Cooking with Alcohol

Transcription

1 Cooking with Alcohol Model 1. Ethanol is a simple organic carbon compound with the hydroxyl group bound to a carbon. Other alcohols include methanol and propanol (1- propanol or 2- propanol). Each of these compounds, and many others are alcohols the hydroxyl group is a polar O- H bond which allows ethanol to mix well with water. The non- polar C- H bonds of ethanol interact with other non- polar bonds via Van der Waals (VDW) attractions. Ethanol s dual capabilities as a solvent make it very useful for extracting flavor molecules from spices, herbs and fruits for example, bitters and liqueurs are both ethanol extracts of plant material: either nuts, seeds, fruits or stems/flowers. Liqueurs differ from bitters in that they contain added sugar. Amaretto, Kahlua and Limoncello are ethanol extracts of almonds, coffee and lemons, respectively. Figure Chemists call any compound with a C- O- H group of atoms an alcohol. Ethanol is the alcohol found in wine, beer and spirits. Since ethanol is such a good solvent it is capable of dissolving both polar and non- polar molecules it is often used in cooking. Ethanol is a kind of third liquid in addition to water and oil/fat into which flavor molecules can be dissolved. While alcohol can improve a dish too much alcohol can change the flavor of the food (and your experience of it!), and so cooks often boil or simmer a dish to remove some of the alcohol. Copyright 2016 Wiley, Inc. Page 1

2 The temperature needed to convert a pure sample of a liquid into a gas/vapor is called its boiling point. Water boils at 100 C/212 F and ethanol boils at 78.5 C/173 F,but if you heat a mixture of ethanol and water it will boil somewhere between 78.5 C and 100 C. The vapor of the ethanol- water mixture will contain both water molecules and ethanol molecules, but the vapor of the ethanol- water mixture is more concentrated in the lower boiling component in this case, the ethanol. Figure 29.2 Evaporation of ethanol If we were to capture this ethanol- water vapor and condense it back into a liquid, the concentration of ethanol would be higher. This is the process of distillation vaporization (boiling) and condensation (cooling the vapor back to a liquid). If we continue the process of vaporizing and condensing the ethanol- water mixture over many rounds of distillation we will eventually get a liquid that is highly enriched in ethanol. This is how distilled liquors like whisky, vodka and rum are made. While boiling your wine- infused sauce will reduce the amount of ethanol it contains, it will not remove the ethanol entirely. The same is true for the showy flambé technique that ignites and burns off the ethanol. The hydrogen bonding between ethanol and water keeps all the ethanol from evaporating away. Table % Alcohol remaining after cooking 1 Technique Alcohol % remaining Adding alcohol to boiling liquid then > 85% shortly removing it from the heat Flambé (igniting and burning off ) 75% Baking/simmering for 25 min, no stirring 45% Baking/simmering with stirring 15 min 40% Baking/simmering with stirring 29 min 35% Baking/simmering with stirring 60 min 25% Baking/simmering with stirring 1.5h 20% Baking/simmering with stirring 2h 10% 1 Augustin, J, Augustin, E, Cutrufelli, R.L, Hagen, S.R, Teitzel, C. Alcohol retention in food preparation. J Am Diet Assoc. 1992;92: Copyright 2016 Wiley, Inc. Page 2

3 Questions: 1. Draw the structures of water and ethanol below and show how they interact via their polar O- H bonds. (Hint: Remember that the polar O- H bond has δ+ and δ- charges). 2. Ethanol can be used for making spice extracts, and vanilla extract is an ethanol extract of the vanilla bean. The primary aroma molecule that we associate with vanilla flavor is vanillin, shown below. Please explain how ethanol is uniquely suited to extract this molecule from vanilla bean. Copyright 2016 Wiley, Inc. Page 3

4 3. Vodka sauce is a tomato sauce to which cream and vodka have been added. A recipe for the classic Italian dish - Penne with Vodka sauce - is shown below: Ingredients 1 pound uncooked penne pasta ¾ teaspoon salt, and more to taste ¼ cup extra virgin olive oil 2 tablespoons vodka 4 garlic gloves, finely chopped ½ cup heavy whipping cream ½ teaspoon red pepper flakes ¼ cup chopped fresh parsley 1 (28 ounce) can crushed tomatoes 2 links (3.5 ounces) sweet Italian sausage Directions: Bring a large pot of water to a boil add salt to taste. Add pasta and return to a rapid boil Cook for 8-10 minutes or until al dente; drain. Heat oil over moderate heat in a large skillet. Remove casing from sausage and add to skillet. Break up the meat and cook until browned. Add garlic and red pepper flakes, then cooking with stirring until garlic is golden brown. Add tomatoes and salt to skillet, then bring mixture to a boil. Reduce heat and simmer for 15 minutes. Add vodka and cream, then bring to a boil. Reduce heat to low and add cooked pasta. Toss for 1 minutes. Stir in parsley and serve. a. What does the Vodka accomplish in this dish? b. Based on the recipe instructions, how much of the alcohol would be retained in this sauce? Give a chemical explanation. 4. The size of the cooking vessel also impacts alcohol retention rates. If you cook the same dish in a tall, deep pot versus a wide, shallow skillet which dish will retain more ethanol and why? Copyright 2016 Wiley, Inc. Page 4

5 Guided Inquiry Activity #29 Fermentability, Color and Flavor in Beer Model 2. Making beer starts with the barley grain. The grain must first be soaked to awaken the seedling and liberate the starch molecules stored within. Figure Yeast metabolize fermentable sugars to ethanol Remember, starch is a polymer of glucose and glucose is food for yeast! In order to make ethanol, the yeast first need glucose. While the ethanol content of beer is provided by yeast, the color and flavor of beer is created during the extraction and degradation of the starch molecules. Figure The steps of beer brewing. * Browning reactions are chemical reactions that occur under high heat to generate flavor molecules. For a lesson on Browning, see Activity 17 Copyright 2016 Wiley, Inc. Page 5

