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

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 ofattributes peculiar to nanoemulsions such as optical clarity, ease ofpreparation, 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

Comparison of Antioxidant and Antibacterial Activities of Free and Encapsulated Garlic Oil with Beta-cyclodextrin

Background and Objectives: Application of garlic oil in food industry can be improved by encapsulation. There is no study about the formation of inclusion complex of garlic oil by beta-cyclodextrin. The aim of the present study is comparison of the antioxidant and antibacterial activities of free and encapsulated garlic oil with beta-cyclodextrin.Materials and Methods: Antioxidant activity was determined by 1, 1- diphenyl-2- picryl-hydrazyl assay, and antibacterial properties by agar well diffusion, minimum inhibitory concentration, minimum bactericidal concentration and bacterial growth assay. Statistical analysis was performed by Minitab statistical software.Results and conclusion: Garlic oil had poor antioxidant activity (EC50, 5222 µg ml-1 ) and EC50 because garlic oil/beta-cyclodextrin (containing 1495 µg ml-1 released garlic oil) was achieved after 5 h and 25 min. Agar well diffusion showed no inhibition zone on Muller Hinton Agar for garlic oil and garlic oil/betacyclodextrin (with initial release (shaking at 150 rpm for 24 h at 37ºC) and without initial release). Staphylococcus aureus was the most susceptible bacterium to garlic oil, and garlic oil/beta-cyclodextrin with and without initial release (minimum inhibitory concentration 10-5 , 10-4 and 10-3 % w v -1 , respectively); however, Bacillus cereus was the most resistant. The effect of initial release for garlic oil/betacyclodextrin on inhibiting the growth of all four bacteria was significant. There was no significant difference (P>0.05) between the inhibitory effect of garlic oil and garlic oil/beta-cyclodextrin with initial release on Staphylococcus aureus and Bacillus cereus, also Salmonella entrica and Escherichia coli. Garlic oil showed a weak antioxidant activity in 1, 1- diphenyl-2-picryl-hydrazyl assay. Garlic oil and its complex were not able to penetrate to the solid media; therefore, no inhibition zone and no antibacterial activity in the agar well diffusion assay were observed. Initial release of garlic oil/beta-cyclodextrin had significant impact on the inhibition of four bacterial growth, similar to free garlic oil. Since encapsulation of garlic oil can cover its drawbacks (low solubility in water, liquid form, and intense odor), garlic oil/beta-cyclodextrin could be considered as an nonsynthetic antibacterial agent.Conflict of interests: The authors declare no conflict of interest

Use of Encapsulated Garlic Oil in Low-Fat Salad Dressings: Physicochemical, Microbial and Sensory Properties

Background and Objective: Fresh garlic includes several preservative and medicinal characteristics; however, its major bioactive components react and convert to other chemical compounds as soon as its tissues are injured. Garlic oil is extracted from garlic and its use in food industries is limited due to its strong odor, taste, volatility and low solubility in aqueous solvents. The aim of the present study was to investigate physicochemical, microbial and sensory properties of low-fat salad dressings containing encapsulated garlic oil in ß-cyclodextrin (GO/ß-CD). Material and Methods: Five types of salad dressing, including control with no garlic oil, a sample with free garlic oil and three samples containing 546, 818 and 1364 mg GO/ß-CD kg-1 salad dressing were prepared. Then, pH, color and antioxidant [(peroxide value and thiobarbituric acid reactive substances], antimicrobial (monitoring of four pathogens of Bacillus cereus, Staphylococcus aureus, Escherichia coli and Salmonella enterica) and sensory (taste, color, odor and acceptability by 8-point hedonic test) properties of the samples were assessed during 41 days of storage at 4 oC. Results and Conclusion: The minimum and the maximum color differences belonged to GO/ß-CD-3 sample containing 1364 mg GO/ß-CD kg-1 salad dressing and sample containing free GO, respectively. Yellowness of samples containing encapsulated GO decreased and direct relationships were seen between decreasing of the sample yellowness and quantity of GO/ß-CD sample. During the storage, pH and peroxide value PV slightly increased. Staphylococcus aureus was the most sensitive strain to free and encapsulated garlic oil. Escherichia coli, Salmonella enterica and Bacillus cereus showed lower sensitivities to the oil. Sensory results showed no significant differences between the tastes of control and free or encapsulated garlic oil and GO/ß-CD-2 samples containing 818 mg kg-1 encapsulated garlic oil, equal to 90 mg kg-1 free garlic oil. However, these two treatments included significant differences with samples containing free garlic oil. Results revealed that encapsulation of garlic oil with ß-CD included no adverse effects on taste of the salad dressings. Therefore, GO/ß-CD-2 (818 mg GO/ß-CD kg-1 salad dressing) can be suggested as a natural antimicrobial agent for the functional mayonnaise production. Conflict of interest: The authors declare no conflict of interest

