Abstract
South Africa's fresh produce industry is focused on developing economically sustainable bio-based solutions to mitigate agricultural waste. One promising avenue is the utilization of phytochemicals from agro-industrial waste, particularly beetroot waste, which is rich in betalains and phenolic compounds. These natural antioxidants and food supplements hold significant potential for enhancing the food industry's sustainability. Non-biodegradable synthetic polymers have caused severe environmental issues, necessitating the exploration of alternative techniques. In this context, bio-based active and intelligent edible films have emerged as a promising solution. These films consist of active ingredients that prolong the shelf life of food products and natural indicators that monitor food quality.
This thesis aimed to explore how the utilization of beetroot waste can foster a sustainable food bioeconomy by reducing waste and enhancing food preservation through innovative techniques like encapsulation and advanced packaging materials. Repurposing agricultural by-products and employing cutting-edge packaging methods contribute significantly to sustainable practices within the food industry.
Beetroot, known for its vibrant color and nutritional benefits, is extensively utilized in the food sector for products such as juices, powders, and natural colorants. However, the processing of beetroot generates large quantities of waste, including peelings, pulp, residual juice, and rejected beetroots regarded as postharvest waste due to blemishes, shrinkages and cracks. This waste stream is abundant in bioactive substances such as phenolics, betalains, and dietary fibers, which possess antibacterial, antioxidant, and health-promoting properties. Therefore, this thesis suggests using encapsulation and the fabrication of functional films to maximize the bioactive potential of beetroot waste, contributing to both waste valorization and sustainable packaging solutions.
The first experimental chapter investigated how maltodextrin (MT), gum Arabic (GA), and various combinations of these two as wall materials to encapsulate bioactive components, mainly betalains, from beetroot waste extracts. The objective was to produce a powdered beetroot waste extract (BWEP) with potential applications in the food industry. Beetroot waste extracts were prepared in a 50% ethanol solution, and a 10% mixture (1:10, w/v) of MT and GA was added to encapsulate the extracts. Different blending ratios of GA to MT (1:1, 0:1, 2:1, and 1:2) were explored. The BWEPs produced with either GA or MT alone demonstrated
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excellent betalain levels, solubility, and encapsulation efficiency. Using a combination of GA and MT resulted in improved oil retention and a higher total phenolic content in the powders. However, parameters such as DPPH radical scavenging activity, powder yield, bulk density, total soluble solids, and titratable acidity did not differ significantly (p > 0.05) between the powders. While the powders from the mixed biopolymers exhibited higher agglomeration, those encapsulated with GA and MT individually were smaller and more homogenous. The BWEPs encapsulated with GA or MT alone contained sixteen metabolites, including two phenolic acids, five flavonoids, and nine betalains. The study concluded that while GA and MT, when used separately, are effective encapsulating agents for BWEP, their combination can further enhance the quality, offering a promising approach for advancing a circular bioeconomy in the food industry.
The second experimental chapter focused on creating smart packaging films using a blend of mucilage, cellulose nanofibers (CNF), glycerol, and the encapsulated beetroot waste extract (EBWE) at varying concentrations (0%, 0.5%, 1%, 1.5%, and 2%) through the solvent casting method. The findings revealed pH-responsive color changes from red to yellow, indicating the potential for pH-sensitive packaging. EBWE improved the film's compactness, with potential hydrogen bonding observed between the betacyanins in EBWE and the mucilage/CNF/glycerol matrix. Incorporating 2% EBWE significantly increased moisture content (37.86%), water solubility (44.63%), swelling capacity (3.06%), and antioxidant properties. The films' water vapor permeability ranged from 0.39 to 0.89 g/(m·s·Pa). Additionally, the films exhibited notable sensitivity to ammonia, with 2% EBWE showing the most significant color change, indicating potential applications in intelligent packaging. The practical application of these films was demonstrated through monitoring the freshness of hake medallions, where the films changed color from red to yellow over six days, reflecting the spoilage process.
In summary, the research establishes the effectiveness of using mucilage/CNF/glycerol bio-based edible films incorporating encapsulated beetroot waste extract (EBWE) to monitor hake medallion freshness. It highlights the value of repurposing agricultural waste for innovative product development. By employing encapsulation and intelligent film fabrication, this approach offers a comprehensive solution to food waste and packaging challenges. The study promotes environmental sustainability and resource efficiency by showcasing the potential of food waste-derived bioactive compounds. Utilizing beetroot waste represents a step towards a circular bioeconomy, reducing waste while maximizing resources in the food sector.