## 1 Introduction  
Spontaneous fermentation has been used for the traditional manufacturing of beer, wine and apple cider. However, use of spontaneous fermentation is rare in beer manufacture because of the lack of control over the fermentation process; nevertheless, lambic beer is still being produced through spontaneous fermentation. Lambic beers are traditionally produced within fifteen kilometers of Brussels [1, 2]. The Senne Valley and the surrounding region provide favorable conditions for spontaneous fermentation to occur. The concentration of fruit orchards and traditional farmhouse breweries provide an ideal environment for wild yeast and bacteria to become air borne so they can reside in the breweries that make lambic beer [3]. The brewing season for lambics begins in September and continues until sometime in April [4]. The tradition is to brew lambic beers during the colder months of the year to prevent the potential spoiling of the wort during the warmer summer months. The wort is allowed to cool overnight in open shallow trays (coolships) and is inoculated by the natural microflora present in the surrounding environment. Once the wort has finished cooling overnight, it is pumped into metal or wooden casks and stored in non-air-conditioned warehouses. The temperature in these warehouses can vary from 0 to 25 \({}^{\circ}\)C [1, 2]. Lambic beers are unique in that they are still being produced using spontaneous fermentation. The fermentation process of lambics can be divided into four distinct stages, with microorganisms contributing key flavor and aroma compounds within each stage. _Hanseniospora uvarum_, formally known as _Kloeckera apiculate_ (a wild yeast) and enteric bacteria dominate the first stage of fermentation. The secondary stage of the fermentation process is dominated by _Sacchromyces sp._ followed by lactic acid bacteria (LAB) in the third stage. _Brettanomyces_, also known as brett, is a wild yeast often associated with the spoilage of red wines and ciders. In lambic beers, brett imparts expected, positive flavor characteristics and brett dominates the fourth and final stage of fermentation [5]. As noted earlier, the initial stage of fermentation for lambic beer is dominated by enteric bacteria and the yeast _H. uvarum_. The actual fermentation process begins three to seven days after the word has been cooled. _H. uvarum_ quickly reaches its maximum concentration of \(10^{5}\) cells/mL within the first week of fermentation, but is quickly out-competed by _Saccharomycesces_. _H. uvarum_ only has the ability to ferment glucose and not maltose or more complex carbohydrates. _Enterobacteriaceae_ and _H. uvarum_ are both fast growing microorganisms and they cause the pH of the word to drop from around 5.1 to 4.6. This pH drop is due to the production of acetic and lactic acids [6]. The second and third stages of fermentation actually overlap one another. The third stage of fermentation begins three to four months after the beer has been brewed. The third stage is dominated by lactic and acetic acid bacteria both peaking around six to eight months, which usually correlates with the warmer summer months. Warmer temperatures are essential for the growth of both lactic and acetic bacteria [6]. The sourness associated with lambic beers can be contributed to by the presence of lactic acid produced by lactic-acid-producing bacteria [6; 7]. The majority of the lactic acid present in lambic beer fall within the _Pediococcus_ genus. While some strains of _Pediococcus_ have been found to be beneficial in beer, others have the ability to produce a \"ropy\" surface layer that will leave the beer with a permanent haziness. While lactic acid is desirable, acetic acid bacteria as well as _H. uvarum_ are undesirable in this particular style of beer because they each have the ability to convert ethanol into acetic acid, causing the beer to become acidic or hard.