Généralités sur les matières premières
L'origine et les caractéristiques de Palmier Thnot
The Thnot palm, scientifically known as "Borassus flabellifer," is commonly referred to as the Thnot in Cambodia and the Palmyra palm, Talouriksha palm, or Toddy palm in English This tropical tree, belonging to the Arecaceae family, is native to tropical regions of Africa and Asia, with Vietnam being one of these countries In Vietnam, the Thnot palm is primarily found in the southern region, particularly abundant in Tinh Bien and Tri Ton within An Giang province, and is utilized for various purposes, including sugar production.
The Thnot tree, known as the sugar palm (Borassus Flabellifer), is a significant element of Cambodia's rural landscape, originating from India Its trunk is used for beams and planks, while its hollowed-out form serves as a canoe The leaves are versatile, utilized for roofing, making mats, hats, and traditional Cambodian boxes called "smock." The tree's large orange-sized fruits have edible pulp, and both the fruits and roots are used in traditional medicine Additionally, the tree's inflorescences are tapped for a nutritious sap that can be consumed fresh or heated to produce syrup and palm sugar, commonly found in pastries, dairy desserts, and hot beverages.
The fermentation of palm sap leads to the production of palm wine or, after distillation, alcohol The harvesting process occurs over six months during the dry season, yielding approximately 400 liters of sap from a mature palm tree Farmers use a bamboo ladder to climb the tree twice daily to collect the sweet nectar that drips into containers Harvesting from 30 palm trees requires climbing a total of 1,000 meters each day This challenging and hazardous profession is primarily undertaken by young individuals from impoverished families lacking rice fields Historically, those who climbed the Thnot palm were exempt from taxes, as they were viewed as potential casualties.
Elément incontournable des paysages cambodgiens, dont la silhouette est aussi célèbre que celle d’Angkor Vat, il est considéré comme le symbole de l’âme khmère.
In ideal conditions, palm trees can grow to heights of 12 to 18 meters as they mature, but in exceptional cases, they may reach up to 30 meters with a trunk diameter of 60 cm This plant is easily identifiable among other trees due to its towering height and fan-shaped leaves The trunk is black and nearly cylindrical, marked by semi-circular scars from the fallen leaf petioles At the crown of the tree, a cluster of 25 to 40 giant leaves emerges, with the petioles being notably thick and sturdy Each leaf, resembling a hand, can extend horizontally up to a maximum of 5 meters.
The Landscape and Flower Techniques Department at Nong Lam University in Ho Chi Minh City has conducted research on the specialized cultivation of the Seven Mountains, yielding significant findings.
The Thnot palm features a thick, cylindrical trunk that widens significantly at the base, reaching heights of 20-25 meters Its leaves are robust and rigid, spreading out in a large circular shape, with deeply cleft lobes that are smaller and pointed, arranged in a helical pattern The petiole is stout and sturdy, with a foliar sheath at the base and spines running along its length.
The plant features a large bouquet of unisexual flowers, with male flowers being particularly abundant while female flowers are less numerous and branch out Its round, brown fruits measure 10-20 cm in diameter and contain a hard pit with three seeds.
The Le Thnot plant thrives in sunlight but experiences slow growth In its early years, it requires shade and well-drained soil This plant propagates from seeds and has moderate water needs.
Le nectar de Thnot
Derived from flower styles, nectar is the primary product of the Thnot tree, also known as arrack or toddy Typically, the nectar ferments after dawn and can be harvested in large quantities before sunrise for its nutritious benefits, including a laxative effect However, the harvesting process is unique and challenging; men must climb 12-18 meters high using a bamboo ladder to access the tree, where they place plastic bottles beneath the flower styles to collect the nectar The average time between harvests on the same tree is approximately 6-12 hours.
Le nectar de Thnot flue pendant 5-6 mois, environ 200 jours Chaque plante mâle produit 5-
Female palm trees produce over 50% more nectar than male trees, yielding up to 6 liters of nectar daily This nectar is harvested to create palm wine, also known as arrack To prevent fermentation, a sulfur compound is added, and the nectar is then concentrated into raw sugar, known as Gur in India and jaggery in Ceylon Additionally, other products such as palm molasses, palm candies, and palm vinegar can be made from this nectar.
Raw palm sugar is more nutritious than other sugars derived from sugarcane, containing 1.04% protein, 0.19% fat, 76.86% sucrose, 1.66% glucose, 3.15% mineral matter, 0.861% calcium, 0.052% phosphorus, and 10.01 mg of iron per 100 g, along with 0.767 mg of copper per 100 g Additionally, fresh palm nectar is a rich source of B-complex vitamins (Morton, JF, 1988).
Most species of Thnot in the Seven Mountains region are of two types: Borassus baethiopium and Borassus flabellifer This plant produces a highly aromatic nectar that is both appealing and rich in nutrients.
2005), ces valeurs nutritionnelles sont indiquées dans le tableau 1.1 Selon certaines études au Viet Nam, la composition de 100ml de nectar de palme comprend:
Tableau 1.1 : La composition chimique de nectar de Thnot (mg/100g) compostion Teneur
(Source : Hoàng Xuân Phương, 2004 d’après Huỳnh Muổi Hên, 2005)
India has conducted extensive studies on this plant due to its prevalence in the region The findings regarding the chemical composition of Thnot nectar, as shown in Table 1.1, reveal the changes in its chemical makeup before and after 24 hours of natural fermentation at approximately 25°C This nectar is harvested from trees aged 15 to 20 years between 4 and 6 a.m and is then transported to the laboratory under sterile conditions for chemical analysis.
Tableau 1.2 : La composition chimique de 100ml de nectar de palme
Près de 24 heures de fermentation
Près de 24 heures de fermentation pH 7,30 5,90 7,20 6,00
(Source : Debmalya Barh and B.C Mazumdar)
The Thnot nectar is rich in various minerals, vitamins, and other beneficial compounds, all of which contribute positively to health.
La valeur de l’arbre de Thnot
The Thnot tree (Borassus flabellifer) is a native plant of Southeast Asia, commonly cultivated by farmers to shield their fields from strong winds and to harvest its nutritious nectar, which begins production at around 15-20 years of age Beyond its nectar, the Thnot tree serves multiple purposes: its roots are used for medicinal purposes, its trunks for construction, its leaves for writing and crafting, and its fruits are edible The nectar is not only a nutritious beverage but also a key ingredient in delicious traditional sugar cakes Additionally, with their deep root systems, Thnot trees contribute to soil nutrient cycling, enhancing soil fertility and agricultural yields.
The Thnot wood is utilized in house construction, with its applications varying based on the plant's age and sex Young trees produce soft, slow, and hard wood, while the heartwood is less dense Female plants yield higher quality products compared to male ones Thnot wood is commonly employed in sectors such as housing and architectural design.
Additionally, the valuable chemical composition of various parts of the Thnot plant contributes to its medicinal properties When the Thnot nectar is combined with rice flour and heated to fermentation temperature, it creates a highly beneficial irritant poultice The fruits of the Thnot are widely recognized for their laxative effects, while the ash produced from burning the flowers is utilized to alleviate nausea and irritability.
Young plants effectively regulate temperature, alleviate stress, and combat dysentery and gonorrhea Their young roots act as diuretics, eliminate helminths, and enhance respiratory function when decocted The bark of Thnot, when decocted with salt, serves as an oral hygiene solution, while charcoal made from the bark is used as a toothpaste Nectar from the petiole acts as a tonic that reduces stress, has a laxative effect, and is an effective anti-inflammatory irritant The sugar derived from this nectar helps combat contamination and is prescribed for functional body disorders Rock sugar is a potent pharmaceutical for treating coughs and lung-related illnesses Fresh nectar is heated to promote fermentation and applied to all types of ulcers Dried buds, leaf petioles, and male flowers are macerated in alcohol for their diuretic properties, while the flesh of ripe fruits contributes to anti-inflammatory skin activity.
Tableau 1.3 L'analyse chimique des parties de la plante Thnot (% de matière sèche)
Partie PB FB Ash EE ALE Ca P
PB : Protéine brute FB : Fibre brute EE : ester extrait ALE : Azote libre extrait
Introduction du vin
Le vin
de fruits, et non distillation (TCVN 4075: 2002).
