Insights into Molecular Interactions between a GAPDH-Related Fish Antimicrobial Peptide, Analogs Thereof, and Bacterial Membranes.

Interactions between SJGAP (skipjack tuna GAPDH-related antimicrobial peptide) and four analogs thereof with model bacterial membranes were studied using Fourier-transform infrared spectroscopy (FTIR) and molecular dynamics (MD) simulations. MD trajectory analyses showed that the N-terminal segment of the peptide analogs has many contacts with the polar heads of membrane phospholipids, while the central α helix interacts strongly with the hydrophobic core of the membranes. The peptides also had a marked influence on the wave numbers associated with the phase transition of phospholipids organized as liposomes in both the interface and aliphatic chain regions of the infrared spectra, supporting the interactions observed in the MD trajectories. In addition, interesting links were found between peptide interactions with the aliphatic chains of membrane phospholipids, as determined by FTIR and from the MD trajectories, and the membrane permeabilization capacity of these peptide analogs, as previously demonstrated. To summarize, the combined experimental and computational efforts have provided insights into crucial aspects of the interactions between the investigated peptides and bacterial membranes. This work thus makes an original contribution to our understanding of the molecular interactions underlying the antimicrobial activity of these GAPDH-related antimicrobial peptides from Scombridae.

In vitro assessment of skin sensitization, irritability and toxicity of bacteriocins and reuterin for possible topical applications.

Bacteriocins and reuterin are promising antimicrobials for application in food, veterinary, and medical sectors. In the light of their high potential for application in hand sanitizer, we investigated the skin toxicity of reuterin, microcin J25, pediocin PA-1, bactofencin A, and nisin Z in vitro using neutral red and LDH release assays on NHEK cells. We determined their skin sensitization potential using the human cell line activation test (h-CLAT). Their skin irritation potential was measured on human epidermal model EpiDerm™. We showed that the viability and membrane integrity of NHEK cells remained unaltered after exposure to bacteriocins and reuterin at concentrations up to 400 µg/mL and 80 mg/mL, respectively. Furthermore, microcin J25 and reuterin showed no skin sensitization at concentrations up to 100 µg/mL and 40 mg/mL, respectively, while pediocin PA-1, bactofencin A, and nisin Z caused sensitization at concentrations higher than 100 µg/mL. Tissue viability was unaffected in presence of bacteriocins and reuterin at concentrations up to 200 µg/mL and 40 mg/mL, respectively, which was confirmed by measuring cytokine IL-1α and IL-8 levels and by histological analysis. In conclusion, the current study provides scientific evidence that some bacteriocins and reuterin, could be safely applied topically as sanitizers at recommended concentrations.

Bacteriocin-Based Synergetic Consortia: a Promising Strategy to Enhance Antimicrobial Activity and Broaden the Spectrum of Inhibition.

Bacteria-derived natural antimicrobial compounds such as bacteriocins, reruterin, and organic acids have recently received substantial attention as food preservatives or therapeutic alternatives in human or animal sectors. This study aimed to evaluate the antimicrobial activity of different bacteria-derived antimicrobials, alone or in combination, against a large panel of Gram-negative and Gram-positive bacteria. Bacteriocins, including microcin J25, pediocin PA-1, nisin Z, and reuterin, were investigated alone or in combination with lactic acid and citric acid, using a checkerboard assay. Concentrations were selected based on predetermined MICs against Salmonella enterica subsp. enterica serovar Newport ATCC 6962 and Listeria ivanovii HPB28 as Gram-negative and Gram-positive indicator strains, respectively. The results demonstrated that the combination of microcin J25 + citric acid + lactic acid; microcin J25 + reuterin + citric acid; and microcin J25 + reuterin + lactic acid tested against S. Newport ATCC 6962 showed synergistic effects (FIC index = 0.5). Moreover, a combination of pediocin PA-1 + citric acid + lactic acid; and reuterin + citric acid + lactic acid against L. ivanovii HPB28 showed a partially synergistic interactions (FIC index = 0.75). Nisin Z exerted a partially synergistic effect in combination with acids (FIC index = 0.625 -0.75), whereas when it was combined with reuterin or pediocin PA-1, it showed additive effects (FIC index = 1) against L. ivanovii HPB28. The inhibitory activity of synergetic consortia were tested against a large panel of Gram-positive and Gram-negative bacteria. According to our results, combining different antimicrobials with different mechanisms of action led to higher potency and a broad spectrum of inhibition, including multidrug-resistance pathogens. IMPORTANCE Reuterin and bacteriocins, including microcin J25, pediocin PA-1, nisin were produced and purified with >90% purity. Using the broth-based checkerboard assay the interaction between these compounds (synergetic, additive, or antagonistic) was assessed. By combining different natural antimicrobials with different modes of action and structure (reuteirn, microcin J25, pediocin PA-1, and organic acids), we successfully developed five different synergetic consortia with improved antimicrobial activity and a broad spectrum of inhibition. These consortia were shown to be effective against a large panel of pathogenic and spoilage microorganisms as well as clinically important multidrug-resistance bacteria. Moreover, because the lower concentrations of bacteriocins and reuterin are used in the synergetic consortia, there is a limited risk of toxicity and resistance development for these compounds.