Statistical Optimization of Tannase Production by Penicillium sp. EZ-ZH390 in Submerged Fermentation

Tannase has several important applications in food, feed, chemical and pharmaceutical industries. In the present study, production of tannase by mutant strain, Penicillium sp. EZ-ZH390, was optimized in submerged fermentation utilizing two statistical approaches. At first step, a one factor at a time design was employed to screen the preferable nutriments (carbon and nitrogen sources of the medium) to produce tannase. Screening of the carbon source resulted in the production of 10.74 UmL-1 of tannase in 72 h in the presence of 14% raspberry leaves powder. A 1.99-fold increase in tannase production was achieved upon further screening of the nitrogen source (in the presence of 1.2% ammonium nitrate). Then the culture condition variables were studied by the response surface methodology using a central composite design. The results showed that temperature of 30°C rotation rate of 85 rpm and fermentation time 24 h led to increased tannase production. At these conditions, tannase activity reached to 21.77 UmL-1, and tannase productivity was at least 3.55 times (0.26 UmL-1h-1) in compare to those reported in the literature. The present study showed that, at the optimum conditions, Penicillium sp. EZ-ZH390 is an excellent strain for use in the efficient production of tannase

The Effect of Non-thermal Processing of Hyssopus officinalis on its Antioxidant and Antimicrobial Activities

Hyssopus of­ficinalis L. is one of the most important medicinal plants. Medicinal herbs are contaminated by microorganisms. Conventional methods for reducing of microbial loads such as ethylene oxide, propylene oxide and also use of steam are hazardous and instead, non-thermal process such as microwave and gamma radiation are being used widely in order to eliminate the microbial contaminations with no or a little side effect. In the present study the effect of gamma and microwave irradiation on antioxidant and antimicrobial activities of Hyssopus of­ficinalis L. was investigated. Hyssopus samples were exposed to gamma  irradiation at doses 10, 15, 20 and 25 kGy and microwave irradiationat power of 300, 450 and 600 W for 5 min. In order to undergo the sequence experiments, the hydroalcoholic (EtOH 50%) extracts of plant were prepared. The antioxidant activities of irradiated and control samples were evaluated by DPPH radical scavenging (RS), ferric reducing power (FRP), β-carotene bleaching (BCB) and total phenolic content (TPC) of sampels. In order to study the antimicrobial activity, for determination of minimal inhibitory concentration (MIC) on E. coli and S. aureus,broth diluting method was used. Results showed that gamma irradiation had no significant effect on antioxidant parameters, phenolic content and antimicrobial activities of sampels. Microwave treatment of Hyssopus at 300, 450 and 600 W for 5 min increased its antioxidant and antimicrobial activities. Results indicated that gamma and microwave irradiation do not have any negative effect on antioxidant and antimicrobial activities of Hyssopus

Optimization of Phospholipase A1 Immobilization on Plasma Surface Modified Chitosan Nanofibrous Mat

Phospholipase A1 is known as an effective catalyst for hydrolysis of various phospholipids in enzymatic vegetable oil degumming. Immobilization is one of the most efficient strategies to improve its activity, recovery and functional properties. In this study, chitosan-co-polyethylene oxide (90:10) nanofibrous mat was successfully fabricated and modified with atmospheric plasma at different times (2, 6 and 10 min) to interact with enzyme molecules. Scanning electron microscopy images revealed that the membranes retained uniform nanofibrous and open porous structures before and after the treatment. PLA1 was successfully immobilized onto the membrane surfaces via covalent bonds with the functional groups of chitosan nanofibrous mat. Response surface methodology was used to optimize the immobilization conditions for reaching the maximum immobilization efficiency. Enzyme concentration, pH, and immobilization time were found to be significant key factors. Under optimum conditions (5.03 h, pH 5.63, and enzyme dosage 654.36 UI), the atmospheric plasma surface modified chitosan nanofibers reached the highest immobilization efficiency (78.50%). Fourier transform infrared spectroscopy of the control and plasma surface-modified chitosan nanofibers revealed the functional groups of nanofibers and their reaction with the enzyme. The results indicated that surface modification by atmospheric plasma induced an increase in PLA1 loading on the membrane surfaces

