Development of Polylactic Acid (PLA)-Based Nanocomposite Films for Smart Food Packaging Applications

Most of current food packaging resources are non-renewable and nonbiodegradable. The use of these materials has resulted in serious environmental issues. In recent years, the recognition of waste disposal problems and their impacts on the environment has risen the demand for packaging manufactured from renewable materials. However, there are some limitations of using biopolymers for food packaging applications. These limitations include unreliable mechanical and barrier properties. These issues may be addressed by combining biopolymers and nanotechnologies. Nanotechnologies are expected to improve the performance of biopolymer-based packaging materials for food packaging applications. Cellulose nanocrystals (CNC) has shown a potential to be implemented as filler to reinforce synthetic polymer for food packaging applications, equating its unique attributes of biodegradability high surface area. In this work, the aim is to develop a friendly environmental nanocomposite film based on combination of polylactic acid (PLA) and CNC for food packaging applications using a solvent casting method. The main problem that restricts the utilization of nanocellulose as a reinforcing filler with hydrophobic polymers is their tendency to aggregate in the polymer matrix. Thus, a homogenization process was applied to the mixture in order to obtain an even dispersion of CNC in the PLA matrix. Three various internal mixtures at CNC content were used to prepare the nanocomposite films, which are 1,3,5 wt%. The prepared nanocomposite films were subjected to morphological analysis, tensile strength, water vapor, and moisture uptake tests. These tests were conducted to test CNC impact on the barrier and mechanical properties of the PLA matrix. The results of scanning electron microscope (SEM) images showed an appropriate dispersion of CNC at low concentration 1% and 3%, while aggregations of CNC were observed in the PLA matrix for the film containing 5%CNC. The tensile strength of the nanocomposite films significantly improved only with the film containing 3% of CNC by 40% compared to the control sample. The water vapor test conducted on the prepared films reviled an improvement of water vapor behavior of the film containing 3%CNC and 5%CNC by 20% and 42% respectively. The water uptake test reviled that the water sensitivity of the nanocomposite films increased with the presence of CNC at different contents (1%,3% 5%) in the PLA matrix. The obtained results from this study indicated that the prepared nanocomposite films presented relatively reliable tensile strength and water permeability compared to the pure PLA film. The improvement of the water permeability and the tensile strength showed a potential of the prepared nanocomposite films to be utilized in food packaging applications. However, further studies on the nanocomposite films properties required to confirm that

Evaluating Thermal and Storage Stability of Selected Food Products Processed Using Microwave and High Pressure Assisted Thermal Processes

Microwave-assisted thermal sterilization (MATS) and pressure-assisted thermal sterilization (PATS) are advanced in-package thermal processing technologies that shorten the processing time. Shortening the processing time in in-package thermal processing is essential in improving the quality of the processed food. However, the polymeric packaging that interacts with the processing conditions of MATS and PATS is subjected to alteration in their gas barrier properties, which can compromise the quality of the pre-packaged food during and after processing. Therefore, compatible polymeric packages with MATS and PATS are crucial for successful MATS and PATS processes. Additionally, a holistic understanding of the effect of the processing conditions of MATS and PATS on food quality attributes including color is essential to improve the overall quality of processed food. This study aims to evaluate the thermal and storage stability of the quality attributes, primarily color and pigments in selected food products after MATS and PATS. The first study explores the feasibility of the development of PATS-treated avocado puree. Two polymeric packaging was used, which were EVOH based film (PP/PA//EVOH//PA/PP) and PET based film (AlOx-coated PET //AlOx-coated PET //AlOx-coated PET //ONy//CPP). The PATS treatment was conducted at a processing pressure of 600MPa at an initial temperature of 90oC for a processing duration of 5 min. The results of this study indicated that PATS can be used to successfully developed shelf stable avocado with limited shelf life.In the second study, the effect of MATS on the quality attributes of red beetroot, red cabbage, and carrot purees. Additionally, the storage stability of the MATS- processed purees at 37.8oC was evaluated. A high barrier package of AlOx-coated PET //AlOx-coated PET //AlOx-coated PET //ONy //CPP was used in this study. The results showed different levels of quality attributes degradation in the puree after MATS and during storage depending on the composition of the puree.The third study evaluate the efficacy of PATS on the inactivation of polyphenol oxide (PPO). Additionally, the effect of PATS on the quality attributes of red cabbage, red beetroot, and carrot purees was also evaluated after PATS and during storage at 37.8oC. A significant reduction in PPO took place after PATS. However, changes in the puree quality attributes were observed after PATS. During storage, a different trend in the PPO activity was observed. Additionally, the PATS-treated purees quality attributes showed different levels of degradation.Overall, MATS and PATS affected the quality attributes in the processed purees such as color and pigments. However, this affects was relatively less compared to the effect of conventional in-package thermal processing. Additionally, the developed kinetic data of quality attribute during storage (from the second and the third study) can be a helpful tool to optimize both MATS and PATS processing condition for higher quality product with bright color pigments

Storage and thermal stability of selected vegetable purees processed with microwave-assisted thermal sterilization

The impact of microwave-assisted thermal sterilization (MATS) on three natural pigments and their storage stability in vegetable purees was investigated. We selected carrot puree for beta carotene, red cabbage puree for anthocyanins, and red beetroot puree for betalains. The purees were packaged in multilayer flexible pouches of AlOx-coated PET (12 μm)//AlOx-coated PET (12 μm)//AlOx-coated PET (12 μm)//ONy (15 μm)//CPP (70 μm), then processed with the MATS system to Fo = 6 to 11 min. After MATS treatment, the pouches were stored for 6 months at a storage temperature of 37.8 °C. The MATS treatment had a significant impact (p < 0.05) on the instrumental colors of three purees, with the total color difference (ΔE) ranging between 6.0 and 10.5. Similarly, the concentration of betalains experienced degradation by 20%−29% after the MATS treatment, while beta-carotene concentration showed a high retention. In addition, the pH of the purees declined considerably (p < 0.05) after the MATS treatment. Over the 6 months of storage at 37.8 °C, the PET-metal oxide pouches maintained the moisture content in all the purees, as the weight loss was only 0.43%−0.45%. The pigments in the MATS-processed purees had different levels of stability; ΔE values varied between 4.23 and 12.3. Beta-carotene was the most stable pigment, followed by betalains and anthocyanins. The degradation of both betalains and anthocyanins during storage was explained by first and fractional conversion models. MATS processing and packages with high gas barriers can therefore be used to preserve selected vegetable purees rich in natural pigments