KOMBUCHA: AN ALTERNATIVE FERMENTED BEVERAGE

Pure Kombucha

 Kombucha (konbu cha (昆布茶), seaweed tea) is an ancient Asian drink that is being introduced in Western markets, with a slightly sour, refreshing taste produced from the fermentation of sweetened tea by yeasts (Saccharomyces, Picchia, Medusomyces) and acetic bacteria (Acetobacter, Gluconobacter,).

This beverage has experienced an enormous growth in demand in recent years, with growth of more than 20% per year as a healthy alternative to sugary soft drinks due to its contribution of antioxidants from tea (detox function), its probiotic characteristics (a large part of the demand is for unpasteurized product) and the perception of a bio/natural product. Due to this rapid growth, the industrial processes involved are still poorly characterized, which poses a real challenge in maintaining a standardized product over time.

As in other fermented beverages, the transformation of the sugars present takes place through the action of bacteria and yeasts. While in wine, for example, these yeasts are natural (or, where appropriate, specifically selected for their characteristics), in kombucha they come from an external mother inoculum called SCOBY (SCOBY, Symbiotic Culture Of Bacteria and Yeast) from previous fermentations. This inoculum has a double function: on the one hand, to initiate the process of transformation of sugar into other organic compounds; on the other hand, to serve as a barrier in more advanced phases to initiate a moderate alcoholic fermentation.

The preparation starts with tea infusions with a sugar content varying between 5 and 15%. Once infused, the tea is cooled to room temperature and a quantity of fermented tea containing the SCOBY (or a gelatinous film of it, called ‘tea fungus’ from previous fermentations) is added and left to ferment at room temperature for 7-10 days, long enough for it to acquire a slightly sour taste and some effervescence. Specific flavors of all kinds can be added to the tea, often vegetable juices or liquefiers, to diversify the range of flavors and mouthfeel and help to reinforce the image of a healthy product with dietary properties.

The yeasts initiate the process by hydrolyzing sucrose to glucose and fructose (a critical step since acetic acid bacteria cannot carry out this hydrolysis) and continue towards the production of ethanol (alcoholic fermentation); the acetic acid bacteria consume part of the glucose to produce organic acids (mainly acetic, gluconic and glucuronic) through aerobic metabolism that progressively reduce the pH of the liquid. At the same time, a gelatinous film (a cellulose matrix) forms on the surface of the culture, generated by the acetic acid bacteria themselves, which reduces the entry of oxygen and causes a second fermentation of the residual sugars into ethanol and carbon dioxide. At the end of the process, the alcohol concentration in the final product is very low, around 0.5%, although it can reach 3% in very prolonged fermentations or with high initial sugar concentrations, and a pH between 3 and 5 is reached. At this point it can be decided to stop the process by pasteurization or cold storage.

The industrial production of kombucha is very recent in time and still has to solve several relevant technical challenges, as the final result is affected by numerous variables derived from both the raw materials used (tea, water, sugar, composition of the SCOBY starter) and the conditions under which the process takes place (infusion time, temperature, fermentation time, aeration). In order to guarantee the consistency over time necessary in industrial production, different physicochemical variables that would affect the different stages of the process must also be carefully monitored.

For example, the extraction of tea components is directly affected by the presence of ions in the water: in particular, hard waters with high calcium content reduce the efficiency of the infusion, while soft waters increase the extraction of organic molecules, including tannins that contribute to bitterness. Also, the content of initial sugars and their nature (sucrose, or glucose syrups) are relevant, since a higher glucose content favors the production of lactic and gluconic acid, while fructose could favor ethanol and acetic acid.

Some of the critical components that would be relevant would be the content of residual sugars, the concentration of acetic acid, the content of polyphenols extracted from the tea, the levels of ethanol or carbon dioxide, in addition to others relevant to the development of the process such as the levels of nitrogen, gluconic acid or ions present in the water used for the infusion, without forgetting that, contrary to what happens with fruits, the level of acidity of the infusion is generally low, which means that its capacity to block the development of other species of non-acetic bacteria is limited. All these components are critical in the final organoleptic sensation and directly affect the palatability of the final product so, in industrial productions, they constitute relevant control elements.

Pure Kombucha

Sinatech has reagents for the determination of quality parameters in kombucha by enzymatic and colorimetric methods, which allow standardizing all the stages of the production process and adjusting them to the desired product. The Dionysos system is an optimal tool for the control of the production process, capable of guaranteeing the quality and food safety requirements demanded by existing regulations.