The origin of wine dates back to the 6th century BC in the South of France, where it was initially fermented from grapes Known as "vin" or "wine," this beverage has evolved to encompass a broader definition, now referring to any type of alcohol that is fermented from fruits without distillation (Luong Duc Pham, 2005, according to Nguyen Phu Cuong).
Wine is regarded as a natural beverage that offers numerous health benefits, primarily due to its composition as fermented fruit juice In addition to the sugars consumed by yeast during fermentation to produce alcohol, wine contains essential nutrients such as vitamins, minerals, organic acids, and proteins Typically, wine has an alcohol content ranging from 10% to 14%, with minimal harmful substances like aldehyde and methanol Therefore, when consumed in moderation, wine can be beneficial for health.
Les effets du vin pour la santé
Red wine has anti-obesity effects due to its active component, resveratrol, which can inhibit the production and development of fat tissues Research presented by Dr Martin Wabitsch's team indicates that resveratrol reduces the division of young fat cells by 40 to 45% within 48 hours in laboratory settings Additionally, this active element decreases the size of fat cells and the production of Interleukin 6 and 8, both of which are linked to diabetes and blood clotting phenomena in blood vessels Resveratrol also activates the SIRT1 gene, which regulates the transformation and lifespan of fat cells.
Red wine has beneficial effects against cardiovascular diseases According to Professor Tomas Prolla from the University of Wisconsin-Madison, red wine positively influences cardiovascular activity, muscle function, and brain activity These interconnected activities can impact an individual's health and the effects of aging For instance, over a thousand cardiac genes change with age and affect bodily functions Consequently, a low-calorie intake can reduce aging genes and prolong life Additionally, Professor Prolla's colleague, Jamie Berger, notes that scientists tested two groups: Group 1 consumed low-calorie foods, while Group 2 drank a small amount of red wine with meals The results showed clear differences, indicating that a glass of red wine during meals significantly contributes to reducing cardiovascular aging.
Wine has been found to be effective against neurasthenia in women Studies from the Sahlgrenska Academy at the University of Gothenburg, Sweden, suggest that just one glass of wine per day can benefit women's brain health and may prevent cognitive disorders at any age An analysis of the intellectual capacities of 1,458 women around the age of 34 concluded that frequent wine drinkers show reduced signs of intellectual asthenia compared to those who drink little or no wine However, doctors advise caution in wine consumption, recommending that women familiarize themselves with wine and drink in moderation It's important to note that alcohol should not become a habit for everyone, as some individuals may be allergic to wine components, leading to health issues Experts have also noted that women today consume more wine than they did 40 years ago The studies focused solely on women's health, leaving the effects of wine on men's asthenia unexamined.
Vin de Thnot
Thnot wine is an alcoholic beverage made from the nectar of the Thnot flower, harvested from the petioles in the Seven Mountains region of An Giang.
The Thnot palm, like other palms in Africa and Asia, can be used to produce wine in addition to sugar This wine is easy to make, inexpensive, and has a relatively low alcohol content After harvesting, the sap ferments almost immediately, reaching up to 4 degrees of alcohol within two hours and exhibiting a pleasant aroma The longer it ferments, the stronger and more acidic it becomes, necessitating fermentation to be halted within a day to prevent vinegar formation Thnot wine has a very short shelf life and is typically consumed right after production Therefore, the challenge is to develop a new production process that enhances the alcohol content and quality of the wine, creating products that not only share characteristics with other fruit wines but also capture the unique flavor of wild Thnot from the Seven Mountains region of Vietnam.
Recent studies have focused on the application of products derived from the Thnot tree to enhance economic resources and improve the living standards of local populations Notably, Dr Nguyen Minh Thuy's research project on the technology for manufacturing and bottling Thnot nectar, conducted in 2000-2001 at the Department of Food Technology, Faculty of Agronomy and Applied Biology at Can Tho University, has been instrumental This project has led to the development of a new product that increases the commercial value of this low-cost raw material, despite its short shelf life Furthermore, it serves as a foundation for future research on this valuable resource.
In addition to the development of fermented Thnot nectar technology at An Giang University in 2008, the project on Thnot wine also presents significant development potential Dr Nguyen Minh Thuy is currently conducting this project at the Food Technology Department of Can Tho University The research aims to explore the effects of harvest factors, harvesting locations, nutritional content, yeast levels, and enzyme concentration used for wine clarification after fermentation on the quality of Thnot wine.
Levure
Morphologie
Yeasts are unicellular eukaryotes that exhibit a variety of shapes depending on the species, including spherical, oval, elliptical, lemon-shaped, cylindrical, or sometimes elongated like a filament The size and form of yeast can change during their development phase and in response to environmental conditions Young yeast species are typically cultivated in standard nutrient media (Luong Duc Pham, 2005).
Yeast cells are significantly larger than bacteria, measuring 5 to 10 times their size, with a typical diameter of about 5 to 10 μm and a length of approximately 8 μm, varying by species This size allows for an estimated surface area of yeast cells in 1 liter of fermentation solution to be around 10 m², indicating a substantial metabolic intensity between yeast cells and their environment (Luong Duc Pham, 2005).
Cette taille change aussi à cause de l’inégalité dans les différentes espèces, des différents âges et des différentes conditions (Tran Minh Tam, 2000).
Le poids privé des cellules de levure est autant que celui de bactérie (pour levure : 1,055-1,06, pour bactérie : 1,05- 1,112) (Luong Duc Pham, 2005).
Reproduction
Il y a deux types de reproduction :
La reproduction sexuée par sporulation
Yeast cells produce spores, known as ascospores, typically in groups of four, which are contained within a sac called an ascus Once mature, the ascus releases the spores, leading to the formation of four haploid yeast cells, each containing a single copy of each chromosome.
In the cultivation process, yeast is transferred from a nutrient-rich environment to a nutrient-poor one while maintaining humidity This process allows for the accumulation of intermediate compounds and provides ample oxygen, leading to the production of spores by the cells.
La reproduction asexuée par bourgeonnement ou par scission
In asexual reproduction, the nucleus and cytoplasm are transferred from the mother cell to the daughter cell Prior to division, the chromosomes within the nucleus are evenly split into two equal parts for both the mother and daughter cells.
Yeast does not undergo budding in the same location twice, except in cases of bipolar budding Under favorable conditions, the generation time of S cerevisiae is approximately 1.5 to 2 hours, during which a single cell can produce around four buds.
Elles utilisent principalement le bourgeonnement, la sporulation n’apparaợt que quand les conditions deviennent défavorables (milieu épuisé en azote et carbone) (http://tpe- levures.ifrance.com/structure.html).
Structure de cellule de levure
Yeast is a unicellular microscopic organism, similar to the cells found in flora and fauna When comparing yeast cell structures to those of bacteria, we can observe a significant evolutionary advancement from prokaryotic to eukaryotic nuclei.
Les cellules de levure (Figure 1.2) ont des composés et une structure compliquée à partir des composants principaux suivants:
(Source : http://parasitoweb.free.fr/images/Mycologie/Generalites/schema_levure.jpg)
The yeast cell is encased in a rigid wall that accounts for approximately 20% of its dry weight, with a thickness ranging from 150 to 230 nm This rigidity provides the cell with its distinctive shape Composed of 80% antigenic polysaccharides, including significant representatives such as mannans, glucans, and chitin, the cell wall also contains 10 to 20% proteins, nearly half of which are mannoproteins The structure is organized into three layers.
La couche interne, de β(1-3)-glucane, insoluble en milieu alcalin, de structure fibrillaire, assure le maintien et la rigidité de la paroi;
La couche moyenne, de β(1-3)-glucane soluble ramifié qui confère une certaine élasticité à la paroi, est aussi le lieu d’ancrage des mannoprotéines ;
La couche externe, de mannanes phosphoryles;
Du β(1-6)-glucane assure le lien entre les différentes couches.
Chitin is located at the healing site during budding, playing a crucial role in maintaining cell wall integrity and ensuring cell survival It is separated from the cytoplasmic membrane by a periplasmic space that houses various enzymes, including invertase, acid phosphatase, β-glucosidase, and β(1-3) and β(1-6) glucanases, the latter of which is involved in cell wall renewal during growth and budding (A Meyer, J Deiana, A Bernard, 2004).
The cell membrane is abundant in sterols, specifically ergosterol and zymosterol, and is composed of proteins and phospholipids It features three layers: a central layer made of lipids and phospholipids, flanked by two layers of proteins These components play crucial roles in substance transfer and enzymatic activities.
