On-Line Estimation and Control of Apparent Extract Concentration in Low-Malt Beer Fermentation

Abstract

Apparent extract concentration, which is defined as the apparent total dry matter concentration in the media calculated by measurement of the specific gravity, is a very important variable in the process of beer and low-malt beer fermentation. In the present study, ethanol formation and the residual apparent extract concentration were estimated using the CO 2 concentration in the exhaust gas. A simple mathematical model involving the CO 2 production rate, temperature and cell activity was constructed and a novel system for on-line estimation and control of apparent extract concentration was developed. In the control system for the residual apparent extract concentration, cell activity was estimated by monitoring the differences in actual CO 2 production rate. In addition, the future trajectory of the apparent extract concentration was predicted. The degree of fermentation, i.e., the residual apparent extract concentration trajectory, was controlled by raising or lowering the temperature, taking into account the estimated cell activity at that time. The residual apparent extract concentration reached the target value at a given time, using the on-line estimation of apparent extract concentration and temperature control.

Influence of valine and other amino acids on total diacetyl and 2,3-pentanedione levels during fermentation of brewer’s wort

“…The apparent extract (AE; in degree Plato) of the samples was estimated from the previously measured specific gravities (SG) using the approximations from Kobayashi et al (2005b). The apparent attenuation (AA; %) of the samples was estimated from the apparent and original extract (i.e.…”

Beer Volatile Compounds and Their Application to Low-Malt Beer Fermentation

“…There are many predictive models of volatile compound formation based on fundamental knowledge of biochemical pathways (40,41); however, the models cannot be applied to actual production sites because fermentation progress indicated by sugar uptake cannot be estimated in situ. Although cell growth cannot be predicted, changes in the specific gravity of wort, an index of fermentation progress, by monitoring CO 2 concentration in exhaust gas has recently been developed (42). Such a CO 2 concentration parameter is valuable because it is measurable during static fermentation.…”

Calculation of pressure growth during fermentation in a closed container.

“…Při kvašení vzniká relativně velké množství tohoto plynu, jehož měření na výstupu z tanku je snadné, přičemž se používá různých principů (Venturiho trubice, ochlazování termočlánku, ultrazvuk) (Kobayashi a Hiroshima, 2005).…”

“…When large amount of gas is formed the measurement is easy using various principles (Venturi tube, thermocouple flowmeter, ultrasound) (Kobayashi and Hiroshima, 2005).…”