Cold Contact Fermentation (CCF), or Cold Contact Process (CCP), is one of the many methods of producing beer with little to no alcohol content through a combination of low fermentation temperatures and extended fermentation contact times. Though this method was first discovered in 1983, its importance in academic and industrial circles has risen only recently, parallel to the rising demand for alcohol-free beer (AFB) recorded worldwide. For the discussion of this topic, the origins of AFB and the current market perspective of the sales and consumption of low or alcohol-free beer (L/AFB) serves as an introduction, followed by an exploration of the various methods of producing L/AFB. After these two introductory sections, an in-depth discussion of the biochemical pathways present in fermentation is presented as well as the mathematical basis upon which fermentation modeling stands in the form of differential and algebraic equation (DAE) modelling. Finally, a sequential review of the organoleptic properties of beer and the previously published fermentation system models in literature segues to the critical evaluation of this study. CCF, either with the use of free mass or immobilized yeast, is considered one of the best available production methods for producing AFB given the relatively minor additional capital investment and the ability to meet the various ethanol concentration specifications. However, several issues are discussed, most notably the difficulty reported in attenuating the contributions of negative flavor compounds that are generally reduced to higher degrees during standard fermentation practices.
The increased commercial presence and comparative health benefits of alcohol-free beer (AFB) provide a substantial impetus for research, particularly in the field of dynamic simulation whereby the development of accurate models can help reduce costs of experimentation. Cold Contact Fermentation (CCF) is an existing method of industrialscale AFB production that utilises reduced fermentor temperatures and altered contact times compared to Warm Fermentation (WF), though requiring continual attention given the production of non-optimal organoleptic compositions, which drastically affect taste. In order to better understand the differences between Warm Fermentation (WF) and CCF, a DAE system is constructed based on previous WF studies whose responses are compared vis-à-vis to simulations of the same model under industrial CCF conditions. Given the significant discrepancies between dynamic results, industrial data can be for the parametrisation of a new CCF model, in order to accurately portray plant operation. Further to these simulations, the sensitivity of final species concentrations to parameter variation and the effect of hypothetical temperature profiles are studied with the aim of evaluating model system flexibility and opportunities for improvement based on changes to fermentor temperature profiles. Overall, disparate relative ethyl acetate sensitivity and clustering of hypothetical CCF responses reflect existing challenges with flavour composition but highlight opportunities for remarkable process improvements.
Global demand for Low-Alcohol Beer (LAB) and Alcohol-Free Beer (AFB) has surged due to flavor attributes, health benefits, and lifestyle changes, prompting efforts for process intensification. This paper aims to offer a detailed modelling basis for LAB manufacturing study and optimisation. A first-principles dynamic model for conventional beer manufacturing has been re-parameterized and used for dynamic simulation of Cold Contact Fermentation (CCF), an effective LAB and AFB production method, with concentrations tracked along plausible temperature manipulation profiles. Parameter estimation is pursued using industrial production data, with a detailed local sensitivity analysis portraying the effect of key parameter variation on sugar consumption, ethanol production, and key flavor component (ethyl acetate and diacetyl) evolution during (and final values after) CCF. Ethyl acetate (esters in general) affecting fruity flavors emerge as most sensitive to CCF conditions.
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