Elle a les fonctions principales suivantes:
La barrière osmotique, contrôle le métabolisme entre le milieu interne et celui externe du cytoplasme.
La biosynthèse de certains composants à l’intérieur de cellule (les éléments de la paroi cellulaire)
La résidence de certaines enzymes et des organes cellulaires.
Hydrogels with a pH around 5 contain a variety of enzymes in the cytoplasm, including those involved in glycolysis and alcoholic fermentation, as well as glycogen and organelles similar to those found in eukaryotic cells.
Mitochondria, present in approximately 50 copies per cell, contain their own DNA and RNA, playing a crucial role in resistance to certain antiseptics and the synthesis of respiratory enzymes Recent genetic studies enable the genetic marking of selected strains, which is vital for oenology Notably, mitochondria degenerate under anaerobic conditions (A Meyer, J Deiana, A Bernard, 2004).
The organelle is surrounded by a single membrane and contains numerous enzymes, including RNases and proteases, such as protease A, which plays a crucial role in the autolysis of yeast protoplasm during the aging of wine on its lees (A Meyer, J Deiana, A Bernard, 2004).
The vacuole continuously changes shape, interacting with the cytoplasm In addition to electrolytic substances dissolved in water, this organelle also contains colloidal substances such as proteins, lipids, carbohydrates, and enzymes.
The nucleus is typically small and singular, measuring approximately 2 μm in diameter It features a shell membrane, a nucleolus, and nuclear substances Most nuclei are either spherical or elliptical in shape.
In Saccharomyces cerevisiae, there are 17 identified chromosomes containing approximately 200 genes The structure of these chromosomes is similar to that of other eukaryotes, featuring DNA wrapped around nucleosomes composed of histones H2A, H2B, H3, and H4 Notably, the nuclear membrane remains intact during cell division.
The core of the cell is primarily composed of deoxyribonucleic acid (DNA), which maintains a stable concentration regardless of external environmental conditions, nutrition, or other influencing factors Throughout various developmental stages, yeast cultures consistently exhibit a DNA content ranging from 0.17 to 0.18 of their dry biomass, even in wine yeasts after heating.
Système de micro-organismes dans la solution fermentée
Le nectar naturel sans traitement est très diversifié et riche en micro-organismes en provenance des insectes, des fleurs, des outils pendant le processus de récolte.
Selon Lodder cette levure est également appeléeSaccharomyces cerevisiae Hansen.
It is highly popular in the fermentation process, accounting for 80% of Saccharomyces in a fermented solution Its sedimentation capacity varies by species, resulting in yeast appearing as either powdery or cotton-like.
(Source: http://en.wikipedia.org/wiki/Saccharomyces_cerevisiae)
Les sources nutritives de cette espèce sont le sucre, l’alcool, les acides organiques et les agents de croissance sont l’acide pantoténique, biotique, mezoinique, tiammin et piridoxin.
Most of its cells are oval-shaped, measuring between 3-8 μm by 5-12 μm Its reproduction occurs through budding or sporulation S Vini produces the enzyme invertase, which converts sucrose into fructose and glucose, allowing for the addition of sucrose during fermentation in the wine production process The alcohol content is approximately 8-10% by volume.
During the final fermentation phase, S vini settles quickly at the bottom, clarifying the wine Different strains of this yeast variety possess unique characteristics that influence alcohol production, sulfite tolerance, and the synthesis of volatile components and secondary products, which contribute to the wine's distinctive flavor Consequently, the quality of the wine is heavily reliant on the type of yeast used.
Lors de la dernière phase de fermentation, les cellules de S Vini sont souvent anciennes et ne peuvent pas transformer le sucre en alcool et meurent très rapidement
Saccharomyces oviformic (S Beuanes saccardoselon Lodder indiqué dans la figure
This yeast is derived from grape juice, although to a lesser extent than S vini In pure culture, it thrives in grape juice and other fruit juices, demonstrating the ability to withstand high sugar concentrations and elevated alcohol levels, fermenting sugars completely up to 18% alcohol content.
Source: http://www.amigasdovinho.com.br/vinho/fermentacao_dir.htm)
Saccharomyces oviformic (figure 1.5) peut fermenter glucose, fructose, manose, saccharose, maltose et 1/3 de rafinose, pas fermenter lactose et pentose.
(Source: http://www.iisalessandrini.it/progetti/studenti/ainvernizzi/immagini/sacc%20uvarium.jpg)
Extracted from grape juice, wine, and naturally fermented currant juice, this species can ferment up to 12 to 13% alcohol in grape juice Some of its strains are utilized in wine production.
(Source: http://eniw.ru/vinnye-drozhzhi.htm)
Hanseniaspora apiculate-Kloeckera apiculata(figure 1.7)
The paniculated yeast is a type of wild yeast characterized by its small, oval or elliptical shape It reproduces through budding, predominantly found on the pericarp, and accounts for 90% of the total yeast present in the must at the onset of fermentation This yeast can ferment to achieve an alcohol content of 6 to 7% and plays a crucial role in spontaneous fermentation due to its rapid reproduction rate However, it also produces volatile acids and esters that can lead to unpleasant odors in wine and can inhibit the growth of primary yeasts in the must, making it sensitive to SO2.
(Source: http://www.lwg.bayern.de/analytik/mikrobiologie/31908/)
En vinification, on ne souhaite pas son développement, on a seulement besoin dans la première étape pour faire 3-4% d’alcool.
Yeasts assimilate sugar through oxidation and can also oxidize alcohol and organic acids They thrive on the surface of wine and in alcoholic environments with less than 12% alcohol content In young wines, this yeast predominates over others On the wine's surface, Pichia forms a membrane with white powdery grains, altering the wine's composition and flavor It also produces volatile organic acids and esters During bottling, with just oxygen, this yeast rapidly develops, consuming residual sugars along with alcohol and glycerin, leading to wine opacity and a decrease in sensory value.
(Source: http://bioinformatics.psb.ugent.be/webtools/bogas/)
This yeast can withstand high levels of sulfites, with a concentration of H2SO3 reaching up to 500 mg/l It effectively assimilates various sugars and alcohols, including glucose, fructose, mannose, ethanol, glycerol, and organic acids such as acetic, lactic, malic, tartaric, and succinic, through an oxidation process.
Les bactéries et les champignons:
During fermentation, fast-growing bacteria produce a strong odor known as mannit, which is responsible for many wine diseases However, in certain cases, these bacteria can be beneficial by facilitating malolactic fermentation, where lactic acid bacteria convert malic acid into lactic acid, resulting in a more pleasant flavor This process enhances the overall taste of the wine.
La péricarpe contient souvent des spores du Mucor, des champignons backées, de la main
Penicillium, also known as blue mold, and A niger, or black mold, thrive on the surface of wine under favorable conditions and are regarded as adversaries in winemaking However, the presence of the lactic bacteria Botrytis cinerea can enhance the quality of the wine.
The spores of Mucor, along with Penicillium (commonly known as blue mold) and A Niger (black mold), can develop on the surface of wine under favorable conditions, posing a threat to the wine industry However, lactic acid bacteria and representatives of Botrytis cinerea can enhance the quality of wine.
Les besoins pour les levures de vin
Yeast effectively ferments fruit juices, utilizing sugar for nearly complete fermentation It quickly settles, clarifying wine and tolerating high alcohol and acid levels Additionally, yeast acts as an antiseptic within the fermentation medium, contributing to the wine's distinctive flavor.
To enhance yeast growth in fruit juice, certain additives can be included, such as ammonium sulfate at a concentration of 100 g/l, thiamine (vitamin B1) at 0.25 g/l, calcium pantothenate at 0.25 g/l, and biotin (vitamin H) at 0.002 g/l.
To combat the antioxidant properties of juices, sulfur dioxide (SO2) is added to fruit juices in the form of sodium bisulfite or sodium metabisulfite before fermentation This chemical, widely used in wine production across many countries, serves multiple purposes: it acts as an antioxidant and effectively reduces or eliminates harmful bacteria, particularly lactic acid bacteria The permissible concentration of SO2 ranges from 30 to 120 mg/L, as it can inhibit the oxidation-reduction enzyme However, excessive dosage can lead to an unpleasant taste in wine and may also harm beneficial bacteria.
