Review Article

Nanoemulsions: Preparation, Structure, Functional Properties and their Antimicrobial Effects

Najmeh Shams, Mohammad Ali Sahari

Applied Food Biotechnology, Vol. 3 No. 3 (2016), 28 Tir 2016, Page 138-149

Background and Objectives: Recently, due to the interest of healthy lifestyle demand for research on novel methods of increasing the shelf-life of food products without the necessity of using preservatives has extended rapidly in the world. Ability of nanoemulsions to improve global food quality has attracted great attention in food preservation. This is as a result of a number of
attributes peculiar to nanoemulsions such as optical clarity, ease of
preparation, thermodynamic stability and increased surface area. This review discusses the potential food applications of nanoemulsions as vehicles for the delivery of antimicrobial compounds. Moreover, the preparation, structure, and functional properties of nanoemulsions and their antimicrobial effects on foodborne pathogens and biofilms will be reviewed in detail. Antimicrobial nanoemulsions are formulated from the antimicrobial compounds that are approved by the Food and Drug Administration (FDA) for use in foods.

Results and Conclusion: The antimicrobial activity of nanoemulsions is nonspecific, unlike that of antibiotics, thus they have a broad-spectrum of antimicrobial activity against bacteria (e.g., Escherichia coli, Salmonella, and Staphylococcus aureus), enveloped viruses (e.g., HIV, and herpes simplex), fungi (e.g., Candida, Dermatophytes), and spores (e.g., anthrax) at concentrations that are nontoxic in animals (while limiting the capacity for the generation of resistance) and kill pathogens by interacting with their membranes. This physical kill-on-contact mechanism significantly reduces the possibility of the emergence of resistant strains. In general, more research is needed to improve the application processes of antimicrobial nanoemulsion, especially sensory aspects, to be appropriate for each product.

Conflict of interests: The authors declare no conflict of interest.

Original Article

Screening for Genetically Modified Maize in Raw and Processed Foods Sold Commercially in Southern Nigeria Boarder States

Christiana Ngozi Opara, Aniekpeno Isaac Elijah, Leonard Governor Adamu, Sylvia Veronica Uzochukwu

Applied Food Biotechnology, Vol. 3 No. 3 (2016), 28 Tir 2016, Page 150-158

Genetically Modified (GM) foods hold the key to ending hunger and malnutrition in Africa.   Due to the increasing number of GMOs cultivation and delay in the approval of biosafety law in Nigeria, it has become necessary to screen maize products in order to determine the identity of the consumed daily foodstuffs. In this study, DNA extraction from raw and processed maize foods sold commercially in Sourthen Nigeria was carried out using the cetyltrimethylammonium bromide (CTAB) method, followed by qualitative PCR to detect genetically modified maize. The recombinant DNA target sequences were detected with primers highly specific for each investigated transgene such as CAMV35S, nopaline synthase (NOS) terminator, Bt-176 and NK603 genes separately. Certified reference materials were used as positive controls while 2008-DTMA-W-STR Federal University of Agriculture Abeokuta (FUNAAB) organic maize grains and absence of template DNA, served as negative control. Based on the gel electrophoresis results, Bt- 176 maize event for insect resistance was detected in two samples, with 420 bp and, the NK603 Maize event for herbicide tolerance was detected in 3 samples, with 320 bp fragments. The GM-positive samples were found in 4 imported raw maize samples, 4 cereal food brands (2 manufactured in Nigeria, 2 imported) and 3 imported canned corn brands. The results confirm that Nigerians are already consuming GM maize, despite the absence of a biosafety law.   

