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Vapor pressure of allyl isothiocyanate (AIT) increased exponentially with temperature (136 to 2267 Pa from 5 to 50°C), with a heat of vaporization of 47.6 kJ/mol. A testing system was developed to study AIT permeation in packaging films. Permeability (P) and diffusion (D) coefficients of AIT in poly(vinylidene chloride/vinyl chloride) copolymer film increased exponentially with vapor activity. At any given vapor activity, P and D correlated positively with temperature, while a negative relationship was observed for solubility. AIT sorption in nylon 6,6 film was minimal when the polymer was dry, but increased to a maximum of 3.5% (w/w) as relative humidity (RH) increased. The decrease in AIT solubility above 70% RH was attributed to competitive sorption of water. Conversely, P and D increased exponentially with RH, indicating that the RH-dependent permeation process was dominated more by the change in diffusion rather than the solubilization process. Water induced a glassy-to-rubbery transition in the polyamide, allowing the penetration of AIT, which further plasticized the polymer. FTIR results suggested that water sorption strengthened H-bonding to the C=O sites, but weakened the N-H groups of the polyamide. AIT sorption further strengthened and weakened H-bonding to the C=O and N-H groups, respectively. Oxygen permeability through nylon 6,6 decreased from zero up to 40% RH, but increased strongly when RH increased further. The lowering permeability at low RH was attributed to the reduction in free volume for oxygen diffusion due to the presence of tightly bound water. The covalent cross-linking of gelatin and egg white by transglutaminase enzyme was confirmed by SDS-PAGE analyses. Protein films prepared from these cross-linked proteins were plasticized synergistically by water and glycerol (a plasticizer additive), resulting in films of greater elongation but lower tensile strengths. Films with higher glycerol contents possessed higher equilibrium moisture content, indicating higher film hydrophilicity. AIT and oxygen permeability coefficients were comparable to those of nylon 6,6 film when RH was low, but increased greatly at higher RH due to the plasticization effect of water. Preliminary studies on three selected fungi showed that the antimicro efficacy of AIT depended on AIT vapor concentration and the exposure time.

Miscanthus × giganteus is a fast-growing and high-yielding perennial grass widely available in North America. This research investigated two pre-treatment techniques to extract cellulose fibers and lignin from miscanthus biomass and determined their potential applications. The first study investigated an ultrasound-assisted-alkali-urea (UAAU) pre-treatment for enhanced delignification of miscanthus. Sonication time, NaOH concentration, and urea concentrations were optimized using a response surface methodology. The UAAU method extracted up to 52% (w/w) cellulose fibers from miscanthus at 5% NaOH, 1.75% urea, and 20 min sonication, resulting in cellulose fibers of higher crystallinity, and thermal stability than the untreated samples. In the second study, a binary enzyme (BE) cocktail (cellulase and laccase) was investigated for the extraction of cellulose fibers from the miscanthus biomass. The cellulase-laccase cocktail extracted up to 47% (w/w) cellulose fibers, whereas the cellulase or laccase treatments alone resulted in 38% (w/w) or 36% (w/w), respectively. Paper-sheets prepared from the fibers from the BE treatment showed higher mechanical properties and water absorption capacity than those prepared from that of the single-enzyme treatments. In the third study, the extracted lignin was subjected to hydroxyethylation by ethylene carbonate, followed by esterification with propionic acid. The esterified lignin was then co-dissolved with cellulose acetate in acetone and applied as a coating on the paper-sheets. The coated paper-sheets exhibited significantly higher hydrophobicity and tensile strength, while lower water vapour transmission rate than the uncoated samples. In the fourth study, an ethyl cellulose-based nonwoven filter (NWF) was developed using a free-surface electrospinning technique. The nonwoven was loaded with silver nanoparticles (AgNPs) synthetized through reducing Ag+ with the extracted lignin. The filtration test against NaCl aerosols (≥ 0.3 µm) yielded desired performance with filtration efficiency (>99%), pressure drop (0.077 Pa-1) at RH (25 ± 2% and > 90%). At 60 min contact time, AgNPs loaded NWFs exhibited antiviral activity against a surrogate virus, bacteriophage Φ6, with more than 5 log10 (PFU/mL) reduction. Overall, this research shows that UAAU and BE pre-treatments could effectively extract cellulose fibers and lignin from miscanthus biomass, while the resulting fibers and lignin could be used for hydrophobic paper-sheet and antiviral mask filter applications. Barrett Sustainable Food Engineering Grant, School of Engineering, University of Guelph, Canada; COVID-19 Research Development and Catalyst Fund, University of Guelph, Canada 2023-08-31

Cold brew coffee is prepared by steeping ground coffee in water at ambient or refrigerated temperatures for 8 to 24 h. Cold brew coffees tend to be less bitter and less acidic than the conventional hot brewed counterparts. In this study, the effects of high pressure processing (HPP) on the extraction and physicochemical characteristics of cold brew coffee and property changes during 60-day storage were investigated. HPP facilitated the cold brew coffee extraction process, especially for whole beans. Moreover, whole bean brew with HPP had smooth and persistent foam and pleasant flavor, which has potential for preparing Nitro coffee. During 60-day storage, pH of cold brew coffee decreased while titratable acidity, caffeine, chlorogenic acid and total polyphenols contents increased, which can be accelerated by HPP. Findings from this project showed that HPP potentially could be used as an innovative method to prepare and preserve cold brew coffees. Natural Sciences and Engineering Research Council of Canada; Ontario Centres of Excellence 2022-06-10