La fermentation dans la vinification
Fermentation is a biochemical process that converts the chemical energy in a carbon source into a usable form of energy for cells without the presence of oxygen Alcoholic fermentation, driven by yeast, transforms sugar into alcohol.
Currently, there are primarily two methods of wine fermentation: natural fermentation and fermentation using pure yeast strains The method utilizing pure yeast strains is more promising due to its rapid and uninterrupted fermentation process, resulting in well-fermented sugar content and a higher alcohol level, approximately 0.1-1% more than natural fermentation Additionally, this method produces a lighter color and a purer flavor in the wine (Lương Đức Phẩm, 2006).
The wine fermentation process consists of two main phases The primary fermentation occurs at temperatures between 20 to 30°C for about 10 days, resulting in a clearer must as proteins and pectins settle Following this, secondary fermentation takes place at cooler temperatures of 15-18°C, allowing sediments to fully deposit and further clarifying the must While this wine can be used, its quality may not be optimal; therefore, it should be stored at low temperatures of approximately 4-10°C to enhance its flavor Storage duration can vary from a few months to several years or even decades.
Les produits formés dans le processus de fermentation
Les produits formés pendant la durée de l'activité vitale des levures:
Yeast produces various substances during its life cycle, which are released into the environment The primary products are ethyl alcohol and carbon dioxide, alongside secondary and other compounds These include proteins, amino acids, and intermediate decomposition products such as higher alcohols Additionally, yeast also generates glycerin, succinic acid, acetaldehyde, acetic acid, propionic acid, lactic acid, citric acid, 2,3-butanediol, acetone, diacetyl, and esters.
During fermentation, glycerin is formed when acetaldehyde binds with sodium bisulfite or ferments in an alkaline medium The glycerin content in wine ranges from 7 to 14 g/l, contributing to the wine's flavor by enhancing its inherent sweetness.
La teneur n’est pas grande : l’acétone représente 2-84 mg/l, le diacétyle 0,1-1,8 mg/l, mais elles ont des effets notables sur la qualité du vin
In wine, various aldehydes such as acetic, propionic, butyric, valeric, and others are consistently present as secondary products resulting from yeast metabolism and oxidation processes While these compounds can enhance the flavor of wine at permissible levels, excessive amounts may lead to headaches for consumers (Nguyen Phu Cuong, 2009).
In wine, volatile acids such as acetic, propionic, isobutyric, butyric, and isovaleric acids accumulate during the initial fermentation phase Certain yeast strains can utilize acetic acid as a nutrient, leading to a decrease in its concentration during the later stages of fermentation.
Lactic acid plays a significant role in the fermentation process of wine, typically utilizing around 5% of sugar for the synthesis of these acids Well-fermented white wine contains approximately 2.5 g/l of acidity, while red wine has a higher acidity level of about 4.5 g/l.
Esters play a crucial role in creating the flavor profile of wine, with ethyl acetate being the most abundant among them Most esters found in wine emit natural fruity aromas, enhancing the overall tasting experience.
Sous les effets d’enzyme invertase, ils favorisent la formation des esters correspondants à partir d’alcool et d’acide qui sont formées lors du processus de fermentation.
RCH OH R COOH 1 2 2 R COO CH R H O 2 2 1 2
Figure 1.9 La réaction de formation d’ester
Et la formation d’ester est plus facile si l’aldéhyde participe à cette réaction
Figure 1.10 La réaction de formation d’ester à partir des aldéhydes
It is a combination of fats, including esters of fatty acids and glycerol, waxes made up of esters of fatty acids and higher alcohols, and phospholipids, which contain fatty acids, glycerol, inorganic phosphates, and either amines or amino acids.
La cellule de S cerevisiae peut accumuler des lipides à l’intérieur de 12,6 à 42,8 % par rapport à la matière sèche
Lipids in wine are influenced by both the type of fruit and yeast used During wine storage, two opposing processes affect lipids: lipid synthesis occurs in living cells from sugars, while lipid extraction takes place from the cytoplasm Additionally, lipid content is higher in anaerobic conditions under CO2 pressure compared to aerobic conditions.
The formation of higher alcohols during wine fermentation occurs through the reduction or transfer of amines from amino acids, the reduction of carboxyl groups in keto acids, and the reduction of aldehydes According to Soviet scientists, these higher alcohols are produced during the yeast growth phase and are synthesized within the constraints of the yeast's carbon and nitrogen metabolism.
In aerobic conditions, the concentration of higher alcohols is generally higher than in anaerobic conditions and under CO2 pressure CO2 pressure fermentation can reduce the levels of undesirable higher alcohols, such as isobutanol and amyl alcohol, while increasing β-phenylethyl alcohol, which can enhance wine quality Isobutanol and amyl alcohol negatively impact the taste of wine, constituting 90% of all higher alcohols present In contrast, cyclic higher alcohols like β-phenylethyl alcohol, thiazole, and tryptophol contribute to a more pleasant flavor profile Additionally, β-phenylethyl alcohol can be synthesized from phenylalanine, which can be added before storage, although its concentration should not exceed 20-25 mg/L (Luong Duc Pham, 2006).
Les produits formés dans le processus d’auto-décomposition de la levure
Autodecomposition refers to the breakdown of cellular components due to the action of hydrolytic enzymes produced by the cells themselves This process involves the degradation of proteins, hydrocarbons, nucleotides, lipids, and other cellular materials The byproducts of autodecomposition subsequently dissolve within the surrounding environment.
Some researchers believe that the autolysis products of yeast can enhance wine quality by keeping it youthful on yeast sediments at a temperature of 80°C Autolysis is rich in B vitamins found in decomposed yeast products, which possess biological activity This is why these products influence the biochemical processes that mature the wine and establish its flavor bouquet.
Les échantillons de vin ó ont été ajoutés des produits décomposés de levure ont une qualité de vin fortement améliorée, en particulier la saveur spécifique et agréable
Alcoholic fermentation is a vital process where yeast, like other microorganisms, requires energy for survival During this intracellular process, yeast metabolizes sugar to generate the energy necessary for its essential functions As a byproduct of this energy production, alcohol is expelled from the yeast.
Enzymatic reactions in the yeast cell membrane are driven by various enzymes that play a crucial role in chemical reactions necessary for yeast survival and influence wine quality Even after yeast cells die, their enzymatic activity persists, facilitating the diffusion of high alcohol content within the wine, which enhances its flavor This is why dead yeast is often added to wine during storage on sediment, such as in Muscadet.
Enzyme pectinase
Pectine
La pectine est des polysaccharides, des substances exclusivement d’origine végétale et des composants qui participent à la formation de la structure des cellules végétales.
Pectins are polymers of α-D-galacturonic acids linked by α (1-4) bonds, with rhamnose molecules interspersed between these monomers through 1-2 and 1-4 linkages They also contain small amounts of D-galactan and arabinans on expansion chains, along with lesser quantities of fucose and xylose on shorter chains, typically consisting of 1 to 3 sugar radicals These short chains are not considered major components of pectin Additionally, the carboxyl radicals of galacturonic acids are esterified to varying degrees with methanol, and the –OH radicals at C2 and C3 can be acetylated at a low rate.
Figure 1.11 Acide polygalacturonique en zig-zag
(Source : http://fr.wikipedia.org/wiki/Pectine)
Les pectines dans les plantes existent sous trois formes : pectine soluble, aide pectine et protopectine.
Quelques propriétés de la pectine
Pectins are soluble in water, ammonia, alkaline solutions, sodium carbonate, and hot glycerin Their solubility in water increases with a higher degree of esterification and a lower molecular weight.
Pectin stability is optimal at a pH of 3-4 In more acidic environments, the ester bond undergoes hydrolysis, while in alkaline conditions, both ester and hydrolysis bonds are hydrolyzed at similar rates.
Pectins are gels that create low viscosity in solution In acidic environments, the solubility of pectin increases with a higher degree of methoxylation Additionally, the gel-forming ability of pectins is directly proportional to their molecular weight and inversely proportional to their degree of esterification.
Les pectines peuvent former deux types de gel selon le degré d’estérification:
High methoxyl pectins (HM, with a degree of methylation > 50) gel in acidic environments (pH between 2.8 and 3.4) when the soluble solids content is between 63% and 80% Gelation conditions vary with the degree of methylation; more esterified pectins require less sucrose and gel at higher pH levels compared to less methoxylated pectins The pKa of pectins is approximately 3.3; in acidic pH, the reduction of ionization of free carboxylic functions decreases electrostatic repulsions between chains Sucrose lowers water activity, thereby affecting pectin hydration Under these conditions, which can occur during the concentration of non-pectinized fruit juices, low-energy bonds may form between galacturonic acid residues from different chains.