Potential Health Effects of Enzymatic Protein Hydrolysates from Chlorella vulgaris

Mahsa Sedighi, Hasan Jalili, Seyed-Omid Ranaei-Siadat, Abdeltif Amrane

Applied Food Biotechnology, Vol. 3 No. 3 (2016), 28 Tir 2016, Page 160-169

Background and Objective: Chlorella vulgaris is a multi-cellular edible algal species with abundant proteins. Extraction of high value protein fractions for pharmaceutical and nutritional applications can significantly increase the commercial value of microalga biomasses. There is no known report on the anticancer peptides derived from the Chlorella vulgaris abundant protein.
Materials and Methods: This study examined the antimicrobial and anticancer effects of peptides from a hydrolyzed Chlorella vulgaris protein with 62 kDa molecular weight. Protein hydrolysis was done by pepsin as a gastrointestinal protease, and was monitored through protein content measurement, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and high performance liquid
chromatography measurements. Inhibitory effect of the produced peptides on Escherichia coli cells and breast cancer cell lines was assayed.
Results and Conclusion: Hydrolyzed peptides induced a decrease of about 34.1% in the growth of Escherichia coli, and the peptides of 3 to 5 kDa molecular weight had strong impact on the viability of breast cancer cells with IC50 value of 50 μg μl-1. The peptide fractions demonstrating antimicrobial and anti-cancer activities have the potential for use as functional food ingredients for health benefits. These results demonstrate that inexpensive algae proteins
could be a new alternative to produce anticancer peptides.

Conflict of interest: The authors declare that there is no conflict of interest.

Background and Objective: Constant use of limited number of lactic acid bacteria species in biopreservation can cause genetic degradation and or rising resistance against food pathogens or antimicrobial substances they produce. For this objective, a newly isolated strain of Lactobacillus acidophilus possessing high antimicrobial activity was evaluated as a candidate for use in biopreservation.

Materials and Methods: Antibacterial activity was evaluated by agar disk diffusion method. Hydrogen peroxide amount was measured by Merckoquant Peroxide test strips. Microbiological analysis of the ground beef infected by Escherichia coli O157:H7 and treated by Lactobacillus acidophilus GH 201was done by plating of serial dilution in physiological saline on Tryptose agar.

Results and Conclusion: The cells (109 CFU ml-1) of Lactobacillus acidophilus produced significant amount of antibacterial substances mainly hydrogen peroxide (28 and 30 μg ml-1) in sodium phosphate buffer (0.2 M, pH 6.5) and LAPTg at 5°C during submerged cultivation with no growth, respectively. Submerged co-cultivation of Escherichia coli O157:H7 with lactobacilli in LAPTg broth at 5°C reduced the total number of the pathogen more than 2 log for 5 days. In case of solid state cultivation on agar-based medium, the maximum inhibitory zones on Escherichia coli O157:H7 lawn around the disks soaked by different amounts of washed Lactobacillus acidophilus cells appear for one-day cold exposition. The size of inhibition zone depends on the concentration of lactic acid bacteria cells. The cell suspension intended for treatment must contain 108-9
CFU ml-1 of lactic acid bacteria. Lactobacillus acidophilus reduced the initial amount (2×105 CFU ml-1) of Escherichia coli O157:H7 in ground beef up to 2 log for 5 days of solid-state co-cultivation. The application of Lactobacillus acidophilus bacteria expanded the shelf-life of ground beef due to inhibition of psychrophilic spoilage microorganisms.

Conflict of interests: The authors declare no conflict of interest.

