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Author: Xiaotong Lyu Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Varietal thiols are crucial aroma compounds present in white wines, and especially contribute to characteristic New Zealand Sauvignon Blanc wines. They provide wines with passion fruit, tropical, stalky and grapefruit aromas. Much research has focused on the formation pathways of these compounds, so as to increase these aromas in Sauvignon Blanc wines. One of the main pathways identified involves conjugated precursors. Recently, an alternative pathway has been proposed, which is through the addition to C6 compounds of a sulfur donor, such as H2S, to form the varietal thiol 3-mercaptohexanol (3MH). Oxygen can be very detrimental to the formation and stability of thiol compounds. Thus, the use of antioxidants is important throughout winemaking practices to protect thiol compounds from oxidation. Elemental sulfur is a common fungicide applied to grapes and leaves in vineyards before harvest. The residues of elemental sulfur have been found to increase the production of H2S, and also varietal thiol compounds. Nevertheless, it also has the potential to generate unwanted reductive sulfur aroma compounds. Micro-oxygenation has been discussed as a way to solve the unpleasant aroma problems caused by elemental sulfur residues. This thesis aims to investigate the effects of different conditions of grape processing or fermentation on the aroma profile of New Zealand white wines. Experiments have been designed to study how alternative antioxidants (glutathione and ascorbic acid) impact on the aroma compounds of Sauvignon Blanc and Pinot Gris wines. Other experiments were undertaken to compare the differences between the aroma compounds in the Sauvignon Blanc, Pinot Gris, and Chardonnay wines with or without antioxidant additions, or with a high level of elemental sulfur addition. Sensory analyses were also performed to compare the Sauvignon Blanc and Pinot Gris wines produced with these treatments. Attention was also paid to the effectiveness of two gas sparging regimes (oxygen and nitrogen), applying during fermentation, on the removal of reductive sulfur aromas in Sauvignon Blanc wines. Additions of glutathione to the grape juices increased the levels of varietal thiols in the finished wines. The lowest levels of varietal thiol compounds were found in the wines with little supplementary antioxidants added. Furthermore, a high level of the joint combination of ascorbic acid and glutathione provided the wines with even higher thiol production. The high level of ascorbic acid addition also protected phenolic compounds from oxidation in the wines. A high level of antioxidants added to the juices at harvest remarkably increased the level of thiol productions, when compared to no supplementary antioxidant addition, in Sauvignon Blanc, Pinot Gris, and Chardonnay wines. Moreover, the varietal thiol levels in the Pinot Gris and Chardonnay wines were just as high as with the Sauvignon Blanc wines, when efficient antioxidant protection was provided. It is also worth noting that the sensory analyses showed the Pinot Gris wines maintained their varietal characteristics, even when high levels of thiols were present. Further increases in the thiol production were observed in the wines with extra elemental sulfur additions. Finally, increasing the amount of elemental sulfur addition to the juice before pressing also led to an increase in the formation of several thiol compounds, including some unwanted reductive compounds, as a consequence of the reduction of elemental sulfur to H2S in the early stages of fermentation. Additions of oxygen added during fermentation were not high enough to effectively remove the undesirable reductive aroma compounds, while a slight decrease was observed in the concentration of the varietal thiols. Likewise, few were observed in the concentrations of unwanted volatile sulfur compounds, or other chemical compounds, with the juices sparged with nitrogen during fermentation.