Ethyl formate (EF) is a generally regarded as safe (GRAS) volatile compound which is naturally occurring in many food products (e.g., rice, barley, grapes, beer, cheese). It is a potent insecticide and antimicrobial promising as an alternative to the fumigant methyl bromide, which is being phased out due to its ozone depletion in the stratosphere and toxic properties. However, EF is highly volatile, flammable, and susceptible to hydrolytic degradation. These properties pose substantial end-use delivery challenges. In this research, a novel solid-state EF precursor (EFP) compound was synthesized via the condensation reaction of adipic acid dihydrazide and triethyl orthoformate to form diethyl N,N'-adipoyldiformohydrazonate, as confirmed by Fourier transformed infrared and solid-state nuclear magnetic resonance spectroscopies. EFP was non-volatile and remained stable under dry conditions but could be hydrolyzed readily in the presence of moisture and acid to trigger the release of EF vapor. To facilitate the end-use applications, EFP was encapsulated in free-surface electrospun ethylcellulose/poly(ethylene oxide) (EC-PEO) nonwovens after optimizing the polymer concentrations to obtain bead-free electrospun fibers. The release kinetics of EF vapor from the neat EFP powder and EFP-loaded EC-PEO nonwovens were evaluated at different conditions using gas chromatography. Scanning electron microscopy revealed that EFP powder was physically entrapped within the electrospun EC-PEO fibers. Fourier transformed infrared spectroscopy detected no specific interactions between EFP and the polymers in the nonwovens. Preliminary studies on strawberries showed that the release of EF vapor from the EFP-loaded nonwovens delayed the growth of spoilage microorganisms on the fruits. Furthermore, EFP powder was used as an EF activated release system for in-packaging fumigation of blueberries to control an invasive insect pest in fruits – spotted-wing drosophila (SWD). Complete control of SWD eggs, larvae, pupae, adults was achieved after EF exposure. There were no significant (p > 0.05) differences in blueberries quality parameters between EF treated and untreated berries. This research shows that the conversion of the highly volatile EF into a solid-state precursor, in conjunction with the activated release strategy, can be useful for active packaging applications of fresh produce to mitigate insect pest risks and prevent microbial growth during distribution. Ontario Agri-Food Innovation Alliance; iFood Packaging Systems Corp. 2022-04-22

Edible Brassicaceae microgreens are gaining popularity due to their unique eating quality, and potential health-promoting benefits (e.g., anticancer and antibacterial properties) from their natural metabolites (e.g., glucosinolates). This thesis studied the effects of photoperiods and electrical conductivity of nutrient solution on sinigrin content and myrosinase activity in kale, mustard, and broccoli microgreens grown in indoor controlled environments. Results showed sinigrin content and myrosinase activity decreased as the photoperiod increased from 6 to 24 h. However, the electrical conductivity of the nutrient solution from 1.00 to 2.00 mS/cm had no effect on sinigrin concentration and myrosinase activity of the microgreens. Supplementing the nutrient solution with black liquor, which is a byproduct from the pulping process of paper manufacturing industries, from 5 to 15% v/v, significantly increased the yield of broccoli microgreen. However, the sinigrin concentration decreased while myrosinase activity marginally increased with increasing black liquor concentration to 10 and 20% v/v. Natural Sciences and Engineering Research Council of Canada (NSERC) and TruLeaf Inc. 2022-04-21

The foaming properties of cold brew coffee have been studied. The variables investigated were coffee variety, roast degree, brewing conditions, and brewing methods. The initial foam volume generated from 37.0±1.0 to 47.0±0.5 mL for light to dark roast degree coffee brews, respectively, due to the higher nitrogen content and lower surface tension of the dark roast brews than that of light roast brews. Brews from dark roast beans had more stable foam due to the higher viscosity and higher total sugar content than the light roast coffee brew. The samples were precipitated with ethanol to investigate the effects of chemical composition on the foaming properties. The reconstituted supernatant fraction presented the foam atbility due to the higher nitrogen content and lower surface tension than that of the reconstituted precipitate fraction. The reconstituted precipitate fraction exhibited foam stability due to the higher total sugar content than that of the reconstituted supernatant. Mother Parkers Tea & Coffee Inc.; Natural Sciences and Engineering Research Council of Canada; Ontario Centres of Excellence 2022-02-03

Fermented coffee beverage is a relatively unexplored product with limited information in the literature. This study investigated the feasibility of making non-alcoholic beverage by fermenting instant coffee fortified with sucrose. Five different commercial Saccharomyces yeast strains were tested for the fermentation of the coffee solutions. Then, the optimal yeast was selected by sensory evaluation to do further study. Further study was focused on making the alcohol content less than 0.5% v/v by fermenting coffee solutions with concentrations from 0.5 to 2.5% w/w. The physiochemical properties and volatile compounds of the products were measured, as well as the sensory profiles evaluating. In result, Safbrew wb-34/70 was selected for this product due to good fermentation performance, the lowest alcohol/ester ratio, and retain typical coffee flavor. Considering the physicochemical and sensory properties, 2% coffee solution with Safbrew wb-34/70 was the most desirable formulation for the preparation of fermented coffee beverage.

Hexanal is an antimicrobial compound with phospholipase D inhibition properties, and effective for extending shelf life of fresh produce. Due to high volatility and susceptibility to oxidative degradation, a system to increase its retention is important. In this research, hexanal was incorporated to zein and hydroxypropyl methylcellulose based coating formulation. Scanning electron microscopy, Fourier transform infrared, and energy dispersive x-ray spectroscopy analyses confirmed the dual-layer coating formation. Hexanal incorporation inhibited mold and bruise development of nectarines. Response surface methodology was used to evaluate the formulation parameters on response variables. Formulations were not effective in decreasing weight loss, but were capable of preserving firmness. pH levels of coated fruits were higher than control (except formulation #11). The fruits coated with central formulation demonstrated 11.98% Brix, whereas, control had 11.3% Brix at the end of 12 days. The developed coating formulation could be promising for extending the shelf life of perishable fruits. 2021-05-21

