One of the most successful and influential products developed by the beer industry was low-calorie beer. Introduced in the 1970s, this "new" type of beer had a dramatic impact, not only in the beer industry, but throughout the food industry, as "light" became one of the most widely used descriptors for reduced calorie foods. In fact, low-calorie beers had been around for at least ten to twenty years prior to the introduction of Miller Lite in 1975, but these products were not very popular. Undoubtedly, highly successful advertising and marketing campaigns, along with more calorie-conscience consumers, led to what is now a major part of the beer industry. Currently, low-calorie beers have about 45% of the total U.S. beer market, and three of the top five selling brands of all beer are in this category (Bud-weiser Light, Miller Lite, and Coors Light). When first introduced for beer, "light" had no official meaning. The widespread use of this term, however, eventually led the FDA to define light foods as those that are significantly reduced in either fat, calories, or sodium. As applied to beer, "light" means that there must be one-third fewer calories.
The most obvious way to reduce the caloric content of beer would be to simply dilute regular beer with water. A typical American-style lager beer ordinarily contains about 150 calories in a 340 ml (12 ounce) serving, so adding 25% water would result in a beer with only 112 calories. Doing so, however, would obviously not only reduce calories, but would also reduce flavor, color, body, and the ethanol content. Instead, to make a "light" beer with fewer calories, but with a minimal loss of flavor and body characteristics, manufacturers had to consider beer composition and the components that contributed calories.
In general, a typical U.S. beer contains (on a weight basis) about 3.7% ethanol, 1% protein, and 0.5% fat.Thus, in 340 ml of beer, the caloric contribution of those components is about 90 (from ethanol) + 15 (from protein) + 15 (from fat) = 120 calories. What is the source of the additional 30 calories (i.e., 150 to 120)?
As discussed earlier in this chapter, the beer fermentation is considered complete or fully attenuated when the fermentable carbohydrates have been depleted. However, that is not to say that there are not carbohydrates in beer. In fact, wort contains a mixture of fermentable sugars (i.e., glucose and maltose), as well as more complex, non-fermentable sugars, in particular, dextrins and limit dextrins. The latter are a result of the incomplete hydrolysis of starch during the mashing step. Whereas the simple sugars are readily fermented, the complex carbohydrate fraction is not. Importantly, however, these carbohydrates are caloric, meaning they can be hydrolyzed to glucose during digestion, adsorbed into the blood stream, and either used as energy or stored as fat. Calories can be reduced by somehow reducing or removing the nonfermentable but caloric carbohydrates from beer.
The strategy that was adopted, and which is still used today, adds enzymes that hydrolyze a portion of the nonfermentable carbohydrates to form free sugars that are then fermented during the primary fermentation step.The enzymes are commercially available and inexpensive glucoamylases (derived from Aspergillus niger and other fungi). Added to the wort during mashing, the exogenous enzymes work in concert with the endogenous enzymes from the malt. Ideally, the fungal enzymes should be temperature labile so there is no residual activity after kettle boil.
Because more fermentable carbohydrate in the wort necessarily results in more ethanol in the beer (and at 7 calories per gram, would defeat the purpose, as well as add to the alcohol excise tax), the extra ethanol is ordinarily removed. The carbohydrate content of these beers is reduced from 9 g per serving to less than 3 g, resulting in a calorie reduction of 25 or more.Thus, a typical light beer contains 100 to 120 calories. Recently (in 2003), even lower calorie beers, containing fewer carbohydrate than conventional light beers,were introduced. These so-called "low-carb beers"are targeted to dieters on carbohydrate-restrictive diets. One popular brand contains only 2.6 g of carbohydrate and 95 calories per 340 ml serving.
An alternate strategy to the use of enzymes replaces even more of the malt or starch adjuncts with adjuncts consisting of simple sugars. For example, if sucrose, fructose, or glucose syrups were used as adjuncts, at the expense of malt, the dextrin fractions would also be reduced. Both of these approaches, however, provide thin-bodied beers, since it is the dextrins that contribute mouth feel and body properties to beer.
Several other approaches for reducing the dextrin (and caloric) content of beer have been considered, and are now being studied. Malt preparations with greater amylolytic activity can be used so hydrolysis of starch is more complete. Alternatively, brewers' yeast strains with greater amylolytic activity can be developed, either via conventional yeast breeding programs or by molecular techniques.The goal is to increase activity of amyloglucosidase, which breaks down a-1,4 and a-1,6 glucosidic linkages in dextrin.
Finally, there is a perception that low-calorie or low-carbohydrate beers also have a much lower alcohol concentration than normal beer. In fact, the alcohol content for most of these beers is somewhat lower, generally by 0.5% to 1.0% (or about 20% less). For example, three of the most popular brands of light beer in the United States each contain 4.2% alcohol (on volume basis), compared to 4.7% to 5% for their conventional counterparts. For other brands, the differences are less than 0.5%
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