Hibiscus Sabdariffa L. Extract as a Natural Additive in Food Packaging Biodegradable Films to Improve Antioxidant, Antimicrobial, and Physicochemical Properties.

In this study, biodegradable active films were prepared from potato starch and polyvinyl alcohol at different proportions, mixed with acetone extract of Hibiscus sabdariffa L. (HS) and using glycerol as a plasticizer. Functional properties, antimicrobial, and antioxidant capacity were evaluated. Potato starch films with a proportion of polyvinyl alcohol up to 50% and HS extract had significant antioxidant capacity and antibacterial effect against most of the analyzed strains. Adding polyvinyl alcohol (PVOH) and HS extract improved the mechanical performance and reduced water vapor permeability of the materials. The active biobased films with HS extract presented good physicochemical, antimicrobial, and antioxidant properties. These materials are considered as suitable for food packaging, and the active compounds in the roselle extract are a natural antibacterial option for the food area. The materials based entirely on biodegradable products are an excellent alternative when developing and marketing biobased materials, minimizing the environmental impact of food packaging.

Effect of retrograded starch with different amylose content on the rheological properties of stored yogurt.

Resistant starch (RS) promotes health benefits; however, when added to foods, it could change the rheological properties. The effect of adding different concentrations (2.5, 5, 7.5, and 10%) of retrograded corn starch with 27% (RNS) or 70% (RHS) amylose content on the properties of yogurt was evaluated through measurements of flow behavior and gel structure. Syneresis and resistant starch content were also assessed. Results were analyzed using multiple regression to describe the effect of starch concentration and storage time on the properties of yogurt added with RNS or RHS. Syneresis was reduced, RNS reinforced the structure increasing the water absorption capacity and the consistency index; meanwhile, RHS provided a yogurt containing up to 10 g of RS in 100 g of sample, allowing obtaining a functional dairy product. Creep-recovery test showed that adding RNS or RHS favored the matrix conformation, and the yogurt samples were able to recover. The final product behaved like a solid material with a firmer and more stable gel structure, resulting in a strengthened gel without weakening the yogurt structure, showing a characteristic like Greek-style or stirred yogurt depending on the type and concentration of retrograded starch. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-023-05735-x.

Effect of adding high concentrations of retrograded starch with different amylose content on the physicochemical properties and sensory attributes of Greek-style yogurt.

It is well known that using retrograded starches confers many technological advantages, as well as health benefits when consumed in adequate doses; however, these properties are closely related to the type of starch and/or the treatment applied, therefore, it is of interest to add retrograded starch to popular products such as Greek yogurt. The aim of this work was to investigate the effect of adding two types of retrograded corn starch with different amylose content to a non-strained type of Greek-style yogurt. Retrograded starch from starch containing 27 % (RNS) or 70 % (RHS) amylose was added to yogurt at 0, 10, 12.5, or 15 g/100 g before storage at 4 °C for 14 d. The resistant starch (RS) content, pH, syneresis, flow behavior index, and consistency index, were measured every week. A sensory test was carried out in yogurt added with 12.5 g/100 g of retrograded starches to evaluate acceptance. Adding retrograded starch significantly reduced syneresis while increased the consistency, firmness, and resistant starch content of the yogurt. No significant differences in general acceptance were observed in samples added with RNS when compared to the control. Although a significant difference was observed after adding RHS, the acceptance of the product is still convenient. Adding a high concentration of retrograded starch could help to ensure doses enough for a prebiotic effect of RS with concentrations of 1.74 ± 0.37 to 2.32 ± 0.09 g/100 g and from 3.5 ± 0.08 to 4.21 ± 0.08 g/100 g when RNS or RHS is added respectively, while maintaining the quality characteristics of Greek-style yogurt during storage without compromising the acceptability.

Structure and Conformation of Novel BODIPY Ugi Adducts.

Two novel BODIPY-Ugi (boron dipyrromethene) adducts exhibit peculiar room temperature (T=20 °C) H-1 NMR spectra in that several protons located at the aromatic aniline-type ring are lost in the baseline. This observation revealed the existence of a dynamic conformational process where rotation around the C-N bond is hindered. Variable-temperature H-1 and C-13 NMR spectroscopic analysis confirmed this conclusion; that is, low-temperature spectra show distinct signals for all four aromatic protons below coalescence, whereas average signals are recorded above coalescence (T=+120 °C). Particularly interesting was the rather large difference in chemical shifts for the ortho protons below coalescence, Δδ=1.45 ppm, which was explained based on DFT computational analysis. Indeed, the calculated lowest-energy gas-phase conformation of the BODIPY Ugi adducts locates one half of the aniline-type ring in the shielding anisotropic cone of the bridge phenyl ring in the BODIPY segment. This is in contrast to the solid-state conformation established by X-ray diffraction analysis that shows a nearly parallel arrangement of the aromatic rings, probably induced by crystal packing forces.

