Production of Cellulose and Nanocellulose Reinforcement Agents from Apple Pomace and Their Utilization in the Development of Low Density Polyethylene Based Biodegradable Food Packaging Materials
Project no. 1189 · Status: Kapanmış · 2017
Summary
In this thesis, the production of biocomposite and nanocomposite packaging materials with bio-based content and biodegradable properties were produced by the extrusion method as a solution to environmental problem of plastic-based packaging waste. The study was carried out in three stages: (i) the production of reinforcing agents from apple pomace, (ii) the production of low-density polyethylene based (LDPE) biocomposite and nanocomposite packaging materials by an extrusion method and (iii) food packaging applications. Stage 1, involved the production of cellulose with a high alpha-cellulose content (85.31%) and a whiteness index (47.79) from dried and ground apple pomace under optimum extraction conditions, determined by using the response surface method (RSM), with a yield of 27.96%. Then, nanocellulose was produced from the cellulose through acid hydrolysis and ultrasonication processes. The chemical structure of the samples (FTIR), degree of crystallinity (XRD) and the surface morphology (SEM and AFM) change in were examined. It was found that chemical treatments applied to apple pomace were effective in the removal of impurities such as hemicellulose and lignin. XRD analysis results were indicated that the nanocellulose had a high degree of crystallinity (78%), while the AFM analysis revealed rod/needle-like shaped cellulose nanocrystals. ix In stage 2, the apple pomace powder, cellulose and nanocellulose obtained from apple pomace were added as reinforcing agents to the LDPE matrix to produce biocomposite and nanocomposite compounds and packaging films. The effect of reinforcing agents on the color and mechanical, chemical, thermal, etc. properties of the composite material was assessed. Due to the increased apple pomace powder and cellulose concentrations in the LDPE-based biocomposite materials, their mechanical strength and transparency decreased, and the opacity of the films increased. In biodegradability analysis, the samples were kept in simulated soil over 12 months, it was found that the weight loss of the material increased with the increase in reinforcing agents concentrations. Approximately 5% loss of weight was noted in the biocomposite materials containing apple pomace powder and cellulose (10–15%), along with weight loss of approximately 1.5% occurring in nanocomposite packaging materials containing 1% nanocellulose. In the final stage, the potential usage of the selected packaging materials effect on the packaging of minimally processed spinach (Spinacia oleracea L. cv. Kuzu), were investigated. The minimally processed spinach samples were stored in a passive modified atmosphere with LDPE (control) and nanocomposite packaging materials containing 1% nanocellulose at +4°C for 17 days. During storage, a decrease was observed in the specific green color of the spinach, and in the total amount of chlorophyll and ascorbic acid, along with an increase in the pH value and weight loss. It was found that the spinach stored in both packaging materials was microbiologically acceptable for consumption over 17 days, although it was found that the spinach stored in the nanocomposite packaging material had higher scores for sensory acceptability than the control group. It was concluded that high value-added products such as cellulose and nanocellulose obtained from apple pomace were effective in providing bio-based content and biodegradation behavior to LDPE as reinforcing agents, and showed high potential to be used as food packaging materials.