6 Barley starch is made of both amylose and amylopectin 2. There are two enzymes in barley grain that are responsible for breaking down the starch into smaller pieces: alpha amylase and beta amylase. Alpha amylase will cut the 1-4 glycosidic bond between glucose units on both amylose and amylopectin. Alpha amylase randomly cleaves starch chains producing shorter chunks of starch. These short glucose polymers called dextrins are still too large to be used as food for yeast, but their size does provide body to the beer. Beta amylase also cleaves 1-4 glycosidic bonds but unlike alpha amylase, cuts off two glucose units at a time, producing the fermentable disaccharide maltose. Amylopectin contains 1-6 glycosidic branch points which are not digested by either amylase. Another enzyme called limit dextrinase (sometimes called debranching enzyme ) is needed to cleave the 1,6 branches allowing the amylases to continue to digest the starch into maltose and glucose. Figure The cleavage of amylose by alpha and beta amylases While the contributions of malting and kilning to beer color and flavor should not be undervalued, home brewing typically begins with mashing. The home brewer (or master brewer) purchases commercially available malts and mixes the ground/powdered malt (or combinations of malts) with hot water to re- activate the amylase enzymes and dissolve the starches into solution. The subsequent action of the amylase enzymes on the starch can be divided into three phases: gelatinization, liquefaction and saccharification. Gelatinization is the gelling of starch that we have studied in previous activities. 2 See Activity 18 for a lesson on types of starch. Copyright 2016 Wiley, Inc. Page 6

7 Figure Gelatinization, Liquefaction, Saccharification Once the water soaked starch granules have disintegrated, and the starch molecules have spilled out, the chains of amylose and amylopectin are chewed apart by alpha and Copyright 2016 Wiley, Inc. Page 7

8 beta amylase. The master brewer will try to control the relative activities of alpha and beta amylase because each yields a different product. One means of controlling enzyme activity is with temperature. Alpha amylase produces the non- fermentable dextrins and is most active between 155 and 158 F. Beta amylase produces the fermentable 3 maltose, and is most active between F. Choosing your malt carefully and using temperature to maximize alpha amylase activity will yield a full- bodied beer. The dextrins produced by alpha amylase are bigger molecules, and the more dextrins present in the wort, the thicker or fuller the liquid will be. A thinner bodied ale is the product of a mash with high beta amylase activity. The quantity of fermentable sugar also impacts dryness. Dryness is the absence of sweetness. Table The relative compositions of highly- fermentable and low- fermentability mashes Glucose, maltose and maltotriose Dextrins 4 Beer body 5 Alcohol content 6 Sweet vs. Dry Highly fermentable High Low Thinner body Higher Dry mash concentration concentration Low- fermentability mash Low concentration High concentration Fuller body Lower Sweet If the yeast consume most of the starch as fermentable sugars, the beer will be dry. When we drink the beer, leftover, non- fermentable dextrins are broken down by enzymes in our mouths to produce glucose. We taste this as sweetness. 3 Remember, fermentable = food for yeast 4 Dextrins are a mixture of short glucose polymers (> 4 units) produced from the breakdown of starch. The glucose units are linked by α (1 4) or α (1 6) glycosidic bonds 5 The body of the beer refers to its mouthfeel. A full- bodied beer has a rounder, fuller mouthfeel (e.g. browns, porters and stouts), a thin- bodied beer has a lighter, weaker mouthfeel (e.g. ale), some describe the weaker mouthfeel as watery. 6 In brewing, the alcohol content is also called attenuation. Attentuation is the extent to which yeast consumes fermentable sugars (converting them into alcohol and carbon dioxide) ( Therefore, greater/more attenuation = higher alcohol content, while lower/less attenuation = lower alcohol content. Copyright 2016 Wiley, Inc. Page 8

9 Questions: 5. Beer is made from barley grain, and while it is possible to make beers from other grains (wheat, corn, millet, oats etc), barley is preferred because it is best at producing starch- digesting enzymes. Why is the production of starch digesting enzymes important for the production of ethanol for beer? 6. (From byo.com Brew Your Own) Many brewers, when first starting out, get what seems like an ingenious idea that will not work. The idea is start out at 158 F to let alpha amylase do its thing and then to cool the mash down to let beta amylase do its thing. Why does this approach not work? 7. If you are perusing the home- brewing forums you will find that a common complaint is beer with good flavor but a thin body. What recommendations could you make to the home brewer to maximize the body of their brew? 8. Beta amylase is also knicknamed the fermentability enzyme why? 9. A Dry Stout is a dry, light- bodied beer (often called a dry Irish stout ). How might the master brewer control amylase activity to obtain these characteristics? Copyright 2016 Wiley, Inc. Page 9

10 Putting it all together: 10. Irish stew is made with a whole bottle of Black William: The bottle contains 500ml of beer of which 5%, or 25 milliliters, is alcohol. The stew is slowly simmered for at least one and a half hours. What is the alcohol content in this stew? 11. Beer is a high calorie drink. A typical American lager contains 14 grams of alcohol and 11 grams of carbohydrate. a. A full bodied beer is typically a high calorie beer. Why is this? b. Light beers are made by adding in additional enzymes to digest more of the carbohydrates into fermentable sugars. i. How does making more fermentable sugars end up producing a lower calorie beer? ii. Light beers have very little body. Why is this? Copyright 2016 Wiley, Inc. Page 10