|Table of Contents for Caveman Chemistry: 28 Projects, from the Creation of Fire to the Production of Plastics
|Chapter 4. Samson (Mead)
You see, honey is a complex, concentrated solution of sugars, mostly glucose and fructose, the solutes, along with pollen and other minor constituents which add color, flavor, and aroma to the solvent in which they are dissolved, which, of course, happens to be water in this case. The bees need to store up food for thousands of bee babies and, not having refrigeration, they have hit upon a natural way of protecting this larder from spoilage. Now I know how crazy this may sound, but spoilage is caused by tiny little animals, microorganisms, so small that you cannot even see them. If a solution is concentrated enough, apparently, these microorganisms cannot thrive. This is why we salt meat and dry fruit to preserve them. The bees have done the same thing with sugar: they produce a solution so concentrated that it cannot spoil.
Add water, though, and it begins to spoil, that is, the little animals begin to eat the sugar. Now, most animals need air to live, and when they eat sugar, they piss out water and fart out carbon dioxide according to Equation 4-1(a). But there is a particular variety of microorganism, yeasts (Figure 4-1), which can thrive both aerobically and anaerobically, with and without oxygen. When there is plenty of air, they digest sugars aerobically as most other organisms do. But in the absence of air, they are able to partially digest sugars in aqueous solution (aq), farting out carbon dioxide, as usual, but pissing out ethanol (ethyl alcohol), rather than water, according to Equation 4-1(b). And so, if you dilute honey with water, and if yeasts are present (and they usually are), and if you protect this honey water from air, you will find yourself with a kind of wine called mead, which has nothing whatsoever to do with grapes and everything to do with the raucousness of Samson's wedding party.
The maturation of a mead depends in large part on the concentration of honey in the original solution, which is called must or wort. Let us suppose, to begin with, that you have really gone overboard in watering down your honey, placed it in a bottle with at least one tiny little yeast, and sealed the bottle to prevent air from getting in. Initially, this yeast finds itself in yeast heaven: plenty of sugar to eat, but not so concentrated that it cannot thrive, and plenty of oxygen to breathe. It goes to town, using up oxygen and glucose, producing carbon dioxide and water. Life is good, and while you should not exactly call it a sex drive since yeasts do not have sex, they do reproduce, so one yeast becomes two, two become four, and soon you cannot swing a jawbone without hitting a yeast. But you have sealed the bottle, and if the air runs out before the sugar, the yeasts move into anaerobic mode, consuming glucose (but not oxygen) and producing carbon dioxide and ethanol. Now, recall that carbon dioxide is a gas, so the pressure will build up inside the bottle. If you do not let it out, the bottle will explode. Brewers have fancy one-way valves, called fermentation locks, that let gas out but not in, but we can make a simple one from a balloon and a bottle cap. The gas escapes the fermenting mead until eventually the sugar runs out, the yeasts starve to death, settle to the bottom as dregs, or lees, and a dry mead results, one which is not at all sweet because the sugar has all been eaten. If the bottle remains sealed, the mead will be naturally carbonated, a kind of apian champagne.
The story ends differently if we were not so liberal with the water at the beginning. The yeasts reproduce more slowly because the concentration is higher. As the sugar is consumed, the alcohol concentration rises, eventually to a level which is toxic even to yeasts, which are, in effect, stewing in their own juices. They die and fall to the bottom as before, but under these conditions, a sweet mead results because of the leftover sugar. If you think about it, the sweet mead will be more alcoholic than the dry one because all of the sugar that can be converted to alcohol, will have been. You may be wondering how we might produce the maximum amount of alcohol using the minimum amount of sugar. We can start with a little honey as if we were producing a dry mead, and every time that the sugar runs out, as evidenced by a slowing of the production of gas, we can simply add more honey. When the addition of honey fails to revive the production of carbon dioxide, we will know that the poor yeasts are dying of alcohol poisoning and we need add no more honey.
There is one more bug in the soup, so to speak. Yeasts are not the only microorganisms around, generally. There is, among other things, a kind of bacterium which thrives on alcohol when oxygen is present. This little fellow breathes oxygen, eats ethanol, and pisses out acetic acid, (CH3COOH) and water, according to Equation 4-1(c). As you know, spoiled food often tastes sour, and this taste comes from the acid. If we allow mead or wine to spoil unintentionally, we call it garbage. If we allow it to spoil intentionally, we call it vinegar. Go figure.