  • Total Sugar, Glucose+Fructose, Glycerol
  • Acetic, Lactic, Malic, Gluconic, Total Acidity
  • Primary Amine Nitrogen, Amonium
  • Polyphenols, Catechins, Antocyanins

For more than 10 years, Sinatech’s commitment to the winemaker has been working side by side to provide the most appropriate analytical solutions to the control and monitoring of the winemaking process. Automated methods easily adaptable to any work routine, with a personalized advisory team to help you quickly and smoothly implement.

Sinatech: TeamWork.

GRAPE SPIRITS

Drink in moderation

Wine pills

Alcoholic drinks, rightly used, are good for body and soul alike, but as a restorative of both there is nothing like brandy.

Picture George Saintsbury

George Saintsbury

George Saintsbury (1845-1933) was an English writer, journalist and literary critic expert in French and English literature but also a famous wine expert, well known for his work Notes on a Cellar-Book (1920) in which he collected detailed notes of all the wines he had tasted from 1894 to 1915, offering a very personal vision of the whole oenological panorama of his time.

That the fermentation of grape must produces wine is a well-known fact; however, other beverages full of aromatic nuances and with very different intensities can be prepared from grape juice. It was the Arabs who introduced the concept of distilling wine to extract its essence, al-ghool, evil spirit, which they used mainly as a disinfectant and in medicine, which in Latin came to be called aqua ardens, eau-de-vie. It is probable that it was used to macerate medicinal herbs giving origin to the cordials from which the whole group of liquors generically called ‘digestives’ would later derive. In this sense, it was the Christian monks who developed the technique of distillation to produce spirits.

Some of the most famous are Brandy, from the Dutch “brandewijn” meaning burnt wine. The production by distillation of young wine was made in Spain for export to Holland; the brandy obtained (called holandas), with an alcoholic concentration between 35 and 60%, was stored in oak casks, where it oxidized and obtained its characteristic dark golden color. Within this group we find specific denominations of origin such as Cognac, (north of Bordeaux and made from white grapes of the ugni blanc variety), or Armagnac (in the Gascony region).

Another type of distillate would be the one made from skins and pips (generically pomace distillates), which would form the group of Grappas (Italy) and Orujos (Spain) Its origin would be in the use of the remaining bagasse from the grape pressing. They are powerful and dry distillates, of high alcohol content, very popular in Italy and Spain, which are drunk cold after a meal, or mixed with coffee (caffè corretto or carajillo).

When these same distillates are flavored with anise seeds, we enter the Eastern Mediterranean: Arak (the national drink of Lebanon, and highly appreciated in Jordan and Syria), Raki (Turkey) and Ouzo (Greece). All of them are liqueurs made by double distillation to which anise seeds are added for flavoring. They are drunk mixed with water or ice, which makes them take on a whitish color of intense turbidity.

If, instead of digestives, we are looking for a liqueur that stimulates the taste, we are talking about aperitifs. Among them we find the well-known Vermouth, a mixture of muscatel wine, sweetened with caramel, aromatic herbs and spices; or the Quina, with a bitter taste due to the bark of quina, a South American shrub, which is drunk with ice and soda. Special mention should be made of Pisco (Chile and Peru) and Singani (Bolivia), a distillate of aromatic grapes (mainly Muscatel) and non-aromatic grapes which have in common their high sugar content, and which are drunk in the form of mixed drinks (Pisco Sour, with lemon, sugar and egg; and Chuflay, with ginger ale).

Picture of a grape distiller

Sinatech: Teamwork.

WINE AND CLIMATIC CHANGE

Photograph of a vine with dry fruit
Picture showing the extreme drought in our planet

Climate change is a scientifically proven reality that will significantly change wine production in the coming years. In its simplest sense, an average temperature increase of around 1.5 ºC is expected over the next 15 years compared to the temperature at the end of the 20th century, but this could reach up to 4.8 ºC in the most extreme scenarios of uncontrolled CO2 emissions. Under these conditions, it is estimated that up to 50% of the current vineyard area could be at risk of disappearing, mainly from the current warm production areas (Mediterranean basin, California), to the benefit of new production areas in higher latitude regions1. The wine industry has for some time now been assessing the challenges and opportunities that this transformation, unfortunately very difficult to reverse, will bring to the sector in the form of adaptation to the new climatic conditions and innovation in cultivation and production technology. Some of the risks associated with climate change identified by the production companies are related to greater production volatility (associated with droughts or extreme weather effects), changes in the harvesting process (less spaced and shorter harvests), greater risks of pests and diseases, or the need to modify current vine varieties for others with greater resistance6.

