The present study was concluded that the vegetable coating affects positively on the physiochemical parameters of tomatoes. The coated sample shows significant difference in almost all parameters as compared to control (uncoated) tomatoes. As far as storage period is concerned as increase the quality parameters like weight loss and antimicrobial activity of tomatoes. Melia azedarach mediated silver nanoparticles were Characterize by UV-vis Spectrophotometer, Fourier infrared spectroscopy (FTIR), and Scanning Electron Microscope (SEM) examine the antibacterial activity of biological medicated silver nanoparticles against the microbial strains of E. coli, Streptococcus sp., Klebsiella sp., Bacillus sp., Salmonella sp., Aspargillus niger
Keywords: AgNPs; Green synthesis; Melia azedarach; Anitimicrobial; vegetables; coating
Silver nanoparticles is the most recent advances in the application and development of edible coatings for fresh and minimally processed fruits, discussing wide range of compounds that can be used in the formulation of edible coatings depending on target application, the available and potential techniques to characterize coated commodities. Have they focusing on the development of new technologies that allow for a more efficient control of coating properties and functionality, and incorporation of nutritional and anti-microbial ingredients to the coatings. Food promotional material have been traditionally conceived as simple containers to transport food from the place where they have been produced to the retail outlet and then to the consumer with no alteration of the food nutritional and organoleptic characteristics [1].
As the important of packaging is saving of vegetables from extraneous pollution, other significant characteristics such as deceleration of impairment, extension of period of time, protective cover from carry affects and sustainment of the food product. Packaging materials should protect food from environmental influences such as heat, moisture, oxygen, enzymes, loss of aromas and unpleasant odor component are contamination from macro-organisms. Moreover, the world commercialize is becoming more demanding and is continuously in need of novel and stable products which, at the same time, could retain the natural properties of food [2].
The term edible coatings in food applications correspond to thin layers of edible materials applied onto surfaces of highly perishable foodstuff, such as fresh-cut fruits and vegetables. The most recent scientific and technological developments in this field will be highlighted and our goal would be to permit the reader getting a complete survey of the increasing use of this biopolymer in food industries [3]. Fruits and vegetables were coated in low molecular of silver nanoparticles, by using sterile cotton swab thrice. Overall encapsulation has been done after drying of vegetables in time period, and stored at room temperature. Samples were stored in aseptic condition for 28 days for further analysis [4].
The major post harvest losses of tomatoes, fresh vegetables are due to fungal infection. Physical disorder many tech have been studied in order to extend the shelf life of fresh products. However, they have advantages and disadvantages. Quality maintenance of fresh products is still a major challenge for the food industry. Nanotechnology will facilitate the development of light and more precise food manufacturing equipment, nonpolluting as well as cheaper packaging techniques [5]. AgNPs were synthesized, characterized, and used for the edible vegetable coating on tomato. The weight loss, firmness and antimicrobial activity of coated vegetables were also determined.
Tomatoes (Lycopersicume sculentum) were purchased from local farm. Fruits with uniform size and shapes, without damage and fungal activity, washed twice water and used for further analysis.
All the chemicals were purchased from the HiMedia, Mumbai, India
Melia azedarach plant leaf samples were collected from Sri Paramakalyani Centre for Environmental Science campus, MS University, Alwarkurichi.
Aqueous extract of plants were prepared from freshly collected leaves. 10 g of fresh leaves were surface sterilized using tween 20 was dissolved in for 30 min at 60°C and double distilled water. Then the leaves were cut into fine pieces and dispersed in 100 ml distilled water and boiled for 15 min at 60°C. After that, the solution was filtered through Whatmann No1 filter paper and stored at 4°C in refrigerator for 2 weeks for further experimental studies.
For silver nanoparticles synthesis, 1 mM silver nitrate solution was prepared in 90 ml of distilled water and the solution was taken in 250 ml Erlenmeyer flask. About 10 ml of plant extract added into silver nitrate solution and kept the flask at room temperature. A control was also maintained without addition of leaf extract. The colour changes observed visually and the synthesis of silver nanoparticles at different time intervals were monitored by UV-vis spectrophotometer of the solution.
Uv- Visible Spectrophotometer – Used for the absorption of biological mediated silver nanoparticles and plant extract.
Fourier Transform Infrared Spectroscopy (FTIR) - Fourier transform spectroscopy was used to identify the functional groups of the biological mediated silver nanoparticles and extract of Melia azedarach were analyzed.
Scanning Electron Microscope and (SEM) - The Scanning Electron microscope was used to analyse the morphology of silver nanoparticles.
Vegetables were coated in biological mediated silver nanoparticle, by using sterile cotton swab thrice. Each coating has been done after drying of vegetables in equal interval of time period, and stored at room temperature. Samples were stored in aseptic condition for 28 days for further analysis [6].
Two replicates of fruits were used for each treatment. (Tomato - four week), a sample of fruits was weighed regularly to determine weight loss.
The colour changes of clean and stored tomatoes were weighted and firmness tester checking the insight depth by concerning an reserve penetrometer tip into the vegetables [7].
To determine the antimicrobial activity of Ag-NPs, nutrient agar medium was sterilized and sterile media was poured aseptically and the plates were seeded with appropriate micro organisms E. coli, Streptococcus sp., Klebsiella sp., Bacillus sp., Salmonella sp., Aspargillus niger by evenly on to the surface of the medium with a sterile cotton swab. The biological mediated synthesized silver nanoparticles solution in respective wells. Then the 0 plates were incubated at 37 C for 24 hours. Zones of inhibition were assessed with a measuring scale.
