http://hdl.handle.net/1957/17881 Theses, Dissertations and Student Research Papers (Food Science and Technology) 2013-06-20T10:32:49Z http://hdl.handle.net/1957/39533 Development of volatile composition and C13-norisoprenoid precursors in Pinot noir grape; Development of volatile composition and C₁₃-norisoprenoid precursors in Pinot noir grape Yuan, Fang This study first investigated the developmental changes in the volatile composition and carotenoids of Pinot noir grapes. Grape berries were sampled every week from pea size to harvest during the 2011 and 2012 season. Carotenoids and organic acids were analyzed by HPLC. Volatile compounds were extracted from crushed berries using headspace solid-phase microextraction (HS-SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS), and C₁₃-norisoprenoids potentials were analyzed by HS-SPME-GC-MS after acid hydrolysis. Malic acid accumulated before véraison and decreased dramatically during ripening. Carotenoids and chlorophylls decreased during entire developmental period although some of carotenoids showed a short accumulation stage before véraison. Pinot noir grapes had a more complex volatile compound composition pre-véraison than post-véraison, which may due to the decreasing of monoterpenes during ripening. C6-aldehydes significantly increased in concentration after véraison. C6-alcohols accumulated around véraison and decreased during ripening. Benzyl and phenylethyl alcohols increased before véraison, reached the highest amount two weeks after véraison and slightly decreased towards harvest. The concentration of volatile phenols reached the highest amount at véraison, decreased in about one week, then stayed relatively stable through maturity. Free-form C₁₃-norisoprenoids was low, but higher after acid hydrolysis, indicating the dominance of C₁₃-norisoprenoids precursors. Total C₁₃-norisoprenoids increased after véraison, corresponding to carotenoid breaking down. The analysis of grape composition in this study demonstrated a quantitative means of assessing the relationships between vineyard management practices and grape-derived secondary metabolites, some of which are important wine aroma and flavor components. Effect of cluster zone leaf removal management on grape composition were further investigated. Three cluster zone leaf removal management, including 0% leaf removal (Control), 50% leaf removal and 100% leaf removal of the cluster zone were studied in commercial vineyards from 2010 to 2012. Grape samples were harvested every year and analyzed for total soluble solids (TSS), organic acids, phenolics and carotenoids. Leaf removal had no impact on grape TSS, citric and tartaric acids but lowered malic acid in year 2012. Leaf removal increased quercetin glycoside content in grape berry in three years, and increased anthocyanin content in year 2010 and 2012. For carotenoids, leaf removal decreased flavoxanthin content in the grape berry and decreased β-carotene in 2012. It is evident that more sun exposure as a result of leaf removal increases degradation of carotenoids, and could potentially increase concentration of norisoprenoids in grapes. Graduation date: 2013 2013-05-29T00:00:00Z http://hdl.handle.net/1957/39387 Addressing sodium reduction and pathogen internalization in non-intact whole muscle beef : evaluation of dehydrated collagen and hydrostatic pressure as impact technologies Lowder, Austin Cole These studies focused on maximizing the nutrition and safety of raw whole muscle beef while minimizing quality and shelf-life alteration. The first study used response surface methodology to predict fluid loss from injected beef strip loins and steaks as influenced by levels of salt and sodium phosphates (SP) in the injection brine. Also, a beef-sourced dehydrated beef protein (DBP) water binding ingredient was evaluated. Paired U.S. select beef strip loins were quartered before being injected to 110% of initial weight with brines containing various concentrations of salt and SP (CON) or salt, SP and 5% DBP. Steaks were sliced, overwrapped and stored in the dark for 4 d. Purge values ranged from 0.6% to 4.6% for CON and 0.3% to 2.1% for DBP. Fluid losses when accounting for the fluid lost from injection to slicing were as high as 6.8% for CON brines, but only 2.8% for DBP brines. The models on fluid loss generated from the study and the DBP product could help processors achieve acceptable purge while reducing sodium use. The second study sought to determine the viability of DBP as a replacement for SP in beef injection brines. U.S. Select strip loins (n=20) were injected to 110% of their initial weight with a brine containing 3.6% salt and 4.5% sodium phosphate (CON) or 3.6% salt and 5% dehydrated beef protein (DBP). DBP loins had less fluid loss after 30 min. Steaks from both treatments lost similar amounts of fluid during storage. Total fluid loss was lower for DBP injected product. Lipid oxidation (TBARS) products were 0.23 – 0.60 mg/Kg higher for DBP steaks, but still within acceptable limits (<1.0 mg/Kg). DBP steaks were slightly less red than CON steaks according to instrumental measurements. Sensory panel evaluation, however, indicated no differences in redness. DBP steaks were less tender according to trained sensory panel. Results indicated the DBP to be effective in increasing brine retention and a suitable alternative to phosphates when used in brines injected into beef strip loins. The third study aimed to determine the interactions between salt (NaCl), sodium phosphate (SP) and mild HPP in brine injected beef, as previous studies on comminuted products have shown the action of hydrostatic pressure to increase the