In vitro investigation of gastrointestinal stability and toxicity of 3-hyrdoxypropionaldehyde (reuterin) produced by Lactobacillus reuteri.

Reuterin (3-hyrdoxypropionaldehyde (3-HPA)) is a highly potent metabolite of L. reuteri, which has applications in food, health, and veterinary sectors. Similar to other natural antimicrobial compounds, the approval of reuterin as a bio-preservative or therapeutic agent by regulatory agencies relies on sufficient data on its cytotoxicity and behavior in the gastrointestinal environment. Although the antimicrobial activity of reuterin has been broadly studied, its safety and toxicity are yet to be explored in detail. In this study, the stability and activity of reuterin were investigated in the gastrointestinal tract using in vitro models simulating gastrointestinal conditions. In addition, hemolytic activity and in vitro cytotoxicity of reuterin were evaluated by neutral red assay and lactate dehydrogenase (LDH) colorimetric assay using the same cell line. Activity of reuterin was observed to be stable during gastrointestinal transit. Viability and membrane integrity of cells remained unaltered by reuterin up to 1080 mM concentration. Furthermore, no hemolysis was observed in blood cells exposed to 270 mM reuterin. This study provides unique and highly relevant in vitro data regarding gastrointestinal behavior and toxicity of reuterin. In conclusion, the current study indicates that within a certain concentration range, reuterin can be safely used in bio-preservation and therapeutics applications. However, further in vivo studies are required to confirm these findings.

Gastrointestinal Stability and Cytotoxicity of Bacteriocins From Gram-Positive and Gram-Negative Bacteria: A Comparative in vitro Study.

Bacteriocins are receiving increased attention as potent candidates in food preservation and medicine. Although the inhibitory activity of bacteriocins has been studied widely, little is known about their gastrointestinal stability and toxicity toward normal human cell lines. The aim of this study was to evaluate the gastrointestinal stability and activity of microcin J25, pediocin PA-1, bactofencin A and nisin using in vitro models. In addition cytotoxicity and hemolytic activity of these bacteriocins were investigated on human epithelial colorectal adenocarcinoma cells (Caco-2) and rat erythrocytes, respectively. Pediocin PA-1, bactofencin A, and nisin were observed to lose their stability while passing through the gastrointestinal tract, while microcin J25 is only partially degraded. Besides, selected bacteriocins were not toxic to Caco-2 cells, and integrity of cell membrane was observed to remain unaffected in presence of these bacteriocins at concentrations up to 400 µg/mL. In hemolysis study, pediocin PA-1, bactofencin A, and nisin were observed to lyse rat erythrocytes at concentrations higher than 50 µg/mL, while microcin J25 showed no effect on these cells. According to data indicating gastrointestinal degradation and the absence of toxicity of pediocin PA-1, bactofencin A, and microcin J25 they could potentially be used in food or clinical applications.

Divergicin M35-Chitosan Film: Development and Characterization.

