The possibililty of using the simple technologies of malting and fermentation to modify endogenously the sorghum grain components, to alleviate the grittiness, dryness and high crumb firmness caused by the inclusion of sorghum flour in composite bread, was investigated. The most suitable grain and the optimal malting time for sorghum for bread¬making, were selected by malting five sorghum cultivars, up to 8 days, and evaluating them for the highest protein modification and lowest dry matter losses. On that basis, a 6¬days malt of Local White, a relatively high protein sorghum (10.7%), was selected. Sorghum malt flour potentially suitable for bread-making was produced by boiling the selected malt, rather than drying it at high temperatures, stewing or steaming. Boiling was most effective in inactivating the amylases and in increasing the pasting viscosity of sorghum malt. The bread made with boiled malt flour (30%) had an improved crumb structure and water-holding capacity, a softer crumb and increased resistance to staling, compared to bread made with sorghum grain flour (30%). Bread-making with reconstituted flours from flour and bran fractions of whole sorghum grain and whole boiled sorghum malt indicated that the bread improving effect of malting and boiling was due to dextrinization and gelatinization of starch, and to the increase of total and water-soluble pentosans, and crude fiber. Dextrinization and gelatinization of starch decreased the gelatinization temperature and the rate of starch retrogradation, thus decreasing the crumb firmness and firming rate of sorghum and wheat composite bread. However, high levels of gelatinized starch decreased dough strength and bread volume. The increase of total pentosans and crude fiber of sorghum malts, caused by germinating grains roots and shoots growth, and the increase of water-soluble pentosans, due to hydrolysis of the non-starch polyssacharides during malting, significantly increased flour and dough water-holding capacity. Thus, crumb structure was improved and crumb firmness and crumb-firming rate decreased. Treatment of sorghum flour with endo-(l-4)-β-xylanase to determine whether endoxylanases could solubilize sorghum pentosans, increased the water-soluble pentosans slightly, indicating the potential of endoxylanases to improve the bread-making quality of sorghum flour. However, heating the endoxylanase treated flour to inactivate the enzyme, so as to determine its specific effect, gelatinized the starch and decreased the bread volume. A natural lactic acid fermentation of sorghum flour, followed by drying at 60°C, decreased the pH of sorghum flour from 6.2 to 3.4 and slightly increased the gelatinized starch and the pasting viscosity of sorghum flour. Apparently, the low pH caused higher loaf volume and improved crumb structure and softness by suppressing the amylases and by increasing the viscosity of dough, and hence increasing its gas-holding capacity. Adding wet fermented sorghum flour directly to wheat flour (sourdough process), as an alternative to drying, further increased the volume and decreased the crumb firmness. Fermentation and drying also improved the protein digestibility of sorghum composite bread. Consumer panel members liked the bread made with boiled sorghum malt flour most, apparently because it was softer, more moist and had a fine malt flavor. They liked the bread made with fern1ented and dried sorghum flour less, apparently because it had a pronounced sour taste. Malting and fermentation can be successfully used to produce acceptable sorghum and wheat composite bread. Fermentation is probably the most suitable technology for poor developing countries because it is simple and effective. Steaming the malt and adding the endoxylanases directly when mixing the dough, to eliminate the flour drying step and to reduce starch gelatinization, should be looked at further. / Thesis (PhD (Food Science))--University of Pretoria, 2005. / Food Science / unrestricted

No description available.

Cheung Hiu-Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 140-150). / Abstracts in English and Chinese. / ABSTRACT --- p.i / ACKNOWLEDGEMENTS --- p.vi / LIST OF FIGURES --- p.xiii / LIST OF TABLES --- p.xv / Chapter CHAPTER 1 --- LITERATURE REVIEW --- p.1 / Chapter 1.1 --- Introduction --- p.2 / Chapter 1.2 --- Soybeans --- p.3 / Chapter 1.2.1 --- Chemistry and nutritional value of soybeans --- p.3 / Chapter 1.2.2 --- Protein composition of soybeans --- p.4 / Chapter 1.2.3 --- Volatile compounds in soybeans --- p.4 / Chapter 1.3 --- Food fermentation --- p.5 / Chapter 1.4 --- Chaw tofu --- p.6 / Chapter 1.4.1 --- Preparation of tofu --- p.7 / Chapter 1.4.2 --- Preparation of chaw tofu --- p.7 / Chapter 1.4.3 --- Microorganisms involved in fermentation of chaw tofu --- p.8 / Chapter 1.4.4 --- Volatile components in chaw tofu --- p.11 / Chapter 1.4.5 --- Proteolytic activity of chaw tofu --- p.12 / Chapter 1.5 --- Stinky brine broth --- p.13 / Chapter 1.5.1 --- The pH value of stinky brine broth --- p.13 / Chapter 1.5.2 --- The salt percentage of stinky brine broth --- p.14 / Chapter 1.5.3 --- Volatile components of stinky brine broth --- p.14 / Chapter 1.5.4 --- Parameters affecting ammonia production of stinky brine --- p.15 / Chapter 1.6 --- Other fermented soy products --- p.16 / Chapter 1.6.1 --- Microorganisms involved in the