Assessing the protection mechanisms against Enterobacter aerogenes by analyzing aggregation, adherence, antagonistic activity, and safety properties of potentially probiotic strain Lactobacillus brevis G145.

The aim of this study was to evaluate the probiotic potential of Lactobacillus brevis G145 isolated from traditional Khiki cheese, analyzing pH and bile resistance, physicochemical properties of the strain (hydrophobicity, auto- and co-aggregation), cholesterol removal, hydroxyl radical scavenging activity, adhesion ability to Caco-2 cells monolayer, and adhesion competition on Enterobacter aerogenes (competition, inhibition and replacement assays). Also, DNase, haemolytic activity, biogenic amine production and antibiotic susceptibility was investigated. L. brevis G145 was resistant to acidic pHs, bile salts, and simulated gastrointestinal conditions, and showed remarkable cell surface hydrophobicity (49.56%), co-aggregation (28.90%), auto-aggregation (34.10%), adhesion (9.40%), cholesterol removal (45.50%), and antioxidant (52.19%) properties. According to the results of well diffusion agar and disc diffusion agar tests, the highest and lowest inhibition zones were accounted for Staphylococcus aureus and Enterobacter aerogenes, respectively. The isolate did not show haemolytic, DNAse, and biogenic amine production properties. It was sensitive to antibiotics erythromycin, ciprofloxacin, and chloramphenicol, and semi-sensitive to imipenem, ampicillin, nalidixic acid, and nitrofurantoin. According to the findings of probiotic tests L. brevis G145 can be used as a in the food industry.

Effect of Malva neglecta and lactulose on survival of Lactobacillus fermentum and textural properties of synbiotic stirred yogurt.

Yogurt is a popular dairy product and its consumption has been progressively growing over the past few decades by raising consumers' health-consciousness. As yogurt is growing in popularity, manufacturers are continuously seeking for bioactive components such as probiotics and prebiotics, to produce functional yogurt with more beneficial health effects. Therefore, this study aimed to evaluate the effect of Malva neglecta (MN, 0, 5, 10 and 15%) and lactulose (0, 1 and 2%) as prebiotic substances on survival of Lactobacillus fermentum in a half-fat synbiotic stirred yogurt. The results revealed that with increasing MN and lactulose concentrations, the count of Lb. fermentum significantly increased (p < 0.05). At the end of 21-day cold storage, the count of probiotics in yogurt sample having 2% lactulose and 10-15% MN significantly was higher than control (8.37-8.4 vs. 7.73 Log cfu/g). With increasing the amount of MN and lactulose, firmness and chewiness of yogurt samples decreased while adhesiveness increased (p < 0.05). Scanning electron microscopy assessment shown that addition of MN and lactulose resulted in a higher moisture retention in the void spaces. The results revealed that by incorporating lactulose and MN in yogurt formulation, an appropriate synbiotic yogurt could be produced as a novel functional product.

Investigation of the chemical properties of Mentha pulegium essential oil and its application in Ocimum basilicum seed mucilage edible coating for extending the quality and shelf life of veal stored in refrigerator (4°C).

Nowadays, the tendency toward the application of natural preservatives to extent the shelf life of food products has grown. The purpose of the present research was to evaluate the effect of the basil seed mucilage (BSM)-based edible coating containing different concentrations of Mentha pulegium essential oil (MPEO) on the shelf life of the veal stored at refrigerator temperature. Firstly, the chemical composition and functional groups of MPEO were detected through gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FTIR). Then, the BSM-based edible coatings containing 0%, 0.5%, 1%, 1.5%, and 2% MPEO were prepared, and the veal samples were coated with them. The physicochemical, microbial, and sensory properties of the samples were investigated during the 9-day storage period at 4°C. Twenty-five compounds were detected in MPEO with limonene being the major one (28.44%). The results revealed that the lightness, hardness, and moisture content of the samples decreased during storage. The coating containing the essential oil could properly restrain the rise in pH, peroxide value (PV), and thiobarbituric acid value (TBA). Based on microbial analyses, the shelf life of the coated sample without the essential oil and those containing 0.5%, 1%, 1.5%, and 2% of the essential oil were, respectively, extended up to 3, 6, 9, 9, and 9 days relative to the control. Moreover, the coating containing the essential oil produced no unfavorable effect on the sensory properties of the meat samples. In conclusion, the BSM-based edible coating containing different concentrations of MPEO can be applied as a natural preservative to enhance the resistance of meat products against microbial spoilage and fat oxidation.

Safety, probiotic properties, antimicrobial activity, and technological performance of Lactobacillus strains isolated from Iranian raw milk cheeses.

