جستجوی مقالات مرتبط با کلیدواژه "ضدمیکروب" در نشریات گروه "صنایع غذایی"

Oxidation and food pathogens are considered two important and influential factors affecting food quality and health. Recently, due to the increasing demand for natural products, the application of synthetic preservatives to control microbial growth and lipid oxidation have been decreased significantly. Therefore, natural antioxidant and antimicrobial compounds are receiving more attention in food preservation technologies. In the last 2 decades, the use of herbal medicines rich in bioactive molecules (including polyphenols, carotenoids and flavonoids) with medicinal and health effects such as delaying the onset of some diseases such as cardiovascular disorders, diabetes, and cancer have increased. Furthermore, secondary metabolites in plant extracts and essential oils are able to control and inhibit free radical-mediated reactions. The olive tree (Olea europaea) is an evergreen plant that grows in tropical and subtropical regions. Iran is one of the most important olive growers in the world due to its suitable conditions for olive cultivation. The leaves of the olive plant have a high potential for the production of various products such as tea and extracts. Olive leaf extract can be used as a raw material in the production of various products, due to exhibiting various biological activities such as antimicrobial and antiviral activity, lipid stabilizer, blood pressure regulator, antioxidant activity, and free radical scavenger. The leaves of the olive tree also contain various phenolic compounds, mainly Oleuropein and hydroxytyrosol, with antioxidant and antimicrobial activities. Therefore, in this study, the amount of phenolic and flavonoid compounds of olive leaf ethanolic extract and its antioxidant effect and antimicrobial properties on Escherichia coli, Enterobacter aerogenesis, Bacillus cereus and Listeria innocua were investigated. 

The olive leaf ethanolic extract was prepared through maceration method and its total phenolic content (Folin-Ciocalteu method), total flavonoids content (aluminum chloride colorimetric assay), antioxidant activity (ABTS and DPPH free radical scavenging methods), and antimicrobial effect on E. coli, E. aerogenesis, B. cereus and L. innocua (based on disk diffusion agar, well diffusion agar, minimum inhibitory concentration, and minimum bactericidal concentration) were determined according to standard methods. Data were analyzed by SPSS software through one-way ANOVA and Duncan test at p<0.05.  

The ethanolic extract of olive leaves contained 176.58 ± 0.72 mg GAE/g total phenol and 69.85 ± 0.26 mg QE/g total flavonoids. In addition, ethanolic extract of olive leaf was able to inhibit free radicals DPPH (70.62 ± 0.59%) and ABTS (76.15 ± 0.43%). The antimicrobial results showed that the antimicrobial effect of the extract depended on its concentration and type of bacteria. Antimicrobial effect was increased as a function of ethanolic extract, and Gram-positive bacteria (B. cereus and L. innocua) were more sensitive to ethanolic extract of olive leaf than Gram-negative bacteria (E. aerogenesis and E. coli). Generally, B. cereus and E. aerogenesis were the most sensitive and resistant microbial strains to ethanolic extract of olive leaf, respectively.The results of this study showed that the high antioxidant and antimicrobial activity of olive leaf ethanolic extract is mainly due to its phenolic and flavonoid compounds. Olive leaf ethanolic extract was able to neutralize DPPH and ABTS free radicals. Also, Gram-positive bacteria were more sensitive to ethanolic extract of olive leaf than Gram-negative bacteria. In general, the ethanolic extract of olive leaf can be used as a nutraceutical to control or prevent the growth of spoilage/infection-causing microorganisms and free radical reactions in food and the human body. However, more in-depth studies are needed to determine the mechanism of antimicrobial and antioxidant effects of olive ethanolic extract in vitro and in vivo.