fermentation --- p.16 / Chapter 1.6.1.1 --- Fermentation of soybean by bacteria --- p.17 / Chapter 1.6.1.1.1 --- Natto --- p.17 / Chapter 1.6.1.1.2 --- Kinema --- p.18 / Chapter 1.6.1.1.3 --- Soy daddawa --- p.19 / Chapter 1.6.1.1.4 --- Hawaijar --- p.20 / Chapter 1.6.1.1.5 --- Thua nao --- p.21 / Chapter 1.6.1.2 --- Fermentation of soybean by moulds --- p.21 / Chapter 1.6.1.2.1 --- Tempe --- p.21 / Chapter 1.6.1.2.2 --- Sufu --- p.22 / Chapter 1.6.1.2.3 --- Soy sauce --- p.22 / Chapter 1.6.1.2.4 --- Soy paste --- p.23 / Chapter 1.6.2 --- Formation of volatile compounds during Bacillus fermentation --- p.24 / Chapter 1.6.3 --- Biochemical changes during fermentation --- p.21 / Chapter 1.7 --- Methods of flavor analysis --- p.30 / Chapter 1.7.1 --- Headspace Analysis --- p.31 / Chapter 1.7.2 --- Aroma characterization --- p.32 / Chapter CHAPTER 2 --- IDENTIFICATION OF ODOROUS COMPOUNDS IN COMMERCIAL CHAW TOFU BASED ON ODOR ACTIVITY EVALUATION --- p.42 / Chapter 2.1 --- Introduction --- p.43 / Chapter 2.2 --- Materials & Methods --- p.46 / Chapter 2.2.1 --- Experimental samples --- p.46 / Chapter 2.2.2 --- Headspace-Gas Chromatography-Mass Spectrometry (GC-MS) --- p.46 / Chapter 2.2.3 --- Conditions of the Gas Chromatography-Mass Spectrometry (GC-MS) --- p.47 / Chapter 2.2.4 --- Compound identifications --- p.48 / Chapter 2.2.5 --- Quantification of compounds --- p.48 / Chapter 2.2.6 --- Statistical analysis --- p.48 / Chapter 2.2.7 --- Calculation of odor activity value (OAV) --- p.49 / Chapter 2.3 --- Results & Discussion --- p.50 / Chapter 2.3.1 --- Odor activity value (OAV) --- p.51 / Chapter 2.3.2 --- Volatile compounds in fresh samples --- p.51 / Chapter 2.3.2.1 --- Comparison of odorous compounds in fresh samples among different locations --- p.52 / Chapter 2.3.3 --- Volatile compounds in deep-fat fried samples --- p.53 / Chapter 2.3.3.1 --- Comparison of odorous compounds in deep-fat fried samples among different locations --- p.54 / Chapter 2.3.4 --- Comparison between fresh and deep-fat fried samples --- p.55 / Chapter 2.3.5 --- Odorous compounds of chaw tofu based on OAVs --- p.56 / Chapter 2.3.6 --- Possible ways for formation of odorous compounds --- p.58 / Chapter 2.3.6.1 --- Protein degradation --- p.58 / Chapter 2.3.6.2 --- Lipid degradation --- p.59 / Chapter 2.3.7 --- Comparison between volatile compounds in chaw tofu and others fermented soybean products --- p.60 / Chapter 2.4 --- Conclusion --- p.61 / Chapter CHAPTER 3 --- IDENTIFICATION OF ODOROUS COMPOUNDS IN COMMERCIAL CHAW TOFU BASED ON GAS CHROMATOGRAPHY-OLFACTOMETRY --- p.67 / Chapter 3.1 --- Introduction --- p.68 / Chapter 3.2 --- Materials & Methods --- p.71 / Chapter 3.2.1 --- Experimental samples --- p.71 / Chapter 3.2.2 --- Gas Chromatography-Mass Spectrometry-Flame Ionization Detection-Olfactometry (GC-MS-FID-O) --- p.71 / Chapter 3.2.3 --- Conditions of the Gas Chromatography-Mass Spectrometry --- p.72 / Chapter 3.2.4 --- Detection of odor active compounds --- p.73 / Chapter 3.2.5 --- Compound identifications --- p.73 / Chapter 3.3 --- Results & Discussion --- p.74 / Chapter 3.3.1 --- "Fecal, rancid and putrid odor" --- p.74 / Chapter 3.3.2 --- "Cabbages, sulfurous and meaty odor" --- p.76 / Chapter 3.3.3 --- Green odor --- p.77 / Chapter 3.3.4 --- Other odor contributing compounds --- p.77 / Chapter 3.3.5 --- Odor generate during deep-fat frying --- p.78 / Chapter 3.3.6 --- Comparison between GC-O and OAVs --- p.79 / Chapter 3.3.7 --- Comparison between volatile compounds in chaw tofu and others fermented soybean products --- p.80 / Chapter 3.4 --- Conclusion --- p.82 / Chapter CHAPTER 4 --- EVALUATION OF CHAW TOFU MODEL FERMENTATION BROTH --- p.86 / Chapter 4.1 --- Introduction --- p.87 / Chapter 4.2 --- Materials & Methods --- p.90 / Chapter 4.2.1 --- Model fermentation broth preparation --- p.90 / Chapter 4.2.2 --- Tofu sample preparation --- p.91 / Chapter 4.2.3 --- Gas Chromatography-Mass Spectrometry --- p.91 / Chapter 4.2.3.1 --- Conditions of Gas Chromatography-Mass Spectrometry (GC-MS) --- p.92 / Chapter 4.2.3.2 --- Compound identification --- p.93 / Chapter 4.2.3.3 --- Quantification of compounds --- p.93 / Chapter 4.2.4 --- Viable cell counts --- p.93 / Chapter 4.2.5 --- pH value and soluble content --- p.94 / Chapter 4.2.6 --- Proteolytic activity --- p.94 / Chapter 4.2.7 --- Statistical analysis --- p.95 / Chapter 4.3 --- Results & Discussion --- p.96 / Chapter 4.3.1 --- Headspaces analysis --- p.96 / Chapter 4.3.1.1 --- Changes in volatile composition in model fermentation broths --- p.97 / Chapter 4.3.1.2 --- Comparison of volatile compositions between the broths --- p.98 / Chapter 4.3.1.3 --- Comparison of volatile compositions among the three deep-fat fried fermented tofu with different broths --- p.101 / Chapter 4.3.1.4 --- Comparison of volatile compositions of deep fat fried fermented tofu with that of the commercial chaw tofu --- p.102 / Chapter 4.3.2 --- Liquid samples analysis --- p.104 / Chapter 4.3.2.1 --- "Changes in viable cell counts, pH values, protease activities and soluble solid contents within model fermentation broths during fermentation" --- p.106 / Chapter 4.3.2.2 --- Viable cell counts --- p.107 / Chapter 4.3.2.3 --- Soluble solid content --- p.108 / Chapter 4.3.2.4 --- Proteolytic activity --- p.106 / Chapter 4.3.2.5 --- pH value --- p.110 / Chapter 4.4 --- Conclusion --- p.112 / Chapter CHAPTER 5 --- GENERAL CONCLUSION --- p.127 / APPENDIX --- p.130 / IDENTIFICATION OF MICROORGANISMS PRESENTED IN THE MODEL CHAW TOFU FERMENTATION BROTHS BY MICROBIAL IDENTIFICATION SYSTEM (MIDI) --- p.130 / Materials & Methods --- p.130 / Model fermentation broth preparation --- p.130 / Viable cell counts --- p.131 / Microbial Identification System (MIDI) --- p.131 / Results --- p.133 / Suggestion on further investigation --- p.134 / REFERNECES --- p.141

