腐乳是中國傳統的黃豆發酵類製品，口感柔滑，風味獨特，與西方的芝士相似。多個世紀以來一直是中國的特色配菜和開胃小吃。以往對腐乳的研究只限於使用水蒸氣蒸餾法，溶劑抽提法，超臨界萃取法以及頂空萃取法提取其揮發性化合物，但它們卻有準備時間長、可能產生製造物、較低靈敏度、使用有機溶劑或需要精密的設備等的缺點。而固相微萃取方法(SPME)是集取樣、提取、濃縮三個步驟為一的提取方法。這是一個簡單、快速、溫和而且有相對靈敏度較高的方法。因此，這項研究的主要目標是開發一個快速的頂空固相微萃取方法，並配合氣相色譜-質譜聯用方法來提取和鑒定巿面上白腐乳的揮發性物質，並研究白腐乳整個發酵週期的理化的變化。 / 第一部份的研究首先對固相微萃取塗層(萃取頭)，提取溫度，提取時間，鹽濃度和水含量等參數進行優化。優化條件的結果如下:(1)樣本對鹽溶液(NaCl溶液(25%飽和濃度))的比例為1:2(w/v)，(2)用Divinylbenzene/Carboxen/ Polydimethylsiloxane 塗層的萃取頭，(3)在55°C的水浴進行30分鐘提取。 / 第二部份的研究是用氣相色譜-質譜聯用方法分析利用以上的方法提取的三種商業白腐乳的揮發性化合物。結果在三個樣品中共檢測出131揮發性化合物。樣品A、B和C，分別檢測出112、112和118種成份，他們均屬於不同的官能團。三種腐乳共有76種相同的化合物。其中包括11種由Chung等人於2005年確定的重要香味化合物。而醇類和酯類化合物的含量最為豐富。另外，許多酯類，醛類和芳香烴化合物都是首次在腐乳中發現的。總括而言，該部份實驗成功開發了一種廉價且溫和的提取技術，讓我們可以簡單及快速地從檢定出腐乳中多種揮發性化合物。 / 研究的最後部份是針對商業白腐乳在發酵(腐乳坯期)和老化(後加入紅酒和鹽水)時，揮發性化合物的種類及濃度和理化參數的變化進行了研究。結果顯示，主要的化學成分的濃度是在發酵及熟成過程中増加，同時新的化合物亦不斷地形成。由腐乳坯階段至36小時、60天、120天和180天的發酵期，分別有37、58、69、83和86種化合物形成。其中酯類及吡嗪佔大多數，其濃度亦不斷地增加。而且，大部份的重要香味化合物的濃度亦顯著地增加。另外，許多在黃酒和芝麻油檢測出來的揮發物也可以從腐乳中找到的。理化分析的結果顯示，水分含量沒有顯著變化，但蛋白質的含量在熟化期的首四個月顯著下降。相反，灰含量則在四個月顯著地增加。此研究為腐乳發酵和熟化過程中的揮發性成分和化學成分的變化提供了更多的資料，然而要進一步了解腐乳發酵對味道和口感的影響則需要更多感官測試方面的研究。 / Sufu is a traditional Chinese fermented product with a soft creamy cheese-like texture and a unique flavour. It has been widely consumed in China as an appetizer for centuries. Previous investigations on its volatile compounds using simultaneous steam distillation and solvent extraction (SDE), supercritical fluid extraction (SFE) or headspace extraction may suffer from drawbacks such as artifact formation, the use of organic solvents and the need for sophisticated equipment. An alternative Solid-phase Microextraction (SPME) method integrates sampling, extraction, concentration into a single step method. However, this technique is highly sensitive to experimental conditions, careful optimization would be required to ensure a good extraction performance. / Our primary objective in this study was to develop a quick volatile profiling method using the Headspace - Solid-phase Microextraction - Gas Chromatography/Mass Spectrometry (HS-SPME-GC/MS) for subsequent studies on commercial products and their changes throughout the fermentation and ageing periods. Parameters including stationary phase (fiber coating), extraction temperatures, exposure times, concentration of salt and water content were optimized. / The optimal conditions found using the Divinylbenzene/Carboxen/ Polydimethylsiloxane (DVB/CAR/PDMS) fiber for sufu sample are (1) sample to 25% of (saturated) NaCl solution is 1:2 (w/v), (2) 30 min of extraction time at 55°C water bath. / The developed method was applied to study the volatile profile of three commercial brands of plain sufu. In total, 131 volatile compounds were detected in the headspace of the examined samples. Samples A, B and C have totals of 112, 112 and 118 compounds, respectively, and they belong to various chemical groups. Seventy-six compounds were found in common among the commercial samples. These included 11 out of the 14 aroma-impact compounds previously identified by Chung et al., 2005. Quantitatively, alcohols and esters were among the most abundant groups of compound found. Many esters, aldehydes and aromatic hydrocarbons compounds were first reported in this study. The results obtained by SPME were comparable to those obtained by SFE and SDE methods and at the same time it is cheaper and less labor intensive method in terms of the extraction and clean-up steps. In short, the developed HS-SPME method is an inexpensive, simple, rapid and mild extraction technique which allows the detection of a wide range of volatiles from sufu. / In the final part of the study, the changes of volatile profile and the physicochemical parameters of a commercially produced plain sufu were studied throughout its fermentation (pehtze period) and ageing (after wine & brine added) processes. The volatile profiles of the key ingredients, namely, yellow rice wine and sesame seed oil were also studied. In general, all the major chemical