Author: Xiaotong Lyu Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Varietal thiols are crucial aroma compounds present in white wines, and especially contribute to characteristic New Zealand Sauvignon Blanc wines. They provide wines with passion fruit, tropical, stalky and grapefruit aromas. Much research has focused on the formation pathways of these compounds, so as to increase these aromas in Sauvignon Blanc wines. One of the main pathways identified involves conjugated precursors. Recently, an alternative pathway has been proposed, which is through the addition to C6 compounds of a sulfur donor, such as H2S, to form the varietal thiol 3-mercaptohexanol (3MH). Oxygen can be very detrimental to the formation and stability of thiol compounds. Thus, the use of antioxidants is important throughout winemaking practices to protect thiol compounds from oxidation. Elemental sulfur is a common fungicide applied to grapes and leaves in vineyards before harvest. The residues of elemental sulfur have been found to increase the production of H2S, and also varietal thiol compounds. Nevertheless, it also has the potential to generate unwanted reductive sulfur aroma compounds. Micro-oxygenation has been discussed as a way to solve the unpleasant aroma problems caused by elemental sulfur residues. This thesis aims to investigate the effects of different conditions of grape processing or fermentation on the aroma profile of New Zealand white wines. Experiments have been designed to study how alternative antioxidants (glutathione and ascorbic acid) impact on the aroma compounds of Sauvignon Blanc and Pinot Gris wines. Other experiments were undertaken to compare the differences between the aroma compounds in the Sauvignon Blanc, Pinot Gris, and Chardonnay wines with or without antioxidant additions, or with a high level of elemental sulfur addition. Sensory analyses were also performed to compare the Sauvignon Blanc and Pinot Gris wines produced with these treatments. Attention was also paid to the effectiveness of two gas sparging regimes (oxygen and nitrogen), applying during fermentation, on the removal of reductive sulfur aromas in Sauvignon Blanc wines. Additions of glutathione to the grape juices increased the levels of varietal thiols in the finished wines. The lowest levels of varietal thiol compounds were found in the wines with little supplementary antioxidants added. Furthermore, a high level of the joint combination of ascorbic acid and glutathione provided the wines with even higher thiol production. The high level of ascorbic acid addition also protected phenolic compounds from oxidation in the wines. A high level of antioxidants added to the juices at harvest remarkably increased the level of thiol productions, when compared to no supplementary antioxidant addition, in Sauvignon Blanc, Pinot Gris, and Chardonnay wines. Moreover, the varietal thiol levels in the Pinot Gris and Chardonnay wines were just as high as with the Sauvignon Blanc wines, when efficient antioxidant protection was provided. It is also worth noting that the sensory analyses showed the Pinot Gris wines maintained their varietal characteristics, even when high levels of thiols were present. Further increases in the thiol production were observed in the wines with extra elemental sulfur additions. Finally, increasing the amount of elemental sulfur addition to the juice before pressing also led to an increase in the formation of several thiol compounds, including some unwanted reductive compounds, as a consequence of the reduction of elemental sulfur to H2S in the early stages of fermentation. Additions of oxygen added during fermentation were not high enough to effectively remove the undesirable reductive aroma compounds, while a slight decrease was observed in the concentration of the varietal thiols. Likewise, few were observed in the concentrations of unwanted volatile sulfur compounds, or other chemical compounds, with the juices sparged with nitrogen during fermentation.
Author: Leandro Dias Araújo Publisher: ISBN: Category : Sauvignon blanc (Wine) Languages : en Pages : 328
Book Description
Important volatile varietal thiol compounds contribute significantly to the aroma of Sauvignon blanc wines. They impart pleasant tropical, passion fruit, gooseberry, and grape fruit notes to wine, among other aromas. The formation of these compounds has been the subject of much research, mainly focused on the release of varietal thiols from conjugated precursors. An alternative pathway was shown to have immense potential to form 3-mercaptohexanol (3MH) via the addition of H2S to C6 compounds. However, both pathways have limitations to their relevance in oenological conditions and were not able to fully explain the high varietal thiol content in Sauvignon blanc wine. The practices undertaken at the early stages of winemaking were found to be important in modulating the level of varietal thiols in wine. The method of harvesting and extent of grape maceration, the addition of antioxidants at harvest, and the extent of grape pressing, all had a significant impact on the formation of varietal thiols. The aim of this thesis was to investigate how the conditions of grape harvesting and processing impact the aroma of Sauvignon blanc wines. To this end, experiments were undertaken to examine the effects of antioxidant additions to machine harvested grapes on the chemical and sensory profile of the wines. Attention was also paid to the formation of C6 compounds in juice and the relationship of their levels to the formation of varietal thiols. The role of elemental sulfur residues in juice in the formation of 3MH became a particular focus as the research developed. The addition of SO2 to machine-harvested Sauvignon blanc grapes in the field produced wines with higher levels of varietal thiols, compared to wines made with no antioxidant protection. Despite large differences in the chemical composition of the wines, the sensory profiles were generally similar between samples from a specific site. High levels of 3MH and 3MHA, together with some reductive sulfur compounds, were observed in wines with a marked flinty character. Another antioxidant compound tested was chitosan. Unlike SO2, the addition of chitosan early in the grape processing stages was severely detrimental to the formation of varietal thiols. However, it was not possible to identify the exact means by which chitosan affected thiol formation, although some impact on enzyme systems was suggested. The investigations regarding the production of C6 compounds during grape processing revealed that the concentrations of these compounds were not correlated with the levels of varietal thiols in wine. Moreover, the addition of leaves to grapes did not increase the levels of C6 compounds. Further, an inconsistent effect of leaves additions on the formation of varietal thiols was observed and related to extrinsic factors rather than a direct contribution of the leaves themselves. Finally, the important role of elemental sulfur in the formation of varietal thiols was demonstrated. Varietal thiols levels were proportional to the levels of elemental sulfur added to the juice prior to fermentation. Unwanted reductive sulfur compounds also remained in the wines if high levels of sulfur were present during fermentation. New insights into the mechanism of the formation of 3MH, via the reduction of elemental sulfur into H2S in grape juice, are proposed.