Supramolecular structure and technofunctional properties of starch modified by high hydrostatic pressure (HHP): A review.

This review focuses on describing and discussing recent findings regarding the effects of high hydrostatic pressure (HHP) on the supramolecular structure and technofunctional properties of starch, as well as on analyzing the hypothesis to explain these changes. The non-thermal modification of starch through HHP involves complex supramolecular structural changes that depend on the botanical source, amylose content, and treatment intensity. Overall, the granular morphology, lamellar and crystalline structures, and double helices undergo different degrees of modification/disorganization during HHP, but these changes are distinguished from thermal modification by an improvement at the same gelatinization degree. The HHP-induced supramolecular modifications determine the properties of starch, including water solubility, swelling power, pasting, water and oil holding capacity, thermal properties, and in vitro digestibility.

Mechanoenzymology in the Kinetic Resolution of ß-Blockers: Propranolol as a Case Study.

Recent advances in biotechnology, protein engineering, and enzymatic immobilization have made it possible to carry out biocatalytic transformations through alternative non-conventional activation strategies. In particular, mechanoenzymology (i.e., the use of the mechanical force produced by milling or grinding to activate a biotransformation) has become a new area in so-called "green chemistry", reshaping key fundaments of biocatalysis and leading to the exploration of enzymatic transformations under more sustainable conditions. Significantly, numerous chiral active pharmaceutical ingredients have been synthesized via mechanoenzymatic methods, boosting the use of biocatalysis in the synthesis of chiral drugs. In this regard and aiming to widen the scope of the young field of mechanoenzymology, a dual kinetic resolution of propranolol precursors was explored. The biocatalytic methodology mediated by Candida antarctica Lipase B (CALB) and activated by mechanical force allowed the isolation of both enantiomeric precursors of propranolol with high enantiomeric excess (up to 99% ee), complete conversion (c = 50%), and excellent enantiodifferentiation (E > 300). Moreover, the enantiomerically pure products were used to synthesize both enantiomers of the ß-blocker propranolol with high enantiopurity.

Long-Term Refrigerated Storage of Beef Using an Active Edible Film Reinforced with Mesoporous Silica Nanoparticles Containing Oregano Essential Oil (Lippia graveolens Kunth).

Beef is a fundamental part of the human diet, but it is highly susceptible to microbiological and physicochemical deterioration which decrease its shelf life. This work aimed to formulate an active edible film (AEF) incorporated with amino-functionalized mesoporous silica nanoparticles (A-MSN) loaded with Mexican oregano (Lippia graveolens Kunth) essential oil (OEO) and to evaluate its effect as a coating on fresh beef quality during refrigerated storage. The AEF was based on amaranth protein isolate (API) and chitosan (CH) (4:1, w/w), to which OEO emulsified or encapsulated in A-MSN was added. The tensile strength (36.91 ± 1.37 MPa), Young's modulus (1354.80 ± 64.6 MPa), and elongation (4.71%) parameters of AEF made it comparable with synthetic films. The antimicrobial activity of AEF against E. coli O157:H7 was improved by adding 9% (w/w) encapsulated OEO, and interactions of glycerol and A-MSN with the polymeric matrix were observed by FT-IR spectroscopy. In fresh beef, after 42 days, AEF reduced the population growth (Log CFU/cm2, relative to uncoated fresh beef) of Brochothrix thermosphacta (5.5), Escherichia coli (3.5), Pseudomonas spp. (2.8), and aerobic mesophilic bacteria (6.8). After 21 days, odor acceptability of coated fresh beef was improved, thus, enlarging the shelf life of the beef and demonstrating the preservation capacity of this film.

Biobased sustainable materials made from starch and plasma/ultrasound modified Agave fibers: Structural and water barrier performance.

