From f8e4ff89a4b740a35b79c39cea550f51dbffa874 Mon Sep 17 00:00:00 2001 From: James Date: Sat, 2 Jul 2022 06:14:45 -0700 Subject: [PATCH] Edits for the Acknowledgements and the How Sourdough Works chapter (#11) * edit acknowledgements * finish edits to section 2.1 * finished editing amylase section * fix italics * began editing the protease section * finished editing protease section * edited the improving enzymatic activity chapter * started editing yeast section * continue to edit yeast section * finished eidts to the yeast section * final edits to the how sourdough works chapter --- book/basics/how-sourdough-works.tex | 549 ++++++++++++++-------------- book/intro/acknowledgements.tex | 11 +- 2 files changed, 284 insertions(+), 276 deletions(-) diff --git a/book/basics/how-sourdough-works.tex b/book/basics/how-sourdough-works.tex index 74fd3c5..120e140 100644 --- a/book/basics/how-sourdough-works.tex +++ b/book/basics/how-sourdough-works.tex @@ -1,10 +1,8 @@ -In this chapter we are looking at the basics of how sourdough ferments. -For that we will first look at enzymatic reactions -that happen in your flour. These reactions are induced -the moment you add water to your flour. They are also -the basis that trigger the fermentation process. To understand -the fermentation process we are having a closer look at the involved -yeast and bacterial microorganisms. +In this chapter, we will cover the basics of how sourdough ferments. +First, we will look at the enzymatic reactions that take place +in your flour the moment you add water, triggering the fermentation +process. Then, in order to better understand this process, we will +learn more about the yeast and bacterial microorganisms involved. \begin{figure}[!htb] \includegraphics[width=\textwidth]{infographic-enzymes} @@ -14,195 +12,207 @@ yeast and bacterial microorganisms. \section{Enzymatic reactions} -When mixing flour and water several enzymatic reactions -start. A plant produces seeds to reproduce. The seed -contains all the nutrients a new plant needs to sprout. -While the seed is dry the seed is in hibernation mode. It -can be sometimes be stored for several years. The moment water is added -to the seed the sprouting process starts. The seed turns -into a germ. The stored nutrients have to be converted -into something that the germ can use. The catalyst for these -reactions is water. The first roots can be produced with the stored nutrients. -Furthermore the seed typically contains the first leaves -of the plant. The first leaves are built to start the photosynthesis -process. This is the plants' engine. With energy from photosynthesis -the plant can keep growing more roots. This way more water -and nutrients can be accessed from the soil. The extended -nutrients allow the plant to form more leaves and thus -increase the photosynthetic activity. +To understand the many enzymatic reactions that take place when flour +and water are mixed, we must first understand seeds and their role in +the lifecycle of wheat and other grains. -Of course a ground flour can no longer sprout. But the enzymes -that trigger this process are still present. That's why it's -important to not mill the grains at a too high temperature. -This could possibly damage some of the enzymes. Normally -the seed of the flour shields the germ against pathogens initially. -However as we grind the flour the contents of the seed -are exposed. This is ideal for our sourdough microorganisms. -The yeast can be considered a saprotrophic fungus. -They can't prepare their own food. As the enzymes start -to be activated more and more food becomes available -for the yeast and bacteria. +Seeds are the primary means by which many plants, including wheat, +reproduce. Each seed contains the embryo of another plant, and must +therefore contain all the nutrients that new plant requires to grow. -The two main enzymes for bread making are amylase and protease. -Understanding their role is a key puzzle piece to be able -to make better tasting bread at home. +When the seed is dry, it is in hibernation mode and can sometimes be +stored for several years. The moment it comes into contact with water, +however, it begins to sprout. The seed turns into a germ, requiring the +stored nutrients to be converted into something the plant can use while +it grows. The catalyst that makes the associated reactions possible is water. + +The seed typically contains the first prototypical leaves of the plant, +and can put down roots using the stored nutrients inside. Once those leaves +break through the soil and come into contact with the sunlight above, they +begin to photosynthesize. This process is the plant's engine, and with the +energy photosynthesis produces, the plant can continue to grow more roots, +enabling it to access additional nutrients from the soil. These additional +nutrients allow the plant to grow more leaves, increasing its photosynthetic +activity so that it can thrive in its new environment. + +Of course, a ground flour can no longer