Author: Jean L. Jacobson Publisher: Springer Science & Business Media ISBN: 0387251200 Category : Technology & Engineering Languages : en Pages : 390
Book Description
In the beginning, for me, winemaking was a romanticized notion of putting grape juice into a barrel and allowing time to perform its magic as you sat on the veranda watching the sunset on a Tuscan landscape. For some small wineries, this notion might still ring true, but for the majority of wineries commercially producing quality wines, the reality of winemaking is far more complex. The persistent evolution of the wine industry demands continual advan- ments in technology and education to sustain and promote quality winem- ing. The sciences of viticulture, enology, and wine chemistry are becoming more intricate and sophisticated each year. Wine laboratories have become an integral part of the winemaking process, necessitating a knowledgeable staff possessing a multitude of skills. Science incorporates the tools that new-age winemakers are utilizing to produce some of the best wines ever made in this multibillion dollar trade. A novice to enology and wine chemistry can find these subjects daunting and intimidating. Whether you are a home winemaker, a new winemaker, an enology student, or a beginning-to-intermediate laboratory technician, p- ting all the pieces together can take time. As a winemaker friend once told me, “winemaking is a moving target. ” Introduction to Wine Laboratory Practices and Procedures was written for the multitude of people entering the wine industry and those that wish to learn about wine chemistry and enology.
Author: George Casella Publisher: CRC Press ISBN: 1040024025 Category : Mathematics Languages : en Pages : 1746
Book Description
This classic textbook builds theoretical statistics from the first principles of probability theory. Starting from the basics of probability, the authors develop the theory of statistical inference using techniques, definitions, and concepts that are statistical and natural extensions, and consequences, of previous concepts. It covers all topics from a standard inference course including: distributions, random variables, data reduction, point estimation, hypothesis testing, and interval estimation. Features The classic graduate-level textbook on statistical inference Develops elements of statistical theory from first principles of probability Written in a lucid style accessible to anyone with some background in calculus Covers all key topics of a standard course in inference Hundreds of examples throughout to aid understanding Each chapter includes an extensive set of graduated exercises Statistical Inference, Second Edition is primarily aimed at graduate students of statistics, but can be used by advanced undergraduate students majoring in statistics who have a solid mathematics background. It also stresses the more practical uses of statistical theory, being more concerned with understanding basic statistical concepts and deriving reasonable statistical procedures, while less focused on formal optimality considerations. This is a reprint of the second edition originally published by Cengage Learning, Inc. in 2001.
Author: Aaron L. Brody Publisher: CRC Press ISBN: 9781420031812 Category : Technology & Engineering Languages : en Pages : 244
Book Description
Based on thousands of citations from peer-reviewed, trade, commercial, and patent literature and interviews with those who have worked in the laboratory, in pilot plants, and in production, Active Packaging for Food Applications provides a state-of-the-art guide to understanding and utilizing these technologies. The book highlights technologies that are currently in commercial use or have the potential to become commercial, including oxygen scavenging, moisture control, ethylene removal from fresh food, antimicrobials, odor removal, and aroma emission. In addition, it explores the pros and cons involved in using antimicrobial agents in package materials. Active Packaging for Food Applications provides you with a detailed guide and reference to the technologies - and their applications - involved in enhancing food and beverage preservation.