Background and Objective: Oxidative stress, due to free radicals, brings injury to the body by attacking large molecules and cell organs, and is the main reason of many diseases. Fermentation of foods containing large amount of proteins such as milk by special species of lactic acid bacteria is a potential way in enhancement of the antioxidative activity of foods. This study aimed at evaluating non-common starter species isolates of Lactobacillus helveticus for their capability to produce fermented milk enriched in antioxidant peptides.
Materials and Methods: Reconstituted skim milk (11%) was inoculated with 7 wild isolates of Lactobacillus helveticus, and after 24 h fermentation at 37ºC, the samples were kept 4ºC and for 14 days. Viable cell number, acidification and proteolysis degree in the milk fermented by each isolate were assessed in 1, 7 and 14 days. Development of antioxidant activity was measured using DPPH and ABTS●+ radial scavenging activities during the storage period.
Results and Conclusion: Though some slight strain-dependent differences were observed in growth, acidification and proteolysis, all the samples showed considerably strong antioxidant activity (at least 62.32±3.66% and 57.64±1.42% measured using DPPH and ABTS●+ radicals, respectively) through the whole storage period. In vitro simulated gastrointestinal digestion indicated that DPPH radical-scavenging activity of the antioxidative peptidic supernatants was not affected significantly by consecutive pepsin-pancreatin hydrolysis in most of the samples. These evidences support Lactobacillus helveticus as a promising functional culture able to promote health benefits in dairy-based functional foods.
Conflict of interest: The authors declare that there is no conflict of interest.

Growth Optimization of Lactobacillus plantarum T5jq301796.1, an Iranian Indigenous Probiotic in Lab Scale Fermenter

Faranak Noori, Maryam Tajabadi Ebrahimi, Parvaneh Jafari

Applied Food Biotechnology, Vol. 3 No. 3 (2016), 28 Tir 2016, Page 188-193

Background and Objective: Lactobacillus plantarum is one of the probiotics species used in functional food products. These bacteria or their purified bacteriocins are used as biological preservatives in the food industry. The first step in production of an array of probiotic products is optimizing production in fermentors. This study aimed to examine factors affecting the in vitro growth optimization of Lactobacillus plantarum T5JQ301796.1 in a lab scale fermentor.
Materials and Methods: Following 24 hours of anaerobic culture of the lactobacillus at 37°C, the pre-culture was ready and was inoculated to a 5 liter fermentor at 37°C and stirred at 40 rpm. Then factors affecting lactobacillus growth including carbon and nitrogen sources and pH were studied. The results were interpreted using response surface methodology (RSM), and optimal conditions for the equipment were determined.
Results and Conclusion: For optimal growth of Lactobacillus plantarum T5JQ301796.1 in lab scale fermentor, the optimal conditions were 25.96 gl-1 of glucose, 1.82% of yeast extract, pH of 7.26, and stirring at 40 rpm at optimum temperature between 37-40°C. In this condition, maximum viable cell in the batch fermentation was 1.25×1010 CFU ml-1. Application of central composite design for the growth optimization of this bacterium led to maximum viable cells equal to 1.25×1010 CFU ml-1. So the mentioned features can lead to optimum industrial scale production and usage of this probiotic strain in probiotic products.
Conflict of interest: The authors declare that there is no conflict of interest.

Effect of Fatty Acids on Hydrophobicity of the Cell Membrane of Lactobacillus Species

Sharareh Shahbazi, Leila Nateghi, Ashot Aghababyan

Applied Food Biotechnology, Vol. 3 No. 3 (2016), 28 Tir 2016, Page 194-200

Background and Objectives: Probiotic bacteria are able to absorb fatty acids present in the culture medium and convert them into intracellular fatty acids, which may affect the physicochemical properties of probiotics. Subsequently, changing the composition of cellular fatty acids of probiotics improves the electron acceptance capacity of these microorganisms, and results in an increased adhesion to the intestinal mucus. In the present study, the effect of fatty acids on the physicochemical and adhesion properties of Lactobacillus species was investigated.
Materials and Methods: Seven fatty acids including palmitic, stearic, α-linolenic, γ-linolenic, oleic, linoleic and arachidonic acids were used for the enrichment of MRS medium. Afterwards, fatty acid content and adhesion property were measured using GC and spectrophotometer, respectively.
Results and Conclusion: The results showed that the type of microorganism and fatty acid had a significant effect (p≤0.05) on the adhesion property of probiotics. According to the results, the highest membrane fatty acid content was found for myristic and elaidic acid, and the lowest content for α-linoleic acid.

Conflict of interests: The authors declare no conflict of interest.