Nutrition & Food Science
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Item DEVELOPMENT OF HORDEIN-PECTIN NANOPARTICLE COMPLEX FOR THE ENCAPSULATION OF BIOACTIVE COMPOUNDS FOR ENHANCED FUNCTIONALITIES(2023) Tarwa, Kevin; Wang, Qin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Nanoparticle delivery systems composed of food polymers are a sustainable and eco-friendly approach to protect functional ingredients and promote healthier food options. In this research, a hordein-pectin nanoparticle complex (HP-NPC) was fabricated using an anti-solvent precipitation and electrostatic deposition (pH 4) method for the encapsulation of hydrophobic bioactive compounds to enhance their functionalities. First, hordein was extracted from whole barley grains to obtain a dried powder to synthesize hordein nanoparticles (HNP). Then pectin with a degree of esterification (DE) around 71% was applied as a coating material. The average particle size of the freshly prepared nanoparticle complex was relatively small (~246 ± 11 nm), and Fourier transform infrared spectroscopy (FTIR) indicated that cationic hordein interacted with anionic pectin mainly though newly formed hydrogen bonds and electrostatic interaction as indicated by their opposite surface charges. Scanning electron microscopy (SEM) revealed that the morphology of the nanoparticle complex was spherical with a smooth surface. The pectin coating was shown to have a protective effect against pH (3.0-9.0), heat (80 °C for 0-120 mins), and salt (0-100 µM) which are all factors known to degrade proteins. Second, lutein, a hydrophobic bioactive xanthophyll was encapsulated into HP-NPC to develop a lutein-hordein/pectin nanoparticle complex (L-HP-NPC). Since lutein has low water solubility and low bioavailability in the gastrointestinal tract (GIT), the effect of the encapsulation system on the functional properties of lutein was investigated. The loading capacity (LC%) and encapsulation efficiency (EE%) was around 15.5 and 82%, respectively. In vitro digestion resulted in a higher bioaccessibility of lutein for encapsulated HP-NPC (~22.3%), which is defined as the percentage of lutein accessible for absorption in the simulated intestinal fluid (SIF) compared to lutein encapsulated into HNP (~9%). The ability of pectin to produce gels in acidic media was shown to have a significant effect against gastric enzymes that can degrade both hordein and lutein. Also, lyophilization (an important step in food processing) had no significant effect on the stability of L-HP-NPC. This encapsulation system could potentially be used as a functional ingredient in the food industry to develop healthy and nutritious foods for consumers. Third, carvacrol, a phenolic monoterpene known for its antimicrobial properties was encapsulated into HP-NPC to develop a carvacrol-hordein/pectin nanoparticle complex (CA-HP-NPC). Special focus was on the solubility of encapsulate carvacrol due to its known low solubility in aqueous solutions. The antimicrobial effectiveness of the encapsulated nanoparticle complex was tested against non-pathogenic gram-positive L. innocua and gram-negative E. coli K12. CA-HP-NPC was still able to maintain a relatively small particle size (~207 ± 8 nm) after being dispersed into water post-lyophilization. Carvacrol was shown to be effective against the two bacteria, however, CA-HP-NPC did not show antimicrobial effectiveness. Although carvacrol was successfully encapsulated into the nanoparticle complex, further studies on their release properties need to be investigated to further understand their functional properties for food applications.Item Food Safety Implications of Biofilms Formed by Resident Bacteria in Fresh-cut Processing Environments(2013) Liu, Tong; Lo, Yangming M.; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biofilms on equipment surfaces can be vectors for cross-contaminations in food processing facilities. A particular problem is that biofilms can protect pathogenic bacteria from daily cleaning and disinfection operations. In the present study, microflora were recovered from fresh-cut processing facilities, identified, and tested for biofilm forming potential. Subsequently, dual-species biofilms of selected isolates and Escherichia coli O157:H7 were investigated. Approximately 30% of the isolates were potent biofilm formers, producing large amounts of biomass. A hundred and seventeen tested isolates were identified into 23 genera, including plant related bacteria and coliforms with some opportunistic pathogens. Dual-species biofilms formed by Burkholderia caryophylli or Ralstonia insidiosa and E. coli O157:H7 manifested increased biomass in comparison to their monocultures. Additionally, about a one-log unit increase of E. coli O157:H7 cell counts were observed for both dual-species biofilms. To test the effects of environmental factors on growth of R. insidiosa and E. coli O157:H7 in dual-species biofilms, factors tested included low temperature (10 oC), media with different composition of nutrient sources (10% TSB, M9, 1.25% Cantaloupe Juice) and a continuous culture system with limited nutrients. E. coli O157:H7 cell counts increased for all tested conditions. To examine bacterial localization within biofilms, confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM) were used. Images showed distinct spatial distributions with E. coli O157:H7 commonly located at the bottom and also interspersed among R. insidiosa cells. To test the interactions with other pathogens, R. insidiosa was co-cultured with Listeria monocytogenes, Salmonella spp., and Shiga toxin-producing E. coli. Cells counts for 7 out of 9 tested pathogenic bacteria strains were increased (0.36-1.60 CFU log units). It is notable that the biomass formed by R. insidiosa and L. monocytogenes was much greater than those produced by other tested combinations. These results indicate that R. insidiosa could be a food safety risk in fresh-cut processing environments by providing protective habitats for pathogenic bacteria.