Colorimetric indicators are versatile materials for intelligent packaging, since they can interact with the food matrices and/or the packaging environment and in turn reveal quality change or spoilage through detectable color responses. In this project, the fundamental aspects of colorimetric indicator systems applicable in intelligent packaging were investigated, including the synthesis of indicator dyes, characterization of indicator’s color response upon analyte exposure, development of scalable indicator fabrication methods, and evaluation of the performance in food packaging conditions. Cinnamil- and quinoxaline-derivative dyes were successfully synthesized. They exhibited significant color responses upon the exposure to volatile amines – fish spoilage volatiles. Quinoxaline-derivative indicators exhibited visually detectable color transition for the detection of fish spoilage at room temperature. Using free surface electrospinning as a manufacturing approach, curcumin-loaded electrospun nonwoven indicators were developed based on either polyvinylpyrrolidone or ethylcellulose/poly(ethylene oxide) carriers. When the curcumin-laden indicators were exposed to volatile amines, visually noticeable color change and fluorescence quenching were detected. In an attempt to scale up the production of the colorimetric indicator, in another study, the piezoelectric inkjet printing technique was investigated. Chemo-responsive indicator inks were formulated by manipulating their solution and rheological properties to optimize the printability in commercially available ink cartridges. The inkjet-printed indicators showed superior sensitivity for discriminating volatile amines, and exhibited strong correlations with the volatile amine levels in package headspace of fresh fish fillets stored at 4 oC over 7 days. To further explore the utility of the colorimetric indicator systems, a preliminary study was conducted for rapid detection of monoterpenes in hemp essential oil through a colorimetric indicator assay. Myrcene and ocimene, which are the main monoterpene components in hemp essential oil, were responsible for the rapid color responses at 55 oC. The colorimetric indicator developed here could be further improved for rapid quality assessment of other cannabis-based products. Overall, this research demonstrated the capability of various indicator dyes (curcumin, sulfonephthalein, cinnamil- and quinoxaline-derivatives, and pararosaniline) for food quality monitoring, using volatile amine fish, and monoterpene as the model system. This research also demonstrated the feasibility of employing electrospinning and inkjet printing for large-scale production of the colorimetric indicators. 2022-04-27

To extend the shelf-life of fresh produce, the control of microbial growth and the delay of ripening are important. In this study, naturally occurring volatiles were investigated. Hexanal and salicylaldehyde are potent antimicrobials with hexanal also capable of delaying senescence in plants due to its phospholipase D (PLD) inhibition properties. The current research synthesized branched polyethylenimine (BrPEI)-aldehyde precursors which were substantially more stable than the free aldehydes. The nucleophilic addition of the carbonyl group of the aldehydes to the secondary amines of the BrPEI produced imidazolidine moieties on the polymer chains, which were hydrolysable under mild acidic conditions to release the original aldehydes. The resulting precursors were further dissolved in a spin dope solution comprising of ethyl cellulose/poly(ethylene oxide) (EC/PEO) blend at 100:1 ratio (w/w) in butanol. The polymer solution was electrospun into ultrafine nonwoven membranes using a free surface electrospinning technique. To trigger the release of aldehydes, two different approaches were investigated: (1) direct triggering by adding citric acid solutions (0.1, 0.5 & 1.0 N) to the BrPEI aldehyde precursors encapsulated in EC/PEO electrospun nonwovens; and (2) indirect triggering by humidity/moisture in the air on BrPEI aldehyde precursors encapsulated in EC/PEO electrospun nonwovens containing citric acid monohydrate. To attain a preservation system with salicylaldehyde’s antimicrobial and hexanal’s PLD inhibition properties, a blend precursor was developed that concurrently released both the aldehydes. The polymeric aldehyde precursor systems developed here could be potentially useful in active packaging applications applied to food systems for preservation and shelf life extensions. 2020-08-25

To extend the postharvest shelf-life of fresh fruits and vegetables, an optimal preservation technology must be applied to control microbial growth and delay ripening. To this end, essential oils from edible plants and their constituents increasingly being exploited by producers to alleviate consumers’ concern on the use of synthetic preservatives. Salicylaldehyde and hexanal are naturally occurring antimicrobial agents. The latter is also an inhibitor of phospholipase D, which is an enzyme present in cell membranes responsible for senescence in plant tissues. However, applications of these aldehydes are limited by their volatility and oxidative degradation. The present research investigated a method to synthetize aldehyde precursors, imidazolidines, through Schiff base reactions using N,N’-dibenzylethane-1,2-diamine as a reactant. The resulting precursors were further embedded into ethyl cellulose-poly(ethylene oxide) (EC-PEO) nonwovens by using a free surface electrospinning technique. An on-demand trigger release system was developed wherein the releases of salicylaldehyde and hexanal vapours were achieved by contacting the precursor-loaded nonwovens with an acidified agarose gel. Studies were conducted on avocado fruits to investigate the effects of the aldehyde precursors on product shelf-life. Results showed that hexanal was potent on delaying the ripening of avocados, while salicylaldehyde enhanced the microbial stability of the fruit samples. Co-release of both aldehydes from their precursors, in conjunction with the use of high-barrier package, delayed the ripening of the fruits by 2 weeks (as determined by changes in skin color), lowered weight loss, and reduced respiration rate, as compared to the untreated controls. The methods developed, and the findings generated from this research, can potentially be used for engineering active packaging systems for the preservation of fresh produce. Natural Sciences and Engineering Research Council of Canada; iFood Packaging Systems Corp.

In this research, the opening/closing behavior of low-profile and button one-way degassing valves were examined with varying silicone oil viscosities (20, 70, 160 and 1100 mPa·s), valves were exposed to darkly roasted fine and coarse grind coffee degas. Furthermore, the degassing rates of fine and coarse coffees were approximated with two-component empirical models, enabling the simulation of CO2 degas behavior via a programmable infusion pump. Oxygen ingress was measured in real-time while the valve was exposed to fine and coarse coffee degas to evaluate the effect of opening/closing behavior on the ingress of air. In addition, consumer acceptability and discrimination testing between reference and treated samples stored in fraction pouches with oiled low-profile and button valves, as well as un-oiled low profile and no valve samples, were conducted in 7 sensory evaluations over a 12-week duration. Headspace analysis of key volatile concentrations was also performed on the brewed coffee. This work was supported by Mitacs through the Mitacs Accelerate program in conjunction with O2i Ltd.