Meat and their products are highly sensitive to microbial growth and lipid oxidation development, which lead to economic losses and health hazards (Kiarsi et al., 2020). Edible coatings are currently receiving a great deal of attention as novel food packaging to increase the quality and shelf-life of various food products through preventing physical, chemical, and biological deteriorations (Barzegar et al., 2020). Okra (Ablemoschus esculentus) is an annual plant and rich in valuable nutrients such as vitamins and elements such as phosphorus, manganese, potassium and calcium and also contains phytosterols, tannins and carbohydrates. Okra contains large amounts of viscous gum with a thickening property. Edible coatings are able to carry active compounds such as antioxidants and antimicrobials, as well as nutrients and essential oils (Ashrafi Yorganloo and Gheybi, 2018). Peppermint (Mentha piperita) is one of the most widely used medicinal plants due to biological effects of its main components, especially menthol. Its essential oil is used as a flavoring in chewing gum, mint chocolate, medicines and toothpaste (Kazem Alvandi et al., 2010). The antimicrobial and antioxidant properties of peppermint essential oil have been investigated. To the best of our knowledge, there is no report in the literature regarding the effect of edible coating of Okra gum containing peppermint essential oil on meat quality and shelf life during refrigeration. This study is therefore aimed to develop a novel edible coating based on Okra gum-peppermint essential oil to improve the shelf life of buffalo meat slices.

Peppermint essential oil and Okra were purchased from Dezful and Ahvaz, respectively. The chemical compounds of the essential oil were identified and quantified by a gas chromatography coupled to a mass spectrometer. The total phenol content (Noshad et al., 2020), total flavonoid content (Rahmati‐Joneidabad and Alizadeh Behbahani, 2021), ABTS-radical scavenging effect (Hojjati and Alizadeh Behbahani, 2021), antimicrobial effect (Disc diffusion agar, well diffusion agar, and minimum inhibitory/bactericidal concentration) of the essential oil were determined. The oil (0, 0.5, 1, 1.5, 2%) was then added to Okra gum solution to prepare edible coatings for buffalo meat coating purposes. The physiochemical (pH, moisture content, peroxide value, and hardness), microbial (Total viable count, psychrotrophic count, E. coli, S. aureus, and Fungi count), color (L*, b*, and a*), and sensory (odor, color, appearance, texture, and overall acceptance) of buffalo meat slices were evaluated during storage period (10 days, 4 °C).

The essential oil contained menthol (47.17%) and menthone (23.29%) and its total phenolic content, flavonoid content, and ABTS radical scavenging effect were 77.20 mg GAE/g, 47.50 mg QE/g, and 62.60% respectively. The essential oil was also able to inhibit the growth of P. aeruginosa, E. coli, S. aureus, B. cereus, and B. subtilis. The functional groups of the compounds of peppermint essential oil were observed at 2955, 2923, 2870, 1711, 1455, 1369, 1247, 1044, 993, and 887 cm-1. The edible coating was able to prevent the pH increase in buffalo meat samples during storage. The control and samples coated with Okra gum containing 0, 0.5, 1, 1.5, and 2% essential oil had 11.26, 11.40, 6.40, 4.51, and 4.39% water loss during storage. The peroxide value of control and Okra gum+2%essential oil coated samples were increased by 7.33- and 2.28-folds, respectively, as the storage time increased up to 10 days. The lower oxidation development in the coated samples could be probably due to the low oxygen permeability of the coating and the antioxidant activity of the essential oil. Although the hardness of samples decreased during storage, the essential oil-rich coated samples had remarkably higher hardness values compared to the control sample, likely due to the inhibitory effect of the essential oil against the activity of endogenous proteolytic enzymes of the buffalo meat. The edible coatings loaded with higher concentration of the oil were more effective in inhibiting microbial growth in buffalo meat samples during cold storage. This could be attributed to the antimicrobial effect of the essential oil and the oxygen-barrier function of the edible coating. The L* and b* of the coated samples were also higher in comparison to the non-coated sample; whilst, they were generally less red, probably due to myoglobin conversion to metmyoglobin under low-oxygen pressure conditions of the edible coating, along with exudate accumulation in the coated buffalo meat samples. The coated samples with higher essential oil concentrations were also generally more acceptable in term of sensory properties. Generally, the sensory attributes were in good agreements with the chemical and microbial results; the lower the microbial growth and oxidation, the higher were the sensory properties.