Low methoxyl pectins (5 < DM < 50) gel in the presence of calcium ions through an "egg box" model The hydrated calcium ion forms two electrovalent bonds with carboxylic functions and hydrogen bonds with various oxygen atoms within these units When approximately fifteen successive uronic units are involved in this structure, the junction area becomes stable.
Enzymes pectinolytiques
L’enzyme pectinase appartient au groupe d’enzyme hydrolase et les produits formés sont de l’acide galacturonique, galactose, méthanol,…
Fruit juices and wine often appear cloudy due to the presence of pectin, which diminishes their sensory quality Pectin compounds are located in the cell walls of plants and are released during the crushing of fruits Their colloidal properties create a suspension network in the wine, preventing the settling of particles However, the addition of the enzyme pectinase hydrolyzes the pectin molecules, disrupting the colloidal system and allowing the suspended particles that cause cloudiness to settle, making it easier to filter and clarify the wine.
Les enzymes pectolytiques se répartissent en deux grands groupes:
Pectin methylesterase (PME) activity has been identified in various higher plants, particularly in fruits, where multiple isoforms of PME can be found, such as in orange juice and tomatoes The molecular weight of these isoforms ranges from 23,700 in tomatoes to 57,000.
The optimal pH for the action of kiwi (Da) is around or above 7, where monovalent and divalent cations activate them, while trivalent and tetravalent cations, such as mercury, lead, aluminum, and iron, lead to inactivation Pectin methylesterases (EC 3.1.1.11) are pectin-degrading enzymes that catalyze the demethylation of pectin, releasing methanol and producing low-methylation pectins They operate through a mechanism of multiple chain attacks along the pectic chain and are weakly bound to the cell wall, partially being carried into the juice during extraction Consequently, they are found associated with turbidity particles and also solubilized in the juice.
Microorganisms, particularly molds, are responsible for the production of PME (polyphenol oxidases) These exogenous enzymes function optimally in acidic environments, with an ideal pH range of 4.5 to 5.5, similar to that of fruit juices, and a temperature range of 40 to 45°C However, according to French regulations, only PME extracted from the culture media of Aspergillus niger and A wentii are permitted in fruit juices.
Dépolymérases : il comprend 2 types d’enzyme, ce sont polygalacturonases et lyases.
Polygalacturonases (PG) are enzymes that hydrolyze the α (1-4) linkages between non-esterified galacturonic acid motifs They are categorized into exopolygalacturonases (exo-PG) and endopolygalacturonases (endo-PG) Exo-PG primarily act from the non-reducing end of the pectic chain, releasing galacturonic acids (EC 3.2.1.67) or digalacturonic acids (EC 3.2.1.82) In contrast, endo-PG (EC 3.2.1.15) randomly attack homogalacturonic acids, resulting in the production of monomers, dimers, and occasionally trimers of galacturonic acid.
Polygalacturonases (PGs) are enzymes sourced from plants, fungi, bacteria, and animals (insects) that function optimally at a pH range of 3.5 to 5.5 Their preferred substrate is pectic acid The endo-PG activity is absent on pectin with a degree of methylation (DM) of 75 but increases as the DM decreases PME and PG work synergistically on natural pectins: PME creates demethylated sequences that facilitate hydrolysis by PG, while PG degrades the homogalacturonic sequences that inhibit PME activity.
PG extraites des milieux de culture d’A.niger ou de A.wentii sont autorisées dans la fabrication des jus de fruits.
Lyases play a crucial role in breaking down pectin by catalyzing the cleavage between two galacturonic acid motifs through a β-elimination mechanism There are two main types: pectin lyases (PL) and pectate lyases (PAL) The latter, which are produced by microorganisms, are inactive at the pH levels found in fruit juices and therefore have no practical applications in technology.
Pectate lyases (EC 4.2.2.10) are responsible for cleaving the links between methoxylated galacturonic acid residues All identified pectate lyases are endo-enzymes produced by fungi, particularly from the Aspergillus genus, and by bacteria such as Erwinia Notably, these enzymes have never been detected in higher plants Their activity decreases with the degree of esterification of pectin, and the optimum pH shifts from 6.5 to 5 as the dry matter of the initial substrate decreases from 95% to 65%.
These enzymes are synthesized from mold, specifically of the Aspergillus type They typically consist of a blend of pectinase, polygalacturonase (PG), pectate lyase (PL), hemicellulase, and endo-β-glucanase (Cx-cellulase) The primary enzyme produced from these molds is pectinase, while C-1-dellulase (cellobiohydrolase) is added for technical purposes The enzyme arabinanase plays a crucial role in fruit juice production.
L’enzyme pectinase qui est présente sur le marché est Pectinex Pectinex est un produit de la société de NOVO NORDISK FERMENT A.G, d’enzyme pectolytique, appelé également Novoferm 14 issu d’Aspergillus aculeatus
Pectinex d’Ultra SP-L se présente sous forme de liquide brun, avec une odeur clairement issue des produits de la fermentation L’activité de cette enzyme est voisine de 4,5.
When stored at 20°C, this enzyme can be preserved for up to three months, though its activity decreases by 1-2% each month if storage is extended However, if kept between 0 and 10°C, the enzyme's shelf life can be extended to one year.
Les facteurs influencent sur l’activité de l’enzyme pectinase
La composition des matières premières
The quality of pectin significantly influences the viscosity and hydrolysis of enzymes Higher esterified pectins exhibit greater viscosity and a reduced effect of polygalacturonase In contrast, de-esterified pectins are hydrolyzed 60 times more than their esterified counterparts Additionally, studies indicate that pectic acids are hydrolyzed 17 times more than partially and fully esterified pectins.
Quelques documents mentionnent les effets inhibiteurs des substances acerbes sur l’enzyme
Willamans extracted different phenols from apple juice before and after oxidation to study their inhibitory effects on the enzyme polygalacturonase The results showed that lencoantoxian and oxidized catechin had the strongest inhibitory effects, while high molecular weight tannins exhibited weaker inhibition Additionally, the inhibitory effects of tannins were confirmed in both apple and pear juices on polygalacturonase Therefore, implementing measures to mitigate the negative effects of tannins is crucial for enhancing the effectiveness of pectinase enzyme products in juice production from fruits that contain significant levels of astringent compounds.
Influences des compositions minérales et le pH du jus de fruits
Various authors have noted that ions such as K+, Na+, Ca2+, and Mg2+ significantly influence the activity of the enzyme pectinase It is generally accepted that calcium (Ca2+) and magnesium (Mg2+) salts enhance pectinase activity, while ions like copper (Cu2+) can inhibit it Additionally, studies have shown that substances like KCl, HCl, HgCl, and H2O2 do not impact pectinase activity in orange juice Conversely, low concentrations of ascorbic acid and sodium bisulfite (NaHSO3) have been found to boost the enzyme's activity (Kretovits, 1982).
Autres applications de l’enzyme pectinase
Pectinase has been studied since the 1930s for its application in fruit and vegetable juice production It works in conjunction with cellulase to create various purees and fruit flours, enhancing juice yield and clarity while improving filtration capacity and reducing sedimentation in cloudy juices By breaking down insoluble polymer components like cellulose, hemicellulose, and pectin, pectinase also enhances the color and flavor of products In red wine and grape juice production, this enzyme system maximizes juice extraction, stabilizes pigments, and enhances the flavor of wines and juices made from immature fruits, while improving clarity and filtration Additionally, pectinase is utilized in coffee production to isolate the mucilage from coffee beans, contributing to the quality of both regular and instant coffee.
Les autres additifs
Le sucre
Avec la formule de structure est montré dans l'image ci-dessous (figure 1.12)
Figure 1.12 Formule de structure du saccharose
(Source: http://loiclecardonnel.free.fr/ion/saccharose.gif)
The nectar of Thnot has a brix level ranging from 9 to 14 degrees, which is insufficient to meet the alcohol requirements after fermentation To enhance the sugar content in the Thnot must, sucrose is added prior to fermentation, increasing the dry substance concentration to between 20 and 22 degrees brix Consequently, the alcohol content achieved after fermentation ranges from 10 to 13 degrees.