Submitted by Gabriela Lopes (gmachadolopesufpel@gmail.com) on 2018-07-30T17:31:21Z No. of bitstreams: 1 tese.pdf: 5070792 bytes, checksum: e3c93d2e0995cdf58a61f24f273d2f40 (MD5) Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2018-07-31T19:13:06Z (GMT) No. of bitstreams: 1 tese.pdf: 5070792 bytes, checksum: e3c93d2e0995cdf58a61f24f273d2f40 (MD5) Made available in DSpace on 2018-07-31T19:13:06Z (GMT). No. of bitstreams: 1 tese.pdf: 5070792 bytes, checksum: e3c93d2e0995cdf58a61f24f273d2f40 (MD5) Previous issue date: 2018-06-04 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES A busca pela minimização do impacto ambiental pelos materiais sintéticos e alternativas naturais para conservação de alimentos, direciona as pesquisas para o desenvolvimento de embalagens biodegradáveis e bioativas. O objetivo desse trabalho foi desenvolver hidrogéis bioativos a base de amido de arroz incorporados com óleo essencial de alecrim. Amidos de arroz com diferentes teores de amilose, nativos e modificados por intercruzamento, e poli(álcool vinílico) foram utilizados para elaboração de hidrogéis via gelatinização alcalina e por aquecimento. O óleo essencial de alecrim (OEA) foi avaliado pela composição química e contra a ação das bactérias: Salmonella Typhimurium ATCC 14028, Escherichia coli O157:H7 NCTC 12900 e Pseudomonas aeruginosa ATCC 15442. O OEA foi encapsulado por electrospraying de uma emulsão de amido modificado pelo reagente anidrido octenil succínico (amido- OSA) com diferentes concentrações de etanol (20-40%, v/v) e OEA (20-50%, p/p). Para a elaboração dos hidrogéis bioativos uma emulsão de amido-OSA e OEA foi adicionada antes e após a gelatinização do amido. A absorção de água, perfil de análise em textura, morfologia e integridade estrutural dos hidrogéis foram avaliadas. A gelatinização alcalina permitiu obtenção de hidrogéis mais rígidos, insolúveis em água e com menor absorção de água em relação aos hidrogéis elaborados pelo método de gelatinização por aquecimento. Estas características também foram influenciadas pelo teor de amilose do amido de arroz. As emulsões foram estáveis e apresentaram baixa tendência a agregação quando utilizado 20% de etanol. O electrospraying das emulsões permitiu a obtenção de cápsulas esféricas e com alta eficiência de encapsulação (82% a 98%). Com base nas propriedades dos hidrogéis, como integridade estrutural e resistência mecânica o amido de arroz modificado de média amilose foi escolhido para elaboração dos hidrogéis bioativos via gelatinização alcalina. Os hidrogéis bioativos apresentaram diferentes características dependendo da etapa de adição da emulsão, com maior absorção de água e menor dureza quando a emulsão foi adicionada antes da gelatinização. O óleo essencial de alecrim apresentou atividade antibacteriana contra S. Typhimurium ATCC 14028, E. coli O157:H7 NCTC 12900 e P. aeruginosa ATCC 15442. O. A ação dos hidrogéis com óleo essencial de alecrim contra proliferação dessas bactérias será foco de estudos futuros. The aim of minimization of environmental impact by synthetic materials and natural alternatives for food preservation, leads the researches for the biodegradable and bioactive packaging development. The objective of this study was to develop bioactive hydrogels based on rice starch filled with rosemary essential oil. Native and crosslinked rice starches with different amylose contents, and poli(vinyl alcohol) were used to prepare hydrogels via alkaline- and heating-induced gelatinization. The rosemary essential oil (REO) had the chemical composition evaluated and antibacterial activities against Salmonella Typhimurium ATCC 14028, Escherichia coli O157:H7 NCTC 12900 e Pseudomonas aeruginosa ATCC 15442. The REO was encapsulated by electrospraying the emulsion of OSA-starch with different ethanol (20-40%, v/v) and REO (20-50%, w/w) contents. For bioactive hydrogels the OSA-starch/REO emulsion was added before and after the starch gelatinization. The water absorption, texture profile analysis, morphology and structure of the hydrogels were evaluated. The alkaline-gelatinization produced a more rigid, insoluble in water and with less water absorption hydrogel than the heating-gelatinization hydrogels. These amylose content also influenced the hydrogels properties. The 20% ethanol content emulsions were more stable and showed low tendency to aggregate than the others ethanol content emulsions. The electrosprayed emulsions formed spherical capsules with high encapsulation efficiency (82% to 98%). Based on the hydrogels properties, such as mechanical strength, the medium amylose modified rice starch was chosen for the bioactive hydrogels preparation via alkaline-gelatinization. Bioactive hydrogels presented different characteristics depending on the time the emulsion was added. When the emulsion was added before the gelatinization a higher water absorption and lower hardness was obtained. Rosemary essential oil presented antibacterial activity against S. Typhimurium, E. coli and P. aeruginosa. Rosemary essential oil presented antibacterial activity against S. Typhimurium, E. coli and P. aeruginosa. The bioactive hydrogels filled with REO activities against these bacteria will be further studied.

This research explored the potential application of encapsulated lytic Listeria phages as an additive in ready-to-eat meats prior to cooking to control L. monocytogenes. The objectives of this research were to: (a) evaluate the thermal stability of Listeria phage; (b) encapsulate Listeria phage to increase its thermal stability during thermal treatment; (c) investigate methods to apply phages in cooked meat product to control L. monocytogenes. The thermal stability of Listeria phages P100 and A511 at temperatures simulating typical preparation of RTE meats was evaluated. Substantial differences were found in thermal stability of the phages, with A511 showed a higher thermal stability than P100. However, P100 exhibited a greater ability to reconstitute during the cooling stage after the thermal treatment (80 °C) compared to A511. Heat treatment was accompanied by morphological changes to phage particles as revealed by transmission electron microscopy. Next, the bacteriophage was encapsulated in food-grade biopolymer matrices and their thermal stability evaluated. Through response surface analysis, the optimal polymer concentrations for achieving maximal thermal stability at 71 °C(30 s) was determined to be 2.91% (w/w) sodium alginate, 1.28% (w/w) gum Arabic, and 1.13% (w/w) gelatin. Encapsulating the phage with this formulation significantly (P0.05) affected pathogen counts. Conversely, applying the phages on the surface inactivated surface-inoculated L. monocytogenes. Overall, this study shows that significant (P