Author: Maria R. Kosseva Publisher: Academic Press ISBN: 0128010347 Category : Technology & Engineering Languages : en Pages : 758
Book Description
Science and Technology of Fruit Wine Production includes introductory chapters on the production of wine from fruits other than grapes, including their composition, chemistry, role, quality of raw material, medicinal values, quality factors, bioreactor technology, production, optimization, standardization, preservation, and evaluation of different wines, specialty wines, and brandies. Wine and its related products have been consumed since ancient times, not only for stimulatory and healthful properties, but also as an important adjunct to the human diet by increasing satisfaction and contributing to the relaxation necessary for proper digestion and absorption of food. Most wines are produced from grapes throughout the world, however, fruits other than grapes, including apple, plum, peach, pear, berries, cherries, currants, apricot, and many others can also be profitably utilized in the production of wines. The major problems in wine production, however, arise from the difficulty in extracting the sugar from the pulp of some of the fruits, or finding that the juices obtained lack in the requisite sugar contents, have higher acidity, more anthocyanins, or have poor fermentability. The book demonstrates that the application of enzymes in juice extraction, bioreactor technology, and biological de-acidification (MLF bacteria, or de-acidifying yeast like schizosaccharomyces pombe, and others) in wine production from non-grape fruits needs serious consideration. - Focuses on producing non-grape wines, highlighting their flavor, taste, and other quality attributes, including their antioxidant properties - Provides a single-volume resource that consolidates the research findings and developed technology employed to make wines from non-grape fruits - Explores options for reducing post-harvest losses, which are especially high in developing countries - Stimulates research and development efforts in non-grape wines
Author: Gerald Reed Publisher: Springer Science & Business Media ISBN: 9401197717 Category : Science Languages : en Pages : 459
Book Description
Yeasts are the active agents responsible for three of our most important foods - bread, wine, and beer - and for the almost universally used mind/ personality-altering drug, ethanol. Anthropologists have suggested that it was the production of ethanol that motivated primitive people to settle down and become farmers. The Earth is thought to be about 4. 5 billion years old. Fossil microorganisms have been found in Earth rock 3. 3 to 3. 5 billion years old. Microbes have been on Earth for that length of time carrying out their principal task of recycling organic matter as they still do today. Yeasts have most likely been on Earth for at least 2 billion years before humans arrived, and they playa key role in the conversion of sugars to alcohol and carbon dioxide. Early humans had no concept of either microorganisms or fermentation, yet the earliest historical records indicate that by 6000 B. C. they knew how to make bread, beer, and wine. Earliest humans were foragers who col lected and ate leaves, tubers, fruits, berries, nuts, and cereal seeds most of the day much as apes do today in the wild. Crushed fruits readily undergo natural fermentation by indigenous yeasts, and moist seeds germinate and develop amylases that produce fermentable sugars. Honey, the first con centrated sweet known to humans, also spontaneously ferments to alcohol if it is by chance diluted with rainwater. Thus, yeasts and other microbes have had a long history of 2 to 3.
Author: Robert S. Igoe Publisher: Springer Science & Business Media ISBN: 1461568382 Category : Technology & Engineering Languages : en Pages : 203
Book Description
The Dictionary of Food Ingredients is a unique, easy-to-use source of infor mation on over 1,000 food ingredients. Like the previous editions, the new and updated Third Edition provides clear and concise information on currently used additives, including natural ingredients, FDA-approved artificial ingredients, and compounds used in food processing. The dictionary entries, organized in alphabetical order, include information on ingredient functions, chemical properties, and uses in food products. The updated and revised Third Edition contains approximately 1 SO new entries, and includes an updated and expanded bibliography. It also lists food ingredients ac cording to U. S. federal regulatory status. Users of the two previous editions have commented favorably on the dictionary's straightforward and clearly-written definitions, and we have endeavored to maintain that standard in this new edition. We trust it will continue to be a valuable reference for the food scientist, food processor, food product developer, nutritionist, extension specialist, and student. R S. Igoe Y. H. Hui vii Ingredients A Acacia See Arabic. Acesulfame-K A non-nutritive sweetener, also termed acesulfame potas sium. It is a white, crystalline product that is 200 times sweeter than sucrose. It is not metabolized in the body. It is relatively stable as a powder and in liquids and solids which may be heated. Acesulfame-K is approved for use in dry food products. Acesulfame Potassium See Acesulfame-K.
Author: Andrew G.H. Lea Publisher: Springer Science & Business Media ISBN: 1461501873 Category : Technology & Engineering Languages : en Pages : 438
Book Description
Fermented Beverage Production, Second Edition is an essential resource for any company producing or selling fermented alcoholic beverages. In addition it would be of value to anyone who needs a contemporary introduction to the science and technology of alcoholic beverages. This authoritative volume provides an up-to-date, practical overview of fermented beverage production, focusing on concepts and processes pertinent to all fermented alcoholic beverages, as well as those specific to a variety of individual beverages. The second edition features three new chapters on sparkling wines, rums, and Latin American beverages such as tequila, as well as thorough updating of information on new technologies and current scientific references.
Author: Xiaotong Lyu
Author: Xiaotong Lyu
Author: Mandy Herbst-Johnstone
Author: Leandro Dias Araújo
Author: Jean L. Jacobson
Author: George Casella
Author: Aaron L. Brody
Author: Maria R. Kosseva
Author: Gerald Reed
Author: Robert S. Igoe
Author: Andrew G.H. Lea