Sucrose is one of the sugars that wine yeasts effectively utilize, thanks to the enzyme invertase located in the cell wall, which converts sucrose into glucose and fructose prior to fermentation.
L'acide citrique (C6H8O7)
Formule de structure de l’acide citrique est montrée dans l’image ci-dessous (figure 1.13).
Figure 1.13 Formule de structure de l’acide citrique
(Source : http://www.vinairium.com)
Citric acid is abundantly found in lemons, contributing to over 95% of the fruit's acidity It serves as an intermediary in the metabolism of aerobic organisms and is also known as the Krebs cycle, or citric acid cycle.
Citric acid is biodegradable and non-toxic to both humans and the environment However, it can be irritating and may cause burns if it comes into prolonged contact with mucous membranes.
L’acide citrique est un additif alimentaire (numéro E330) utilisé largement dans l’industrie alimentaire comme les boissons, c’est aussi un bon agent de conservation.
Wine is often used to enhance fixed acidity, improving the taste of specific wines, particularly in dry white varieties However, its use in red wines raises concerns due to stability issues, as it may be fermented by lactic bacteria, leading to increased volatile acidity.
Agents de pasteurisation
There are many types of wild yeasts in the winemaking process, which can significantly affect the quality of the final product due to the uncontrollable fermentation processes and the byproducts formed Therefore, an effective measure currently employed is the use of pasteurization agents before adding pure yeast This step is crucial in vinification, with SO2 recognized as the best antiseptic substance for wine and widely used in many countries around the world (Luong Duc Pham, 2005).
Le SO 2 est souvent ajouté sous forme de bisulfite de sodium ou métabisulfite de sodium et il existe sous forme de non dissociation H2SO3 ou d’ion (HSO3 - et SO3 2-).
Sodium metabisulfite is an effective sterilizing agent that helps control the growth of mold, wild yeasts, and bacteria It enhances the action of selected yeasts and prevents wine from yellowing, preserving its aroma and freshness Additionally, it promotes maturation, clarification, and overall conservation of the wine.
Dans cette expérience, métabisulfite de sodium est utilisé comme un agent stérilisant efficace pour traiter des matières premières pendant le temps de récolte de 6 à 8 heures
Figure 1.14 Formule de structure de méthabesulfite de sodium
(Source: http://tjyxgj.en.chemnet.com/suppliers/product/798285/Sodium-Metabisulfite.html)
When diluted in an acidic liquid, metabisulfite releases sulfur dioxide (SO2), with 1 gram of metabisulfite yielding 0.5 grams of SO2 in water This process, known as sulfiting, is designed to inhibit wild yeast and prevent bacterial growth.
When working with a barrel, burning sulfur wicks produces a similar effect, although it is very challenging to control the amount of SO2 generated through this method.
10 gr de soufre donne 10 gr de SO2.
Le métabisulfite s'utilise à dose de 0,5 - 1 ou 1,5 gr/10l suivant les cas:
Le métabisulfite est inoffensif s'il est utilisé raisonnablement mais peut provoquer des maux de tête si utilisée à trop forte concentration.
It is not recommended to use more than 2 grams of metabisulfite per kilogram of fruit before fermentation, as it is altered by yeast At high doses, the byproduct can be harmful, potentially causing headaches and resulting in a stronger intoxication than alcohol itself.
Par contre après la fermentation, à chaque soutirage et surtout à la mise en bouteille, l'utilisation de 1 gr pour 10 litres contribuera à la stabilisation et à la conservation du vin.
Sodium bisulfite is a versatile and essential product in the winemaking process It serves multiple purposes, including sterilizing grape must prior to fermentation, effectively disinfecting equipment, and being added to wine during bottling to reduce harmful effects during storage, such as oxidation and flavor degradation.
Il est essentiellement un type de cristal fin, existant sous la forme de gaz de SO2 dans l’eau
Ce gaz va s’échapper de la solution puis ajouter du SO 2 après quelques heures.
Sodium bisulfite releases sulfur gas, which serves as a disinfectant by eliminating mold, wild bacteria, and unwanted microorganisms during fermentation Additionally, it protects wine by displacing saturated air within the wine.
A small amount of sodium bisulfite can be added to sterilize fruit juices before fermentation, as fresh fruit juices are often sources of microbial contamination and natural yeasts The uncontrolled growth of these microorganisms poses a risk of spoilage for the wine later on Additionally, sodium bisulfite can be used in conjunction with acids such as citric or tartaric acid to enhance its effectiveness, as the SO2 is released more rapidly in acidic environments.
Sodium bisulfite is essential for wine preservation during storage, as oxygen poses a significant threat during fermentation and consumption Excess oxygen can cause wine to develop a light brown or orange hue By adding sodium bisulfite to the wine before bottling, oxidation reactions can be mitigated, helping to maintain the wine's quality.
(http://www.eckraus.com / vinification-sodium-bisulfite.html)
Figure 1.15 Formule de structure de NaHSO3
(Source: http://www.sigmaaldrich.com/structureimages/30/mfcd00003530.gif)
Matériels
Lieu et durée de recherche
─ Lieu de recherche: Laboratoire du Département d’agro-alimentaire, Faculté d’Agronomie et de Biologie Appliquée, Université de Cantho.
Matériels d’expérimentation
─ Autres matériels: verre, flacon en verre, burette, pipette, autres outils du laboratoire.
Matières premières et agents chimiques
Tinh Bien and Tri Ton in An Giang Province, Vietnam, are renowned for their Thnot nectar, which is carefully processed with organic agents immediately after extraction to ensure quality before being used in wine production.
─ Enzyme pectinase (en forme de Pectinex)
─ Autres produits chimiques utilisés dans l’analyse.
Méthode d’étude
Expérience 1 Etude de l’influence de la concentration en levure utilisée sur la qualité du vin de thnot
Determining the appropriate yeast concentration during fermentation is crucial for producing high-quality thnot wine This optimal yeast level enhances the wine's flavor, aroma, and color, while also achieving the desired alcohol content.
Le nectar de thnot Récolte Filtration
L’expérience est disposée tout à fait fortuitement selon un facteur et une fois de répétition Facteur A : Concentration en levure (%) avec 5 niveaux
Rộpộtition: une fois de la mờme faỗon
Schéma de la disposition de l’expérience est présenté à la figure 2.2.
Figure 2.2 Schéma de disposition de l’expérience 1
To prepare fermentation containers, the process follows the outlined scheme in Figure 2.2 Once all fermentation conditions are standardized, samples are fermented at room temperature, approximately 28-32°C After fermentation is complete, the samples are analyzed for key indicators, including alcohol concentration, methanol levels, and residual sugar.
La teneur en sucre résiduel, la concentration alcoolique à la post-fermentation (les deux derniers jours de la fermentation)
La teneur en méthanol (le dernier jour de la fermentation).
Expérience 2: Etude de l’influence des moments de récolte et des variétés des
plantes sur la qualité du vin "Thnot"
This study aims to identify the optimal type of plant and the appropriate harvest time to achieve high-quality Thnot nectar and, consequently, superior Thnot wine.
L’expérience est disposée tout à fait fortuitement selon deux facteurs et deux fois de répétition.
Rộpộtition: deux fois de la mờme faỗon
Schéma de la disposition de l’expérience est présenté au tableau 2.1
Tableau 2.1 Schéma de disposition de l’expérience 2
The nectar of Thnot is harvested in the morning or evening from male and female plant species and processed under optimal conditions After collection, containers are prepared for fermentation, followed by the manufacturing activities Finally, the quality of Thnot wine is assessed through the analysis of physicochemical indicators.
La teneur en sucre résiduel, la concentration alcoolique à la post-fermentation (les deux derniers jours de la fermentation)
Les indices chimiques: l’acide, le SO 2 , le méthanol (dernier jour de la fermentation)
2.2.3 Expérience 3: Etude de l’influence de pectinase sur la clarification du vin de thnot 2.2.3.1 Objectif
The objective of this experiment is to determine the optimal concentration of pectinase needed to effectively clarify Thnot wine after fermentation, thereby enhancing the sensory quality of the final product.
L’expérience est disposée aléatoirement avec 1 facteur et 2 répétitions.
Facteur D: Concentration d’enzyme (%) avec 9 doses.
DC: le témoin (non-traité avec pectinase)
Le schéma de la disposition d’expérience est présenté à la figure 2.3.