腐乳是中國傳統豆類發酵製品，具有綿軟的口感和特殊的風味。其是豆腐通過真菌固態發酵，并加入鹽，米酒和香料等進行後期熟化而成的產品。本文的研究分為兩部份，第一部份對腐乳發酵過程中的毛胚，鹽胚，熟化第一天，熟化一個月以及熟化六個月的腐乳樣本進行採樣，并採用傳統微生物培養法和克隆文庫法對每個階段真菌和細菌的生態結構和動態變化進行研究。第二部份重點比較了四株腐乳產品中分離的微生物和購自台灣生物資源保存及研究中心的四株細菌的產揮發性含硫化合物能力，并挑選了最高產的一株微生物進行紫外誘變，最後獲得理想的突變株。本研究的結論如下： / 1. 真菌和細菌的總數均是在毛胚階段為最高，在進入熟化階段后開始下降。在傳統微生物培養方法下分別分離出了三株真菌和九株細菌，通過18S rDNA和16 rDNA測序，發現絲孢酵母屬（Trichosporon spp.）是真菌中的優勢菌種，蠟狀芽孢桿菌（Bacillus cereus）和解澱粉芽孢桿菌（Bacillus amyloliquefaciens）為細菌中的優勢菌種； / 2. 本研究建立了五個真菌18S rDNA克隆文庫和五個細菌16 rDNA克隆文庫用于研究真菌和細菌的生態結構和動態變化。通過聚合酶鏈式反應-限制性片段長度多態性（PCR-RFLP）的研究，分別在真菌和細菌克隆文庫中發現23和38種圖譜類型，并計算其相應比例。在進行真菌細菌測序之後，對優勢菌群進行了定性和定量分析； / 3. 在對比傳統微生物培養方法和克隆文庫技術的結果后發現，二者的結果存有差異，有些在克隆文庫中鑒定到的微生物在傳統培養方法中未能分離鑒定，而有些微生物則只能在傳統培養方法中被分離鑒定。因此，本研究中將這兩種方法結合有助於我們更為全面、客觀地研究腐乳發酵過程中真菌和細菌的生態結構和多樣性。 / 4. 對四株腐乳中分離純化的微生物和四株外來購入細菌的產揮發性含硫化合物能力進行比較，結果發現，從腐乳產品中分離純化的B-1菌株擁有最高的產揮發性含硫化合物能力，通過紫外誘變后，突變株#3在產揮發性含硫化合物以及L-蛋氨酸代謝酶活力都比初始菌株有了顯著的提升。B-1菌經測序比對后鑒定為絲孢酵母（Trichosporon sp.）。 / 本研究結果對于傳統腐乳發酵的有效控制和現代腐乳生產工藝的建立有一定指導意義，並且對於腐乳產品中的風味物質，特別是揮發性含硫化合物的產生和優化提供信息。 / Sufu (fermented soybean curd) is a soft creamy cheese-type product with a pronounced flavor and is made by fungal solid state fermentation of tofu (soybean curd) followed by aging in brine containing salt and alcohol. In first part of this research, the eco-structure and the dynamic changes of microbes during sufu production process (Pehtze, Salted pehtze, 0 Month sufu, 1 Month sufu and 6 Month sufu sample) were studied by combined microbiology techniques, including plate culture, 16S rDNA and 18S rDNA clone library and restriction fragment length polymorphism (RFLP) analysis. The second part of this research focus on the comparison of volatile sulfur-containing compounds (VSCs) production ability within isolated strains in sufu product and bacteria purchased commercially, the strain that possessed highest ability was selected and followed by a UV mutation experiment, finally obtained the desired mutant. The results of this research are as followed: / 1. The population of both fungi and bacteria were all at highest number in Pehtze stage and started to decrease in ripening stages. A combined total of three and nine living strains of fungi and bacteria were obtained from the plate culture, respectively. Through 18S rDNA and 16S rDNA sequencing, Trichosporon spp. was the dominant fungi and Bacillus cereus and Bacillus amyloliquefaciens were the dominant bacteria; / 2. Five 18S rDNA clone libraries and five 16S rDNA clone libraries from different stages of sufu production were constructed to analyze the structure and dynamic changes of fungi and bacteria. A total of 23 and 38 RFLP patterns were found, and the ratio of each pattern were calculated. After sequencing, qualitative and quantitative analysis on the dynamic changes of dominant strains was performed; / 3. After comparing the results of plate culture and clone library, it was found that there were some differences between the two. Some strains were only found in clone library while some only found in plate culture approach. Therefore, the combination of the two microbiology methods will help us to objectively and completely analyze the structure and dynamic changes of microbes in the sufu production process; / 4. The ability to produce VSCs within four strains (B-1, B-2, B-3 & B-4) isolated from a commercial sufu manufacturing process and four commercial strains (B. acetylicum, L. Lactics, S. thermophilus and L. Paracasei) were compared. Results showed that B-1 possessed both the highest VSCs production ability and L-methionine metabolism enzymatic activities among the eight strains. After UV light mutagenesis of B-1 strain, its mutant #3 significantly increased in DMDS and DMTS production and all four L-methionine-related enzymatic activities in reference to that of the starting strain (B-1). B-1 was identified as Trichosporon sp. by sequencing. / These results would make a profound significance on the control of traditional sufu production and the development of new technology for modern sufu manufacturing. They will also help to provide some important information of optimal production of VSCs in sufu ripening and the overall flavor in sufu product. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Huang, Ruolan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 106-117). / Abstracts also in Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgement --- p.v / Table of contents --- p.vi / List of Figures --- p.x / List of Tables --- p.xiii / Chapter Chapter 1 --- : Introduction --- p.1 / Chapter 1.1 --- Sufu --- p.1 / Chapter 1.1.1 --- Classification --- p.1 / Chapter 1.1.1.1 --- Classified by processing technology --- p.1 / Chapter 1.1.1.2 --- Classified by color and flavor --- p.1 / Chapter 1.1.1.3 --- Other classifications --- p.2 / Chapter 1.1.2 --- Typical commercial manufacturing process --- p.2 / Chapter 1.1.2.1 --- Production process of naturally fermented sufu --- p.2 / Chapter 1.2.2.2 --- Production process of traditional mold-based sufu --- p.5 / Chapter 1.2.2.3 --- Production process of traditional bacteria-based sufu --- p.5 / Chapter 1.2.2.4 --- Acceleration of sufu ripening process --- p.6 / Chapter 1.1.3 --- Important ingredients in sufu production --- p.6 / Chapter 1.1.4 --- Flavor components in sufu --- p.7 / Chapter 1.1.4.1 --- Volatile flavor components --- p.7 / Chapter 1.1.4.2 --- Essential odor in sufu product --- p.8 / Chapter 1.1.4.3 --- Volatile sulfur compounds in sufu --- p.9 / Chapter 1.1.4.4 --- Using Head Space-Solid phase Microextraction (HS-SPME) to analyze the volatile sulfur components --- p.9 / Chapter 1.1.5 --- Relationship between microbes and sufu --- p.12 / Chapter 1.1.5.1 --- Microbes involved in fermentation process --- p.13 / Chapter 1.1.5.2 --- Microbial changes during the production of sufu --- p.14 / Chapter 1.1.6 --- Study on microbial ecology in food product --- p.15 / Chapter 1.1.6.1 --- PCR-based molecular techniques --- p.16 / Chapter 1.1.6.2 --- Non-PCR based molecular techniques --- p.16 / Chapter 1.1.6.3 --- The common techniques used in microbial ecology research --- p.17 / Chapter 1.1.6.4 --- Microbial ecology study by molecular biological techniques --- p.18 / Chapter 1.2 --- Objectives --- p.19 / Chapter Chapter 2 --- : Analysis of fungi diversity during sufu fermentation process --- p.21 / Chapter 2.1 --- Introduction --- p.21 / Chapter 2.2 --- Materials and methods --- p.21 / Chapter 2.2.1 --- Sample collection and preparation --- p.22 / Chapter 2.2.2 --- Plate count of fungi during sufu fermentation process --- p.22 / Chapter 2.2.3 --- Change of pH values and moisture content --- p.22 / Chapter 2.2.4 --- Total DNA extraction from fungi --- p.23 / Chapter 2.2.5 --- Preparation of competent cell --- p.23 / Chapter 2.2.6 --- 18S rDNA PCR amplification and construction of 18S rDNA clone library --- p.24 / Chapter 2.2.7 --- RFLP analysis of 18S rDNA clone library --- p.25 / Chapter 2.2.8 --- DNA sequencing for fungi identification --- p.26 / Chapter 2.2.9 --- Analysis of the diversity of 18S clone library --- p.26 / Chapter 2.2.10 --- Frequency percentage analysis --- p.27 / Chapter 2.2.11 --- Enzyme Solutions --- p.27 / Chapter 2.2.12 --- Determination of protease activity --- p.28 / Chapter 2.2.13 --- Determination of lipase activity --- p.29 / Chapter 2.2.11 --- Microtox test --- p.30 / Chapter 2.2.12 --- Statistical analysis --- p.30 / Chapter 2.3 --- Results and discussion --- p.30 / Chapter 2.3.1 --- Fungi growth on plate counting result --- p.30 / Chapter 2.3.2 --- Changes in pH and moisture content of sufu during production --- p.33 / Chapter 2.3.3 --- Construction and selection of 18S rDNA clone library --- p.35 / Chapter 2.3.4 --- Fungal diversity based on 18S rDNA clone library analysis --- p.38 / Chapter 2.3.5 --- Protease and lipase activities in Actinomucor elegans and Trichosporon japonicum --- p.45 / Chapter 2.3.5.1 --- Protease activity --- p.46 / Chapter 2.3.5.2 --- Lipase activity --- p.47 / Chapter 2.3.6 --- Toxicity of Actinomucor elegans and Trichosporon japonicum --- p.49 / Chapter 2.3.7 --- Analysis of fungi eco-structure and function during sufu fermentation process --- p.50 / Chapter 2.3.8 --- The influence of PCR bias and artifact --- p.53 / Chapter 2.2 --- Summary --- p.55 / Chapter Chapter 3 --- : Analysis of bacteria diversity during sufu fermentation process --- p.57 / Chapter 3.1 --- Introduction --- p.57 / Chapter 3.2 --- Materials and methods --- p.57 / Chapter 3.2.1 --- Sample collection and preparation --- p.57 / Chapter 3.2.2 --- Plate count of bacteria during sufu fermentation process --- p.57 / Chapter 3.2.3 --- Total DNA extraction from bacteria --- p.58 / Chapter 3.2.4 --- Preparation of competent cell --- p.58 / Chapter 3.2.5 --- 16S rDNA PCR amplification and construction of 16S rDNA clone library --- p.58 / Chapter 3.2.6 --- RFLP analysis of 16S rDNA clone library --- p.59 / Chapter 3.2.7 --- DNA sequencing for bacteria identification --- p.60 / Chapter 3.2.8 --- Analysis of the diversity of 16S rDNA clone library --- p.60 / Chapter 3.3 --- Results and discussion --- p.60 / Chapter 3.3.1 --- Bacteria growth on plate counting result --- p.60 / Chapter 3.3.2 --- Construction and selection of 16S rDNA clone library --- p.63 / Chapter 3.3.3 --- 16S rDNA clone library analysis of bacteria diversity --- p.65 / Chapter 3.3.4 --- Analysis of bacteria eco-structure and function during sufu fermentation process --- p.74 / Chapter 3.4 --- Summary --- p.77 / Chapter Chapter 4 --- : Screening the mutant possess higher capacity of forming volatile sulfur compounds (VSCs) from non-starter microbes of sufu product --- p.80 / Chapter 4.1 --- Introduction --- p.80 / Chapter 4.2 --- Materials and methods --- p.82 / Chapter 4.2.1 --- Strains and culture conditions --- p.82 / Chapter 4.2.2 --- Head space-solid phase microextraction (HS-SPME) analysis --- p.83 / Chapter 4.2.3 --- Gas Chromatography-Mass Spectrometry (GC-MS) analysis --- p.84 / Chapter 4.2.4 --- UV mutation --- p.85 / Chapter 4.2.5 --- Ellman’s method --- p.86 / Chapter 4.2.6 --- Preparation of cell-free extracts (CFE) for enzymatic assays --- p.86 / Chapter 4.2.7 --- Enzymatic assay --- p.86 / Chapter 4.2.7.1 --- L-methionine aminotransferase activity assay --- p.86 / Chapter 4.2.7.2 --- L-methionine demethiolase activity assay --- p.87 / Chapter 4.2.7.3 --- α-keto acid decarboxylase activity assay --- p.87 / Chapter 4.2.7.4 --- C-S lyase activity --- p.88 / Chapter 4.2.8 --- Statistical analysis --- p.88 / Chapter 4.3 --- Results and discussion --- p.89 / Chapter 4.3.1 --- Optimization of SPME extraction condition --- p.89 / Chapter 4.3.2 --- Selecting the start strain --- p.90 / Chapter 4.3.4.1 --- Comparison of VSCs production ability --- p.90 / Chapter 4.3.4.2 --- Comparison of enzymatic activity in L-methionine metabolism --- p.92 / Chapter 4.3.3 --- Optimization of UV exposure time --- p.95 / Chapter 4.3.4 --- Screening the mutants --- p.96 / Chapter 4.3.4.1 --- Comparison of VSCs production ability among the mutants --- p.96 / Chapter 4.3.4.2 --- Comparison of the L-methionine related enzymatic activities among the mutants --- p.99 / Chapter 4.3.4.3 --- Identified of strian B-1 --- p.101 / Chapter 4.4 --- Summary --- p.102 / Chapter Chapter 5 --- : General conclusions and future work --- p.103 / References --- p.106

Kam, Shuk Fan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 124-134). / Abstracts in English and Chinese. / Abstract --- p.ii / Abstract in Chinese --- p.iv / Acknowledgements --- p.vi / List of Figures --- p.xi / List of Tables --- p.xii / Chapter Chapter 1 --- Literature Review --- p.1 / Chapter 1.1 --- Soybeans as Food --- p.1 / Chapter 1.1.1 --- Backgrounds --- p.1 / Chapter 1.1.2 --- Soybean Composition --- p.1 / Chapter 1.1.3 --- Diseases Prevention of Soybean Consumption --- p.3 / Chapter 1.1.4 --- Traditional Soyfoods --- p.3 / Chapter 1.2 --- Sufu --- p.5 / Chapter 1.2.1 --- Historical Information and Synonyms --- p.5 / Chapter 1.2.2 --- Features --- p.5 / Chapter 1.2.3 --- Manufacturing Techniques --- p.5 / Chapter 1.2.4 --- Types and Varieties of Sufu --- p.10 / Chapter 1.2.5 --- Compositional Changes during Fermentation and Ripening --- p.11 / Chapter 1.2.5.1 --- Proteins and Amino Acids --- p.11 / Chapter 1.2.5.2 --- Fats and Free Fatty Acids --- p.13 / Chapter 1.2.5.3 --- Carbohydrates --- p.14 / Chapter 1.2.5.4 --- Isoflavones --- p.15 / Chapter 1.2.6 --- Volatile Flavor Compounds --- p.15 / Chapter 1.3 --- Accelerated-Ripened Sufu --- p.17 / Chapter 1.4 --- Objectives of Project --- p.18 / Chapter Chapter 2 --- Contribution of Lipid to the Fatty Acids and Ethyl Esters in Model Plain Sufu --- p.20 / Chapter 2.1 --- Introduction --- p.20 / Chapter 2.2 --- Materials and Methodology --- p.23 / Chapter 2.2.1 --- Sufu Preparation --- p.23 / Chapter 2.2.1.1 --- Preparation of Tofu --- p.23 / Chapter 2.2.1.2 --- Preparation of Inoculum --- p.23 / Chapter 2.2.1.3 --- Spore Count in Spore Suspension --- p.24 / Chapter 2.2.1.4 --- Preparation of Pehtzes --- p.25 / Chapter 2.2.1.5 --- Brining and Ripening --- p.26 / Chapter 2.2.1.6 --- Sampling --- p.26 / Chapter 2.2.1.7 --- Free Fatty Acid Analysis --- p.26 / Chapter 2.2.1.7.1 --- Extraction --- p.26 / Chapter 2.2.1.7.2 --- Gas Chromatography-Mass Spectrometry Analysis (GC-MS) for Free Fatty Acid Analysis --- p.27 / Chapter 2.2.1.7.3 --- Compounds Identification and Quantification --- p.28 / Chapter 2.2.1.8 --- Ethyl Ester Analysis --- p.29 / Chapter 2.2.1.8.1 --- Extraction --- p.29 / Chapter 2.2.1.8.2 --- Gas Chromatography-Mass Spectrometry Analysis (GC-MS) for Ethyl Ester Analysis --- p.29 / Chapter 2.2.1.8.3 --- Compounds Identification and Quantification --- p.30 / Chapter 2.2.1.9 --- Enzymatic Activities --- p.30 / Chapter 2.2.1.9.1 --- Enzyme Extracts --- p.30 / Chapter 2.2.1.9.2 --- Lipase Activity Measurement --- p.31 / Chapter 2.2.1.9.3 --- Lipoxygenase Activity Measurement --- p.32 / Chapter 2.2.1.10 --- Determination of Peroxide Value --- p.33 / Chapter 2.2.1.11 --- pH Value Determination --- p.34 / Chapter 2.2.1.12 --- Moisture Content --- p.34 / Chapter 2.2.1.13 --- Statistical Analysis --- p.34 / Chapter 2.3 --- Results and Discussions --- p.35 / Chapter 2.3.1 --- Change of Free Fatty Acids with Sufu Processing Stage --- p.35 / Chapter 2.3.2 --- Change in Ethyl Esters with Sufu Processing Stage --- p.41 / Chapter 2.3.3 --- Activity of Lipase in the Sufu Enzyme Extracts --- p.47 / Chapter 2.3.4 --- Activity of Lipoxygenase in the Sufu Enzyme Extracts --- p.50 / Chapter 2.3.5 --- Lipid Oxidation determined by Peroxide Value --- p.50 / Chapter 2.3.6 --- pH Value Change during Sufu Production --- p.54 / Chapter 2.3.7 --- Moisture Content during Sufu Production --- p.56 / Chapter 2.3.8 --- Overall Discussions --- p.58 / Chapter 2.3.8.1 --- Lipolysis and Ester Synthesis --- p.58 / Chapter 2.3.8.2 --- Lipid Oxidation --- p.58 / Chapter 2.4 --- Conclusion --- p.61 / Chapter Chapter 3 --- A Study on Ripening Model Systems of Sufu --- p.63 / Chapter 3.1 --- Introduction --- p.63 / Chapter 3.2 --- Materials and Methodology --- p.68 / Chapter 3.2.1 --- Partial Purification Lipase from Mucor hiemalis --- p.68 / Chapter 3.2.1.1 --- Inoculum --- p.68 / Chapter 3.2.1.2 --- Culture --- p.68 / Chapter 3.2.1.3 --- Protein Precipitation --- p.68 / Chapter 3.2.1.4 --- Gel Filtration Column Chromatography --- p.69 / Chapter 3.2.1.5 --- Enzyme Assay --- p.69 / Chapter 3.2.1.6 --- Lipase Activity Confirmation --- p.70 / Chapter 3.2.1.7 --- Protein Determination --- p.70 / Chapter 3.2.2 --- Model Studies of the Formation of Free Fatty Acids and Ethyl Esters --- p.70 / Chapter 3.2.2.1 --- "A System with Lipid, Alcohol, and Lipase" --- p.70 / Chapter 3.2.2.2 --- A