Vitis vinifera, in all its varieties, is particularly sensitive to growing temperature. Most varieties have a very narrow temperature range (barely 2-3 ºC)3 in which their qualities are optimally expressed, which means that their preferred growing areas extend around the 50 N and 45 S parallels: too hot and unbalanced and uninteresting wines are produced; too cold, and acidic wines with low alcohol content are produced. The phenology of the vineyard is conditioned by the temperature factor and the harvest date is expected to be more than 20 days earlier than at the end of the last century in some Mediterranean areas2. Although in the short term it will be possible to adjust harvesting times and growing conditions by means of appropriate agricultural techniques, in the medium term, the combination of both factors suggests that traditional varieties in certain areas will be displaced by new varieties better adapted to the new climatic conditions, radically affecting the expected characteristics of the wine produced, something that would particularly affect those territories with PDO regulations such as Spain, France or Italy. These varieties could be either chosen from among those best adapted to higher temperatures, or hybridized or genetically selected for their better resistance4.

Photograph of a vine with dry fruit

The increase in temperature has a direct correspondence with the composition of the wine, increasing the concentration of sugars in response to the heat stress suffered by the plant, which means a higher potential alcohol content. Under the effect of heat, berries accelerate their ripening and increase their metabolic processes, leading to a change in the ratio of sugars (increase, mainly due to berry dehydration) and acids (decrease, mainly due to thermal degradation of malic acid) that directly impact the characteristics of the must produced5. Potassium levels also increase, resulting in a higher pH of the must, even reaching values above 4.0. Phenolic compounds are also affected, although in this case not only the temperature is relevant but also the degree of exposure to sunlight; thus, for example, the synthesis of anthocyanins is inhibited at high temperatures, while the presence of astringent phenols increases. The result is a significant mismatch between technical and phenolic maturity.

Some of the effects of climate change would have a direct impact on the cultivation techniques used to counteract the effect of increased temperatures in the form of increased presence of irrigation in the vineyard (especially in areas where precipitation is expected to decrease), changes in cropping and pruning patterns to reduce sun exposure, applications of sunscreens to reduce the effect of UV radiation, or shifting cultivation to higher altitudes. The biggest problem for its implementation lies in the strict conditions required by the regulatory councils to grant the ‘protected designation’, which reduces the attractiveness for consumers who have traditionally identified these PDs as a guarantee of certain characteristics.

Having methods to control winemaking processes, to be able to verify and, if necessary, correct through the application of appropriate oenological techniques, is an essential tool to support winemakers in the production of wines that maintain the desired quality standards in a process of constant adaptation to the effects of climate change. Sinatech offers the most advanced analytical systems on the market that incorporate the most innovative technologies to provide optimal results.

REFERENCES

  1. Intergovernmental Panel on Climate Change (IPCC). (2013). Summary for policymakers. Stocker, T.F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S.K., Boschung, J., Nauels, A., Xia, Y., Bex, V., and Midgley, P.M. (Eds.), Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press, 3–29.
  2. Ferrise, R., Trombi, G., Moriondo, M., and Bindi, M. (2016). Climate change and grapevines: A simulation study for the Mediterranean basin. Journal of Wine Economics, 11(1), 88–104.
  3. Jones, G.V. (2006) Climate and Terroir: Impacts of Climate Variability and Change on Wine. In: Fine Wine and Terroir – The Geoscience Perspective. Macqueen, R.W., Meinert, L.D. (eds) Geoscience Canada Reprint Series Number 9; Geological Association of Canada; St. John’s, Newfoundland: 247 p.
  4. Duchene, E.; Butterlin, G.; Dumas, V.;Merdinoglu, D. Towards the adaptation of grapevine varieties to climate change: QTLs and candidate genes for developmental stages. Appl. Genet. 2012, 124, 623–635.
  5. Coombe, B.G. (1987). Influence of temperature on composition and quality of grapes. Acta Horticulturae, 206, 23–36.
  6. 2019 ProWein Business Report: Climatic Change (http://www.prowein.de)

For more than 10 years, Sinatech’s commitment to the winemaker has been working side by side to provide the most appropriate analytical solutions to the control and monitoring of the winemaking process. Automated methods easily adaptable to any work routine, with a personalized advisory team to help you quickly and smoothly implement.

