No description available.

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

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Par-baked pizza was prepared with three different additives treatments and was packaged in three packaging treatments namely: air (A), 100% CO2 modified atmosphere (MAP) and 100% CO2 modified atmosphere with an oxygen absorber (MAP + OA). The additive treatments were diacetyl tartaric acid esters of mono- and diglycerides (DATEM), an enzyme combination treatment (EC) namely: lipase and maltogenic á-amylase and par-baked pizza without additives (C). The aim of the study was to determine the effects of the different additive and packaging treatments on the shelf life of par-baked pizza. Therefore the following physical measurements and microbiological analysis were conducted: water activity, crumb moisture content, thickness, firmness, stress, strain, springiness, aerobic plate count, lactic acid bacterial count and yeast and mould count. The results showed that the water activity of par-baked pizza was between 0.95–0.98 . Thereafter the water activity remained stable at 0.96. As the storage time (d) progressed, the moisture content of the par-baked pizza crumb increased, from 36% on d0 to 41% on d16. The par-baked pizza with added additives was thicker than par-baked pizza without additives. The thickness for par-baked pizza + DATEM, + EC and + C was 21.7 mm, 22.0 mm and 18.3 mm respectively. The compression test and the three-point bend test showed that the firmness of parbaked pizza increased as the storage time increased until d8. The firmness then decreased from d12 to d16. The par-baked pizza packaged + MAP had a lower firmness than par-baked pizza + A. The firmness of par-baked pizza + EC was lower than par-baked pizza + DATEM and par-baked pizza + C respectively. The results also showed that the re-baked pizza was even softer than originally. The springiness of par-baked pizza decreased as the storage time progressed. The par-baked pizza + C had the highest springiness of 39% compared to the springiness of par-baked pizza + EC; 37%, and + DATEM; 35%, respectively. The springiness of the re-baked pizza showed trends similar to those of the par-baked pizza in terms of the main effects of the different additives. The springiness of the re-baked pizza was also higher than that of the par-baked pizza. Thus, the additive treatments, DATEM and EC, had beneficial effects on the texture and thickness of par-baked pizza. The microbial analysis showed that the APC and the mould count were mostly affected by the different packaging treatments. The par-baked pizza + A showed visible mould growth from d12. Hence par-baked pizza + A reached the end of shelf life at d12. The par-baked pizza + MAP showed reduced APC levels, however, and as expected the yeast and lactic acid bacterial levels were unchanged. There were no signs of visible mould growth on any par-baked pizza + MAP. The microbial levels were the lowest with the par-baked pizza + MAP + OA packaging treatment. / Dissertation (MSc)--University of Pretoria, 2010. / Food Science / unrestricted

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.

No description available.

Typescript, etc.

The purpose was to find the adjustments needed to make acceptable pies, cookies and muffins baked in the electronic oven. The products were evaluated by a taste panel and by objective tests. The results of both tests supported each other. The best bottom pie crust had an extra tablespoon of liquid added to the pastry and was precooked before the filling was added. It was both flaky and tender. No leavening and one-fourth more liquid produced the most acceptable cookies. They were more like standard cookie in height, texture, moisture and tenderness. It was found that one-half the amount of egg and two tablespoons more liquid made the best muffins. No treatment of the muffins as used in this study resembled the standard, but were half way between a standard muffin and cake in their texture, flavor and appearance.

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LD2668 .T4 1954 G74 / Master of Science