System with Different Lipase Concentrations --- p.71 / Chapter 3.2.2.3 --- A System with an Exogenous Fatty Acid --- p.71 / Chapter 3.2.3 --- Characterization of the Crude Lipase from Mucor hiemalis Culture on the Formation of Free Fatty Acids and their Ethyl Esters --- p.72 / Chapter 3.2.3.1 --- Effect of a Phospholipid --- p.72 / Chapter 3.2.3.2 --- Effect of Ethanol Concentration --- p.72 / Chapter 3.2.3.3 --- Effect of Sodium Chloride Concentration --- p.72 / Chapter 3.2.3.4 --- Effect of initial pH --- p.73 / Chapter 3.2.4 --- Orthogonal Design Experiment L9 (33) --- p.73 / Chapter 3.2.5 --- Free Fatty Acids Identification and Quantification --- p.76 / Chapter 3.2.5.1 --- Extraction --- p.76 / Chapter 3.2.5.2 --- Gas Chromatography-Mass Spectrometry Analysis (GC-MS) --- p.76 / Chapter 3.2.5.3 --- Compounds Identification and Quantification --- p.77 / Chapter 3.2.6 --- Ethyl Esters Identification and Quantification --- p.77 / Chapter 3.2.6.1 --- Extraction --- p.77 / Chapter 3.2.6.2 --- Gas Chromatography-Mass Spectrometry Analysis (GC-MS) --- p.78 / Chapter 3.2.6.3 --- Compounds Identification and Quantification --- p.78 / Chapter 3.2.7 --- Statistical Analysis --- p.79 / Chapter 3.3 --- Results and Discussions --- p.80 / Chapter 3.3.1 --- Lipase Partial Purification --- p.80 / Chapter 3.3.2 --- Lipase Activity Confirmation --- p.80 / Chapter 3.3.3 --- Model Studies on the Formation of Free Fatty Acids and Ethyl Esters --- p.84 / Chapter 3.3.3.1 --- "A System with Lipid, Alcohol and Lipase" --- p.84 / Chapter 3.3.3.2 --- A System with Different Lipase Concentrations --- p.84 / Chapter 3.3.3.3 --- A System with an Exogenous Fatty Acid --- p.89 / Chapter 3.3.3.4 --- Summary --- p.92 / Chapter 3.3.4 --- Characterization of the Crude Lipase from Mucor hiemalis Culture on the Formation of Free Fatty Acids and their Ethyl Esters Formation --- p.92 / Chapter 3.3.4.1 --- Effect of a Phospholipid --- p.92 / Chapter 3.3.4.2 --- Effect of Ethanol Concentration --- p.96 / Chapter 3.3.4.3 --- Effect of Sodium Chloride Concentration --- p.103 / Chapter 3.3.4.4 --- Effect of initial pH --- p.109 / Chapter 3.3.5 --- Orthogonal Design Experiment L9 (33) Optimizing the Ethyl Esters Formation --- p.114 / Chapter 3.4 --- Conclusion --- p.118 / Chapter 4 Overall Conclusions --- p.120 / References --- p.124

Thesis (MSc Food Sc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Maas is a traditional fermented milk drink of the indigenous people of Southern Africa and can thus be used to uplift the nutritional status of the South African population, especially for the lower income groups. Furthermore, the problem of lactose intolerance among the Black population can also be addressed by the consumption of Maas. The objective of this study was to screen mesophylic lactic acid bacterial strains (25 in total) from the University of Stellenbosch Food Science Culture Collection for suitable metabolite production and then to produce traditional Maas with a starter culture combination that produces a distinctive acid and traditional flavour. The representative 25 single lactic acid starter strains were identified as Lactococcus lactis subsp. leetis biovar diacetylactis (12 strains), L. leetis subsp. leetis (four strains) and L. leetis subsp. cremoris (nine strains). These strains were inoculated into pasteurised full cream milk and activated for 8 h at 22°C. Pasteurised full cream milk was then inoculated with each of the activated starter strains, incubated at 22°C for 16 h and assessed for acid production abilities (pH = 4.6) under controlled time-temperature conditions. The results of this study showed that nine of the single strains, L. lactis subsp. leetis biovar diacetylactis (S1, S2, S3 and S5), L. teetis subsp. lactis (S13, S15 and S16) and two L. leetis subsp. cremoris strains (S17 and S22), produced sufficient acid, rendering them suitable for the use as starters in the production of traditional Maas. A pH range of 4.3 - 5.1 was reached by the nine single strains after 16 h at 22°C. Two-strain starter combinations were then formed by combining the most suitable single L. leetis subsp. leetis biovar diacetylactis, L. lactis subsp. lactis and L. lactis subsp. cremoris strains, respectively. From the data, it was concluded that acceptable Maas could be produced with four two-strain combinations (S3S 17, S3S22, S5S17 and S5S22). This selection was again based on suitable acid and metabolite production, as well as on sensory evaluation of the final product. These four two-strain combinations produced sufficient acid to reach a pH in the 4.6 - 4.8 range, and showed a high metabolite concentration for the most suitable compounds and formed a thick, smooth and creamy body texture after 16 h at 22°C. Three-strain combinations formed between the two-strain starter combinations and L. leetis subsp. teetis strains (813, 815 and 816), were also evaluated. With these combinations a lack of a pronounced Maas flavour was found. Thus, it was decided to add aroma producing strains of the species Leuconostoc mesenteroides subsp. dextranicum (strain L1) and L. mesenteroides subsp. citrovorum (strain L2) to the three-strain combinations. Four culture combinations (A, B, C and D) were then formed by combining the selected Leuconostoc strains (L1 and L2) with the most suitable Lactococcus strains (83,817,813 and 822). These