Call number: LD2668 .T4 1952 H31 / Master of Science

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Initial challenge studies with spores of proteolytic Clostridium botulinum types A and B (~104 spores/g) showed that while air- and gas-packaged English-style crumpets (aw 0.990) and pizza crust (aw 0.960) were toxic after 42-days storage at ambient temperature (25°C), no neurotoxin was detected in bagels (a w 0.944). Further challenge studies with similarly packaged crumpets inoculated with C. botulinum (~102 spores/g), pre- or post-baking, demonstrated that all crumpets were toxic within 4 to 6 days at 25°C and that toxigenesis preceded spoilage. Furthermore, reformulating crumpets to pH 8.3 and packaging in 100% CO2 had little effect in delaying the growth of C. botulinum compared to crumpets formulated to pH 6.5 and packaged in 60% CO2. / Subsequent studies were directed at determining the levels of additional barriers that could be used to ensure the safety of high-moisture MAP crumpets. While ethanol vapour proved to be an effective additional barrier in crumpets (100-g, [aw 0.990, pH 6.5]) challenged with ~102 spores/g of C. botulinum, spoilage preceded toxigenesis due to absorption of ethanol from the package headspace by crumpets. Modelling studies in Trypticase Peptone Glucose Yeast (TPGY) broth confirmed the anti-botulinal nature of ethanol and showed that a level of ~4% (vol/vol) could be used for complete inhibition of this pathogen, depending on the aw and pH of the growth medium. However, while ethanol vapour could be used to inhibit the growth of C. botulinum in high-moisture crumpets, its anti-botulinal efficacy was influenced by the method of crumpet leavening (yeast v chemical). / Preliminary studies were also done to assess the potential of mastic oil, a novel inhibitor, against C. botulinum. While direct and indirect application of ethanolic extracts of mastic oil inhibited the growth of C. botulinum in vivo, they failed to do so in crumpets.

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Digitized by Kansas Correctional Industries