Figure 2.3 Schéma de la disposition de l’expérience
Le vin du Thnot après la fermentation est clarifié par le pectinase à des différentes concentrations Le processus de clarification se fonctionne dans environ 7 jours.
La limpidité du produit fini est mesurée par la spectrophotométrie grâce à la transmission optique après le traitement l’enzyme pectinase.
2.2.4 Méthode d’analyse des indices chimiques
Les indices de la qualité et les méthodes d’analyse sont représentés au tableau 2.2
Tableau 2.2 Les indices de la qualité et les méthodes d’analyse
Les indices chimiques Méthodes d’analyse
Teneur en sucre Méthode de Lane-Eynon :
La réaction entre le sucre réducteur et le cuivre dans la solution Fehling formée Cu2O rouge brique.
Teneur en SO2 Oxydation de SO2 par la solution I2
Teneur en méthanol Réaction entre KMnO4 et le méthanol
Teneur en alcool Distillation, puis mesure avec un alcoomètre
Les données ont été analysées statistiquement en utilisant le logiciel EXCEL de Microsoft qui est aussi utilisé pour calculer l’écart-type, et faire des graphiques.
De l’écart-type est calculée a variance
X i :Valeurs des observations x :Moyenne arithmétique n : Nombre d’échantillons
Pour la comparaison des moyennes, nous avons utilisé le logiciel STAGRAPHIC XV.I VERSION FRANÇAISE
The current method for discriminating between means is the Fisher's Least Significant Difference (LSD) procedure This approach carries a 5.0% risk that any pair of means will be deemed significantly different even when the true difference is zero.
TROISIEME PARTIE RESULTATS ET DISCUSSION
3.1 LES RESULTATS D’ANALYSE DE LA COMPOSITION DU NECTAR DE THNOT
The nectar compositions of thnot, presented in Tables 3.1 and 3.2, were analyzed in the laboratory following the harvest in the raw material regions of Tinh Bien and Tri Ton.
Tableau 3.1 Les compositions de nectar de thnot à Tinh Bien
Plante mâle Plante femelle Plante mâle Plante femelle
Tableau 3.2 Les compositions de nectar de thnot à Tri Ton
Plante mâle Femelle Plante mâle Plante femelle
Analysis results indicate that thnot nectar has a high dry matter content, with females typically exhibiting higher levels than males However, this content frequently varies throughout the harvesting process.
The sugar content of thnot nectar ranges from 10 to 14 o Brix, occasionally reaching 15 or 16 o Brix during the dry season, making the addition of sugar essential for optimizing fermentation in wine production Additionally, the nectar's low pH, between 4.5 and 5.5, promotes the growth of microorganisms that can damage raw materials, particularly wild yeast present during harvest Consequently, the quality of thnot nectar often deteriorates during storage, as rapid declines in sugar content, pH, and the emergence of fermentation odors occur shortly after harvest This significantly reduces the nutritional value of the nectar, making it unsuitable for use after a brief period Without proper treatment measures to control contaminating microorganisms during harvest, and if the nectar is not utilized promptly, it undergoes complete decomposition, resulting in increased viscosity, the development of fermentation flavors, and substantial color changes.
Research by Nguyen Minh Thuy (2000-2001) indicates that sodium metabisulfite is the most effective chemical agent for preventing natural fermentation and extending the shelf life of thnot nectar When treated with a sodium metabisulfite concentration of 0.9% or higher, the effects on fermentation inhibition are significantly positive Sulfite compounds can prevent oxidative reactions that degrade ascorbic acid due to their reducing properties, making metabisulfite an effective means of protecting vitamin C in food products Based on these findings, our team has decided to add metabisulfite in varying concentrations of 0.7 to 1.4 g/l during the harvesting process to reduce fermentation and degradation of the raw material, ensuring the quality of the nectar prior to fermentation.
Additionally, the pectin content in nectar poses a significant concern as it can lead to methanol formation in fruit wine or cause the wine to appear cloudy Analysis results indicate that the pectin levels in female nectar are often higher than those found in male nectar.
3.2 LES EFFETS DE LA PROPORTION DE LEVURE SUR LA QUALITE DU VIN
The thnot nectar is an emerging material in the wine production industry, known for its beneficial nutritional composition Its versatility and low cost make it an attractive option for creating high-value food products, particularly in winemaking.
Due to its novelty, it is essential to study the factors influencing the quality of thnot wine to uncover new insights and characteristics Our research team has gained a comprehensive understanding of this unique material, which is highly perishable and requires immediate fermentation after being harvested from the thnot tree The natural microbial systems, particularly the yeast from flower petioles, tools, and insects, significantly affect the nectar's quality during its time on the tree Therefore, we aimed to investigate the impact of pure yeast proportions on thnot wine quality, specifically using Saccharomyces cerevisiae added to the must after pasteurization with NaHSO3 Additionally, we referenced previous studies, such as Nguyen Binh's thesis from Can Tho University, which recommended a yeast proportion of 0.04% for fruit wine fermentation Consequently, we selected a variable yeast proportion ranging from 0.02% to 0.1% to examine its effects on this new nectar.
Les résultats des impacts de la proportion de levure sur la qualité du vin de thnot qui sont indiqués dans le tableau de 3.3, les figures 3.1, figure 3.2 et figure 3.3.
Statistical results in Table 3.3 indicate that the proportion of yeast significantly affects the quality of Thnot wine Specifically, the highest alcohol content in the final product corresponds to a yeast proportion of 0.04%, showing a significant difference from other proportions at a 5% significance level.
The fermentation of samples occurs at a relatively uniform rate, except for the sample with 0.02% yeast, which exhibits a slower fermentation speed and extended fermentation time The fermentation duration for the samples ranges from 12 to 15 days Additionally, figures 3.2 and 3.3 illustrate the effects of yeast proportion more clearly As the yeast proportion increases, the residual sugar content tends to decrease However, the methanol content across all samples does not significantly differ and remains within the acceptable limit for wine in Vietnam, as per the TCVN 7045:2002 standard (≤ 3 g/l), although it tends to increase with higher yeast proportions.
Tableau 3.3 Les résultats statistiques de la concentration d’alcool, de méthanol et la teneur en sucre résiduel dans le produit fini après la fermentation Échantillon
Les valeurs avec des lettres différentes dans une même colonne sont significativement différentes à seuil de 5%
Les valeurs obtenues sont le moyen de deux fois répétés
Les valeur en caractère gras sont meilleures
According to Luong Duc Pham (2005), yeast in anaerobic conditions requires more nutrients than in aerobic conditions to generate the energy necessary for its activities J.P Larpent (1991) notes that approximately 10% of glucose is utilized for yeast biomass, while the remainder is converted into ethyl alcohol and other by-products such as glycerol and pyruvate Consequently, a low yeast concentration of 0.02% results in insufficient biomass, leading to longer fermentation times and higher residual sugar content Furthermore, inadequate yeast levels can create favorable conditions for the growth of other microbes, particularly wild bacteria and yeasts As a result, many nutrients are converted into non-essential products, resulting in lower alcohol content and increased perishability of the final product.
L a te n eu r en a lc oo l ( % v /v )
Figure 3.1 La teneur en alcool de produit fini correspondant les proportions de levure différentes
Figure 3.2 La teneur en sucre résiduel correspondant aux proportions différentes de levure
Figure 3.3 La teneur en méthanol correspondant aux proportions différentes de levure
Légende: les erreurs au graphique sont les écart-types des moyennes
Excessive yeast quantities can lead to insufficient nutrients for yeast growth and metabolism, quickly depleting the nutrient medium and potentially causing yeast death due to competition for resources Additionally, as noted by Luong Duc Pham (2005), fermentation byproducts such as alcohol and organic acids can also inhibit yeast activity at certain concentrations, as demonstrated by the experimental results of Hugnet Josselin and colleagues.
Méthode d’analyse des indices chimiques
Les indices de la qualité et les méthodes d’analyse sont représentés au tableau 2.2
Tableau 2.2 Les indices de la qualité et les méthodes d’analyse
Les indices chimiques Méthodes d’analyse
Teneur en sucre Méthode de Lane-Eynon :
La réaction entre le sucre réducteur et le cuivre dans la solution Fehling formée Cu2O rouge brique.