Sinatech: TeamWork.

WINE HISTORY

Picture of olive trees and vineyards

Wine pills

The peoples of the Mediterranean began to emerge from barbarism when they learned to cultivate the olive tree and the vine.

Thucydides stautu

Thucydides

Thucydides (486 BC- 396? BC) is considered the father of scientific historiography, in which for the first time the stories appear stripped of divine interventions, trying to collect sources and records in a rigorous way, analyzing the facts in the form of cause-effect. His work History of the Peloponnesian War is considered a model of a rigorously scientific account of a historical event.

Vine cultivation is as old as the history of civilization, dating back to the Neolithic period, when the first permanent settlements began to be established. In its wild state, the vine (Vitis vinifera sylvestris) was a vine that grew abundantly in riparian forests hugging trees. Its berries, with a pleasant sweet and sour taste and the ability to be preserved for a long time (raisining), were probably a food reserve for the winter. The first archaeological records of grape consumption are found in northern Iran, Turkey and Georgia, more than 8,000 years ago. It is probable that, at some point, an accidental fermentation took place that originated an euphoric drink. 

From that moment on, its domestication would begin, through the selection of the most promising plants for their flavor or abundance. Over time, some mutations appeared that gave rise to hermaphrodite plants, such as the current vines (Vitis vinifera vinifera or sativa). Around 3000 BC, in the Bronze Age, the first records of vine cultivation and wine production already begin to be found in what is the oldest known account, the ‘Epic of Gilgamesh’ and even, around 2000 BC, the first Hittite laws referring to vineyard cultivation: “If a man puts his flock into a cultivated vineyard and ruins it, if it has not yet been harvested, he shall pay 10 shekels of silver for each vine; and so he shall make restitution. But if it is harvested he has to pay only 3 shekels of silver”. 

The trade and geographical expansion of the peoples of the area (Phoenicians, Assyrians, Babylonians, Egyptians) throughout the Mediterranean brought the vine to other territories, and even spread to the East, reaching China. The Egyptians made wine in large earthenware vessels and engravings and mosaics have been found in the pyramids depicting the cultivation of the vine, the harvesting, preparation and enjoyment of wine at festivals and religious events. It reached Greece around 700 BC and Italy around 200 BC. To the Romans we owe the first wooden barrels to store and transport it, as recorded by Julius Caesar in his “War of the Gauls”, and the appearance of the first oenological techniques to clarify it. From Italy, the cultivation of the vine spread to Gaul and Iberia; from there, the Visigoths extended it to the rest of Europe.

It is believed to have arrived in North America by the Vikings, around 1000 AD; in South America, by the Spanish colonizers, already in the 16th century (Hernán Cortés, in 1525 in Mexico; in the second half of the century, to Chile, Peru and Argentina; at the end of the 17th century to California); to Australia at the end of the 18th century….

And then came phylloxera, but that’s another story…

Sinatech: Teamwork.

ACETIC/VOLATILE ACIDITY IN WINE, CIDER, VINEGARS AND JUICES

Picture facilitated to illustrate the post acetic in wine, cider, vinegars and juices

Acidity is a characteristic determined by the total sum of acids that a sample contains. We can quantify the set of all of them in an undifferentiated way (total acidity) or in a grouped way (fixed acidity and volatile acidity). Fixed acidity corresponds to the set of low volatility organic acids such as malic, lactic, tartaric or citric acids and is inherent to the characteristics of the sample; volatile acidity corresponds to the set of short chain organic acids that can be extracted from the sample by means of a distillation process: formic acid, acetic acid, propionic acid and butyric acid. Of all of them, the acid responsible for approximately 99% of the volatile acidity corresponds to acetic acid, so that its determination is often enough to reliably determine the total volatile acidity. Furthermore, volatile acidity appears as a consequence of the metabolic transformations of the fruit and is zero or very close to it for fresh fruit.