The Okra gum-peppermint essential oil based edible coating could be introduced as a novel edible coating to inhibit the microbial growth and lipid oxidation of buffalo meat and increase its shelf-life and other food products. Keywords: Antimicrobial, Antioxidant, Chemical composition, Edible coating, Okra gum, Peppermint essential oil, Shelf-life.

Lipid oxidation leads to the generation of off-flavors and potential toxic compounds. Synthetic antioxidants are frequently applied for inhibiting this reaction, however; there is a concern regarding to the potent toxic effects of synthetic antioxidants on human health. The non-enzymatic glycosylation reaction (Maillard reaction) has been broadly used to ameliorate the biological and functional features of proteins and polysaccharides. The Maillard reaction produces products with versatile functions such as antioxidant, antimicrobial, antihypertensive, anti-browning, and prebiotic properties. In this regard, the Maillard reaction products (MRPs) can be used in the food industry to inhibit the oxidation reaction due to their superb antioxidant effect. In this study, chitosan was glycosylated with inulin, fructose, and glucose. Chitosan is a chitin derivative with cationic nature having antimicrobial, antioxidant, metal chelation, and film-forming features. Inulin is recognized as a prebiotic sugar with vast applications in food and pharmaceutical sciences. The purpose of this study was to chemically modify chitosan through the Maillard reaction in order to boost its antioxidant and antimicrobial properties.
 

Chitosan (0.5% w/v) was dissolved in 1.0% v/v acetic acid solution followed by stirring for 1.0 h at room temperature. Afterwards, sugars inulin, glucose, and fructose were separately added to the chitosan solution at final concentration of 1.0% w/v. The obtained solutions were then stirred until complete sugar dissolution. The pH of solution was adjusted to 6.07 by adding 2.0 M sodium hydroxide and then the chitosan-sugar Maillard conjugates were fabricated through autoclaving the solutions at 121 °C. Changes in pH after the reaction were measured using a pH meter. The extent of the Maillard reaction was estimated via measuring the absorbance of the conjugated solutions at 294 nm (the intermediate products) and 420 nm (final products). Fourier transform infrared (FTIR) spectroscopy at transmission mode and 400-4000 cm-1 was employed to evaluate the structural changes of chitosan upon conjugation. Antioxidant activity of the conjugates was evaluated based on the reducing power assay. One mL of the samples was charged with 1.0 mL of distilled water and 1.0 mL of potassium ferricyanide (1.0% w/v). The solution was mixed and incubated at 50 °C for 20 min. After adding 2.5 mL of tri-chloroacetic solution (10% w/v), the obtained solution was centrifuged at 5000 g for 5.0 min. Afterwards, 2.0 mL of the supernatant was mixed with 2.0 mL of distilled water and 1.0 mL of ferric chloride (0.1% w/v). The solution was stand for 10 min at ambient temperature and then its absorbance was recorded at 700 nm. Antimicrobial effect of the conjugates against pathogenic microorganisms (E. coli, S. aureus, B. subtilis, P. aeruginosa, A. niger, and C. albicans) was measured according to the minimum inhibitory (MIC) and microbiocidal (MBC) concentrations. SPSS software (version 21) and one-way ANOVA were applied for data analysis. Duncan’s multiple range test was employed to determine the differences between means.
 