effectiveness of salt and phosphates on protein functionality. Beef strip loin segments were injected to 10% over initial weight with solutions containing water and various levels of salt (0, 2 or 4% of solution) and/or SP (0 or 4% of solution). Pieces from the loin sections were exposed to varying pressure levels (0.1, 152 or 303 MPa) and evaluated for selected quality and biochemical characteristics. Use of SP and pressure application increased pH additively. L* values were increased by pressure and decreased by SP. Redness (a*) increased at 303 MPa. Purge increases due to pressure were mitigated by SP. Pressure application at 303 MPa reduced total and sarcoplasmic protein solubility. This study determined there was no interaction between salt or SP and mild HPP. However, results indicate SP may have use in preventing yield loss due to HPP. The final study attempted to use high pressure-low temperature (HPLT) processing to achieve E. coli O157:H7 inactivation in non-intact, whole muscle roasts while maintaining acceptable quality characteristics. Beef semitendinosus was internally inoculated with a four strain E. coli O157:H7 cocktail and frozen at -30 °C, then subjected to 550 MPa for 4 min (HPLT). Compared to frozen, untreated control (F), HPLT reduced microbial population by 1.7 log colony forming unit (CFU)/g on selective media (Cefixime-Tellurite Sorbitol MacConkey agar) and 1.4 log on non- selective media (Trypticase soy agar). High pressure without freezing (550 MPa/4 min/3 °C) increased pH and lightness while decreasing redness, cook yield, tenderness, and protein solubility. High pressure low temperature, aside from a 4% decrease in cook yield, had no significant effects on quality relative to the control. High pressure low temperature is an effective way to subject red meat to high pressures without compromising quality. However, its diminished effect on internalized E. coli limits its effectiveness as a food safety intervention. Graduation date: 2013 2013-06-03T00:00:00Z http://hdl.handle.net/1957/39150 New development of β-chitosan from jumbo squid pens (Dosidicus gigas) and its structural, physicochemical, and biological properties; New development of beta-chitosan from jumbo squid pens (Dosidicus gigas) and its structural, physicochemical, and biological properties Jung, Jooyeoun β-chitin/chitosan extracted from newly utilized jumbo squid (Dosidicus gigas) pens were investigated in respect to their physicochemical properties, polymeric structures, deacetylation and depolymerization characteristics, and antioxidant and antibacterial activities. These functional properties were further compared with α-chitin/chitosan prepared from shrimp shells. Due to the low mineral content (< 1%) and negligible pigment in squid pens, demineralization and depigmentation steps could be omitted when extracting β-chitin. Molecular weight (Mw) and moisture content of deproteinized β-chitin were significantly higher than those of α-chitin. Crystallographic structure of β-chitin was distinguished from that of α-chitin, in which β-chitin had less inter-molecular hydrogen bond than α-chitin along with lower crystallinity (CI). β-chitin could convert into α-form as the result of alkali treatment, and the resulted α-chitin exerted significantly higher moisture absorption ability than the native α-chitin, thus retaining higher susceptibility of native β-chitin by means of the polymorphic destruction. The Kurita method using NaOH was an effective deacetylation treatment to obtain β-chitosan with high Mw and a wide range of DDA, and cellulase was more susceptible than lysozyme to degrade β-chitosan for obtaining low Mw of product. To obtain similar DDA of α- and β-chitosan, lower concentrations of NaOH and shorter reaction times were required for β-chitin than that for α-chitin. In addition, β-chitosan was more susceptible to cellulase hydrolysis than α-chitosan. High Mw (280-300 kDa) of β-chitosan exerted extremely lower half maximal effective concentrations (EC₅₀) than α-chitosan, i.e., higher antioxidant activity based on DPPH radical scavenging activity and reducing ability. The 75% DDA/31 kDa β-chitosan exerted higher inhibition against E. coli (lower MIC) than that of 75% DDA/31 kDa α-chitosan, whereas opposite result was observed in 90% DDA/74-76 kDa α- and β-chitosan. This difference could be due to the impact of the different structural properties between α- and β-chitosan on chitosan conformations in the solution, altering the surface phenomenon of protonated chitosan with negatively charged bacterial cells in the suspension. Therefore, jumbo squid pens can be commercially employed to extract functional β-chitin/chitosan with desirable structural, physicochemical, and biological activities. Graduation date: 2013 2013-05-29T00:00:00Z http://hdl.handle.net/1957/38463 Clostridium perfringens spores : inactivation, germination, and formation Udompijitkul, Pathima The enterotoxin-producing Clostridium perfringens type A isolates are responsible for the third most common foodborne illness in the United States and can also cause non-foodborne human gastrointestinal (GI) diseases such as antibiotic- associated and sporadic diarrheas. Three important factors contribute to the ability of C. perfringens to cause GI diseases, including its extremely rapid growth rate, its ubiquitous distribution in foods and environments, and its capability to form highly resistant endospores. In the first study, the antimicrobial peptide nisin was evaluated for its antimicrobial effect against enterotoxigenic C. perfringens food poisoning (FP) and non-foodborne (NFB) GI disease isolates. Nisin did not affect spore