Hexanal and benzaldehyde are naturally occurring antimicrobial aldehydes with (Generally recognized as safe) GRAS status. They are useful for shelf-life extension of perishable fruits and vegetables. Their high volatility and susceptibility towards oxidative degradation present considerable challenges during end-use applications. In this research, precursors of these aldehydes with enhanced stability were synthesized using a straightforward partial Schiff base reaction which converted them into imidazolidine compounds. Nuclear magnetic resonance (NMR) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic analyses confirmed the heterocyclic ring-structure of the synthesized precursors. The release of aldehyde from the imidazolidine precursors can be achieved by an acid catalyzed hydrolysis reaction. To facilitate the end-use applications of these aldehyde precursors, they were encapsulated in poly(lactic acid) (PLA) or ethylcellulose (EC) polymer carrier by using electrospinning and electrospraying processes, respectively. The addition of an aqueous citric acid solution to the precursor-containing carriers triggered the release of aldehydes, the release rate and maximal quantity of which were carrier polymer and temperature dependent. Scanning electron micrographs (SEM) illustrated substantial morphological differences between pristine and precursor loaded carriers. FTIR analyses confirmed that the encapsulation of precursors inside PLA and EC carriers was mainly due to physical entrapment. This controlled release system developed in this project can potentially be used as a component of active packaging to deliver hexanal, benzaldehyde, and other aldehydes.

Thymol and carvacrol are naturally-occurring antimicrobial agents in herb essential oils. This study investigated the encapsulation of thymol and carvacrol using electrospun ethyl cellulose-poly(ethylene oxide) (EC-PEO) and cellulose acetate-poly(ethylene oxide) (CA-PEO) nonwovens, respectively. EC-PEO nonwovens were electrospun from dopes prepared in 80% (v/v) aqueous ethanol solution, and CA-PEO nonwovens were electrospun from acetic acid:acetone blend solvents (1:0, 3:1, and 1:1 weight ratios), respectively. The solution properties of the spin dopes were evaluated, including surface tension, electrical conductivity, viscosity, as well as solvent vapor pressure and dielectric constant. Moreover, polymer-polymer, polymer-solvent, polymer-antimicrobial and solvent-antimicrobial compatibilities were explained using Hansen solubility parameters. Antimicrobial-incorporated electrospun nonwovens were further analyzed using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy to elucidate how thymol and carvacrol interact with the polymers. The encapsulation efficiency (EE) of antimicrobial agents decreased as their loading in the spin dope increased. On the other hand, increasing PEO molecular weight increased the EE values. For the encapsulation of carvacrol in CA-PEO nonwovens, increasing acetic acid ratio in the binary solvent resulted in an increase in carvacol EE. Both EC-PEO and CA-PEO electrospun nonwovens exhibited humidity-dependent release behavior; as the relative humidity increased from 33 to 93%, the release rates and equilibrium concentrations for thymol and carvacrol increased considerably. The thymol-loaded EC-PEO and cavacrol-loaded CA-PEO nonwovens potentially can be useful as substrates for antimicrobial applications, such as in active packaging for the extension of food shelf life. Natural Sciences and Engineering Research Council of Canada; iFood System Corporation

Antimicrobial volatiles are gaining increasing interest for active packaging applications. However, many hurdles remain unresolved, especially on delivering antimicrobial compounds in a controlled manner to minimize undesired impacts on the packed products. In this thesis, two carriers were developed and characterized for controlled release of allyl isothiocyanate (AITC), diacetyl, and cinnamaldehyde. Controlled releases of AITC and diacetyl were achieved by incorporating these volatile compounds into polymer blends of different molecular weights. Results showed that increasing proportion of high molecular weight polymer in the blends resulted in lower diffusion rate of the volatiles due to higher proportion of crystalline phase in the polymeric carrier, but increased the zero order release kinetics due to exclusion of the antimicrobial compounds as the polymer crystallized. Exposing the polymeric carries to elevated RH induced plasticization and partial solubilisation of the polymer, thus accelerated the release of AITC and diacetyl vapors. The controlled release of cinnamaldehyde was achieved by encapsulating cinnamaldehyde in PLA-based nonwovens produced by electrospinning. Both DSC and FTIR data revealed the presence of interactions between cinnamaldehyde and PLA. The release rate of cinnamaldehyde from PLA-based nonwovens was accelerated when exposed to elevated RH (80 to 100% RH). The efficacies of the antimicrobial compounds, as well as antimicrobial-loaded carriers, were evaluated against mould, yeast, and bacteria. The optimal weight ratio was found to be 1:4:60 AITC:diacetyl:cinnamaldehyde. The antimicrobials-loaded carriers successfully extended the shelf life of mung bean sprouts, a model food system. Natural Sciences and Engineering Research Council of Canada (NSERC) and iFood Systems Corporation.

Intelligent packaging systems with enhanced communication functions are getting an increasing amount of attention in the food packaging field, because they can inform the consumer of the actual quality of the products. This thesis is an investigation of the development of colorimetric indicators intended for use in intelligent food packaging. Two colorimetric indicators have been successfully developed to detect CO2 and NH3. The first CO2 colorimetric indicator described in this thesis used pH dyes and certain phase transfer agent to prepare the sensing inks. Thermal inkjet printing technology and multiplexing method were used to fabricate indicators and modify the indicator performances respectively. The effect of different printing substrates and printing passes on the indicator performance were studied. It was found that 10 printing passes on paper has the optimal color response towards CO2. The influence of multiplexing ratios using inkjet printer on indicator performance was also investigated. Results showed that the indicators based on multiplexed inks exhibited higher sensitivity upon the changes of CO2, and a multiplexing ratio of 5:5 was the most sensitive to CO2 and presented the most pronounced color change. The second colorimetric indicator outlined in this thesis is a 4×4 array indicator, targeted at CO2 and NH3. These 16 sensing elements were prepared using pH dyes with or without dopants in binding material (ethylcellulose polymer). ∆RGB patterns were generated by subtracting the “before” exposure image from the “after” exposure image. Multivariate analysis, e.g. PCA, was used to interpret the ∆RGB patterns. The influence of temperature was also studied. The array was found to be more sensitive at 4 than 25℃. At both temperature, the array successfully discriminate CO2 from NH3, as well as their mixtures. Different ∆RGB patterns were obtained for NH3 and CO2 of different concentrations, as well as their mixtures with different blending ratios. pKa and chemical structures of the pH dyes were found to be crucial for indicator sensitivity upon detection of CO2 and NH3. The observed results clearly indicate that for these colorimetric indicators, there is a potential application in food packaging systems, especially modified atmosphere packaging systems for perishable foods. Natural Sciences and Engineering Research Council of Canada (NSERC) and Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA).