The Maillard reaction led to a significant decrement in pH value of chitosan-saccharide systems, mainly due to the covalent coupling of amino groups of chitosan to carbonyl groups of reducing sugars in conjugation with the production of acetic and formic acids. The highest intermediate compounds (A 294nm) and lowest browning intensity (A 420nm) observed in chitosan-fructose conjugate, which was likely attributed to the lower reactivity of fructose. Chitosan-inulin conjugate presented the highest A 420nm and lowest intermediate-to-final ratio (A 294nm/A 420nm), probably due to the lower inulin molecules and subsequently carbonyl groups compared to fructose and glucose. These groups may react with amino groups of chitosan at initial reaction times, leading more conversion rate of the intermediate compounds to the final ones. FTIR spectra of the chitosan and conjugates revealed that absorbance peak at 1661 cm-1 in chitosan spectrum decreased and shifted to 1578 cm-1 (in chitosan-fructose conjugate), 1579 cm-1 (in chitosan-glucose conjugate), and 1580 cm-1 (in chitosan-inulin conjugate), indicating the stretching C-N group and -C=N group and the formation of Schiff base (-C=N) between reducing end of the saccharides and amino groups of chitosan. Reducing power of the chitosan-saccharide systems improved after the thermal process. Although, chitosan-glucose and chitosan-fructose conjugates had significantly higher reducing power than unconjugated counterparts, but chitosan-inulin conjugate showed non-significantly improved antioxidant activity compared to its non-heated mixture. Antioxidant activity of the Maillard conjugates was ascribed from the electron donating ability of their hydroxyl and pyrrole groups. The conjugates had lower MIC and MBC in comparison to their unconjugated pairs, except for chitosan-glucose conjugate, which showed no differences in MIC and MBC compared with its non-heated mixture. Antimicrobial property of the Maillard products, especially melanoidins has been attributed to their metal chelating features; melanoidins exert a bacteriostatic effect at low concentration and bactericidal effect at high levels through sequestering ionic iron from medium and magnesium from outer membrane, leading to the cell membranes destabilization. Additionally, antioxidant capacity, high surface activity, and inhibiting effect towards catabolic enzymes have been reported as another antimicrobial mechanisms of the Maillard products. In general, it can be concluded that chitosan-saccharide Maillard-based conjugates, particularly inulin-chitosan one could be used in the food sector as a novel prebiotic-based active bio-compound with antioxidant and antimicrobial features.

Essential oils and extracts of medicinal plants with antimicrobial, anticancer and antioxidant activity are important as a new drug compounds in the field of health and protection of raw and processed foods or healthier food products. The aim of this study was to compare the antioxidant and antibacterial properties of ethanol extracts of Hypericum perforatum
and Hibiscus gossypifolius. The antibacterial properties against pathogenic bacteria (Salmonella enterica, Bacillus cereus, Escherichia coli and Staphylococcus aureus) using well diffusion and antioxidant activity were also tested using Trolox Equivalent Antioxidant Capacity (TEAC) method with ABTS+●. The results revealed that Staphylococcus aureus was the most sensitive bacteria to Hypericum and Hibiscus extracts and there was no significant difference between two extracts (P≥0.05). The results revealed that there was a significant difference between antioxidant activity of Hibiscus and Hypericum (P<0.05). Evaluation of antioxidant activity showed that the IC50 of Hypericum and Hibiscus was 1.56±0.31 mg/mL and 0.78±0.2 mg/mL, respectively. Therefore, Hibiscus gossypifolius had higher antioxidant capacity than Hypericum perforatum. The results showed that ethanol extracts of Hypericum and hibiscus had antioxidant and antibacterial activity; therefore, they can be used in food and pharmaceutical industries as natural additive.

Todays, the tendency to use of natural preservatives to increase food security has expanded. The objective of this study was to use of lemon and green tea essential oils as antimicrobial and antioxidant compounds in oily cake. For this purpose, lemon and green tea essential oil in concentrates 0.1, 0.2, and 0.3% separately and in combination (0.2% green tea essential oil and 0.2% lime essential oil) were added to oily cake. Physico-chemical properties, anti-oxidant properties, microbial and sensory properties of the samples were evaluated, 2 hours after production and as well as at 7, 14, 21 and 28 days. The results showed that with increasing storage time, moisture content and pH in all treatments significantly decreased and acidity increased in all treatments. Comparison of the antioxidant and antimicrobial properties of oily cake containing green tea and lemon essential oils with control showed that the use of essential oils significantly prevented of the increase of peroxide and thiobarbituric index and the growth of mold and yeast during storage. The antioxidant properties of the treatments showed that the lowest levels of thiobarbituric and peroxide index were observed in a sample containing 0.3% green tea essential oil and combined treatment after 28 days of storage. Antimicrobial properties of the treatments indicated that there was no mold or yeast growing in the cake containing 0.2% and 0.3% lime essential oil and combined treatment after 28 days of storage. The results of sensory evaluation showed that the combined treatment had higher scores in terms of odor, color, taste, texture and overall acceptance and it was introduced as superior treatment.