Chitosan films loaded with bacteriocin were examined by FTIR spectroscopy, tested for color, puncture strength, water vapor permeability, and as antimicrobials of Listeria innocua HPB13. Divergicin M35, a bacteriocin produced by Carnobacterium divergens, was incorporated into films made with chitosan of molecular mass 2 kDa, 20 kDa, or 100 kDa and de-acetylated either 87% or 95%. Only 100 kDa chitosan yielded films that could be peeled and handled easily. The higher degree of de-acetylation increased the total color factor (ΔE) of bacteriocin-loaded films, their permeability, and puncture strength. Incorporation of divergicin M35 into the films increased amide I peak intensity but otherwise did not induce significant structural change. The FTIR spectra of divergicin M35 shed from the films did not differ from those of the original free bacteriocin, except in overall peak intensity. The release of active divergicin M35 from the film was faster into the buffer than into tryptic soy broth and peaked at 10-12 h in both cases. Chitosan 95% de-acetylated and loaded with divergicin M35 was the most active, producing a six-log drop in Listeria innocua HPB13 viable count within 24 h. These results suggest that the biocompatible and biodegradable films developed here have the potential for application as antimicrobials of Listeria spp. in foods, especially ready-to-eat, minimally processed products.

Novel design for alginate/resistant starch microcapsules controlling nisin release.

This study aimed to develop a novel nontoxic, biocompatible, biodegradable, and cost-efficient matrix for the encapsulation of antimicrobial component (nisin) to be used as bio-preservative agent in cheddar cheese. Nisin A loaded beads were prepared from alginate at 0.5%, 1% and 2%; and hi-maize resistant starch at 0.5 or 1%. Beads were characterized by microscopic examination and transmission electron microscopy. Molecular structures were investigated by FTIR, and particle size distributions were measured. The Entrapment efficiency (EE) was measured microbiologically by agar diffusion. The encapsulated nisin showed similar inhibition activities in all developed formulas with an inhibition zone of 15 ± 2 mm. The FTIR analysis confirmed the compatibility of the nisin with sodium alginate and starch. The formulas composed of 1% Alginate and 0.5% Non-Gelatinized Starch had the highest encapsulation efficiency among other formulas (33%). Moreover, that formula allowed the protection and gradual release of the encapsulated nisin during a long-term storage for up to two months. Application in cheddar cheese proved the inhibition of encapsulated nisin on the growth of C. tyrobutyricum at the large-scale production. In conclusion, the alginate (Alg)/non-gelatinized resistant starch formula is suitable for the protection and controlled release of nisin in food applications.

Interaction of oil bodies proteins with phospholipid bilayers: A molecular level elucidation as revealed by infrared spectroscopy.

It is crucial to develop new natural sources of emulsifiers to substitute the synthetic molecules. An ideal emulsifying system exists in plants that is consisting of oil bodies proteins and phospholipids. In this study, Fourier transformed infrared (FTIR) spectroscopy was used to investigate the interactions between oil bodies proteins (OBP) and model phospholipid (PL) membranes. The secondary structure and PL thermotropism were investigated. Different PL varying in chain length and polar head were used including two zwitterionic phospholipids, dimyristoylphosphatidylcholine and dioleoylphosphatidylcholine, and two anionic phospholipids, dimyristoylphosphatidylglycerol, dipalmitoylphosphatidylglycerol. The changes in lipid physical state and protein denaturation were investigated as a function of temperature from 20 to 80 °C. OBP in solution is composed of unordered structures and ß-sheets with signs of aggregation. Anionic PL interacts with OBP whereas zwitterionic PL does not or only slightly interacts with the protein. Unsaturated PL promoted the α-helix structure in OBP. The interactions between OBP and PL depended on the protein charge inducing different protein conformations. Overall, the study showed that OBP and commercial anionic phospholipids have a potential in developing stable emulsifier for food industry.

The Impact of Chitosan-Divergicin Film on Growth of Listeria monocytogenes in Cold-Smoked Salmon.