Fat Bloom and Polymorphism in Chocolate Prepared with Modified Tea Seed Oil

Abstract In order to produce cocoa butter replacer (CBR), tea seed oil was modified with enzymatic interesterification. The modified product was then added to dark chocolate formulation as a replacement for 10%, 15% and 20% of cocoa butter (CB) to study fat bloom formation and polymorphic structure in these samples. Keywords Fat bloom; Polymorphism; Chocolate; Modified tea seed oil Practical Applications According to our results, higher levels of fat bloom occurred in the chocolate sample without CBR (chocolate containing 100% CB, CBCH), compared with other chocolate samples. However, among the chocolates containing enzymatic interesterified sample (EIS) at various levels of 10%, 15% and 20%, the chocolate sample containing 10% of EI (EICH) showed lower fat bloom development during storage period (20 days). The results of polymorphic structure evaluation using X-ray diffractometer (XRD) showed new β-crystalline form with the XRD pattern close to that of β-VI and the m.p. appeared similar to β-V in CB. Also, XRD pattern of EIS showed β′-crystalline form in this sample. Presence of two crystalline forms (β and β′) in the EICH revealed that, adding 10% of the CBR prepared in the current study to chocolate formulation had probably no adverse effect on β-crystal formation in the chocolate sample

Investigation of creep fatigue crack propagation in aluminium tube

Tubular structure is extensively used from domestic to aviation kind of applications. Life and safety are most considered in designing tube structure that against failure. For the last 200 years of research output and understanding, it was estimated that about 90% of metal failures were due to the external or surface defect and environmental attacks. The present work had focused on damage tolerant fatigue life prediction on aluminium cylindrical structures. Endurance tests were conducted with a constant amplitude repetitive loading at both, in room and high temperatures. A notch is introduced by wire cut machined on external surface and in a straight line with circumferential orientation to represent an external defects and flaws. Crack growth rates were measured by imaging technique. The experimental results suggested that the creep fatigue life is shorter than conventional fatigue life. The effect of stress ratio is also presented. The fully reversed with high temperature results registered the most severe damage with tremendous of life reduction

Investigation of Measurement Methods of Antioxidant Activity and Involved Mechanisms

Bioactive food components are active ingredients in food or dietary supplements proven to have a role in health and they are safe for human consumption. These compounds exert their antioxidant effects by different mechanisms such as hydrogen atom transfer (HAT) or single electron transfer (SET) and their efficiencies can be evaluated by several methods such as ferric reducing ability of plasma (FRAP), trolox equivalent antioxidant capacity (TEAC), dipheny-picrylhydrazil (DPPH), Folin-Ciocaltue method (FCM), etc. In this review, these mechanisms and methods will be discussed in details

Statistical Optimization of Tannase Production by Penicillium sp. EZ-ZH390 in Submerged Fermentation

Tannase has several important applications in food, feed, chemical and pharmaceutical industries. In the present study, production of tannase by mutant strain, Penicillium sp. EZ-ZH390, was optimized in submerged fermentation utilizing two statistical approaches. At first step, a one factor at a time design was employed to screen the preferable nutriments (carbon and nitrogen sources of the medium) to produce tannase. Screening of the carbon source resulted in the production of 10.74 U/mL of tannase in 72 h in the presence of 14% raspberry leaves powder. A 1.99-fold increase in tannase production was achieved upon further screening of the nitrogen source (in the presence of 1.2% ammonium nitrate). Then the culture condition variables were studied by the response surface methodology using a central composite design. The results showed that temperature of 30°C rotation rate of 85 rpm and fermentation time 24h led to increased tannase production. At these conditions, tannase activity reached to 21.77 U/mL, and tannase productivity was at least 3.55 times (0.26 U/mL.h) in compare to those reported in the literature. The present study showed that, at the optimum conditions, Penicillium sp. EZ-ZH390 is an excellent strain for use in the efficient production of tannase.</p