The presence of acetic acid in a fermentation product is a consequence of the metabolism of yeasts and bacteria, both in their anaerobic (fermentation) and aerobic (glycolysis) metabolism. These bacteria transform ethanol into acetaldehyde first and then, if there is sufficient oxygen (as occurs in partially filled tanks), into acetic and ethyl acetate by esterification with ethanol. The problem appears when, due to a growing population (especially Gluconobacter, Acetobacter and Bretanomyces bacteria, but also Saccaromyces mycoderma and cerevisiae), acetic levels increase to a level where its characteristic odor begins to be perceived clearly (from 0.8 g / L) and modifies the aromatic characteristics (‘chopped’ flavor, ethyl acetate, acetoin). The formation of a whitish superficial veil is a clear sign of the presence of these organisms. In the case of juices, the presence of acetic acid is indicative of a fermentation (deterioration) process started and therefore a good indicator of its quality. This phenomenon can occur immediately in juices, which is avoided by cold treatment of the juice and subsequent pasteurization.

Initially G. oxydans, the species with the highest presence in fruits including grapes, starts the acetification process by consuming the available sugars and converting them into ethanol (this genus of bacteria lacks enzymes of the Krebs cycle, so they cannot completely oxidize the sugar up to CO2), but it inhibits its growth at moderate concentrations of alcohol, which is why it tends to be replaced by A. aceti once fermentation has started. A. aceti is especially dominant in botiritis infected berries and is capable of surviving in wine, even under anaerobic conditions, and multiplying rapidly in the presence of minimal amounts of oxygen, which makes it necessary to establish additional protection mechanisms (sulphites, low temperature).

Acetic values ​​above 1.2-1.5 g / L are no longer legal for wine (the specific limit depends on local legislation), with the exception of botirised wines, where it can reach up to 2.1 g / L. In cider, the legal limit is 2.2 g / L. The acetification process can be carried out intentionally in the production of vinegars by raising the acetic concentration to beyond 50 g / L (5%).

The determination of the acetic content is a process control requirement in the production of wine, cider, beer, or vinegar (and by extension, of any product in which a natural fermentation takes place as part of its production process), and industrial juices, must or any other food in which fermentation should be avoided. The traditional procedure (included in many of the official standards) consists of a distillation or steam stripping of all the volatile components that are subsequently titrated with sodium hydroxide with phenolphthalein as an indicator of change (official AOAC method). These volatile components, in addition to acetic, formic, butyric and propionic, include free and total sulfites in the sample (which also contribute acidity), therefore, in the same procedure they are evaluated immediately afterwards. The main drawbacks of this method are the subjectivity associated with accurately determining the turning points (solvable through the use of potentiometers), the errors inherent in a manual method in the preparation and handling of the reagents and, very especially, the time required to carry out the distillation process itself (from 10 to 15 minutes, depending on the sample volume), which makes it especially tedious in case of having to process a significant number of samples, increasing the risk of unintentional errors.

Since a few years ago, the OIV has included the enzymatic method, it has been included among the official methods for the determination of acetic acid (OIV Resolution 621-2019). Enzymatic methods are based on the ability of enzymes to act specifically on a substrate, in this case acetic acid, and can be performed directly on the sample with little or no manipulation. The proposed method is based on the transformation of acetic acid to acetylphosphate by consuming ATP by means of acetate kinase; the ADP formed is regenerated to ATP by quantitatively transforming phosphoenolpyruvate to pyruvate by pyruvate kinase and, then, into lactate by lactate dehydrogenase with consumption of NADH, so that the reaction can be quantified by the spectrophotometric measurement of the disappearance of NADH.

The main advantage of this method is that it does not require any type of sample manipulation, it is highly specific for acetic acid, fast (results in five minutes) and can be automated, with minimal reagent consumption. By means of the enzymatic method, it is possible to determine acetic acid with a high sensitivity (from 0.03 g / L) and up to values ​​of approximately 1.2-1.4 g / L of acetic acid, sufficient for the vast majority of samples, both juice (need for sensitivity) and wine (intermediate values); in the case of vinegars, a predilution of the sample is required (around 1/50) until it reaches values ​​suitable for the measurement range.

Sinatech offers a range of highly reliable and precise enzymatic reagents for the specific and precise determination of sugars and acids in fruit juices and derivatives accepted among official methods of analysis. The Dionysos system is an optimal tool for the control of the production process, capable of guaranteeing the quality and food safety requirements demanded by the existing regulations.

Picture facilitated to illustrate the post acetic in wine, cider, vinegars and juices

For more than 10 years, Sinatech’s commitment to the winemaker has been working side by side to provide the most appropriate analytical solutions to the control and monitoring of the winemaking process. Automated methods easily adaptable to any work routine, with a personalized advisory team to help you quickly and smoothly implement.

Sinatech: TeamWork.