Modified Cellulose Nanocrystals (CNC) for Functional Foods
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Date
2021-06-02
Authors
Baek, Jiyoo
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
In recent years, food safety has attracted increasing attention, as consumers desire a healthier lifestyle and a prolonged lifespan. The interests in food to satisfy hunger have taken a shift towards providing more functional ingredients that offer a better state of well-being while also providing satiety to the consumer. With this shift, the primary focus has been directed towards replacing conventional chemical, synthetic additives with healthier and natural ingredients. Additionally, the interest in general health care and nutritious functional foods that can improve immunity is also generating much attraction, especially with the rising desire to boost our immunity against viruses, such as COVID-19. These efforts are evident in the food industry, with companies actively looking into the development of natural emulsifiers to replace artificial or synthetic ones, which can lower the health risks while providing the same taste and state of well-being.
Cellulose nanocrystals (CNC) in food applications have attracted a great deal of interest due to their biodegradability, biocompatibility, sustainability, and abundant supply. CNC is extracted from traditional raw materials, such as cotton or wood, exposed to physical and chemical processes like homogenization and acid hydrolysis. During these steps, the cellulose plant wall experiences the following changes to its hierarchical structure: the plant wall is broken down into hemicellulose and lignin, which is further reduced to the elementary fibers. With further chemical treatment, such as with acids, sustainable rod-like nanoparticles are produced. Recently, a new trend in producing CNC from agri-food waste, such as fruit peels, has emerged (tomato, mango, pineapple etc.). CNC is easily dispersible in water and possesses a high aspect ratio due to its rod-like structure and surface charges. This allows for facile chemical modification to tune and introduces new properties to the CNC. The modified CNC makes it a suitable material for applications in food packaging, food thickeners, and emulsion stabilizers.
Phosphorylated cellulose nanocrystals (PCNC) were prepared via acid hydrolysis using phosphoric acid, and chitosan was modified with glycidyltrimethylammonium chloride (GTMAC). The PCNC was simultaneously used as a “nanoparticle” cross-linker (similar to sodium tripolyphosphate (TPP)) and a Pickering emulsifier. The PCNC and GTMAC-Chitosan (GCh) were complexed via ionic gelation to produce GCh-PCNC nanoparticles. The nanocomplexes transformed from a rod-like to hard-sphere and random coil morphology with increasing GTMAC-Chitosan/PCNC. Pickering emulsions prepared using the GCh-PCNC complex were more stable over 3 months without coalescence or phase separation.
Vitamin C (VC) is necessary for human health. However, it is susceptible to oxidation during processing or storage. To increase its stability, VC was encapsulated via electrostatic interaction with GCh cross-linked with PCNC to form VC-GCh-PCNC nanocapsules. VC-GCh-PCNC possessed a broad-spectrum antibacterial activity with a minimum inhibition concentration (MIC) of 8-16 ug/mL. These results demonstrated that modified CNC-based nano-formulations could preserve, protect, and control the release of active compounds with improved antioxidant and antibacterial properties for food and nutraceutical applications.
CNC was modified with ferulic acid (FA) and starch nanoparticles (SNP) to produce a new, natural emulsifier that is environment-friendly and beneficial to human health. This new approach was developed and utilized to formulate a multiple Pickering emulsion (W1/O/W2) for probiotic encapsulation. The adsorption capacity of FA on CNC was evaluated, and the highest adsorption capacity below the pKa of FA (4.5) was 1.91 mg FA/g of CNC and greater than 4.5. The adsorption capacity decreased to 0.03 mg FA/g of CNC. At high pH, carboxyl groups from the CNCFA-based Pickering multiple emulsions were deprotonated, inducing phase separation. The newly developed emulsifiers were used to reduce the interfacial tension between the oil and water phase to prepare stable emulsions that could be stored over a long period.
With the worldwide emergence of health challenges facing humanity and the associated immunity and intestinal health, the use of probiotics is becoming prevalent. We developed a sustainable, biocompatible, rigid, and long-lasting enteric coating system using pH-responsive natural-based materials, shellac (Sh), and cellulose nanocrystals (CNC). Yeast (Saccharomyces cerevisiae) was encapsulated in the ShCNC microcapsules and CaCl2. We elucidated the 3D structure of ShCNCCa microcapsules using a confocal laser microscope, where a 1-1.3 um shell consisting of shellac and CNC nanocomplex protected the yeast resulting in high yeast viability and retention of 602.35%. During processing, storage and transport through the gastric environment, the yeasts were protected and then triggered to release in the intestinal environment of pH 7-8. Viscosity synergism and mucoadhesion analysis revealed that the microcapsules bound strongly to the mucus membrane in the presence of pancreatin.
This Ph.D. study explores new strategies to improve current functional food systems using modified CNC. In the design and development of the project, replicable methods, simple processes, and fewer chemicals are being considered. The research has contributed to the development and understanding of functional cellulose nanocrystals, which are suitable for use in the food industry.
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Keywords
cellulose nanocrystals, Pickering emulsions, functional foods, encapsulation system