sprout. But the enzymes that +trigger this process are still present. That's why it's important not to +mill grains at too high a temperature, as doing so could damage some of +these enzymes. + +Normally, the grain seed shields the germ against pathogens. However, as the +grain is ground into flour, the contents of the seed are exposed. This is ideal +for our sourdough microorganisms. + +% I removed the line referencing yeast as a saprotrophic fungus since you +% cover this later on in the chapter and removing that helps the text to +% flow more smoothly. +Neither the yeast nor the bacteria can prepare their own food. However, as +the enzymes are activated, the food they need becomes available, allowing them +to feed and multiply. + +The two main enzymes involved in this process are \textit{amylase} and +\textit{protease}. For reasons that will soon be made clear, they are of the +utmost importance to the home baker and their role in the making of sourdough +is a key puzzle piece to making better-tasting bread. \subsection{Amylase} -Sometimes when you chew on a potato or a piece of bread -for a prolonged period of time you will notice a bit of sweetness -arising in your mouth. That's because your salivary glands -are also producing amylase. Amylase breaks down complex -starch molecules into easier digestible sugars. The germ -needs this in order to be able to produce more plant matter. -Your body needs this in order to start the digesting process. -Normally your microorganisms can't consume the freed maltose molecules -as they are hidden in the germ. But as we ground the flour -a feeding frenzy starts. Generally the warmer the temperature -the faster this reaction happens. That's why a long fermentation -is a key factor to make great bread. It takes time -for your amylase to break down most of the starch. Furthermore -not all sugars are consumed by the yeast. Some remain and -are responsible for enhanced browning during the baking -process. +Sometimes, when you chew on a potato or a piece of bread for a long period +of time, you'll perceive a sweet flavor on your tongue. That's because your +salivary glands produce amylase. Amylase breaks down complex starch molecules +into easily-digestible sugars. The germ needs this to produce more plant +matter, and your body needs this to kick-start the digestive process. Normally, +the microorganisms on the surface of the grain can't consume the freed maltose +molecules, which remain hidden inside the germ. But as we grind the flour, a +feeding frenzy takes place. Generally, the warmer the temperature, the faster +this reaction occurs. That's why a long fermentation is key to making great +bread. It takes time for the amylase to break down most of the starch into +simple sugars, which are not only consumed by the yeast but are also essential +to the \textit{Maillard reaction}, responsible for enhanced browning during the +baking process. -If you are a hobby brewer you will know that it's -important to keep your brew on certain temperatures for a -while to allow the different amylases to convert starches -into sugar \cite{beer+amylase}. There's a test frequently used by brewers -to determine that all the starches have been converted. -It's called the Iodine starch test. You take a bit of your brew -and then add a bit of iodine. If the color is blue/black -you know that you still have starches left that haven't been -converted by amylases yet. I wonder if such a test would work -for a bread dough as well? Now industrial bakeries -that use yeast to make speed doughs in a short period of -time face this issue. Their approach is to add malted -flour to the dough mix. The malted flour contains a lot -of enzymes and will thus help to have a faster fermentation -period. Check the packaging of the breads that you bought, -if you find {\it malt} in the list of ingredients chances -are that this strategy has been used. There are two categories -of malts. You have enzymatically active malt and inactive -malt. The active malt hasn't been heated to above 70°C -when the amylases start to degrade under heat. The inactive -malt has been heated to higher temperatures and thus -has no impact on your flour. +If you're a hobby brewer, you'll know that it's important to keep your beer at +certain temperatures to allow the different amylases to convert the contained +starches into sugar \cite{beer+amylase}. This process is so important that +there's a frequently used test to determine whether or not all the starches +have been converted. + +This test, called the \textit{Iodine Starch Test}, involves mixing iodine into +a sample of your brew and checking the color. If it's blue or black, you know +you still have unconverted starches. I wonder if such a test would also work +for bread dough? + +Industrial bakers that add especially active yeast to produce bread in a short +period of time face a similar issue. Their approach is to add malted flour to +the dough. The malted flour contains many enzymes and thus speeds up the +fermentation process. The next time you're at the supermarket, check the +packaging of the bread you buy. If you find {\it malt} in the list of +ingredients, chances are this strategy was used. + +Note that there are actually two categories of malt. One is {\it enzymatically +active malt}, which has not been heated to above 70°C, where the amylases begin +to degrade. The other is {\it inactive malt}, which has been heated to higher +temperatures and thus has no impact on your flour. \subsection{Protease} -The second very important enzyme is the protease. Proteases -break down proteins into smaller proteins or amino acids. -Gluten for instance is a storage protein built by wheat. -The gluten is broken down and converted the moment the -seed starts to sprout. That's because the seed needs -smaller amino acids to build the roots and other plant material. -If you ever try to make a wheat based dough and just keep -it for several days at room temperature you will notice -how your gluten network starts to break down. The dough -no longer holds together. You can just fully tear it apart. -I have had this happen to me when I was trying to make -doughs directly with dried sourdough starter. The fermentation -speed was so low that it took 3-4 days for the dough -to be ready. The root cause for this issue is the protease. -By adding water to the dough the protease was activated -and started to ready amino acids for the germ in order to be -able to sprout. Another interesting experiment that viusalises -the importance of protease is the following. Try to make a -fast dough within 1-2 hours. Simply use a large quantity -of dry yeast. Your dough will be leavened and increase in size. -Bake your dough and notice the crumb of your baked dough. -You will notice that the crumb is quite dense and not as -fluffy as it could be. That's because the protease enzyme -didn't have enough time to do its job. At the start -when kneading your dough is very elastic. It holds together -very well. Over the course of the fermentation process -your dough will become more extensible \cite{protease+enzyme+bread}. -Some of the gluten bonds start to naturally break -down due to the protease proteolysis. This makes it easier -for your dough to be inflated. That's why a long -fermentation process is important when you want to -achieve very fluffy and open crumbs with your sourdough -bread. Next to using great ingredients, the long and -slow fermentation is one of the main reasons why -Neapolitan pizza tastes so great. The soft and fluffy -edge of the pizza is achieved because of the protease -creating a very extensible easy to inflate dough. Because -the fermentation process is typically longer than 8 -hours a flour with a higher gluten content is used. There -is more gluten that can be broken down by the protease. -By using a weaker flour you might end up with a dough -that's already broken down too much and will then tear -when trying to make a pizza pie. Traditionally the pizza -has probably been made with sourdough. In modern times -it is made with yeast as handling a yeast based -dough can be done easier on a larger scale. The dough -stays good for a longer period of time. If you were to use -sourdough you might have a window of 30-90 minutes when -your dough is perfect. Afterwards the dough might -start to deteriorate because of bacteria breaking -down the gluten network too much. +Just as amylase breaks starches down into simple sugars, protease breaks +complex proteins down into simpler proteins and amino acids. Because wheat +contains gluten, a protein that's essential to the structure of bread, +protease necessarily plays a crucial role in the baking of sourdough. + +Since the grain seeds require smaller amino acids to build roots and other +plant materials, the gluten in those seeds will begin to break down the moment +they sprout, and since adding water to flour activates those same enzymes, +the same process occurs in bread dough. + +If you've ever tried to make a wheat-based dough and kept it at room +temperature for several days, you'll have discovered for yourself that the +gluten network breaks down so that the dough can no longer hold together. Once +this happens, the dough easily tears, holds no structure, and is no +longer suitable for baking bread. + +This happened to me once when I tried to make sourdough directly from a dried +starter. At three to four days, the fermentation speed was so slow that the +gluten network broke down. The root cause for this issue was protease. + +By adding water to your dough, you activate the protease, and this gets to work +in readying amino acids for the germ. + +Here's another interesting experiment you can try to better visualize the +importance of protease: Make a fast-proofing dough using a large quantity +of active dry yeast. In one to two hours, your dough should have leavened and +increased in size. Bake it, then examine the crumb structure. You should see +that it's quite dense and nowhere near as fluffy as it