LD2668 .T4 1954 G74 / Master of Science

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Cheung, Wing Kwun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 101-116). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / List of Tables --- p.v / List of Figures --- p.viii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Dietary fiber --- p.1 / Chapter 1.1.1 --- Introduction of dietary fiber --- p.1 / Chapter 1.1.2 --- Sclerotia of Pleurotus tuber-regium as a source of dietary fiber --- p.2 / Chapter 1.2 --- Bakery products --- p.3 / Chapter 1.2.1 --- Wheat --- p.3 / Chapter 1.2.2 --- Flour --- p.4 / Chapter 1.2.2.1 --- Flour protein --- p.4 / Chapter 1.2.2.2 --- Rheological test of flour quality --- p.5 / Chapter 1.2.3 --- Bread --- p.8 / Chapter 1.2.3.1 --- Ingredient --- p.8 / Chapter 1.2.3.2 --- Bread-making process --- p.10 / Chapter 1.2.4 --- Crackers and cookies --- p.12 / Chapter 1.2.5 --- Effect of addition of dietary fiber in bakery products --- p.14 / Chapter 1.3 --- Extrusion cooking --- p.18 / Chapter 1.3.1 --- Introduction of extrusion cooking --- p.18 / Chapter 1.3.2 --- Food extruders --- p.19 / Chapter 1.3.3 --- Application of extrusion --- p.21 / Chapter 1.3.4 --- Extrusion of starchy materials --- p.23 / Chapter 1.3.5 --- Effect of extrusion dietary fiber content --- p.24 / Chapter 1.3.6 --- Effect of extrusion on other nutritional properties --- p.26 / Chapter 1.4 --- Objectives --- p.28 / Chapter 2 --- Materials and Methods --- p.29 / Chapter 2.1 --- Mushroom powder --- p.29 / Chapter 2.2 --- Flour --- p.29 / Chapter 2.2.1 --- Crude protein content --- p.29 / Chapter 2.2.2 --- Moisture content --- p.30 / Chapter 2.2.3 --- Farinograph --- p.30 / Chapter 2.3 --- Bakery products --- p.31 / Chapter 2.3.1 --- Bread --- p.31 / Chapter 2.3.2 --- Crackers --- p.33 / Chapter 2.3.3 --- Cookies --- p.35 / Chapter 2.4 --- Extrudates --- p.36 / Chapter 2.5 --- Physical measurement --- p.37 / Chapter 2.5.1 --- Bread --- p.37 / Chapter 2.5.1.1 --- "Weight, volume and density" --- p.37 / Chapter 2.5.1.2 --- Hardness --- p.38 / Chapter 2.5.2 --- Crackers --- p.40 / Chapter 2.5.2.1 --- "Weight, dimensions and thickness" --- p.40 / Chapter 2.5.2.2 --- Volume --- p.40 / Chapter 2.5.2.3 --- Hardness --- p.40 / Chapter 2.5.2.4 --- Moisture --- p.41 / Chapter 2.5.3 --- Cookies --- p.42 / Chapter 2.5.3.1 --- "Weight, thickness and diameter" --- p.42 / Chapter 2.5.3.2 --- Hardness --- p.42 / Chapter 2.5.4 --- Extrudates --- p.43 / Chapter 2.5.4.1 --- Expansion ratio --- p.43 / Chapter 2.5.4.2 --- Density --- p.43 / Chapter 2.5.4.3 --- Hardness --- p.43 / Chapter 2.5.4.4 --- Water absorption index (WAI) --- p.43 / Chapter 2.5.4.5 --- Water solubility index (WSI) --- p.44 / Chapter 2.6 --- Dietary fiber content --- p.44 / Chapter 2.6.1 --- Preparation of samples --- p.44 / Chapter 2.6.2 --- "Total dietary fiber (TDF), Insoluble dietary fiber (IDF) and Soluble dietary fiber (SDF)" --- p.45 / Chapter 2.6.3 --- Protein and ash correction --- p.46 / Chapter 2.7 --- Nutritional evaluation of extrudates using rat model --- p.47 / Chapter 2.7.1 --- Determination of crude protein content in extrudates --- p.47 / Chapter 2.7.2 --- Diet preparation --- p.47 / Chapter 2.7.3 --- Feeding experiments --- p.50 / Chapter 2.7.4 --- Nitrogen balance experiment --- p.50 / Chapter 2.7.5 --- Determination of serum lipid profile --- p.51 / Chapter 2.7.5.1 --- Serum total triglyceride (TG) --- p.51 / Chapter 2.7.5.2 --- Serum total cholesterol (TC) --- p.51 / Chapter 2.7.5.3 --- Serum high-density lipoprotein cholesterol (HDL-C) --- p.52 / Chapter 2.8 --- Statistical analysis --- p.53 / Chapter 3 --- Results and Discussion --- p.54 / Chapter 3.1 --- MP-enriched flours --- p.54 / Chapter 3.1.1 --- Crude protein content of plain flour --- p.54 / Chapter 3.1.2 --- Moisture content of plain flour --- p.55 / Chapter 3.1.3 --- Farinograph of MP-enriched flours --- p.56 / Chapter 3.2 --- Physical characteristics of MP-containing bakery products --- p.59 / Chapter 3.2.1 --- MP-enriched bread --- p.59 / Chapter 3.2.1.1 --- "Weight, volume and density" --- p.59 / Chapter 3.2.1.2 --- Hardness --- p.61 / Chapter 3.2.2 --- MP-enriched crackers --- p.63 / Chapter 3.2.2.1 --- "Weight, dimensions and thickness" --- p.63 / Chapter 3.2.2.2 --- Volume --- p.65 / Chapter 3.2.2.3 --- Hardness --- p.66 / Chapter 3.2.3 --- MP-enriched cookies --- p.68 / Chapter 3.2.3.1 --- "Weight, thickness and diameter" --- p.68 / Chapter 3.2.3.2 --- Hardness --- p.70 / Chapter 3.2.4 --- Extrudates of MP-enriched pastry flour --- p.71 / Chapter 3.2.4.1 --- Expansion ratio --- p.71 / Chapter 3.2.4.2 --- Density --- p.75 / Chapter 3.2.4.3 --- Hardness --- p.75 / Chapter 3.2.4.4 --- Water absorption index (WAI) --- p.78 / Chapter 3.2.4.5 --- Water solubility index (WSI) --- p.80 / Chapter 3.2.4.6 --- Effect of extrusion condition on physical attributes of extrudates --- p.81 / Chapter 3.3 --- Dietary fiber content in MP-containing bakery products --- p.87 / Chapter 3.3.1 --- MP-enriched bread --- p.87 / Chapter 3.3.2 --- MP-enriched crackers --- p.88 / Chapter 3.3.3 --- MP-enriched cookies --- p.89 / Chapter 3.3.4 --- Extrudates produced form MP-enriched pastry flour --- p.90 / Chapter 3.4 --- Nutritional evaluation of extrudates using rat model --- p.93 / Chapter 3.4.1 --- Weight of animals --- p.93 / Chapter 3.4.2 --- Weight of vital organs --- p.93 / Chapter 3.4.3 --- Nitrogen balance experiment --- p.94 / Chapter 3.4.4 --- Serum lipid profile --- p.96 / Chapter 4 --- Conclusion --- p.98 / Chapter 5 --- References --- p.101

Bakery products are important sources of nutrients in our diet. However, spoilage occurs shortly after baking. After microbial spoilage, the main spoilage problem is staling. / Therefore, methods to control staling are of great importance to the bakery industry since staling results in millions of dollars annually in lost revenues. / Initial studies using a one variable at a time approach showed that enzymes, guar, algin and pectin gums and high fructose corn syrup could delay staling and resulted in an organoleptically acceptable product. Subsequent optimization studies using a Response Surface Methodology (RSM) approach show the appropriate levels of enzyme (Novamyl), guar gum and HFCS resulted in bagels with a textural and sensorial shelf life of 6 weeks at ambient temperature. / Furthermore, the cost of reformulating ($ sim$0.5 cent/bagel) is minimal and could easily be recovered through reduced production costs, reduced losses due to staling and additional sales and market areas.