Teneur en SO2 Oxydation de SO2 par la solution I2
Teneur en méthanol Réaction entre KMnO4 et le méthanol
Teneur en alcool Distillation, puis mesure avec un alcoomètre
Les données ont été analysées statistiquement en utilisant le logiciel EXCEL de Microsoft qui est aussi utilisé pour calculer l’écart-type, et faire des graphiques.
De l’écart-type est calculée a variance
X i :Valeurs des observations x :Moyenne arithmétique n : Nombre d’échantillons
Pour la comparaison des moyennes, nous avons utilisé le logiciel STAGRAPHIC XV.I VERSION FRANÇAISE
The current method for distinguishing between means is Fisher's Least Significant Difference (LSD) procedure This approach carries a 5.0% risk of indicating that each pair of means is significantly different when the actual difference is zero.
TROISIEME PARTIE RESULTATS ET DISCUSSION
3.1 LES RESULTATS D’ANALYSE DE LA COMPOSITION DU NECTAR DE THNOT
The nectar compositions of thnot, as presented in Tables 3.1 and 3.2, were analyzed in the laboratory following harvest in the raw material regions of Tinh Bien and Tri Ton.
Tableau 3.1 Les compositions de nectar de thnot à Tinh Bien
Plante mâle Plante femelle Plante mâle Plante femelle
Tableau 3.2 Les compositions de nectar de thnot à Tri Ton
Plante mâle Femelle Plante mâle Plante femelle
Analysis results indicate that thnot nectar has a high dry matter content, with female nectar typically exhibiting higher levels than that of males However, this content often fluctuates during the harvesting process.
During the dry season, the sugar content of thnot nectar ranges from 10 to 14 o Brix, occasionally reaching 15 or 16 o Brix To ensure optimal fermentation in wine production, adding sugar to adjust the sweetness is essential Additionally, the nectar's pH is low, varying from 4.5 to 5.5, which promotes the growth of harmful microorganisms, including wild yeasts, during harvest Consequently, the quality of thnot nectar often deteriorates during storage due to rapid declines in sugar content and pH, along with the swift onset of fermentative odors This deterioration significantly reduces the nectar's nutritional value, making it unsuitable for use after a short period Therefore, if no measures are taken to control contaminating microorganisms during harvest and the nectar is not utilized promptly, it may fully decompose, resulting in increased viscosity, the emergence of a fermentative flavor, and noticeable changes in color.
Research by Nguyen Minh Thuy (2000-2001) indicates that sodium metabisulfite is the most effective chemical for preventing natural fermentation and extending the shelf life of thnot nectar Treatment with a sodium metabisulfite concentration of 0.9% or higher significantly inhibits fermentation Sulfite compounds help prevent oxidative reactions that degrade ascorbic acid, making metabisulfite an effective means of protecting vitamin C in food products Based on this, our team has decided to add metabisulfite in varying concentrations of 0.7 to 1.4 g/l during harvest to reduce fermentation and degradation processes, ensuring the quality of the nectar before fermentation.
Additionally, the pectin content in nectar poses a significant concern, as it can lead to methanol formation in fruit wine or cause the wine to appear opaque Analysis results indicate that the pectin levels in female nectar are often higher than those found in male nectar.
3.2 LES EFFETS DE LA PROPORTION DE LEVURE SUR LA QUALITE DU VIN
Thnot nectar is an innovative material in the wine production industry, offering not only beneficial nutritional properties for human health but also enhancing the creation of high-value food products Its diverse applications and low cost make it particularly advantageous for winemaking.
Due to its novelty, it is essential to study the factors influencing the quality of thnot wine to uncover new insights and characteristics Our research team has gained a general understanding of this special material through studies conducted in the thnot cultivation region and in the laboratory Thnot nectar is highly perishable, requiring immediate fermentation once harvested, as the natural microbial systems, particularly the yeast from the flower's petiole, tools, and insects, can contaminate the nectar during its time on the thnot tree Therefore, our team aimed to investigate the effects of varying proportions of pure yeast on thnot wine quality, specifically using Saccharomyces cerevisiae added to the must after pasteurization with NaHSO3 Additionally, we referenced previous theses that discussed yeast proportions in fruit wines, such as the study by Ly Nguyen Binh from Can Tho University, which recommended a yeast proportion of 0.04% for fermentation Consequently, we selected a variable yeast proportion ranging from 0.02% to 0.1% to examine its effects on this new nectar.
Les résultats des impacts de la proportion de levure sur la qualité du vin de thnot qui sont indiqués dans le tableau de 3.3, les figures 3.1, figure 3.2 et figure 3.3.
Statistical results in Table 3.3 indicate that the proportion of yeast significantly affects the quality of Thnot wine Specifically, the highest alcohol content in the finished product is associated with a yeast proportion of 0.04%, showing a significant difference from other levels at a 5% significance level.
The fermentation of samples occurs at a relatively uniform rate, except for the sample with 0.02% yeast, which exhibits a slower fermentation speed and longer completion time Fermentation durations range from 12 to 15 days Additionally, Figures 3.2 and 3.3 illustrate the impact of yeast proportion, indicating that residual sugar content decreases as yeast proportion increases However, the methanol content across all samples remains within the acceptable limit for wine in Vietnam, as per the TCVN 7045:2002 standard (≤ 3 g/l), although it tends to rise with higher yeast proportions.
Tableau 3.3 Les résultats statistiques de la concentration d’alcool, de méthanol et la teneur en sucre résiduel dans le produit fini après la fermentation Échantillon
Les valeurs avec des lettres différentes dans une même colonne sont significativement différentes à seuil de 5%
Les valeurs obtenues sont le moyen de deux fois répétés
Les valeur en caractère gras sont meilleures
According to Luong Duc Pham (2005), yeast in anaerobic conditions requires more nutrients than in aerobic environments to generate the necessary energy for its activities J.P Larpent (1991) notes that approximately 10% of glucose is utilized for yeast biomass, while the remainder is converted into ethyl alcohol and other by-products such as glycerol and pyruvate A low yeast concentration of 0.02% results in insufficient biomass, leading to prolonged fermentation times and higher residual sugar levels Additionally, inadequate yeast levels can create favorable conditions for the growth of other microbes, particularly wild bacteria and yeasts Consequently, a significant amount of nutrients is wasted, resulting in lower alcohol content and increased perishability of the final product.
L a te n eu r en a lc oo l ( % v /v )
Figure 3.1 La teneur en alcool de produit fini correspondant les proportions de levure différentes
Figure 3.2 La teneur en sucre résiduel correspondant aux proportions différentes de levure
Figure 3.3 La teneur en méthanol correspondant aux proportions différentes de levure
Légende: les erreurs au graphique sont les écart-types des moyennes
Excessive yeast quantity can lead to insufficient nutrients for yeast development and metabolism, causing rapid depletion of the nutrient medium and potential yeast death due to competition for these nutrients Additionally, as noted by Luong Duc Pham (2005), fermentation products such as alcohol and organic acids can inhibit yeast activity at certain concentrations, as demonstrated by the experimental results of Hugnet Josselin et al.
In 2010, it was observed that an increase in yeast quantity accelerates the fermentation process initially; however, excessively high yeast levels can hinder subsequent fermentation Consequently, when yeast concentrations reach 0.06%, 0.08%, or 0.1%, the alcohol content remains lower while sugar levels remain relatively high This phenomenon occurs due to the unfavorable conditions created by the yeast itself in a closed system, which inhibits its own fermentation activity.
The results presented in Table 3.3 indicate that the methanol concentration in wine samples post-fermentation is not significantly different This aligns with Hang's (2010) theory on methanol formation in wine, where methanol is primarily produced from pectin found in raw materials, influenced by the enzyme pectinase, as illustrated in Figure 3.4.
Figure 3.4 Schéma de la réaction d’hydrolyse de pectine par l’enzyme pectinase
The results indicate that a yeast concentration of 0.04% yields the highest alcohol content, significantly differing from concentrations of 0.02%, 0.06%, 0.08%, and 0.1% While the residual sugar content is relatively high, it does not negatively impact the final product and may enhance its flavor For wine producers and technicians, considering both alcohol and methanol levels post-fermentation, a yeast concentration of 0.04% is deemed most suitable for producing thnot wine.
3.3 LES EFFETS DES VARIETES DE PLANTE ET LE MOMENT DE RECOLTE SUR LA QUALITE DU VIN DE THNOT A DEUX REGIONS DE TINH BIEN