Food Biotechnology
Mostafa Rahmati-Joneidabad; Behrooz Alizadeh Behbahani; Mohammad Noshad
Abstract
IntroductionStrawberry and grapes are generally infected with pathogenic fungi (e.g., Aspergillus niger, Botrytis cinerea, Rhizopus stolonifera, etc.). Synthetic fungicides are commonly used as the first line of defense against post-harvest pathogens on packaging lines. However, disposal of toxic waste ...
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IntroductionStrawberry and grapes are generally infected with pathogenic fungi (e.g., Aspergillus niger, Botrytis cinerea, Rhizopus stolonifera, etc.). Synthetic fungicides are commonly used as the first line of defense against post-harvest pathogens on packaging lines. However, disposal of toxic waste is a costly process and the hazardous waste causes serious environmental problems. In addition, fungal pathogens have shown a worrying trend of resistance to these fungicides, thus shortening the shelf life of products. Compounds that can be equally effective in controlling pathogens, but preventing or minimizing the waste problems will be inevitable. The large volume of internationally processed agricultural products, as well as the increasing demand for organically produced fruits, emphasizes the need to replace synthetic fungicides with safer and biodegradable alternatives. Natural plant-derived products effectively meet this criterion and have great potential to influence modern agricultural research. Catechins and other polyphenols in green tea show strong antioxidant activity. Also, the antimicrobial activity of green tea extract against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans has been reported. Therefore, the present study was performed to prepare the ethanolic extract of green tea and to determine the content of total phenol, total flavonoids, antioxidant activity, and its antifungal effect against Aspergillus niger, Botrytis cinerea, and Rhizopus stolonifer (causing rot in strawberry and grapes). Materials and MethodsFresh green tea leaves were dried at room temperature and then powdered. Then, ethanol (70%) was added to the powdered leaves (solvent to powder ratio of 10:1 v/w) and the mixture was refluxed for 120 min. The resulting mixture was filtered through a filter paper and then concentrated under vacuum and finally dried in an oven.Total phenol content (by Folin-Ciocalteu reagent at 756 nm), total flavonoid content (spectrophotometrically at 510 nm), antioxidant activity (by DPPH and ABTS radical scavenging methods), and antifungal effect (by disk diffusion agar, well diffusion agar, minimum inhibitory concentration, and minimum fungicidal concentration) of the extract were evaluated. Results and DiscussionThe extract contained 175.60 mg GAE /g total phenol and 47.53 mg QE/g total flavonoids and its antioxidant activity using DPPH and ABTS free radical assays was 78.89% and 86.57%, respectively. The results of antifungal activity showed that the diameter of the growth inhibition zone increased significantly with increasing the concentration of the extract, and Botrytis cinerea and Rhizopus stolonifer were the most sensitive and resistant fungal strains to the extract, respectively. The minimum fungicidal concentrations for the strains of Botrytis cinerea and Rhizopus stolonifer were 64 and 512 mg/ml, respectively. ConclusionThe results of the present study showed that the ethanolic extract of green tea could be considered as potential source of natural antioxidant and antifungal agents. The presence of phenolic and flavonoid compounds may be responsible for the antifungal and antioxidant effects of the extract. However, due to the fact that this study was performed with the crude extract of green tea, it is difficult to identify compounds responsible for antifungal and antioxidant activity. On this point, only the separation of the components of the extract allows the detection of antifungal and antioxidant compounds. This study provides a basis for further researches, in particular the use of these antioxidants and antifungal compounds. Green tea extract is especially suitable for products with high sensitivity to lipid oxidation and infection with molds.
Akram Arianfar; Fakhri Shahidi; Rassoul Kadkhodaee; Mehdi Varidi
Abstract
Introduction: Tea (Camellia sinensis), is the most widely beverage after water across the world. The most important chemical composition in tea is phenolic compounds (catechins) that have antioxidant and anticarcinogenic properties and are benefited for cardiovascular disease. There are two major kinds ...