germination, whereas germinated spores were very susceptible to low concentration of nisin and thus spores outgrowth were arrested. Nisin also exerted its inhibitory effect against vegetative growth of C. perfringens FP and NFB isolates in rich medium; however, FP cells were less resistant to nisin than NFB cells. Nevertheless, nisin was not effective in controlling germination and outgrowth of C. perfringens spores in cooked meat products during storage at abusive temperature, even at ~ 4 times elevated concentration than the regulatory approved level. Strikingly, spores of NFB isolates also exhibited higher resistance to nisin than that of FP isolates in both laboratory medium as well as in meat systems. Collectively, despite its effectiveness in controlling spore outgrowth and vegetative cell growth in laboratory conditions, nisin showed no antimicrobial activity against C. perfringens spores inoculated into meat model systems. The main focus of the second study was to develop an effective spore inactivation strategy on food contact surfaces by inducing spore germination prior to inactivation of the more susceptible spores with commonly used surface disinfecting agents. The mixture of L-asparagine and KCl (AK) was the most effective germinant for spores of enterotoxigenic C. perfringens type A. Germination temperature had a significant influence on the germination extent and subsequent inactivation by variety of surface disinfectants. Implementation of germination step significantly increased the inhibitory effect of all tested disinfecting agents against spores of C. perfringens FP strain SM101 with lower efficacy against the spores of NFB strain NB16. Furthermore, spores of C. perfringens FP isolates could germinate with AK upon their adhesion onto stainless steel chips and were subsequently inactivated with disinfectant agents by i.e. 1.53 to 2.70 log reductions of colony forming units per chip. Overall, AK-induced germination followed by treatment with iodophore represents a promising strategy to inactivate spores of C. perfringens FP isolates on food contact surfaces. Spore germination is initiated upon sensing a variety of compounds, termed germinants, via the cognate germinant receptors. In the third study, we identified sodium ions and inorganic phosphate (NaPi) at pH ~ 6.0 as a novel germinant for spores of enterotoxin-producing C. perfringens FP isolates. The spores lacking germination proteins GerAA and GerKA-KC were severely impaired in their ability to germinate with NaPi, whereas GerKB-negative spores germinated to a similar extent as wild type spores with NaPi, but their initial rate of germination was lesser. Spores lacking GerO or GerO GerQ germinated to a lower extent and with a significantly slower rate than wild type spores. In contrast, gerQ spores exhibited only a slightly slower and lesser extent of germination with NaPi than its parent strains. Therefore, the germinant receptor proteins GerKA-KC, GerAA, and the putative antiporter GerO are essential for normal germination of C. perfringens spores with NaPi. In the fourth study, we demonstrated that polar, uncharged amino acids at pH 6.0 could efficiently trigger germination of spores of enterotoxigenic C. perfringens. While L-glutamine is a unique nutrient germinant for spores of C. perfringens FP isolates, L-asparagine, L-cysteine, L-serine, and L-threonine can induce germination of both FP and NFB spores. The germinant receptor GerKC is the major receptor involved in cysteine- and glutamine-induced germination and release of dipicolinic acid (DPA) from the spore’s core, whereas less pronounced germination defects were observed in gerAA and gerKB spores. GerKC also has a key role in L-asparagine germination. For serine and threonine (pH 6.0)-induced germination, GerKA is the dominant receptor and GerKC and GerKB are also required for efficient germination of FP spores. The objectives of the fifth study were to identify and characterize the putative sensor histidine kinases of C. perfringens. We identified six genes encoding putative sporulation-associated sensor histidine kinases in the genome of C. perfringens SM101. These putative kinase genes were highly expressed under sporulation- stimulating conditions. Two genes encoding putative orphan sensor histidine kinases, cpr1728 and cpr1055, were inactivated and roles of each putative kinase on various aspects in the life cycle of C. perfringens had been characterized. Inactivation of cpr1728 and cpr1055 significantly lowered C. perfringens sporulation capacity in two sporulation-inducing conditions. Moreover, sporulation delayed phenotype was also observed in strain lacking CPR1055. Inactivation of either cpr1728 or cpr1055 led to a marked defect in C. perfringens spore germination with all known germinants. Spores of two kinase mutants also exhibited slower outgrowth than their parental strain; however, no difference in colony forming efficiency was observed among tested strains. Additionally, mutations in cpr1728 and cpr1055 did not affect vegetative growth; however, both mutants grew at higher rate under sporulation-inducing conditions. In conclusion, this dissertation reports the experimental results that are relevant to various aspects of C. perfringens spores. These include the development of spore inactivation strategies in food products as well as on food contact surfaces, the identification of compounds triggering germination of spores of CPE-producing C. perfringens, and the insights into the roles of putative sensor histidine kinases in the process of spore formation and spore germination under a variety of conditions. Graduation date: 2013 2013-04-15T00:00:00Z