groups experienced an increase in concentration during ageing. Many new compounds were formed in the first few months of ageing. A total of 37, 58, 69, 83 and 86 compounds were identified in pehtze stage, days 0 (36 hour since bottling), 60, 120 and 180, respectively. Esters and pyrazines account for most of the quality difference. Their concentrations increased throughout the ageing period. Concentration for most of the aroma-impact compounds increased significantly throughout ageing. Many of the volatiles detected in the yellow rice wine and the sesame oil were found in common with the ageing or matured sufus (6th month). Proximate analysis showed that there were no significant changes in moisture content but a significant decline in both the lipid, protein contents were observed. On the other hand, the ash content was significantly increased in the first four months, but leveled off afterwards. While this study provides some more information to understand the changes in both volatile components and chemical composition during the fermentation and ageing processes, further studies will be needed to explain the flavour and textural changes. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chiang, Tsz Kei Jackie. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 153-195). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Thesis Committee / Acknowledgements / Abstract --- p.I / 摘要 --- p.IV / Table of Contents --- p.VI / List of Tables --- p.XI / List of Figures --- p.XII / List of Abbreviations --- p.XIV / Chapter Chapter 1 --- Literature Review --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Sufu --- p.3 / Chapter 1.2.1 --- History and Background of Sufu --- p.3 / Chapter 1.2.2 --- Sufu Classification --- p.5 / Chapter 1.2.2.1 --- White Sufu --- p.5 / Chapter 1.2.2.2 --- Red Sufu --- p.5 / Chapter 1.2.2.3 --- Grey Sufu --- p.6 / Chapter 1.2.2.4 --- Other Types --- p.6 / Chapter 1.2.3 --- Manufacturing of Sufu --- p.7 / Chapter 1.2.4 --- Microbes Used in Sufu Fermentation --- p.10 / Chapter 1.2.5 --- Biochemical Changes during Sufu Ageing --- p.10 / Chapter 1.2.5.1 --- Protein Faction --- p.11 / Chapter 1.2.5.2 --- Lipid Fraction --- p.12 / Chapter 1.2.5.3 --- Carbohydrate Fraction --- p.12 / Chapter 1.2.6 --- Flavour Origin of Sufu --- p.13 / Chapter 1.2.7 --- Volatile Components of Sufu --- p.14 / Chapter 1.2.7.1 --- Alcohols --- p.14 / Chapter 1.2.7.2 --- Esters --- p.15 / Chapter 1.2.7.3 --- Aldehydes --- p.16 / Chapter 1.2.7.4 --- Furans --- p.17 / Chapter 1.2.7.5 --- Ketones --- p.17 / Chapter 1.2.7.6 --- Sulphur-containing Compounds --- p.18 / Chapter 1.2.8 --- Aroma-impact Compounds --- p.20 / Chapter 1.2.8.1 --- Aroma-impact Compounds in Sufu --- p.23 / Chapter 1.3 --- Flavor Extraction Techniques --- p.23 / Chapter 1.3.1 --- Headspace Methods --- p.24 / Chapter 1.3.1.1 --- Static Headspace Sampling --- p.25 / Chapter 1.3.1.2 --- Dynamic Headspace Sampling --- p.25 / Chapter 1.3.2 --- Solvent Extraction --- p.26 / Chapter 1.3.3 --- Steam Distillation Techniques --- p.27 / Chapter 1.3.3.1 --- Simultaneous Steam Distillation and Solvent Extraction (SDE) --- p.27 / Chapter 1.3.3.2 --- High-vacuum Distillation Techniques --- p.28 / Chapter 1.3.4 --- Supercritical Fluid Extraction Methods (SFE) --- p.28 / Chapter 1.3.5 --- Solid-phase Extraction (SPE) --- p.30 / Chapter 1.3.6 --- Solid-phase Microextraction (SPME) --- p.31 / Chapter 1.4 --- Objectives --- p.35 / Chapter Chapter 2 --- Optimization of Headspace Solid-phase Microextraction Conditions for the Determination of Volatile Compounds in Sufu --- p.36 / Chapter 2.1 --- Introduction --- p.36 / Chapter 2.2 --- Materials and Methods --- p.40 / Chapter 2.2.1 --- Materials --- p.40 / Chapter 2.2.1.1 --- Commercial Plain Sufu --- p.40 / Chapter 2.2.1.2 --- SPME Accessories --- p.40 / Chapter 2.2.2 --- Sample Preparation --- p.41 / Chapter 2.2.3 --- Optimization of Sample Preparation Method for HS-SPME-GC/MS Analysis --- p.41 / Chapter 2.2.3.1 --- Effect