The maximum absorption band occurs at the wavelength of 360 nm due to the excitations of surface plasmon resonance in the nanoparticles and the broadening peak indicates particles are polydispersed. While adding the Melia azedarach leaf extract into the silver nitrate solution the reduction starts with in 10 min and steadily increases in absorbance as function of reaction time indicates that the continuous formation of silver nanoparticles (Figure 1). After 3 hours of reaction time the absorbance was decreased indicates the completion of reaction [8]. The optimum time required for completion of reaction was recorded as 3 hours. Silver nanoparticle formation was started at 10 min is similar to the report of [9] where they used Solanum xanthocarpum berry extract.
Fourier transform Infra-Red spectroscopy is a technique for obtaining high quality infrared spectra by mathematical conversion of an interference pattern into a spectrum. Infrared -1 radiations consisting of all wavelengths (eg. 5000-400 cm ) split into two beams, which recombine after a path difference has been introduced. Entire IR region is divided into group frequency region and fingerprint region. In group frequency region, the peaks corresponding to different functional groups can be observed. According to corresponding peaks, functional group can be determined. Each atom of the molecule is connected by bond and each bond requires different IR region so characteristic peaks are observed.
FTIR measurements were carried out to identify the potential functional groups of the biomolecules in the leaf extracts of Melia azedarach responsible for the reduction of the silver ions -1 into silver nanoparticles (Figure 2). The band at 3306 cm corresponds to O-H Stretch of hydrogen bonded alcohols, -1 phenols. The absorbance peak at 2918 cm was indicates to C- -1 H stretch, alkenes. The band at 1605 cm shows characteristics -1 of C=O stretch of alkynes. The absorbance peak at 1413 cm was indicates C-C stretch (in ring), aromatics. The band at 1162 -1 cm corresponds to C-H, bend of alkynes. The absorbance peak at 1030 cm-1 was indicates to C-N. The presence of aliphatic amine, might act as reducing agents for the synthesis of silver
The surface morphology and size of the silver nanoparticles was identified by Scanning Electron Microscope. SEM image had shown shape and size of the silver nanoparticles synthesized by using leaf extract of Melia azedarach. Figure 3 shows individual silver nanoparticles as well as number of aggregates synthesized using leaf extract Melia azedarach. It illustrates the particles are preponderantly spherical in form and a few particles aggregates into larger particles with no welldefined morphology and also the size of the silver
Three replicate of fruit were used for each treatment, every week a sample of vegetable was removed from each treatment. The vegetable were weighed regularly to determine the weight loss. Weight loss depends upon transpiration of the vegetable. Permeability of coating material is another factor that could reduce the weight loss of tomatoes (Table 1). The results showed that significant weight loss was observed in 20.8% in silver coated vegetable followed by green synthesised silver nanoparticle. The transpiration rate of tomatoes and grapes depended on the thickness of film.
The tomatoes loss of colour changes during ageing which contribute greatly to its short postgrad life and susceptibleness to microbial pollution. Change in firmness between control coated and Ag NPs coated vegetable samples during four week of storage at room temperature have been studied. Starting colour change evaluate were standardized for control and coated samples. On the second week of storage, uncoated tomatoes began to show a loss of firmness.
Ag nanoparticle was coated in the outer layer of Tomato done under the sterile condition at room temperature. The results conclude that when compared with non-coating, the coated vegetables showed the good shelf life period from 16 to 21 days at room temperature (Figure 4). Ag nanoparticle coated in the outer layer of vegetables (Tomato) was done under the sterile condition at room temperature. It is concluded that when compared with non-coating, figure 4 the coated fruits and vegetables showed the good shelf life period from 20 to25 days at room temperature Moreover, since many of the research, there is still a lot of room for variation and maturation in the development of edible coatings for application in food
Further the nanoparticles syntheses by green route are found non-toxic against Bacillus subtilis, Klebsiella pneumonia, E. coli, Streptococcus. sp and Aspergillus niger were investigated and compared their Antimicrobial activity (Table 2). Gram positive bacteria differ from gram negative bacteria in the structure of their cell walls. The cell wall of gram negative bacteria was made up of lipopolysaccharide layer at the exterior, followed underneath by a thin layer (7-8 nm) of peptidoglycan [11] and it was not as rigid as peptidoglycon because of the covalent linkage between the lipid and polysaccharide. Lipopolysaccharides contain negative charge, and attract the weak, positively charged Ag nanoparticle [12]. The rigid and extended cross-linking not only endows the cell wall with fewer anchoring sites for the Ag nanoparticle, but also makes it difficult to penetrate. However the highest inhibition rate of silver nanoparticles was observed for 1mM concentration [13]. So that nanoparticles penetration was much more in gram negative bacteria than the gram positive bacteria. Thus Ag nanoparticles are more toxic to gram negative bacteria than gram positive bacteria [13].
Organism name Zone of inhibition (diameter in mm) 10 μl 20 μl 30 μl E.coli 5 5 7 Streptococcus sp. 7 5 8 Klebsiella sp. 4 6 6 Bacillus sp. 6 7 8 Salmonella sp. 3 3 5 Aspargillus niger 7 8 11
In conclusion typically, the biological mediated synthesis of silver nanoparticle can be used as a surface coating on perishable vegetables to enhance microbial safety and extend food shelf life. It is a green, high yield, fast and low cost approach. Therefore the presence study clearly provides novel antimicrobial material which is potentially useful in food packing.
Authors gratefully acknowledge the DST-FIST sponsored programme, Department of science technology, New Delhi, India for funding the research Development (Ref no: S/FST/ESI-101/2010) to carry out this work.
The authors declare that there is no conflict of interests regarding the publication of this paper.