LEE- Gıda Mühendisliği-Yüksek Lisans

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http://hdl.handle.net/11527/19293

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Konu "Biodegradable polymers" ile LEE- Gıda Mühendisliği-Yüksek Lisans'a göz atma
  • Öge
    Development of pea protein agar based biodegradable film with the incorporation of essential oils
    (Graduate School, 2022) Ozhan, Selin ; Yeşilçubuk Şahin, Neşe ; Saygun, Ayşe ; 725922 ; Food Engineering Programme
    In recent years, there is an increased awareness of sustainability in the world. People are looking for more sustainable solutions in packaging the industry since it is seen as one of the most polluting agents in the environment. Edible films and coatings are alternatives to reduce plastic packaging usage in the food industry. While it has an advantage for being sustainable, it also provides a good barrier, sensory, and quality properties in the foods. This study aimed to investigate the characterization of pea protein and agar edible film and then add essential oils to increase the antimicrobial effect of the edible film. For this purpose, 4 different essential oils are used; eucalyptus, thyme, lemon and niaouli in 1%, 2%, 3%, 4% and 5% (v/v) concentrations. Edible films are produced by using the solvent casting method. As the first step of this study, different film-forming materials were investigated and prepared in the laboratory to observe their edible film-forming capability. According to the results, pea protein and agar were chosen as the main edible film materials because they can form flexible and transparent films. Furthermore, essential oils were researched in the literature. The proper essential oil combination with edible films and the concentration were investigated. Thyme, eucalyptus, niaouli, and lemon oil were chosen because of their high antimicrobial activities and being capable to incorporate with edible films. After the decision of main materials, the pea protein and agar films were produced and thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) was checked to understand the characterization of the main film. After the addition of essential oils, swelling analysis, antimicrobial activity, and color analysis were done. TGA indicates the weight decrease of the film due to the water, volatiles, and plasticizer losses during the analysis. In DSC analysis, the Tg value is observed as 73℃. Since the pea protein and agar film seems flexible structure at room temperature, having a higher Tg value than room temperature may show that it is not mechanically strong for processing and it will be in more rubbery and softer structure at the higher temperatures. Lastly, DMA analysis was unsuccessful due to the weak mechanical strength of the film. After essential oils addition to pea protein based film, antimicrobial activities of essential oil incorporated edible films were analyzed. Based on the results, swelling and color analysis were conducted for the films that showed antimicrobial effect and also 5% oil concentration. For antimicrobial analysis, the agar disc diffusion method was used and essential oil incorporated film's antimicrobial activity was investigated against Escherichia coli, Staphylococcus aureus, and Aspergillus niger. According to the results, 1% addition of essential oil to the edible film did not show any antimicrobial effect against any of the microorganisms. In 2% essential oil addition, thyme and niaouli oil started to show antimicrobial effects against gram (+) and Gram (-) bacteria. After 3% addition of thyme oil, antimicrobial effects were observed against both bacteria and fungus. In bacteria, there is no direct correlation between the concentration of essential oil and the antimicrobial zones in the Petri dishes. The largest zone which was 2.7 cm observed against E. coli is 3% thyme oil incorporated edible film, and the largest zone against S. aureus is from all 3%, 4%, and 5% thyme oil that all give 2.3 cm in one of the analysis. On the other hand, there was a direct correlation between the concentration of essential oil and the antimicrobial activity against fungus. In 5% thyme oil incorporated film, there was almost no growth in the Petri dishes however the growth of the fungus increases as the concentration of thyme oil decreases. Additionally, swelling analysis was conducted for 5% essential oil incorporated films and 2% niaouli, 2% thyme, 3% thyme, and 4% thyme incorporated films that show antimicrobial effects against bacteria. It is found that 5 ml thyme oil is the least absorbent one in the both water and saline water environment. In a saline water environment, it started to lose its weight from the first hour. Hence, it can be said that it is not suitable for salted food application or any salty environment. On the other hand, 2 ml niaouli oil incorporated edible film is seen as the most absorbent one in both environments. During the analysis, all edible films show some peaks in different time zones. The reason can depend on the oil concentrations and hydrophobicity rates. In terms of color analysis, the same samples were used for swelling analysis. According to the average of six repetitive measurements, 2 ml niaouli oil incorporated edible film gives the least yellowish color, and the 4 ml thyme oil incorporation of the film gives the most yellowish. The results are evaluated by using the b* parameter which provides the rate of yellow color on the materials. In conclusion, this study shows that pea protein and agar can yield an edible film, and when incorporates with the proper amount of thyme oil, it can show antimicrobial activity against gram-positive and gram-negative bacteria and fungus.