The fermentation process is summarized visually in Figure 4-2. This reactor, a fermenter, is symbolized by a stack of three circles, labeled by the alchemical symbols for air, water, and earth. This stack resembles a bottle, if you use a good bit of imagination, from which gas can escape at the top and solids can settle to the bottom. In the next section, we will use a 2-liter soft-drink bottle as a fermenter. The reactants, honey, water, and yeast enter from the left of the figure. The solid waste product, dead yeasts, exits the bottom of the figure from the circle labeled by the alchemical symbol for earth. The gaseous waste product, carbon dioxide, exits the top of the figure from the circle labeled by the alchemical symbol for air. The good stuff, the main product, a solution of ethanol in water, exits the right of the figure from the circle labeled by the alchemical symbol for water. You should familiarize yourself with these conventions, as similar schematics will be used throughout the book.
People will say that my vision of the fermentation of mead is just a theory, but it is unjust to use the qualifier, "just." Without a theory, all you have are a collection of isolated observations; the Sun rose today, it rose yesterday, and it rose the day before yesterday. Theory, not observation, leads you to expect that it will rise tomorrow. Theory provides a vision of why the Sun rises and projects that vision into the future. One theory might hold that the Sun revolves steadily around the Earth; another that the Earth rotates steadily on its axis. Without theory you would neither expect the Sun to rise nor would you expect it not to rise. You would simply shrug your shoulders and say, "que sera, sera."
A theory may be right or it may be wrong. If you add yeast to honey and water but no gas is produced you will be justified in doubting my theory of mead. If you add yeast to honey and water and it smells of ammonia rather than alcohol you should definitely doubt my theory. If you leave your fermenting mead open to the air and it does not turn to vinegar you should probably flush my theory down the toilet. If my theory fails to account for any of your observations, either my theory is wrong or you have not really observed what you think you have observed. Perhaps your yeasts were dead. Perhaps your bottle contained urine instead of honey. Perhaps your bottle had no bacteria to oxidize ethanol to acetic acid. But if your observations check out then my theory is not "just a theory;" it is a failed theory. Perhaps you can modify it or extend it to account for your observations, but if you cannot then you ought to flush the old theory and start over with a new one.
Suppose, however, that all of your observations support my theory. Does that make it right? No. Perhaps there is an observation you have yet to make which, once made, will contradict my theory. Perhaps there is another theory which would also account for all of your observations. A working theory is simply a survivor. It exhibits fidelity when its predictions are confirmed by observation. It exhibits fecundity when it makes many, many such predictions. It exhibits longevity when it has survived test after test without contradiction. But history is littered with theories which thrived for generations, only to be driven to extinction by emerging competitors. In this sense every theory is "just" a theory. The word just, then, is not so much a criticism as a redundancy. Let us accept the theory of mead in the spirit in which it is offered, provisionally. As long as it accounts for the observations made to date, we might say that we understand those observations. It provides a framework for predicting the future without which we would be left, not with different expectations, but with no expectations at all.
OK, so back to my riddle. Under pressure from her relatives, my new wife wheedled the story of the lion out of me. They won the bet, I went off in a snit and killed 30 other Philistines, gave their clothes to my 30 "friends," and the honeymoon was over before it even got started. By then I had touched more dead bodies than you can shake an ass's jawbone at and it turns out that mead "counts" as wine, even though it does not come from grapes. All that remained of my Nazarite vow was my hair, but that is another story. In the end, I should not have said "Out of the strong came forth sweetness", but rather, "Out of the sweet comes something strong."
Look up an MSDS for ethanol (CAS 64-17-5). The MSDS was introduced in Chapter 3 as a handy reference on chemical hazards. You can find one on the Internet by searching on the keyword MSDS and the CAS number. Summarize the hazardous properties of ethanol in your notebook, including the identity of the company which produced the MSDS and the potential health effects for eye contact, skin contact, inhalation, and ingestion.
If you look on any bottle of beer, wine, or liquor, you will see a warning about the dangers of alcohol consumption. You must know that over-consumption is the biggest hazard involved in drinking alcoholic beverages. One of my students brewed two liters of mead and saved it for his 21st birthday. Having never touched a drop in his life, he proceeded to down the whole two liters in one evening. He passed out and his roommate took him to the emergency room, which, of course, was a sensible thing for him to do. This fellow made a full physical recovery, though his ego suffered a bruise or two. His parents chalked the whole thing up to growing pains, though I doubt they would have been so understanding if he had kicked the bucket. And this bucket gets kicked more often than it should by young people eager to taste the forbidden fruit. I can only advise you to start small and work your way up. Remember the old adage, "When your nose feels numb, it is time to put a cork in it."
|Research and Development
You are probably wondering what you need to know for the quiz. I will tell you.