of Ionic Strength (NaCl Concentration) --- p.42 / Chapter 2.2.3.2 --- Optimization of Water Content --- p.42 / Chapter 2.2.4 --- Optimization of the Extraction Conditions for HS-SPME- GC/MS Analysis --- p.42 / Chapter 2.2.4.1 --- HS-SPME Procedures --- p.43 / Chapter 2.2.5 --- Gas Chromatography/Mass Spectrometry (GC/ MS) Conditions --- p.43 / Chapter 2.2.6 --- Identification and Quantification of Selected Volatiles in Sufu --- p.44 / Chapter 2.3 --- Results and Discussions --- p.46 / Chapter 2.3.1 --- Method Development --- p.46 / Chapter 2.3.1.1 --- Choice of Fibers --- p.46 / Chapter 2.3.1.2 --- Effect of Time --- p.48 / Chapter 2.3.1.3 --- Effect of Temperature --- p.49 / Chapter 2.3.1.4 --- Effect of Ionic Strength (NaCl Concentration) --- p.51 / Chapter 2.3.1.5 --- Effect of Water Content --- p.52 / Chapter 2.3.2 --- Application of the HS-SPME-GC/MS Method for the Analysis of Sufu Volatiles --- p.61 / Chapter 2.3.2.1 --- Alcohols --- p.62 / Chapter 2.3.2.2 --- Aldehydes --- p.63 / Chapter 2.3.2.3 --- Aliphatic Hydrocarbons --- p.64 / Chapter 2.3.2.4 --- Aromatic Hydrocarbons --- p.65 / Chapter 2.3.2.5 --- Esters --- p.67 / Chapter 2.3.2.6 --- Furans --- p.69 / Chapter 2.3.2.7 --- Ketones --- p.70 / Chapter 2.3.2.8 --- Pyrazines --- p.71 / Chapter 2.3.2.9 --- Sulphur-containing Compounds --- p.73 / Chapter 2.3.3 --- Comparison of Different Extraction Techniques --- p.74 / Chapter 2.4 --- Conclusion --- p.86 / Chapter Chapter 3 --- Changes in Volatile Constituents and Physicochemical Characteristics of Commercial Plain Sufu throughout the Fermentation and Ageing Process --- p.87 / Chapter 3.1 --- Introduction --- p.87 / Chapter 3.2 --- Materials and Methods --- p.90 / Chapter 3.2.1 --- Sufu Sampling --- p.90 / Chapter 3.2.2 --- Flavour Analysis --- p.90 / Chapter 3.2.2.1 --- Sample Preparation --- p.90 / Chapter 3.2.2.2 --- Solid-phrase Microextraction (SPME) --- p.91 / Chapter 3.2.2.3 --- Gas Chromatography/ Mass Spectrometry (GC/ MS) Conditions --- p.92 / Chapter 3.2.2.4 --- Identification and Quantification of Selected Volatiles in Sufu --- p.93 / Chapter 3.2.3 --- Proximate Analysis --- p.93 / Chapter 3.2.4 --- Statistical Analysis --- p.94 / Chapter 3.3 --- Results and Discussions --- p.95 / Chapter 3.3.1 --- Overall Finding --- p.95 / Chapter 3.3.2 --- Flavour Analysis of Sufu at Different Fermentation and Ageing Stages --- p.97 / Chapter 3.3.2.1 --- Alcohols --- p.97 / Chapter 3.3.2.2 --- Aldehydes --- p.99 / Chapter 3.3.2.3 --- Esters --- p.101 / Chapter 3.3.2.4 --- Furans --- p.104 / Chapter 3.3.2.5 --- Ketones --- p.105 / Chapter 3.3.2.6 --- Pyrazines --- p.107 / Chapter 3.3.2.7 --- Sulphur-containing Compounds --- p.108 / Chapter 3.3.2.8 --- Miscellaneous Compounds --- p.110 / Chapter 3.3.2.9 --- Aroma-impact Compounds --- p.111 / Chapter 3.3.3 --- Potential Volatile Flavour Contributors from the Key Ingredients (Yellow Rice Wine and Sesame Seed Oil) --- p.112 / Chapter 3.3.3.1 --- Volatile Compounds in Yellow Rice Wine --- p.113 / Chapter 3.3.3.2 --- Volatile Compounds in Sesame Seed Oil --- p.114 / Chapter 3.3.4 --- Proximate Composition of Sufu at Different Fermentation and Ageing Stages --- p.115 / Chapter 3.3.5 --- Overall Discussion --- p.144 / Chapter 3.4 --- Conclusion --- p.146 / Chapter Chapter 4 --- OverallConclusion --- p.148 / Chapter 4.1 --- Conclusions and Significance of the Study --- p.148 / Chapter 4.2 --- Future Work --- p.151 / References --- p.153 / Chapter Appendix A --- p.196 / Chapter Appendix B --- p.199
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_328184 |
| Date | January 2012 |
| Contributors | Chiang, Tsz Kei Jackie., Chinese University of Hong Kong Graduate School. Division of Life Sciences. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, bibliography |
| Format | electronic resource, electronic resource, remote, 1 online resource (xiv, 199 leaves) : ill. |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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