Ahmed Gomaa

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 Youngs 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.

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

Abstract 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.

Electro-activation of sweet defatted whey: Impact on the induced Maillard reaction products and bioactive peptides

Electro-activation was used to add value to sweet defatted whey. This study aimed to investigate and to characterize the bioactive compounds formed under different electro-activation conditions by molecular and proteomic approaches. The effects of electric current intensity (400, 500 or 600mA) and whey concentration (7, 14 or 21% (w/v)) as a function of the electro-activation time (0, 15, 30 or 45min) were evaluated. The targeted dependent variables were the formation of Maillard reaction products (MRPs), protein hydrolysates and glycated compounds. It was shown that the MRPs derived from electro-activated whey at a concentration of 14% had the highest potential of biological activity. SDS-PAGE analyses indicated the formation of hydrolysates and glycated compounds with different molecular weight distributions. FTIR indicated the predominance of intermediate MRPs, such as the Schiff base compounds. LC-MS/MS and proteomics analysis showed the production of multi-functional bioactive peptides due to the hydrolysis of whey proteins.

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 β-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.

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 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.

Predictive Response Surface Model for Heat‐Induced Rheological Changes and Aggregation of Whey Protein Concentrate

Whey proteins are now far more than a by-product of cheese processing. In the last 2 decades, food manufacturers have developed them as ingredients, with the dairy industry remaining as a major user. For many applications, whey proteins are modified (denatured) to alter their structure and functional properties. The objective of this research was to study the influence of 85 to 100 °C, with protein concentration of 8% to 12%, and treatment times of 5 to 30 min, while measuring rheological properties (storage modulus, loss modulus, and complex viscosity) and aggregation (intermolecular beta-sheet formation) in dispersions of whey protein concentrate (WPC). A Box-Behnken Response Surface Methodology modeled the heat denaturation of liquid sweet WPC at 3 variables and 3 levels. The model revealed a very significant fit for viscoelastic properties, and a lesser fit for protein aggregation, at temperatures not previously studied. An exponential increase of rheological parameters was governed by protein concentration and temperature, while a modest linear relationship of aggregation was governed by temperature. Models such as these can serve as valuable guides to the ingredient and dairy industries to develop target products, as whey is a major ingredient in many functional foods.

Effect of electro-activated sweet whey on growth of Bifidobacterium , Lactobacillus , and Streptococcus strains under model growth conditions

Recently, we demonstrated the efficacy of electro-activation to improve the functionalities of whey that can be used as a prebiotic and antioxidant agent through lactulose and Maillard reaction products formation. The aim of the present study was to evaluate the effect of electro-activated sweet whey (EA-whey) on growth of probiotics of Bifidobacterium, Lactobacillus, and Streptococcus strains in pure cultures and to compare EA-whey with non-electro-activated whey, lactulose, lactose, sucrose, glucose and galactose at different concentrations (1.25, 2.5 and 5%). The bacterial growth was monitored through maximum optical density (ODmax) and maximum growth rate (μmax) measurements. Moreover, the effects of EA-whey on the growth of L. johnsonii La-1 in the presence of oxygen was assessed. FTIR spectroscopy analyses of the bacterial membrane structure were monitored as a function of EA-whey concentration. The results showed that EA-whey enhanced the growth of all the test bacteria. They clearly demonstrated a promoting bifidogenic effect of EA-whey compared to lactulose. The growth of L. johnsonii La-1 was greatly enhanced under aerobic conditions by the supplementation of the growth medium with EA-whey. This growth promoting effect could be related to the ability of EA-whey to prevent the accumulation of hydrogen peroxide, its high antioxidant capacity and lactulose content. Moreover, FTIR spectra showed that EA-whey acts as an antioxidant in regards to cell membrane lipids oxidation by oxygen species and limited their adverse effect on probiotic bacteria during their growth. Thus, EA-whey, a potential prebiotic and antioxidant, could be used as active ingredient in manufacturing functional fermented dairy products.

Design and Synthesis of Lasso-Inspired Peptides with Antibacterial Activity

Microcin J25 (MccJ25) is a 21-residue ribosomally synthesized bactericidal peptide produced by Escherichia coli strains with an unusual lariat protoknot structure [1]. MccJ25 exhibits bactericidal activity toward several Gram-negative food-borne pathogens, including Salmonella, Shigella and E. coli [2]. The particular lasso topology of MccJ25 makes the peptide highly resistant to denaturation by high temperatures or proteolysis. These are attractive properties to both pharmaceutical and food industries. MccJ25 structure consists of an 8-residue cycle (lariat ring) formed by a lactam bond between the N-terminal amine and the Glu side chain, which is followed by a 13-residue tail that loops back to thread through the ring (Figure 1). The C-terminal tail (residues 9-21) of the peptide is tightly trapped in the lariat ring due to the presence of two aromatic side chains at positions 19 and 20. RNA polymerase appears to be the principal intracellular target of MccJ25 but other mode of actions have also been identified including inhibition of the respiratory chain [3-5]. SAR studies by site-directed mutagenesis revealed that the inhibitory activity of MccJ25 tolerates a number of residue substitutions [6]. Recent attempts to produce the lasso structure of MccJ25 by chemical synthesis have not yielded successful microbial inhibitors. Nevertheless, two synthetic peptides derived from MccJ25 without lasso folding were found to be bactericidal [7]. The current lack of information on MccJ25 structure and its essential features for antimicrobial activity could be overcome by chemical engineering and computational studies. We hypothesized that lasso formation is important but not a prerequisite for the activity of MccJ25 and that it may be possible to obtain derivatives that are active without the lasso structure [8]. In this study, we report synthetic peptides based on the MccJ25 sequence but devoid of lasso folding yet retaining activity against bacteria (S. enterica and E. coli) and specific intracellular targets (RNA polymerase and the respiration chain).