The aim of this study was to evaluate the impact of chitosan film, with bacteriocin divergicin 35 incorporate, on growth of Listeria monocytogenes in Cold smoked salmon. The simples of Cold-smoked wild salmon were inoculated with L. monocytogenes and treated with chitosan (100 kDa, 94.7% de-acetylated) and divergicin M35 was stored for 3 weeks at 4-8°C. The compounds were applied to the fish flesh in the form of solution or dried film. The film reduced L. monocytogenes to below the detection limit (<50 cfu/g) and kept total counts below 104 cfu per g compared to 109 cfu per g in control samples while the effectiveness of the solution was very limited. The inhibitory activity of the film lasted for 3 weeks, while the solution had no effect on L. monocytogenes counts measured on day 14. The film provided a better preservation of fish color (redness) and firmness than others treatments, while the solution had little impact on these parameters. It kept the volatile basic nitrogen (17.5 mg N/100 g) below the control value 29.9 mg N/100 g. Divergicin-loaded chitosan film thus may represent an interesting alternative for the bio-preservation of cold-smoked fish.

Oral administration of lipid oil-in-water emulsions performed with synthetic or protein-type emulsifiers differentially affects post-prandial triacylglycerolemia in rats.

In this study, we compared the impact of administration of size-calibrated lipid emulsions prepared with either synthetic or natural emulsifiers on the post-absorptive plasma triacylglycerol responses in rats. We did this using four types of size-calibrated (10 µm diameter) and metastable (3 days) emulsions with 20% of an oleic acid-rich sunflower oil and 1% of either synthetic emulsifiers (Tween 80 or sodium 2-stearoyl-lactylate) or two proteins (ß-lactoglobulin or sodium caseinate). An oral fat tolerance test was performed in fasted rats by oral administration of each of these formulations in continuous or emulsified forms. Kinetic parameters (AUC0-inf., AUC0-6h, Cmax, Tmax, and T1/2) for the description of the plasma triacylglycerol responses were calculated. AUC0-6h and AUC0-inf. calculated for the protein groups were significantly lower than those of the control and the synthetic groups. These lower values were associated with significant decreases in the Cmax, exacerbated by the emulsion form and with marked decreases in the Tmax as compared to the control group. T1/2 values were differentially affected by the lipid administration forms and by the nature of the emulsifiers. As compared with the control group, T1/2 was largely increased in the sodium stearoyl-2-lactylate group, but on the contrary, largely lowered in the casein group. We concluded that the use of proteins as natural emulsifiers in lipid emulsions decreased the magnitude of post-prandial triacylglycerolemia for the same amount of ingested lipids, when the emulsion size is controlled for. Proteins could be a promising alternative to the widespread use of synthetic emulsifiers in the food industry.

Study and Understanding Behavior of Alginate-Inulin Synbiotics Beads for Protection and Delivery of Antimicrobial-Producing Probiotics in Colonic Simulated Conditions.

According to the World Health Organization (WHO), using antibiotics as growth promoters for livestock-particularly swine-is the principal cause of antibiotic resistance. It is therefore clear that finding an alternative to antibiotics becomes an emergency. Hundreds of recent studies have appointed probiotics as potential candidates to replace or to be used in combination with antibiotics. However, bringing probiotics alive to the colon-their site of action-remains a big challenge because of different physiological barriers encountered in proximal gastrointestinal tract (GIT) such as acidic pH and bile salts that may affect the viability of probiotic cultures. To overcome this problem, in previous studies, we developed and characterize a synbiotic formula consisting of beads of a mixture of alginate and inulin. Three potential probiotics strains namely Pediococcus acidilactici UL5 (UL5), Lactobacillus reuteri (LR), and Lactobacillus salivarius (LS) were encapsulated to study their release and the behavior of this synbiotic formula throughout the GIT using in vitro models. The survival and the release of bacteria from beads were studied by specific PMA-qPCR counting. The microscopic aspects of the beads were studied using scanning electron microscopy (SEM). Moreover, the microbial dynamics inside beads were studied by fluorescence microscopy using the live/dead test. Our results have shown that the beads containing 5% inulin were the most stable in the stomach and throughout the small intestine. However, beads were completely degraded in approximately 3 h of incubation in the fermented medium that mimic the colon. These results were confirmed by SEM and fluorescence microscopy images. Therefore, it can be stated that the AI5 formulation well protected the bacteria in the upper part of the digestive tract and allowed their controlled release in the colon.