This research investigated the entering and spreading phenomena of emulsion droplets at the air-water interface, as it relates to ring formation and oil spreading in beverage emulsions. Drop shape tensiometry was employed to observe the adsorption, entering or spreading of oil droplets. A flavor emulsion, resembling a beverage was employed as the model system for this thesis. The spreading coefficient was not an effective indicator for oil spreading at the air-water interface in the complex emulsion systems. In biopolymer based emulsion systems, the dilational elastic modulus is a better parameter than surface tension for predicting the entering and spreading events. It was also shown that instability may be prevented by addition of a low molecular weight emulsifier. For the first time, confocal microscopy was employed to observe adsorption and spreading of oil droplets in model beverage emulsions.

Solid particle stabilized emulsions have gained attention due to their surfactant free nature and high stability. However, insights on the interactions between solid particles stabilizing emulsions and surface active species found in food are important in formulation and use of such emulsions in real food applications. The properties of chitin nanocrystal (ChN) stabilized emulsions in the presence of beta-lactoglobulin (β-Lg), a commonly used emulsifier protein were studied as a function of pH. SDS-PAGE established that the protein co-existed with ChN at the interface. In vitro digestion studies demonstrated that, addition of β-Lg did not alter the rate of lipolysis observed with ChN stabilized emulsions. Electrophoresis on digestion end products also showed evidence for some protection offered by ChN to β-Lg at the interface against proteolysis. The results of cytotoxicity studies using Caco-2 cells, indicate that ChN dispersions do not have a detrimental effect on the proliferation of cells.

In the present study, the effect of roasting temperature-time conditions on residual CO2 content and its degassing behaviours in roasted coffee was investigated. The results show that the residual CO2 content in the roasted coffee beans was only dependent on the degree of roast and independent on the roasting temperature applied. However, CO2 degassing was shown significantly faster (p0.9) between total CGA and residual CO2 content during coffee roasting was detected, and vanishing of IR bands of the C=O group in caffeic acid and quinic acid moieties during heating of pure CGA at coffee roasting temperature was observed, the quantification analysis of CO2 generation from pure CGA heating indicated only ~ 8% yields at 230°C, which led us to conclude that CGA was one of the CO2 precursors but not the principal one. Accordingly, an alternate idea was put forward, hypothesizing that Maillard reaction could account for the CO2 formed. Roasting studies of glycine-sucrose simple models showed that large amount of CO2 was formed from Maillard reaction under coffee roasting conditions, confirming the importance of Maillard reaction in CO2 formation in roasted coffee. The isolation and roasting studies of green coffee fractions showed that CO2 was generated from various green coffee components, including water insoluble proteins and polysaccharides. Around 50% of CO2 was formed from lower molecular weight compounds with this fraction representing ~25% of green coffee by weight.

There is a growing interest in using antimicrobial components from edible plants to prolong the shelf-life of food due to consumer preference for naturally occurring preservatives. In this thesis research, the release of allyl isothiocyanate (AITC), a potent antimicrobial volatile from mustard seed, was investigated. The formation of AITC in mustard seed is mediated by an enzymatic reaction, in which myrosinase catalyzes the hydrolysis of sinigrin - a glucosinolate naturally presents in mustard seed. The effects of relative humidity (85 to 100% RH), temperature (5 to 35°C), and lipid content on the release kinetics of AITC from mustard seed meal powder (MSMP) were evaluated using headspace gas chromatography. The MSMP samples were prepared by a ball milling treatment, resulting in particle diameters ranging from 10 to 500 µm. The kinetic data showed that both the release rate and the maximum amount of AITC released significantly (p < 0.05) increased with elevated RH and temperature. The finer the particle size of the MSMP, the higher the AITC release rate. To manipulate the AITC release kinetics, defatted ground MSMP samples were encapsulated within electrospun fibers. The defatted ground MSMP was dispersed into 9% poly(lactic acid) (PLA), 3% poly(ethylene oxide) (PEO), or blends of the two polymer solutions at weight ratios of 75:25, 50:50 and 25:75, respectively. The release kinetics of AITC from the composite fibers were monitored using a headspace gas chromatograph. The AITC release data in the headspace air showed that the addition of PEO into PLA polymers significantly increased (p< 0.05) the AITC release rate comparing to that from the 100PLA0PEO MSMP-containing membrane and indicated that electrospun fibers with different PLA and PEO ratios could be used as carriers to control the release of AITC from MSMP. In view of the antimicrobial properties of AITC, MSMP and MSMP-containing electrospun fibers could control the release of AITC and may be feasible for use in food active packaging applications to extend food shelf-life. NSERC; Biofumes Technologies Inc.