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Introduction: Tea (Camellia sinensis), is the most widely beverage after water across the world. The most important chemical composition in tea is phenolic compounds (catechins) that have antioxidant and anticarcinogenic properties and are benefited for cardiovascular disease. There are two major kinds of tea, black tea and green tea. Green Tea, is originated in China and dates back to several thousand years ago. In the production of green tea, young leaves are rolled and oxidized to decreasing oxidation but in production of black tea, tea leaves are oxidized (fermented) for 90-120 min after rolling and then catechins are converted to complexe compounds (theaflavins and thearubigins). The conventional method for extraction of green tea polyphenols compounds are heating, boiling, cold and heathing refluxe extraction, with long extraction periods and low extraction efficiency. In this study 3 techniques for extraction of polyphenol compounds from Green tea leaves were investigated and compored together.The main objective of this study was to determine the effects of differrent extraction conditions, temperature ( 40, 60, 80 and 100° C), different time ( 15, 30, 45 and 60 min ), microwave power (300, 600 and 900 % ) and ultrasound amplitude (40, 60, 80 and 100 W) on Green tea polyphenol content and antioxidant activity in three methods including Heat Reflux Extraction(HRE), Microwave Assisted Extraction(MAE) and Ultasound Assisted Extraction(UAE).Materials and Methods: Dried green tea leaves (supplied from Lahijan (Iran))were grinded for increasing the contact surface area between the solvent and solute. 1 g of green tea was extracted with 100 mL of water at various methods, Heathing Reflux Extraction(HRE), Microwave Assisted Extraction(MAE), by microsynth laboratory system (Milestone-ACT-36-Rev01) at 50 Hz and output 2450 MHz with adjustable power output (100-1000 W), temperature 180° C and Ultrasound Assisted Extraction (UAE) in double jacket vessel by using a 25 kHz ultrasonic system (model VCX 750, Sonics & Materials, Inc., USA), at a maximum nominal power output of 750W. All measurements were carried out in triplicate. The results were analysed statistically using the minitab 16 Program to determine the average value and standard error. Variance analysis, with a significant level of α= 0.05% was performed to determine the effect of time, temperature, microwave power and ultrasound amplitude on polyphenols content and antioxidant activity. Total phenol were determined spectrophotometerically by Folin-Ciocalteu method at 765 nm )Hewlett- Packard spectrophotometer model 8452A, Rockville). The antioxidant activity evaluated with the DPPH test spectrophotometrically at 517 nm. Results and Discussion: These results showed that polyphenol content is increased with increasing the time, temperature, ultrasound amplitude and microwave power of extraction. By increasing temperature to 80°C , time to 45 min, ultrasound amplitude from 40 to 80 and microwave power from 300 to 600, polyphenol content and antioxidant activity was increased and after that was constant. These results showed that, H.R.E require long extraction time and have low efficiency. Polyphenol compounds are thermally unstable and maybe degredate in thermal processing. Also, the best method for extraction was MAE, because of higher yield, higher contents of pol-yphenol and shortend time and this method was very efficient in the extraction of polyphenl compounds. The efficiency of extraction by UAE method is higher than HRE and lower than MAE method. Conclusion: UAE method compared to HRE method is enhanced the extraction of polyphenol, facilating solvent peneteration and increase the product releasing from intracellular. This method agitated the solvent to material and increased the contact surface between material and solven, and peneteration of solvent in to the green tea leaves. UAE canbe carried out at a lower temperature than HRE and decreased thermal damage.
Elham Ranjbar Nedamani; Alireza Sadeghi Mahoonak; Mohammad Ghorbani; Mahdi Kashani-Nejad
Abstract
The aim of present study was to investigate and compare antioxidant properties of green tea and rosemary extracts and determine the effect of their combination on the antioxidant properties. Results of total phenols, DPPH free radical scavenging assay, total antioxidant capacity, reducing power and their ...
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The aim of present study was to investigate and compare antioxidant properties of green tea and rosemary extracts and determine the effect of their combination on the antioxidant properties. Results of total phenols, DPPH free radical scavenging assay, total antioxidant capacity, reducing power and their addition into soybean oil, showed that the green tea extract was significantly (p<0.05) more effective than rosemary, and both of these extracts showed better antioxidant activity than BHT. Combined extracts showed different behavior; in DPPH free radical scavenging assay and reducing power, a significant (p<0.05) synergistic effect was observed, while in total antioxidant capacity and soybean oil the interaction was antagonism, although even in antagonism interaction, these combinations did better than BHT. Consequently, these natural antioxidant combinations can be used as an appropriate alternative for BHT, and that means, lower doses of natural antioxidants results in better protective effect compared to a synthetic ones.
Reza Nassiri Rad; Mohammad Hossein Hadad Khodaparast; Amir Hossein Elhami Rad; Shiva Roufigari Haghighat
Abstract
Green Tea is prepared from the leaves of Camellia sinensis. Catechins of Green tea are well known as natural antioxidants and have effective beneficial on the body. One of the most important processes in the extraction of catechins and producing green tea beverage is brewing process. The object of this ...
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Green Tea is prepared from the leaves of Camellia sinensis. Catechins of Green tea are well known as natural antioxidants and have effective beneficial on the body. One of the most important processes in the extraction of catechins and producing green tea beverage is brewing process. The object of this study is to investigating the effect of brewing temperatures (60٫70 and 80˚c) and duration (5٫10 and 15 min) also the season effect of plucking on green tea that was produced in the Tea Research foundation of lahijan. results of total phenolic content on brewed green tea, is showed that plucking in summer and spring seasons samples have much total phenolic content are rather than plucking in autumn season samples also percent extraction of brewing green tea at 15 minuets has most highest total phenolic content than other seasons and brewing times .brewing temperature are not significant effected on the total phenolic content.