The Tape Measure Protein Is Involved in the Heat Stability of Lactococcus lactis Phages.

Virulent lactococcal phages are still a major risk for milk fermentation processes as they may lead to slowdowns and low-quality fermented dairy products, particularly cheeses. Some of the phage control strategies used by the industry rely on heat treatments. Recently, a few Lactococcus lactis phages were found to be highly thermo-resistant. To identify the genetic determinant(s) responsible for the thermal resistance of lactococcal phages, we used the virulent phage CB14 (of the Lactococcus lactis 936 [now Sk1virus] phage group) to select for phage mutants with increased heat stability. By treating phage CB14 to successive low and high temperatures, we were able to select two CB14 derivatives with increased heat stability. Sequencing of their genome revealed the same nucleotide sequences as the wild-type phage CB14, except for a same-sized deletion (120 bp) in the gene coding for the tape measure protein (TMP) of each phage mutant, but at a different position. The TMP protein sequences of these mutant phages were compared with their homologues in other wild-type L. lactis phages with a wide diversity in heat stability. Comparative analysis showed that the same nucleotide deletion appears to have also occurred in the gene coding for the TMP of highly thermo-resistant lactococcal phages P1532 and P680. We propose that the TMP is, in part, responsible for the heat stability of the highly predominant lactococcal phages of the Sk1virus group.IMPORTANCE Virulent lactococcal phages still represent a major risk for milk fermentation as they may lead to slowdowns and low-quality fermented dairy products. Heat treatment is one of the most commonly used methods to control these virulent phages in cheese by-products. Recently, a few Lactococcus lactis phages, members of the Sk1virus group, have emerged with high thermal stability. To our knowledge, the genetic determinant(s) responsible for this thermal resistance in lactococcal phages is unknown. A better understanding of the thermal stability of these emerging virulent lactococcal phages is needed to improve industrial control strategies. In this work, we report the identification of a phage structural protein that is involved in the heat stability of a virulent Sk1virus phage. Identifying such a genetic determinant for heat stability is a first step in understanding the emergence of this group of thermostable phages.

Dual Coating of Liposomes as Encapsulating Matrix of Antimicrobial Peptides: Development and Characterization.

Antimicrobial peptides have been proposed as a potential biopreservatives in pharmaceutical research and agribusiness. However, many limitations hinder their utilization, such as their vulnerability to proteolytic digestion and their potential interaction with other food ingredients in complex food systems. One approach to overcome such problems is developing formulations entrapping and thereby protecting the antimicrobial peptides. Liposome encapsulation is a strategy that could be implemented to combine protection of the antimicrobial activity of the peptides from proteolytic enzymes and the controlled release of the encapsulated active ingredients. The objective of this study was to develop dual-coated food grade liposome formulations for oral administration of bacteriocins. The formulations were developed from anionic and cationic phospholipids as models of negatively and positively charged liposomes, respectively. Liposomes were prepared by the hydration of lipid films. Subsequently, the liposomes were coated with two layers comprising a biopolymer network (pectin) and whey proteins (WPI) in order to further improve their stability and enable the gradual release of the developed liposomes. Liposomes were characterized for their size, charge, molecular structure, morphology, encapsulation efficiency, and release. The results of FTIR, zeta potential, size distribution, and transmission electron microscopy (TEM) confirmed that the liposomes were efficiently coated. Ionic interactions were involved in the stabilization of the positively charged liposome formulations. Negatively charge liposome formulations were stabilized through weak interactions. The release study proved the efficiency of dual coating on the protection of liposomes against gastrointestinal digestion. This work is the first to study the encapsulation of antimicrobial peptides in dual-coated liposomes. Furthermore, the work successfully encapsulated MccJ25 in both negative and positive liposome models.