could have been. That's +because the protease enzyme wasn't given enough time to do its job. + +At the start, while kneading, a dough becomes elastic and holds together very +well. As that dough ferments, however, it becomes more loose and extensible +\cite{protease+enzyme+bread}. This is because some of the gluten bonds have +been broken down naturally by the protease through a process known as +\textit{proteolysis}. This is what makes it easier for the yeast to inflate the +dough, and it's why a long fermentation process is critical when you want to +achieve a fluffy, open crumb with your sourdough bread. + +Aside from using great ingredients, the slow fermentation process is one of the +main reasons Neapolitan pizza tastes so great; because the protease creates an +extensible, easy-to-inflate dough, a soft and airy edge is achieved. + +Because the fermentation process typically takes longer than eight hours, a +flour with a higher gluten content should be used. This gives the dough more +time to be broken down by the protease without negatively affecting its +elasticity. If you were to use a weaker flour, you might end up with a dough +that's broken down so much that it tears during stretching, making it +impossible, for example, to shape it into a pizza pie. + +Traditionally, pizza has been made with sourdough, but in modern times it is +made with active dry yeast, as the dough stays good for a longer period of time +and is much easier to handle on a commercial scale. If you were to use +sourdough, you might have a window of thirty to ninety minutes before the dough +begins to deteriorate, both because of the protease acting for a longer period +of time and the byproducts of bacteria, which we'll discuss in more detail later +in this chapter. \subsection{Improving enzymatic activity} -As explained previously malt is a common trick used -to speed up enzymatic activity. I personally prefer -to avoid malt in most of my recipes. Instead I use -a trick I observed when making whole wheat doughs. -No matter what I tried I could never achieve baking -a whole wheat bread with the desired crust and crumb -texture I was looking for. My doughs would tend to -overferment relatively quickly. When using a flower -with a similar amount of gluten that didn't contain -bran and other outer parts of the grain my doughs turned -out great. I was utilizing an extended autolyse. -That's a fancy word for just mixing flour and water in -advance and letting that mixture sit. Most recipes -call for it as the help to make a dough that has already -started to break down by enzymes. In general it's a great -idea but at the same time you can just reduce the amount -of leavening agent you use. This way the same biochemical -reactions happen and you don't have to mix your dough -several times. My whole wheat game drastically improved -when I stopped using the autolysis. It makes sense if I -think about it now. The first parts of the seed that -are in contact with water are the outer parts. Water -will slowly enter the center parts of the grain. The -moment the seed starts to sprout it needs to outcompete -other nearby seeds. Furthermore it also directly becomes -exposed to other animals and potential hazardous bacteria -and fungi. To accelerate this process most of the enzymes -of the grain are in the outer parts of the hull. They -are being activated first (source needed). So by just -adding a little bit of whole flour to your dough you -will improve enzymatic activity of your dough. That's -why most of my plain flour doughs typically contain -at least 10-20 percent whole wheat flour. +As explained previously, malt is a common trick used to speed up enzymatic +activity. Personally, however, I prefer to avoid malt and instead use a +trick I learned while making whole-wheat breads. + +When I first started making whole-wheat bread, I could never achieve the +crust, crumb, or texture I desired no matter what I tried. Instead, my dough +tended to overferment rather quickly. When using a white flour with a similar +gluten content, however, my bread always turned out great. + +At the time, I utilized an extended autolyse, which is just a fancy word for +mixing flour and water in advance and then letting the mixture sit. Most +recipes call for it as the process gives the dough an enzymatic head start, and +in general it's a great idea. However, as an equally effective alternative, +you could simply reduce the amount of leavening agent used (in the case of +sourdough, this would be your starter). This would allow the same biochemical +reactions to occur at roughly the same rate without requiring you to mix your +dough several times. My whole wheat game improved dramatically after I stopped +autolysing my doughs. + +Now that I've had time to think about it, the result I observed makes sense. +In nature, the outer parts of the seed come into contact with water first, and +only after penetrating this barrier would the water slowly find its way to the +center of the grain. The