This study aims to investigate the effect of green modification methods (ultrasound and plasma treatment) on a by-product of the tequila industry (Agave fibers), which can be useful as raw material to elaborate biodegradable and hydrophobic starch films. FTIR analysis indicated a decrease of hydrophilic lignocellulosic components, since the cavitation and etching effect of ultrasound/plasma treatment reduced the large number of hydroxyl groups of the fibers. The inclusion of ultrasound/plasma modified fibers in the starch matrix limited the starch-glycerol interactions, reducing the free volume of the starch and the binding sites for water. Therefore, the solubility (%S), swelling (%W) and water vapor permeance (WVPe) of the films decreased from 27 to 16%, 57 to 50% and 0.37 to 0.21 g/day m2Pa, respectively. Furthermore, the water contact angle (WCA) and relative crystallinity values increased. The results indicated that the treatments are suitable green technologies to obtain hydrophobic fillers useful to develop sustainable materials.

Improving of Gelling Capacity of Cooked Crab Meat Proteins.

Cooked crab meat subjected to a cutting process can aggregate again, forming weak gels. The objective of this work was to determine the effect of two mixing methods, combined with the addition of the microbial enzyme TGase (MTGase) on the mechanical and functional properties of gels from washed or unwashed blue crab (Callinectes sapidus) meat. Live crabs were obtained from Laguna Madre, Tamaulipas, Mexico, and cooked at 120°C for 20 min before hand-picking the meat from the shell. Cooked meat was processed by mixing and cut at temperatures of 25 or 60°C, without (control) or 0.5% of MTGase. Then cooked at 90°C for 15 min. Changes in texture profile analysis, percentage of extractable water, and color were evaluated. The mixing method at 60°C allowed increasing the textural properties of the gels, and the addition of MTGase significantly improved the mechanical properties. The results allowed stablishing a viable technique to obtain restructured gels from cooked crab meat with no need to extract the soluble compounds responsible for their distinctive odor and taste which often affect the mechanical properties.

Production of rhamnolipids by the Thermoanaerobacter sp. CM-CNRG TB177 strain isolated from an oil well in Mexico.

This study aimed to produce and characterize biosurfactants using the Thermoanaerobacter sp. CM-CNRG TB177 strain isolated from an oil field in Mexico, as well as assessing the influence of different carbon and nitrogen sources on the capacity of the produced surfactant to reduce the surface tension of water. The thin-layer chromatography (TLC) revealed that the obtained extract corresponds to a mono-rhamnolipid; the results of the ultra-performance-liquid chromatography/mass spectrometry (UPLC/MS) analysis revealed that the Thermoanaerobacter sp. CM-CNRG TB177 strain produces a mixture of three rhamnolipids, whose masses correspond to mono-rhamnolipid. The rhamnolipids mixture obtained using 2.5% molasses as carbon source diminished the surface tension of water to 29.67 mNm-1, indicating that the concentration of molasses influenced the capacity of the produced surfactant to reduce the surface tension of water. Also, the microorganism was not capable of growing in the absence of yeast extract as nitrogen source. To the best of our knowledge, the presented results describe for the first time the nature of the biosurfactant produced by a bacterium of the Thermoanaerobacter genus.Key points• Thermoanaerobacter sp. CM-CNRG TB177 produces biosurfactants, and its glycolipid nature is described for the first time.• The HPLC analysis revealed a mixture of three rhamnolipid congeners, and UPLC/MS analysis determined that two of the congeners are the rhamnolipids Rha-C8-C10 and Rha-C12-C10.• The lowest surface tension of 29.67 mNm-1 was obtained with molasses as source of carbon at a 2.5% concentration.

Interactions of the molecular assembly of polysaccharide-protein systems as encapsulation materials. A review.

Studying the interactions of biopolymers like polysaccharides and proteins is quite important mainly due to the wide number of applications such as the stabilization and encapsulation of active compounds in complex systems. Complexation takes place when materials like proteins and polysaccharides are blended to promote the entrapment of active compounds. The interaction forces between the charged groups in the polymeric chains allow the miscibility of the components in the complex system. Understanding the interactions taking place between the polymers as well as between the wall material and the active compound is important when designing delivery systems. However, some features of the biopolymers like structure, functional groups, or electrical charge as well as extrinsic parameters like pH or ratios might affect the structure and the performance of the complex system when used in encapsulation applications. This work summarizes the recent progress of the polysaccharide/protein complexes for encapsulation and the influence of the pH on the structural modifications during the complexation process.

Dual modification of achira (Canna indica L) starch and the effect on its physicochemical properties for possible food applications.