Molecular and biopharmaceutical investigation of alginate-inulin synbiotic coencapsulation of probiotic to target the colon.

Colon targeting, as a site-specific delivery for oral formulation, remains a major challenge, especially for sensitive bioactive components such as therapeutic forms of phages, live attenuated virus and prebiotics-probiotics association. Synbiotics could be used to protect encapsulated probiotics during the gastrointestinal tract and control their release in the colon. To achieve these goals, effective prebiotics, such as inulin, could be combined with alginate - the most exploited polymer used for probiotic encapsulation - in the form of beads. This work aimed to study the biopharmaceutical behaviour of alginate beads (A) and inulin-alginate beads of different inulin concentrations (5 or 20%) in 2% alginate (AI5, AI20). Beads were loaded with three probiotic strains (Pediococcus acidilactici Ul5, Lactobacillus reuteri and Lactobacillus salivarius). Dissolution of beads was studied by USP4 under conditions simulating the gastrointestinal condition. The survival rates of the bacterial strains were measured by a specific qPCR bacterial count. Mucoadhesiveness of beads was studied by an ex vivo method using intestinal mucosa. To understand the behaviour of each formulation, the ultrastructure of the polymeric network was studied using scanning electron microscopy (SEM). Molecular interactions between alginate and inulin were studied by Fourier transform infra-red spectroscopy (FTIR). Dissolution results suggested that the presence of inulin in beads provided more protection for the tested bacterial strains against the acidic pH. AI5 was the most effective formulation to deliver probiotics to the colon simulation conditions. FTIR and SEM investigations explained the differences in behaviour of each formula. The developed symbiotic form provided a promising matrix for the development of colonic controlled release systems.

Molecular Structure of Lactoferrin Influences the Thermal Resistance of Lactococcal Phages.

The protective effect of whey proteins on phages of lactic acid bacteria during heat treatment limits the recycling of whey proteins into cheese. To investigate this protective effect, we used lactoferrin (LF) as a whey protein model as a result of its unique physicochemical properties and its antiviral activity. First, the thermal inactivation of lactococcal thermoresistant virulent phage P1532 was measured in LF at 95 °C and under different pH values. Phage inactivation results revealed a strong protective effect of LF on P1532 phage at pH 5 but none at pH 7. The structural conformational changes of LF were then monitored by Fourier transform infrared and circular dichroism spectroscopies. Spectroscopic analysis showed that LF was unfolded after heating at pH 7, while it preserved its tertiary and secondary structures when heated at pH 5. There is a direct correlation between the thermal stability of LF and its ability to protect P1532 phage from heat treatment.

Collagencin, an antibacterial peptide from fish collagen: Activity, structure and interaction dynamics with membrane.

In this study, we first report characterization of collagencin, an antimicrobial peptide identified from fish collagen hydrolysate. The peptide completely inhibited the growth of Staphylococcus aureus at 1.88 mM. Although non-toxic up to 470 µM, collagencin was hemolytic at higher concentrations. The secondary structure of collagencin was mainly composed by ß-sheet and ß-turn as determined by CD measurements and molecular dynamics. The peptide is likely to form ß-sheet structure under hydrophobic environments and interacts with both anionic (phosphatidylglycerol) and zwitterionic (phosphoethanolamine and phosphatidylcholine) lipids as shown with CD spectroscopy and molecular dynamics. The peptide formed several hydrogen bonds with both POPG and POPE lipids and remained at membrane-water interface, suggesting that collagencin antibacterial action follows a carpet mechanism. Collagenous fish wastes could be processed by enzymatic hydrolysis and transformed into products of high value having functional or biological properties. Marine collagens are a promising source of antimicrobial peptides with new implications in food safety and human health.

A prebiotic matrix for encapsulation of probiotics: physicochemical and microbiological study.