The objective of this study was to investigate probiotic, antimicrobial, technological and safety properties of lactobacillus strains isolated from local Iranian cheese made from raw milk. Six different samples were prepared, after serial dilution, culture was performed on MRS culture medium. The gram-positive and catalase-negative lactobacillus strains were subjected to grouping and identifying using biochemical tests, carbohydrates fermentation profiles, and 16S rDNA analysis. The results of sequence analysis showed the Lactobacillus spp. belonged to Lactobacillus brevis, Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus casei. After 3 hr incubation at pH=2, 3-6 log units of strains decreased which Lactobacillus acidophilus (B14) and Lactobacillus brevis (B2) showed highest resistance to low pH as well as simulated GIT juices. The highest and lowest hydrophobicity degree was belonged to L. acidophilus (B14) (65.9%) and L. casei (B22) (25.6%), respectively. Also, the highest auto-aggregation and coaggregation were observed in L. acidophilus (B14) (51.3%) and L. plantarum (B20) (43.6%). The adhered percentage of strains varied from 2.5% to 14.6%. L. plantarum (B20) showed highest proteolytic activity followed by L. acidophilus (B14). Also, the highest autolytic activity belonged to L. acidophilus (B14). All of the strains showed low acidifying potential, except for L. acidophilus (B17) which decreased 2.05 unit of pH after 24 hr. The isolates did not show lipolytic activity as well as biogenic amines production (except L. brevis B3). All of the strains were sensitive to chloramphenicol and erythromycin except L. acidophilus (B15) and L. casei (B22). All strains showed no hemolysis activity which make them safe for consumption. Based on the obtained results, L. acidophilus (B14) presented the best probiotic and technological characteristics and is proposed for using as coculture in the dairy industrial.

Quality retention and shelf life extension of fresh beef using Lepidium sativum seed mucilage-based edible coating containing Heracleum lasiopetalum essential oil: an experimental and modeling study.

The instability and strong flavor or odor of essential oils (EO) limit their direct incorporation into food products. In this study, the antioxidant and antimicrobial Heracleum lasiopetalum essential oil (HLEO) was added to Lepidium sativum seed mucilage (LSSM) solution at four concentrations (0, 0.5, 1, and 1.5%) to develop a novel edible coating and expand its food application. HLEO-loaded LSSM coating was then used to improve the shelf life and quality of beef as a model food system. The coated and control beef samples were periodically analyzed for physicochemical analysis, microbiological, and sensory characteristics over a period of 9 days at 4 °C. The HLEO-enriched LSSM coating, particularly 1.5% loaded one resulted in a significant (p < 0.05) increase in oxidative and microbiological stability and overall acceptance of the beef samples, compared to the control counterpart. HLEO-loaded LSSM coating, therefore, provides a promising alternative to preserve the meat products under cold storage.

The preparation, characterization and in vitro application evaluation of soluble soybean polysaccharide films incorporated with cinnamon essential oil nanoemulsions.

In this study, we developed the new bioactive film from soluble soybean polysaccharide (SSPS) incorporated with different concentrations of cinnamon essential oil nanoemulsions (CNO) and the functional properties of them were evaluated. Then CNO-SSPS film was applied on the meat during refrigerate for 8 days. The use of CNO in film production has reduced thickness, water vapor permeability, water solubility, lightness (L*), redness (a*) and whiteness (WI) and increased antioxidant activity of SSPS-films. Also, the SSPS- film containing 0.6% CNO activity only on gram-positive bacteria (Staphylococcus aureus and Streptococcus pyogenes) and SSPS- film containing 0.8% CNO had antimicrobial activity on gram-positive and gram-negative bacteria. In vitro application, the pH of the meat treated with CON remained in the natural pH of meat during storage (8 days). Based on the results, the highest and lowest hardness values were for the samples of CNO- 0.8 and control, respectively. Incorporating CON at 0.6 and 0.8% concentration of cinnamon reduced 4.14 and 5.71 log cycle in the total aerobic viable count compared to uncoated and decreased of yeast and molds on 8th day by 1 log cycle compared uncoated. These resulted showed CNO-SSPS film can be used as a good preservative in meat products.

Effect of potassium sorbate on antimicrobial and physical properties of starch-clay nanocomposite films.

Using fresh foods which undergo the least processing operations developed widely in recent years. Active packaging is a novel method for preserving these products. Active starch-clay nanocomposite films which contained potassium sorbate (PS) at a level of 0, 5, 7.5 and 10 g PS/100 g starch were produced and their physical, mechanical and antimicrobial properties were evaluated. In order to evaluate antimicrobial properties of films Aspergillus niger was used. The results showed that 5% of the PS did not produce antimicrobial property in the film, but by increasing the content of the additive in film formulation, antimicrobial effect increased. PS increased water permeability and elongation at break of the films, but decreased tensile strength. The rate of PS migration into the semi-solid medium in starch-nanocomposites was lower than starch films. This shows that nanocomposite films could retain their antimicrobial property for longer time.