The aim of this study was to evaluate the effect of acid hydrolysis and succination upon single and a combination of both of them as a dual modification on the morphological, structural, thermal, and pasting profile of the achira starch in order to expand its potential food applications. The surface of achira starch granules was eroded with acid hydrolysis, while the succination resulted in the formation of pores or cavities, having a slight impact on the crystallinity and the gelatinization enthalpy. Succinated starch presented the lowest transition temperatures (To = 60.29 °C, Tp = 65.03 °C and Te = 69.86 °C) compared to other starches in this study. The succination increased the final viscosity (3808 cp) when compared with the native starch (3114 cp), while acid hydrolysis resulted in a decreased value (735 cp). These are desirable properties for its possible use as an additive in bakery industry processes.

Rheological performance of film-forming solutions made from plasma-modified starches with different amylose/amylopectin content.

Normal and high amylose corn starches were modified using HMDSO plasma at different time treatments. Changes in functional properties of starch granule, film-forming solutions (FFS) and films were investigated. SEM analysis revealed HMDSO coating deposition on the granule surface, which limited the amylopectin leach out from the granules to the continuous matrix, affecting the rheological properties of the FFS. The amylopectin restriction resulted in a low reinforcement of the network decreasing the viscosity as indicated by n and k values. Also, a gel-like behavior (G' > G″) was observed when the amylose and time treatment increased, suggesting that the matrix becomes less elastic with softer entanglement. This behavior was confirmed by creep test and Burger model parameters. The plasma treatments allowed obtaining FFS with low viscosity, suitable for developing soft and hydrophobic films with low flexibility, as indicated by the decrease of the maximum stress, Hencky strain and permeance values.

Retrogradation of autoclaved corn starches: Effect of water content on the resistant starch formation and structure.

In this study, the resistant starch (RS) formation, crystallinity, and double helical order of autoclaved (120 °C) normal (ANS) and high amylose (AHS) corn starches retrograded at ~4-26% of water content were investigated. ANS and AHS retrograded at ~25-26% of water content were more crystalline (~35-40%) and formed by more close-packed double helices (R1000/1022 cm-1 = 1.145-1.290). The highest content of RS (38.8%) was found in AHS retrograded at 25.52% of water content meanwhile in ANS, the maximum content of RS was 6.6% at 21.60% of water content despite its structural order was increased with the increase of water content. The recrystallization of amylopectin interfered with the formation of homogeneous crystalline structures of amylose preventing the formation of retrograded RS in ANS, while in AHS, a relationship between structure and RS formation was observed, suggesting that the close-packed double helices and the proportion of homogeneous amylose crystallites increased the resistance to enzymatic digestion.

Six hundred years of South American tree rings reveal an increase in severe hydroclimatic events since mid-20th century.

South American (SA) societies are highly vulnerable to droughts and pluvials, but lack of long-term climate observations severely limits our understanding of the global processes driving climatic variability in the region. The number and quality of SA climate-sensitive tree ring chronologies have significantly increased in recent decades, now providing a robust network of 286 records for characterizing hydroclimate variability since 1400 CE. We combine this network with a self-calibrated Palmer Drought Severity Index (scPDSI) dataset to derive the South American Drought Atlas (SADA) over the continent south of 12°S. The gridded annual reconstruction of austral summer scPDSI is the most spatially complete estimate of SA hydroclimate to date, and well matches past historical dry/wet events. Relating the SADA to the Australia-New Zealand Drought Atlas, sea surface temperatures and atmospheric pressure fields, we determine that the El Niño-Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) are strongly associated with spatially extended droughts and pluvials over the SADA domain during the past several centuries. SADA also exhibits more extended severe droughts and extreme pluvials since the mid-20th century. Extensive droughts are consistent with the observed 20th-century trend toward positive SAM anomalies concomitant with the weakening of midlatitude Westerlies, while low-level moisture transport intensified by global warming has favored extreme rainfall across the subtropics. The SADA thus provides a long-term context for observed hydroclimatic changes and for 21st-century Intergovernmental Panel on Climate Change (IPCC) projections that suggest SA will experience more frequent/severe droughts and rainfall events as a consequence of increasing greenhouse gas emissions.

Films made from plasma-modified corn starch: Chemical, mechanical and barrier properties.