This work aims to develop an encapsulated oral-synbiotic supplement by studying the effect of adding inulin in alginate beads and observing its ability to protect three probiotic strains: Pediocucus acidilactici, Lactobacillus reuteri and Lactobacillus salivarius. Beads of different inulin concentrations 0%, 5%, 10%, 15% and 20% (w/v) in 2% (w/v) alginate solution were prepared by the extrusion/ionotropic gelation method. Polymer distribution within beads was characterised using confocal laser scanning microscopy. Interactions between alginate and inulin were monitored by Fourier transform infra-red spectroscopy (FTIR). Effect of encapsulation on viability, antimicrobial ability, acid tolerance and bile tolerance of probiotic strains were investigated. Antimicrobial and probiotic properties of bacterial strains were not affected by encapsulation. Bacterial protection against acidity was increased by adding inulin. Beads with 5% w/v inulin were the most effective in bacterial protection against bile-salts. To our knowledge, this work is the first to use such high concentrations of inulin.

Effect of resveratrol or ascorbic acid on the stability of α-tocopherol in O/W emulsions stabilized by whey protein isolate: Simultaneous encapsulation of the vitamin and the protective antioxidant.

Food proteins have been widely used as carrier materials due to their multiple functional properties. Hydrophobic bioactives are generally dissolved in the oil phase of O/W emulsions. Ligand-binding properties provide the possibility of binding bioactives to the protein membrane of oil droplets. In this study, the influence of whey protein isolate (WPI) concentration and amphiphilic resveratrol or hydrophilic ascorbic acid on the decomposition of α-tocopherol in the oil phase of WPI emulsions is considered. Impact of ascorbic acid, in the continuous phase, on the decomposition depended on the vitamin concentration. Resveratrol partitioned into the oil-water interface and the cis-isomer contributed most of the protective effect of this polyphenol. About 94% of α-tocopherol and 50% of resveratrol were found in the oil droplets stabilized by 0.01% WPI. These results suggest the feasibility of using the emulsifying and ligand-binding properties of WPI to produce carriers for simultaneous encapsulation of bioactives with different physicochemical properties.

Edible film production from chia seed mucilage: Effect of glycerol concentration on its physicochemical and mechanical properties.

This study investigated the physicochemical and mechanical properties of a novel edible film based on chia mucilage (CM) hydrocolloid. CM (1% w/v) films were prepared by incorporation of three concentrations of glycerol (25%, 50%, and 75% w/w, based on CM weight). As glycerol concentration increased, water vapor permeability (WVP), elongation at break (EB), and water solubility of CM films increased while their tensile strength (TS), and Young's modulus (YM) decreased significantly (p<0.05). CM films containing a high concentration of glycerol were slightly reddish and yellowish in color but still had a transparent appearance. CM films exhibited excellent absorption of ultraviolet light, and good thermal stability. The scanning electron micrographs showed that all CM films had a uniform appearance. This study demonstrated that the chia mucilage hydrocolloid has important properties and potential as an edible film, or coating.

Investigation of the protective effect of whey proteins on lactococcal phages during heat treatment at various pH.

The incorporation of whey protein concentrates (WPC) into cheese is a risky process due to the potential contamination with thermo-resistant phages of lactic acid bacteria (LAB). Furthermore, whey proteins can protect phages during heat treatment, thereby increasing the above risk. The main objective of this work was to understand this protective effect in order to better control LAB phages and maximize whey recycling in the cheese industry. First, the inactivation of a previously characterized thermo-resistant lactococcal virulent phage (P1532) was investigated at 95 °C in WPC, in individual whey components ß-lactoglobulin, α-lactalbumin, and bovine serum albumin as well as under different heat and pH conditions. The structural changes of the tested proteins were also monitored by transmission FTIR spectroscopy. Phage inactivation results indicated that the protective effect of whey proteins was pH and time dependent at 95 °C and was not restricted to one component. FTIR spectra suggest that the protection is related to protein molecular structures and to the level of protein aggregates, which was more pronounced in acidic conditions. Moreover, the molecular structure of the three proteins tested was differently influenced by pH and the duration of the heat treatment. This work confirms the protective effect of WPC on phages during heat treatment and offers the first hint to explain such phenomenon. Finding the appropriate treatment of WPC to reduce the phage risk is one of the keys to improving the cheese manufacturing process.