Page 104

T

his is the first in an anticipated series of notes covering the general chemical principles behind the flavors in alcoholic beverages. A vast assortment of fruit and vegetable raw materials find their way into beverage production today — think flavored vodkas and gins for starters, as well as liqueurs (1). In addition, fermentative yeasts and even other microorganisms are at play in producing metabolites that are both volatile and flavorful and add to the rich tapestry of flavors we find in our alcoholic beverages. Flavor molecules are comparatively strong-smelling, low molecular weight and low boiling point organic compounds with characteristic and usually pleasant odors. Though unpleasant aromas can arise if careful control of spirits production is not ensured (2). Volatile chemical compounds are thus involved in our sensory perceptions. Describing them is not always an easy task yet understanding a little of the chemistry involved goes a long way towards the appreciation of the highly complex and nuanced world of taste and flavor. By way of an introduction to the vast array of flavors Table 1 presents a generalized list of flavor descriptors and associated generic descriptive notes. These terms will form a solid platform on which to build the necessary sensory vocabulary in understanding flavors described in this article and the forthcoming papers in the series. In addition, the Spring 2018 issue of Artisan Spirit provided a discussion of the latest findings in our understanding of human sensory perception and will be a good companion article to this new series (3). This short series will thus consider flavors derived from or that are reminiscent of fruit, flowers, herbs and spices or, in other words, those derived from or emanating from a wide array of plant-based raw materials or from fermentation. In certain cases, raw or fresh ingredients may be used. Today, with careful extraction techniques the resultant purees or essences of authentic fruit, herbs or spices allows for desired flavors to be conveyed to the beverage of choice. In addition, yeast choice and control of fermentation can lead to fruity ester formation and add other flavor nuances by providing some of the same components that are derived through plant metabolism. Controlling all variables is both science and art, design and balance. For this first part we start with fruit flavors — the citrus, fruity, and green attributes noted in Table 1.

CHEMISTRY & THE LANGUAGE OF FLAVOR As noted in the introduction, the odors of single chemical compounds are extremely difficult to describe unequivocally (2,3). The odors of complex mixtures are often impossible to describe unless one of the components is so characteristic that it largely determines the odor or flavor of the entire composition. However, while an objective classification is not possible, an odor can be described by adjectives such as flowery, fruity, woody, or hay-like, which relate the fragrances to natural or other known products with similar odors (Table 1) (3). As noted

104 

in Reference 3 and below, one uses terms like those in Table 1 and then delves deeper into the meaning and relevance of that first impression. This is the only way — using language and a vocabulary to unravel the complexity of a spirit or other beverage’s flavor profile.

FLAVORS & VOLATILITY Over 10,000 volatile compounds have so far been detected in foods — yet only several hundred are noted as aroma compounds (4). Those of high odor value (a term noted as OAV or odor activity) have been determined. An OAV or odor unit/ odor value is used to estimate the odor potency of a compound in terms of the ratio of the concentration of that volatile compound to its odor detection threshold. The detection threshold is the concentration of that substance at which it is positively identified on a statistical basis by human subjects. We learn this for general foods, beverages and other items as we develop through childhood or, later, with training on specific foods or beverages of interest — whiskies, gins, rums etc. This then makes us better tasters, judges or sensory panelists etc., (see 3). For many though no second thoughts are given once it is established that the meal or drink before them is “good enough." We must learn to appreciate more fully the raw materials, the processes and the final, hopefully pleasing and potable, products we deal with. While there is much more information in the literature on all of this, the point to be made here is that, through many different chemical groups, there are chemical families or classes that exhibit a set of general “flavor characteristics” when it comes to flavor profiling. Once we have the general classes and characteristics noted (and memorized) we can begin to drill down into the more specific flavor nuances — Apple? Yes. Green, red, sour, sweet apple and so forth. These flavor impressions in our brains are conveyed by the classes of chemical species of low molecular weight and of high volatility. In using several different fruits, herbs or botanicals in a formulation many of the same or related volatile components will add to the concentration of those species present in the beverage and maybe raise the concentration to detection threshold levels. These additions could become balanced or unbalanced, or certain notes become enhanced in combination with related or unrelated classes of constituents or even masked-off from perception. Understanding how flavors play together is crucial to quality control. And is why the big distillation and brewing companies implement sensory programs and train staff to become experienced tasters. Even on a small scale, tasting raw materials and products on the way to the final packaging, and even beyond, makes good sense! To summarize, beverage flavors that delight the senses through their perception must be volatile to be perceived. Chemical functional groups, the molecular structure and the chemical mass of flavorants are important factors in this WWW.ARTISANSPIRITMAG.COM

Artisan Spirit: Fall 2018  

The magazine for craft distillers and their fans.

Artisan Spirit: Fall 2018  

The magazine for craft distillers and their fans.