combinations produced sufficient acid to reach the pH 4.5 - 4.6 range after 14 h at 22°C. Acetaldehyde was the major flavour metabolite formed in the Maas made with these four combinations, with concentrations ranging between 26.6 - 89.3 mg.l ̄ ¹, while other flavour metabolites (ethanol, acetone, diacetyl and 2-butanone) were present at lower concentrations. It was found that three of the four culture combinations (A, C and D) were characterised by a superior, but delicate flavour and a typical characteristic Maas body texture. Fruit flavoured Maas was subsequently prepared with the three most suitable culture combinations (A, C and D) using 11 flavours and a sensory evaluation performed. The statistically evaluated data showed that the appearance, smoothness, flavour intensity, sweetness and overall acceptability were influenced by the type of fruit flavour and the culture combination. Fruit flavour 4 (banana) was the most preferred flavour. The sensory panellists also indicated that the culture combination C gave the best overall acceptability over a three week study period. Data on the shelf-life study of natural unflavoured Maas, prepared with the three culture combinations (A, C and D), showed that the Maas still had an acceptable appearance, taste and good microbiological quality after 15 d at refrigerated temperatures. / AFRIKAANSE OPSOMMING: Maas is 'n tradisionele gefermenteerde melkdrankie onder die inheemse bevolking van Suid-Afrika en kan gebruik word om die voedingstatus van die Suid-Afrikaanse bevolking te verhoog, veral vir die laer inkomste groepe. Bowendien, kan die probleem van laktose intoleransie onder die Swart gemeenskap ook aangespreek word deur die verbruik van Maas. Die doel van hierdie studie was om enkelstam mesofiliese melksuur bakterieë (25 in totaal) van die Universiteit van Stellenbosch Voedselwetenskap Kultuur Versameling te ondersoek vir geskikte metaboliet produksie en tradisionele Maas met 'n kenmerkende suurheid en tradisionele geur met 'n geskikte kultuur kombinasie te produseer. Die toonaangewende 25 enkelstamme is Lactococcus lactis subsp. leetis biovar diacetylactis (12 stamme), L. lactis subsp. lactis (vier stamme) en L. lactis subsp. cremoris (nege stamme). Hierdie stamme was in gepasteuriseerde volroom melk geïnokuleer en geaktiveer vir 8 h teen 22°C. 'n Inokulum van die onderskeie geaktiveerde stamme is hierna in gepasteuriseerde volroom melk geplaas, vir 16 h teen 22°C geïnkubeer en hul vermoë om suur te produseer (pH = 4.6) onder beheerde tyd-temperatuur kondisies is bepaal. Die resultaat van die studie het aangedui dat nege enkelstamme, naamlik L. leetis subsp. lactis biovar diacetylactis (S1, S2, S3 en S5), L. lactis subsp. leetis (S13, S15 en S16) en twee L. leetis subsp. cremoris (S 17 en S22), geskikte suurheidsvlakke vir die produksie van Maas bereik het. 'n pH vlak van 4.3 - 5.1 is na 16 h teen 22°C deur hierdie nege enkelstamme bereik. Twee-stam kombinasies is onderskeidelik gevorm tussen die geskikte enkel L. lactis subsp lactis biovar diacetylactis, L. lactis subsp. lactis en L. lactis subsp. cremoris stamme. Die gevolgtrekking gemaak uit die data, is dat aanvaarbare Maas voorberei kan word met vier van die twee-stam kombinasies (S3S17, S3S22, S5S17 en S5S22) op grond van suurvorming, metaboliet produksie en sensoriese evaluasie. Hierdie vier kombinasies het genoegsame suur geproduseer om 'n pH vlak van 4.6 - 4.8 bereik, hoë metaboliet konsentrasies geproduseer en 'n dik, gladde en romerige tekstuur aangeneem na 16 h teen 22°C. Drie-stam kombinasies is gevorm tussen die onderskeie twee-stam kombinasies en L. lactis subsp. lactis stamme (813,815 en 816) en ook geëvalueer. Die tekort aan 'n skerp Maas geur in die drie-stam kombinasies het daartoe gelei dat Leuconostoc mesenteroides subsp. dextranicum (stam L1) en L. mesenteroides subsp. citrovorum (stam L2) bygevoeg is. Vier kultuur kombinasies (A, B, C en D) is gevorm deur die geselekteerde Leuconostoc stamme (L1 en L2) te kombineer met die mees gepaste Lactococcus stamme (83, 817, 813 en 822). Hierdie kombinasies het genoegsame suur geproduseer wat 'n pH vlak van 4.5 - 4.6 na 14 h teen 22°C bereik het. In die Maas wat met bovermelde kombinasies gemaak is, was die asetaldehied die mees geproduseerde geur metaboliet teen konsentrasies van 26.6 - 89.3 mg.l ̄ ¹. Ander geur metaboliete (etanol, asetoon, diasetiel, 2-butanoon) is in laer konsentrasies geproduseer. Daar is gevind dat drie uit die vier kultuur kombinasies (A, C en D) 'n superieur, delikate geur wat 'n tipies karakteristiek van die Maas gehad het. Vrugte gegeurde Maas geproduseer met die drie kultuur kombinasies (A, C en D) deur 11 geursels te gebruik, is sensories geëvalueer. Die statistiese geëvalueerde data het getoon dat die voorkoms, gladheid, geur intensiteit, soetheid en die algehele aanvaarbaarheid beïnvloed is deur die tipe vrugte geursels en die kultuur kombinasies. Die vrugte geursel 4 (piesang) het voorkeur geniet. Die sensoriese paneellede het ook aangedui dat kultuur kombinasie C die algehele mees aanvaarbare Maas geproduseer het oor die studie periode van drie weke. Data van die rakleeftyd van die natuurlike ongegeurde Maas wat geproduseer is met die drie kultuur kombinasies (A, C en D) het aangedui dat die Maas na 15 d by yskas temperatuur steeds 'n aanvaarbare voorkoms, smaak en goeie mikrobiologiese kwaliteit gehad het.

