Fuzzy predictor for fermentation time in a commercial brewery

Abstract A study was conducted at a commercial brewery to investigate the feasibility of an expert-system control strategy that used fuzzy logic to make inferences based on uncertain process information. The predictor made an initial estimate of fermentation time based on the yeast variables (pitching rate, pitched volume and viability). The predicted fermentation times were within 24 h of the actual fermentation time for 9 batches in the validation data set of 13 process histories. A second rule set followed the pH and specific gravity during fermentation and predicted the level of vicinal diketone (VDK). When the VDK level reached a threshold level, a third rule set updated the estimate of time required to complete the fermentation. Seven data sets were used to validate the predictions based on VDK level and 4 estimates were within 24 h of the recorded fermentation release times. All 7 predictions were within 32 h of the actual release time and 6 of the 7 estimates indicated that the batches were held longer than necessary.