 genes and expression in Saccharomyces cerevisiae

Pichia sorbitophila grows rapidly in the presence of very high NaCl concentrations. Under these conditions, even when the K(+) concentration is low, P. sorbitophila cells can maintain low Na(+) and high K(+) contents. This remarkable capacity of P. sorbitophila fails when the external pH is not acidic. This indicates that Na(+) efflux is mediated by an electroneutral Na(+)/H(+) antiporter. We have cloned and sequenced two genes designated as PsNHA1 and PsNHA2, which probably encode two antiporters of this type. The genes present high similarity with the corresponding genes from other yeasts. The heterologous expression of PsNHA1 or PsNHA2 in a Saccharomyces cerevisiae mutant lacking the Na(+) efflux systems and sensitive to high concentrations of Na(+) and K(+) rescued the tolerance and the ability to extrude both cations. The Accession Nos of the sequenced DNA fragments are: PsNHA1, AJ496431; PsNHA2, AJ496432. (TC 2.A.36) Copyright 2002 John Wiley & Sons, Ltd.     

Termites as human foods—A comprehensive review

Global food production is anticipated to rise along with the growth of the global population. As a result, creative solutions must be devised to ensure that everyone has access to nutritious, affordable, and safe food. Consequently, including insects in diets has the potential to improve global food and nutrition security. This paper aims to share recent findings by covering edible termites as the main aspect, from their consumption record until consumer acceptance. A total of 53 termite species are reported as edible ones and distributed in 6 biogeographic realms. Generally, termites have a nutrient composition that is suitable for human consumption, and cooked termites are a better dietary choice than their raw counterparts. Besides, increasing customer interest in eating termite-based food can be achieved by making it more palatable and tastier through various cooking processes, that is, boiling, frying, grilling, roasting, smoking, and sun-drying. Moreover, edible termites can also be used as a new source of medication by exhibiting antimicrobial activity. Regarding their advantages, it is strongly encouraged to implement a seminatural rearing system to sustain the supply of edible termites. Overall, this paper makes it evident that termites are an important natural resource for food or medicine. Hence, the long-term objective is to stimulate scientific inquiry into the potential of edible insects as an answer to the problem of global food security.