Poly(ethylene oxide) (PEO) is known for facilitating the electrospinning of biopolymer solutions, that are otherwise not electrospinnable. The objective of this study was to investigate the mechanism by which PEO enables the formation of whey protein isolate (WPI) electrospun fibers under different pH conditions. This investigation revealed that the addition of PEO increased the viscosity of WPI/PEO (10% w/w WPI; 0.4% w/w PEO) solutions. Difference in pH levels of the polymer solutions affected electrospinnability and fiber morphology. Acidic solutions resulted in smooth fibers (700 ± 105 nm) while neutral solutions produced spheres (2.0 ± 1.0 um) linked with ultrafine fibers (138 ± 32 nm). In comparison, alkaline solutions produced fibers (191 ± 38 nm) that were embedded with spindle-like beads (1.0 ± 0.5 um). Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analyses revealed that the native globular configuration of WPI was not altered under neutral conditions. By contrast, the electrophoresis and spectrometry data indicated that WPI was denatured and hydrolyzed under acidic conditions, which facilitated the formation of smooth fibers. C13 nuclear magnetic resonance (NMR) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopies showed that the increase random coil and a-helix secondary structures in WPI contributed to the formation of bead-less electrospun fibers. Also, C13 NMR analysis showed no evidence of chemical interaction between WPI and PEO. Scanning transmission electron microscopy coupled with energy dispersive X-rays (STEM-EDAX) revealed that WPI was uniformly distributed within WPI/PEO electrospun fibers. Observations by scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) indicated that fibers possessed a solid core. All these findings suggested that PEO enables the formation of WPI/PEO electrospun fibers by entanglement/entrapment/deposition. Preliminary studies were conducted on hydroxypropyl methyl cellulose (HPMC). In the absence of PEO, HPMC enabled the formation of WPI electrospun fibers under acidic conditions (124 ± 46 nm). FTIR analyses indicated that there was no interaction between HPMC and WPI, suggesting that HPMC aided in the electrospinning of WPI fibers, also by entanglement/entrapment/deposition. Hence, HPMC and PEO aid in the electrospinning of WPI fibers by entanglement/entrapment/deposition, which can be manipulated by alterations in the protein configuration and solution properties. Natural Sciences and Engineering Research Council (NSERC) of Canada and the Dairy Farmers of Ontario (DFO)

This thesis explored the use of sodium alginate-pectin-poly(ethylene oxide) electrospun fibers as a carrier to stabilize folic acid - an essential micronutrient that is susceptible to degradation when exposed to light and acidic conditions. In the first phase of this research, electrospinning behaviour of aqueous alginate-pectin solutions was investigated. Aqueous polysaccharide solutions could not be electrospun unless poly(ethylene oxide) (PEO) was added (≥20% w/w), resulting in electrospun alginate-pectin fibers that varied from fiber to fiber-bead, depending on the polymer blend ratio, and concentration of the polymer solutions. Polymer solutions properties (surface tension, viscosity, conductivity) were determined to study their effects on the electrospinning behaviour of the polymer solutions. In the second phase of this research, folic acid was incorporated into the polymer solutions and electrospun. The efficacy of these fibers in improving the stability of folic acid under different pH conditions was investigated. FTIR and NMR spectroscopies were employed to elucidate the nature of polymer-polymer and folic acid-polymer interaction. In phase three, the release behaviour of folic acid under simulated gastrointestinal conditions was evaluated. Overall, this research showed that electrospun fibers with different morphologies could be produced by manipulating the polymer concentration, polysaccharide/PEO blend ratio, extent of sonication treatment during sample preparation, and electrospinning process parameters. The positive effect of PEO on the electrospining of alginate-pectin fibers was attributed to its electrical conductivity and surface tension lowering effects on the polymer solutions. Electrospun fibers produced from the combination of alginate-pectin resulted in higher retention of folic acid compared to that of alginate alone. Folic acid encapsulated in crosslinked electrospun fibers achieved close to 100% retention when stored in the dark at pH 3 after 41 days of storage. Minimal release of folic acid from the electrospun fibers was observed at pH 3, although the release was significantly higher at pH 1.2. On the other hand, the release of folic acid was nearly 97% at pH 7.8, a condition that simulated the pH condition in the intestine. From NMR and FTIR data, the stabilization effect of electrospun fibers on folic acid was attributed to physical entrapment and not specific chemical interaction. The research suggests that ethanol-treated crosslinked alginate-pectin electrospun fibers can potentially be used as a folic acid carrier to protect the micronutrient in food products, especially acidic food products such as fruit juices and acidified beverages. Natural Sciences and Engineering Research Council of Canada (NSERC) and Heinz Company of Canada

A biodegradable alternative to synthetic plastics was explored in this study through the extrusion of a soy-based protein/fiber composite film. Two fractions of fibers with different size distributions (nano- to micro-) were isolated from soy pods and stems using a chemi-mechanical method. Fibers through successive treatments were characterized via microscopy, x-ray diffraction, and Fourier Transform infrared analysis (FTIR). The continuous extrusion of homogenous SPI film (0.08 to 0.3 mm thick) was reported for the first time. Processing window was limited by protein sensitivity to moisture and heat. With the incorporation of extracted fibers, homogenous films were obtained with a concentration below 0.5% w/w fiber/SPI. Increasing fiber content resulted in the formation of aggregates. At the optimal concentration of 0.25% w/w fiber/SPI, films exhibited mild improvements in mechanical performance most noticeable at a high RH (84%). Film properties with and without fiber addition were negatively affected by relative humidity. Titanium dioxide addition suggested mild coupling effects for SPI and fiber. Hannam Soy Foundation / Ontario Ministry of Agricultural, Food, and Rural Affairs (OMAFRA)

The application of current soy protein films are limited due to their low mechanical strength and high moisture sensitivity compared to synthetic materials. This research studied several methods to improve the mechanical properties [tensile strength (TS), elongation at break (EAB), Young’s modulus of elasticity (YM)] of solvent cast soy protein isolate (SPI) films. Drying times were significantly reduced through the use of a heated casting surface. Neutral (pH 7) SPI films were prepared but were found to have lower TS, EAB and YM than control films prepared under alkaline conditions. Cellulose was extracted from soybean wastes and transmission electron microscopy (TEM) verified the existence of nano-sized fibres. Composite SPI films were prepared using either extracted cellulose fibres or titanium dioxide (TiO2) nanoparticles and their mechanical and barrier properties (water vapour, and oxygen permeability) were evaluated under different relative humidity (RH) conditions. In general, TS and YM decreased and EAB increased with increasing RH. Films with 5% (w/w) added cellulose exhibited significant (p-value < 0.05) improvements in TS and YM but decreased EAB. TiO2 composites possessed similar TS, YM, and EAB values to control films. Barrier properties were comparable across all samples, and decreased with increasing RH. Samples were characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Preliminary work investigating synthesis of filler materials using cross-linked sodium alginate particles increased the TS and YM of SPI films to a similar extent as extracted cellulose. A method for electrospinning cellulose using ionic liquids was developed, but requires further process optimization to be used for fibre/filler synthesis. OMAFRA; Hannam Soy Utilization Fund