Pacific whiting and its by-products were good raw materials for high quality fish sauce production. Heat stable and salt activated enzymes were responsible for autolytic activity in Pacific whiting and by-products. According to temperature profiles of raw materials at various salt concentrations, two fermentation temperatures, 35°C and 50°C, were selected and compared at 25% salt under static atmospheric condition. Higher yields and faster production rate were obtained from samples incubated at 50°C. Therefore, the apparent optimum condition for fish sauce fermentation using Pacific whiting and its by-products was at 50°C with 25% salt under static atmospheric condition. All physicochemical characteristics, except color and browning color, reached the level of commercial fish sauce within 20 days. Nitrogen contents in all samples reached the level of commercial fish sauce (16.3 g-N/mL) within 112 days. Predominant microorganisms found during fermentation were Staphylococcus, Bacillus and Micrococcus. Alpha-amino acid content appeared to be identified as a good parameter to estimate total nitrogen content during fermentation (adjusted R²=0.84). Soluble solid was a good index for protein degradation in fermentation (adjusted R²=0.71). Proteolytic activity in Pacific whiting and its by-products were investigated using hemoglobin as substrate. Specific substrates and specific inhibitors were also used to classify the types of enzymes responsible for protein degradation in fish sauce fermentation. Serine proteases, cathepsin L-like enzymes and metalloproteases were active at 50°C in whole fish. However, trypsin-like enzymes, and cathepsin L-like enzymes were responsible for protein degradation in by-products at 50°C. At 35°, whole fish was degraded by serine proteases, cathepsin B-like enzymes, trypsin-like enzymes, and metalloproteases. Cysteine proteases were mainly responsible for the degradation of proteins in by-products, and serine proteases and trypsin-like enzymes had a minor role in hydrolyzing of by-products during fermentation. / Graduation date: 2000

Soy flour was inoculated with Lactobacillus delbrueckii ssp. lattis R0187, and incubated for 8 h, to evaluate the protein hydrolysis and identify peptides generated by this fermentation, and the impact on ACE and trypsin inhibitory activities. Aqueous protein extracts prepared from different fermentation time periods showed a decrease in soluble protein content (from 2.83 to 0.02 mg/mL), while soluble inorganic nitrogen and free amino acid contents increased (from 0.029 to 0.062% w/w, and from 0.75 to 0.90% w/w, respectively). The protein extracts were analyzed by SDS-PAGE; proteolysis was observed after 5 h incubation of inoculated soy flour, suggesting that glycinin, beta-conglycinin, and trypsin inhibitors, were hydrolyzed. Peptides were isolated by tricine-SDS-PAGE, and analyzed by MS/MS; fragments of soy anti-nutritional factors (Kunitz and Bowman-Birk trypsir, inhibitors), as well as of other soybean proteins, were identified, confirming that these proteins were hydrolyzed. The protein extracts at time 0 h and 8 h were analyzed by RP-HPLC; one fraction was analyzed by MS/MS, which identified peptides from Lactobacillus species. Determination of trypsin inhibitory activity showed less inhibition of the enzyme with inoculated soy flour compared to the control (un-inoculated soy flour), confirming the deactivation of trypsin inhibitors by fermentation. Determination of ACE inhibitory activity showed a higher inhibition with the control (86% +/- 3.0) compared to inoculated soy flour (66% +/- 7.6).

The incidences of diarrhoeal episodes in infants and children have mostly been associated with the consumption of contaminated weaning foods. This is especially true in developing countries where factors such as the lack of sanitation systems and electricity have been found to contribute to an increase in the incidence of microbiologically contaminated weaning foods. The process of fermentation has been found to reduce the amount of microbiological contamination in such foods as a result of the production of antimicrobial compounds such as organic acids, peroxides, carbon dioxide and bacteriocins. In this study, microbiological surveys were conducted on sorghum powder samples and their corresponding fermented and cooked fermented porridge samples collected from an informal settlement of the Gauteng Province of South Africa. The process of fermentation was found to result in significant decreases (P>0.05) in Gram-negative counts and spore counts, while aerobic plate counts decreased slightly. Lactic acid bacteria counts, however, increased significantly (P>0.05). The cooking process was found to result in further significant decreases (P>0.05) in all counts. Sorghum powder samples and fermented porridge samples were found to be contaminated with potential foodborne pathogens, including Bacillus cereus, Clostridium perfringens and Escherichia coli, however, none of the pathogens tested for were detected in any of the cooked fermented porridge samples. SDS-PAGE and phenotypic analysis of 180 lactic acid bacteria isolated from sorghum powder samples and their corresponding fermented and cooked fermented porridge samples showed that a majority of the isolates were lactobacilli and leuconostocs, however, some isolates were identified as pediococci and lactococci. These results demonstrated the heterogeneity of the lactic acid bacteria isolates that were associated with fermentation processes in this study. Of the lactic acid bacteria identified, Lactobacillus plantarum and Leuconostoc mesenteroides strains were found to have the highest distribution frequencies, being distributed in 87% and 73% of the households, respectively. Analysis of Lactobacillus plantarum (58) and Leuconostoc mesenteroides (46) strains isolated from sorghum powder samples and corresponding fermented and cooked fermented porridge samples by AFLP fingerprinting showed that they originated from a common source, which was sorghum powder. There was, however, evidence of strains that may have been introduced at household level. Antimicrobial activity of selected lactic acid bacteria was found to be mainly due to a decrease in pH in fermented and cooked fermented porridge samples. None of the lactic acid bacteria tested seemed to produce bacteriocins.

Thesis (M.Sc.)(Hons)--University of Western Sydney, Hawkesbury,1998. / "Thesis submitted in partial fulfillment of the requirements for the Degree of Master of Science (Honours) in Food Science." Includes bibliographical references.