In this study, the chemical, mechanical and barrier properties of films made from plasma-modified corn starch (MSF) were evaluated as a function of the amylose content (30, 50 and 70 %). SEM analysis revealed the presence of remnant starch granules (RSG) in all films, which promoted the ordering of helices as suggested by the FTIR results. Moreover, XPS analysis was used to identify the oxidation mechanism in all MSF as the atomic proportion of hydroxyl, carbonyl and carboxyl groups changed. Also, the increase of C-C proportions suggested crosslinking in MSF70. TGA analysis indicated low interaction between starch and the plasticizer as the tensile strength and elongation at break diminished in MSF50 and MSF70 due to the low plasticizing effect of glycerol, the oxidation phenomena and the depolymerization of starch chains. However, the crosslinking of MSF70 showed characteristics of rigid films with good hydrophobic performance.

Double helical order and functional properties of acid-hydrolyzed maize starches with different amylose content.

Two maize starches (Normal and Hylon VII) were hydrolyzed using HCL for 15 days at room temperature. The water holding capacity -WHC and oil holding capacity- OHC were evaluated to describe the changes during the reorganization of hydrolyzed material. The structure was assessed using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR). A hydrolysis degree of 20% was reached with a complete granular structure disruption. During acid hydrolysis, the rearrangement of decoupled double helices favored the order degree. The hydrolysis of the amorphous region decreased the enthalpy of gelatinization. This effect was more noticeable in the normal starch. The changes promoted during the hydrolysis favored the reorganization of the network resulting in high values in WHC and OHC for both starches. The acid-treated starches obtained could be used as fillers, employing these materials with induced crystalline regions.

Regenerated cellulose films with chitosan and polyvinyl alcohol: Effect of the moisture content on the barrier, mechanical and optical properties.

The aim of this research was to evaluate the effect of moisture content on the mechanical, barrier and optical properties of films obtained from regenerated cellulose with chitosan and polyvinyl alcohol equilibrated at several relative humidity conditions. The experimental moisture adsorption isotherms were fitted using the Guggenheim-Anderson-DeBoer model. The adsorption isotherm showed a typical type II sigmoidal shape. The highest moisture content (27.53 %) was obtained at a water activity of 0.9. The water vapour permeability values increased up to 6.34·10-11 g/ m s Pa as the moisture content of the films increased. Tensile strength, percentage of elongation, Young's modulus, burst strength and distance to burst showed a significant plasticizing effect of the water molecules. Results suggest that interactions between film components and water molecules decrease the transmittance in the UV region and the transparency. Consequently, water molecules improve the UV-barrier properties of the films and increasing the opacity.

Environmentally Friendly Films Combining Bacterial Cellulose, Chitosan, and Polyvinyl Alcohol: Effect of Water Activity on Barrier, Mechanical, and Optical Properties.

The interest in developing new materials intended for food packaging based on bacterial cellulose is growing in the recent years. Flexible and transparent films from bacterial cellulose-chitosan-polyvinyl alcohol have shown excellent UV-barrier properties. However, this material interacts with ambient moisture modifying its water activity due to its hydrophilic nature. In this work, a study was carried out to evaluate the changes caused by the water activity. Results showed a plasticizing effect of water molecules increasing the water vapor permeability of the samples from 1.86 × 10-12 to 1.17 × 10-11 g/m·s·Pa, percentage of elongation from 3.25 to 36.55%, and distance to burst from 0.64 to 5.12 mm. The increase of the water activity decreased the Young's modulus and tensile strength. The values of the UV-barrier were maintained at the wide range of water activity. Consequently, water molecules do not affect the UV-barrier properties of the films.

HMDSO plasma treatment as alternative to modify structural properties of granular starch.

In the present study, the effect of plasma treatment on the structural properties of three granular corn starches (normal, Hylon V and Hylon VII) was investigated. Thermal (TGA/DSC), structural (XRD/FTIR) and chemical (XPS) properties were evaluated. Plasma treatment resulted in partial evaporation of water molecules changing the organization level of the double helices in the crystalline lamellae. Moreover, XRD results suggested a decrease of the long-range crystallinity and suggested changes in amylose chains after treatments. The crosslinking of modified amylose chains measured by XPS analysis resulted in variations in the gelatinization parameters as well as in its heterogeneous crystalline structure. The results indicate that the type and extent of changes in the structure of plasma-treated corn starch depends on the distribution of the water molecules inside the crystalline regions (helical water) and on the amylose content. In addition, the obtained results indicated that plasma treatment is a suitable method to modify starch without any incorporation of new elements from hexamethyldisiloxane (HMDSO), which only promotes stronger interactions between the starch main components.