Heat sealing is commonly used for making form-fill-seal packages fabricated from thermoplastic films. One of the challenges frequently faced by the industry is inadvertent contamination of the film–film interface by the product during filling, an event that can compromise package seal strength and integrity. In the present study, the effects of dwell time (0.5–1.5 s), jaw pressure (28–1,860 kPa), jaw configuration, jaw temperature (150–180°C), and liquid (water and oil) on the interface temperature and seal strength of a linear low-density polyethylene (LLDPE) film were investigated. In the presence of liquid contaminants, jaw pressure played an important role in displacing the liquid from the seal area allowing the formation of intact seals. Within the experimental conditions investigated, interface temperatures of 130–140°C resulted in optimal seal strength for both water-contaminated and clean film specimens. Thermophysical properties of LLDPE and the contact angle between the contaminant liquid and the polymer films were invoked to explain the seal strength behaviour of the liquid-contaminated LLDPE seals. Further, finite element analysis (FEA) heat transfer models were developed to describe the heat transfer phenomena for LLDPE film during heat sealing, when a liquid contaminant layer is present or absent at the film-film interface. The model predicted the observed temperatures well with root mean square errors (RMSE) ranged from 1.6 to 2.5°C. The FEA approach can potentially be applied to analyze the effect of different contaminant liquids on transient heat transfer during heat sealing. In the second part of this thesis research, an UV-activated oxygen indicator was developed to detect the headspace oxygen within sealed package. The detector involved encapsulating TiO2 nanoparticles, glycerol, and methylene blue within poly(ethylene oxide) fibers using electrospinning. The sensitivity characteristics of the indicator to UV-activation and oxygen detection were investigated. The color recovery rate of the electrospun indicator related negatively to the UV exposure time and to the TiO2 fraction in formulation, possibly due to the ratio of higher free electrons to methylene blue concentration. The indicator can potentially be used as a method to analyze heat seal integrity in modified atmosphere packaging applications. Natural Sciences and Engineering Research Council (NSERC) of Canada and E.I. Du Pont Canada Co.

In this research, physicochemical changes that took place during roast processing of coffee beans using fluidized air roaster were studied. The results showed that high-temperature-short-time resulted in higher moisture content, higher pH value, higher titratable acidity, higher porous structure in the bean cell tissues, and also produced more aldehydes, ketones, aliphatic acids, aromatic acids, and caffeine than those processed at low-temperature-long-time process. Fourier transform infrared (FTIR) spectroscopy and chemometric analysis showed that clusters for principal components score plots of ground coffee, extracted by a mixture of equal volume of ethyl acetate and water, were well separated. The research indicated that variations in IR-active components in the coffee extracts due to different stages of roast, roasting profiles, and geographical origins can be evaluated by the FTIR technique. Natural Sciences and Engineering Research Council of Canada (NESRC) and Mother Parkers Tea & Coffee Inc.

In this research, a method was developed to continuously electrospin zein-ethanol polymer solutions into ultrafine zein fibers. Scanning electron microscopy results showed that the morphology of zein fibers was affected by aqueous ethanol concentration, zein concentration, and the applied voltage. The electrospun zein fibers were tested to encapsulate (-)-epigallocatechin gallate (EGCG), a green tea polyphenol, under optimal electrospinning conditions. Zein fibers aged at 0% RH for 1 day were found to achieve an enhanced EGCG retention (> 98%) in fibers when they were submerged in water. Fourier transform infrared spectroscopy results showed that hydrogen bonding and hydrophobic interactions were the major contributors involves in the stabilization of EGCG in zein fibers. The stability of EGCG in various aqueous solutions (pH 4 - 9, 4 - 100°C) was evaluated by using high performance liquid chromatography to determine the kinetics of degradation and epimerization reactions of EGCG. Pseudo first-order degradation kinetic models were developed for both reactions, of which the rate constants increased as the temperature and pH increased. Overall, the electrospun zein fibers enhanced considerably the stability of EGCG. Potentially, the electrospun zein fibers may be used as a carrier to stabilize the fortified EGCG in food.

In this study, glucose oxidase (GOX) was immobilized in electrospun polylactide (PLA) fibers to activate the lactoperoxidase (LP) system in milk. The GOX-containing microfibers were electrospun from emulsions prepared by dispersing aqueous GOX in PLA dissolved in a chloroform and N,N-dimethylformamide blend, using sorbitan monopalmitate as an emulsifier. The enzymatic activity of GOX-in-PLA fibers (1100 ± 400 nm diameter) was more than 19 times higher than that of the GOX-in-PLA membrane formed by direct casting, due to the larger surface area of the electrospun fibers. The activation of LP system in model solutions using GOX-in-PLA fibers provided a more sustained generation of antimicrobial OSCN- than direct activation using H2O 2. Preliminary evaluation on milk samples showed that the electrospun GOX-in-PLA microfibers are capable of activating the naturally present LP system. Microbial analysis of LP system activated in milk exerted antimicrobial effect, indicating that they may be promising for active food packaging applications to extend the shelf life of milk.

In this project, electrospinning technique was investigated to produce ultrafine soy protein isolate (SPI) and poly(lactic acid) (PLA) fibers. SPI fibers (~200 nm) were produced by electrospinning denatured protein (10-15% wt/wt) in aqueous solution (pH 12, 60 °C) in the presence of poly(ethylene oxide) (0.6-0.8% wt/wt) and Triton X-100 (0.5-1% wt/wt). In contrast, PLA fibers (~4 [mu]m) were spun from polymer (10% wt/wt) dissolved in a mixture of chloroform and dimethylformamide DMF (90:10). Fiber morphology can be manipulated readily by changing the fiber-forming formulation. An antimicrobial agent, allyl isothiocyanate (AITC), was incorporated in SPI and PLA electrospun fibers by direct addition of the antimicrobial into the fiber-forming solution. AITC concentration significantly affected the fiber morphology. AITC loss was reduced when cyclodextrins were used as a secondary carrier. Exposing these fibers to elevated humidity (>50% RH) triggered the release of AITC, with concomitant change in visual appearance and fiber micro-morphology. Preliminary studies showed that electrospun SPI fibers with AITC prevented mold growth on bread, indicating promising active and smart packaging applications.