seed needs to sprout first to outcompete other nearby +seeds, requiring water to enter quickly. Yet the seed must also defend itself +against animals and potentially hazardous bacteria and fungi, requiring some +barrier to protect the embryo inside. A way for the plant to achieve both goals +would be for most of the enzymes to exist in the outer parts of the hull. As a +result, they are activated first (source needed). Therefore, by just adding a +little bit of whole flour to your dough, you should be able to significantly +improve the enzymatic activity of your dough. That's why, for plain white flour +doughs, I usually add 10\textendash20\% whole-wheat flour. \begin{figure} \includegraphics[width=\textwidth]{whole-wheat-crumb} - \caption{A whole wheat sourdough bread} + \caption{A whole-wheat sourdough bread} \label{whole-wheat-crumb} \end{figure} -By understanding the 2 key enzymes amylase and protease -you will better be able to understand how to make a -dough to your liking. Would you like a dough a softer -or stiffer crumb? Would you like to achieve a darker crust? -Would you like to reduce the amount of gluten in your -final bread? These are all factors you can influence -by adjusting the speed of fermentation. +By understanding the two key enzymes \textit{amylase} and \textit{protease}, you +will be better equipped to make bread to your liking. Do you prefer a softer +or stiffer crumb? Do you desire a lighter or darker crust? Do you wish to reduce +the amount of gluten in your final bread? These are all factors that you can +tweak just by adjusting the speed of your dough's fermentation. \section{Yeast} -Yeasts are single celled microorganisms that are part of -the fungus kingdom. Yeast spores that are hundreds -of million years old have been identified by scientists. -There is a wide variety of species and so far around 1500 -different species have been recognized. Yeasts are not creating -a mycelium network like mold does for instance -\cite{molecular+mechanisms+yeast}. +% Yeast is both the singular and plural form of the word unless you're +% specifically referencing a plural number of varieties or types, in which case +% "yeasts" would be correct. +Yeast are single celled microorganisms belonging to the fungi kingdom, and +spores that are hundreds of millions of years old have been identified by +scientists. There are a wide variety of species: So far, about 1,500 have been +identified. Unlike other members of the fungi kingdom, such as mold, yeast do +not ordinarily create a mycelium network \cite{molecular+mechanisms+yeast} +\footnote{For one interesting exception, skip ahead to the end of this +section.}. \begin{figure}[!htb] \centering @@ -211,106 +221,105 @@ a mycelium network like mold does for instance \label{saccharomyces-cerevisiae-microscope} \end{figure} +Yeast are saprotrophic fungi. This means that they do not produce their own +food, but instead rely on external sources that they can decompose and break +down into compounds that are more easily metabolized. -Yeasts are saprotrophic fungi. This means they are not -producing their own food. They rely on external food sources -which they decompose and break down. For yeasts -carbohydrates and broken down to carbon dioxide and -alcohols. The products of this fermentation process -have been used for thousands of years when making -bread or alcoholic beverages. Yeasts can grow -in both aerobic and anaerobic conditions. When oxygen -is present the yeast almost completely produces -carbon dioxide and water. When no oxygen is present -the yeast starts switches its metabolism. The -yeast starts to produce alcoholic compounds \cite{effects+oxygen+yeast+growth}. -The temperatures at which the yeast grows vary. Some -yeasts such as {\it Leucosporidium frigidum} grows -best at temperatures between -2°C up to 20°C. Other -yeast grows better at higher temperatures. The warmer -it is the faster the yeast's metabolism works. The yeast -that you cultivate in your sourdough starter works best -at the temperatures where the grain was grown and at -the point when it was harvested. So if you are from a -cooler place and cultivate a sourdough starter from -a nordic rye variety, then chances are your yeast -prefers this colder environment. As an example -beer makers discovered that a beneficial yeast lives -in the cold caves around the city of Pilsen, Czech Republic. -This yeast has produced excellent tasting beers at -lower temperatures. Varieties of these strains -are now used to make popular lager beers. +Yeast breaks down carbohydrates into carbon dioxide and alcohol in what we today +refer to as the fermentation process. This process has been known for thousands +of years and has been used since ancient times for the making of bread as well +as alcoholic beverages. -Yeasts in general are very common in the environment. -They can be found on cereal grains, fruits, other plants -in the soil and also in your gut. Very little is known -about the ecology of why yeasts we use for baking -are cultivating the leaves of the plants. The plants -are protected via the cell walls and hardly any -fungi and other bacteria can penetrate. Some fungi and -bacteria are producing enzymes that are able -to break down the cell walls and infect the plant. -There are fungi and bacteria that live within the plant -without causing any distress. These are known as {\it endophytes}. -They are not damaging the plant per se. In fact they are -living in a symbiotic relationship with the host. They -help the plant to protect itself from additional pathogens -that might enter through the leaves of the plant. They -help with water stress, heat stress and nutrient availability. -In exchange for the service they receive carbon for energy -from the plant host. They are not always strictly mutualistic though. -Sometimes under stress conditions they can become pathogens -on their own \cite{endophytes+in+plants} and decay begin -decaying the plant. +Yeast can grow and multiply under both aerobic and anaerobic conditions. When +oxygen is present, they produce carbon dioxide and water almost exclusively. +When oxygen is not present, their metabolism changes to produce alcoholic +compounds \cite{effects+oxygen+yeast+growth}. -The yeasts we use for baking are -living as as epiphytes on the plant. Compared to -the previously mentioned endophytes they are not -breaching the walls of the cells. Most of them -receive nutrients from rain water, the air or other animals. -These sources also include honeydew produced -by aphids. Pollen that lands on the leaf's surface -is an additional source of food. Interestingly -though when you remove that external food source, -you still find a large variety of epiphytic fungi -and bacteria on the plant's surface. The food -for them is coming directly from the plant it seems. -Some research has shown that the plants are -on purpose releasing some compounds such as sugars, -organic acids, amino acids, some methanol and various -salts via the surface. These nutrients would -then attract the epiphytes to live on the surface. -The plants benefit from enhanced protection against -mold and other pathogens. It is in the best interest -of the epiphytes to keep the plants alive -as long as possible \cite{leaf+surface+sugars+epiphytes}. -More and more research is conducted on using yeasts -as a biocontrol agents to protect plants. These bio-agents -would be food-safe as yeasts are generally considered save. -The yeasts would start to grow on the leaves on the plant -and essentially shield the plants from other molds. This -could be a game changer for wineyeards suffering from mildew. -This could also be helpful to shield the plant against the -psychoactive ergot fungus. The ergot fungus likes to grow -in more humid colder environments and poses a huge -problem to rye farmers. The fungus parasites the plant -and infects it. Consumption of ergot is not recommended -as it is highly toxic to the liver. That's why lawmakers -have recently reduced the amount of allowed ergot contamination -in rye flour. Another interesting experiment from Italian scientists -visualized how important yeasts could be when protecting -plants. They added tiny incisions into some of the grapes. -They would then infect some of the damaged surfaces with -mold. The other wounds they infected with some of the 150 -different wild yeast strains isolated from the leaves plus -the mold. When mixing the mold with the yeast the grape +The temperatures at which yeast grows varies. Some yeasts, such as +{\it Leucosporidium frigidum}, do best at temperatures ranging from -2°C to +20°C, while others prefer higher temperatures. In general, the warmer the +environment, the faster the yeast's metabolism. The variety of yeast +that you cultivate in your sourdough starter should work best within the range +of temperatures where the grain was grown and harvested. So, if you are from a +cooler place and cultivate a sourdough starter from a nordic rye variety, +chances are your yeast will prefer a colder environment. + +As an example, beer makers discovered a beneficial yeast living in the cold +caves around the city of Pilsen, Czech Republic. This yeast has since become +known for producing excellent beers at lower temperatures and varieties of +these strains are now used for brewing popular lagers. + +Yeasts in general are very common organisms. They can be found on cereal +grains, fruits, and many other plants in the soil. They can even be found +inside your gut! As it happens, the types of yeast we use for baking are +cultivated on the leaves of plants, though very little is known about the +ecology involved. + +Plants are protected by thick cell walls that few fungi or bacteria can +penetrate. However, there are some species that produce enzymes capable of +breaking down those cell walls so they can infect the plant. + +Some fungi and bacteria live inside plants without causing them any distress. +These are known as {\it endophytes}. Not only do they \textit{not} damage their +host, they actually live in a symbiotic relationship, helping the plants in +which they dwell to protect themselves from other pathogens that might also +come to infect them through their leaves. In addition to this protection, they +also help with water and heat stress, as well as the availability of nutrients. +In exchange for their service to their host plants, these fungi and bacteria +receive carbon for energy. + +However, the relationship between endophyte and plant is not always mutually +beneficial, and sometimes, under stress, they become invasive pathogens and +ultimately cause their host to decay \cite{endophytes+in+plants}. + +There are other microorganisms that, unlike endophytes, do not penetrate cell +walls but instead live on the plant's surface and receive nutrients from rain +water, the air, or other animals. Some even feed on the honeydew produced by +aphids or the pollen that lands on the surface of the leaves. Such organisms +are called \textit{epiphytes}, and included among them are the types of yeast +we use for baking. + +Interestingly, when you remove external food sources, a large number of +epiphytic fungi and bacteria can still be found on the plant's surface, +suggesting that they must somehow be feeding directly from the plant. +Indeed, there is some research indicating that some plants intentionally release +compounds such as sugars, organic and amino acids, methanol, and various +salts along the surface. These nutrients would then attract the epiphytes that +live on the plant's surface. + +Epiphytes are advantageous to a plant's survival, as they are provided with +enhanced protection against mold and other pathogens. Indeed, it is in the +best interest of the epiphytes to keep their host plants alive for as long as +possible \cite{leaf+surface+sugars+epiphytes}. + +More research is conducted every day in ways that yeasts can be used as +biocontrol agents to protect plants, the advantage being that these bio-agents +would be food-safe as the relevant strains of yeast are generally considered +harmless to humans. The yeasts would grow and multiply on the leaves, +esentially shielding them from other types of mold. This could be a potential +game changer for vineyards that suffer from mildew. + +Such bio-agents could also be used to shield plants against the psychoactive +ergot fungus, which likes to grow in colder, more humid environments and +poses a significant problem for rye farmers. Because it infects the grain +and makes it unfit for consumption due to its high toxicity to the liver, +lawmakers have recently reduced the amount of allowed ergot contamination in +rye flour. + +There is another interesting experiment performed by Italian scientists that +shows how crucial yeasts could be in protecting our crops. First, they made +tiny incisions into some of the grapes on a vine. Then, they infected the +wounds with mold. Some incisions were only infected with mold. Others were also +innoculated with some of the 150 different wild yeast strains isolated from the +leaves. They found that when the wound was innoculated with yeast, the grape sustained no significant damage \cite{yeasts+biocontrol+agent}. -In another experiment however scientists have shown -how the brewer's yeast became an aggressive pathogen to wine plants. -Initially the yeast lived in symbiosis with the plant. After the grapevine -sustained damages the yeast became opportunistic and started to -attack the plant event producing hyphae to deeply -penetrate the plants tissue. + +Intriguingly, there was also an experiment performed that showed how brewer's +yeast could function as an aggressive pathogen to grape vines. Initially, the +yeast lived in symbiosis with the plants, but after the vines sustained heavy +damage, the yeast became opportunistic and started to attack, even going so far +as to produce hyphae, the mycellium network normally associated with a fungus, +so that they could penetrate the tissue of the plants. \section{Bacteria} diff --git a/book/intro/acknowledgements.tex b/book/intro/acknowledgements.tex index c8f4093..3733acc 100644 --- a/book/intro/acknowledgements.tex +++ b/book/intro/acknowledgements.tex @@ -1,14 +1,13 @@ This book would not have been possible without the help of the community. -All the donations have made it possible that I was able to take -some time off from my job and YouTube to write this free book. -By providing this information free to everyone we can -enable more people around the world to bake delicious -sourdough bread at home. Thank you very much!\\ +Because of the donations received, I have been able to take time off from +my job and from YouTube to write it. By providing this information free +of charge, we can help more people around the world bake delicious sourdough +bread at home. Thank you very much!\\ \begin{filecontents}{supporters.csv} \end{filecontents} - {\large All supporters sorted by name} + {\large All supporters, sorted by name:} \pgfplotstableset{ begin table=\begin{longtable},