NON-VOLATILE ORGANIC ACID AND pH CHANGES DURING THE FERMENTATION OF DISTILLER'S WORT

Abstract

The only non‐volatile organic acids found in significant amounts in distiller's wort were citric and malic acids. During the fermentation of penicillin‐treated wort by yeast, the levels of citric and malic acid remained unchanged, succinic acid appeared and small amounts of lactic acid were also found. Without added penicillin, citric and malic acids disappeared, succinic acid was produced as before and lactic acid appeared in large amounts especially towards the end of the fermentation period of 65 hr. After 16 hr. fermentation, the pH of penicillin‐treated wort had fallen from 5·6 to 3·6; by 40 hr. it had risen to 4·2 and by 65 hr. to 4·4; without added penicillin the changes up to 40 hr. were similar but the final pH at 65 hr. was 3·8. These pH changes are considered to be due first to the production of organic acids and loss of wort buffering power during the period of rapid yeast growth, secondly, to a period of yeast autolysis which returns to the fermenting liquor phosphate buffering capacity and, finally, to wash lactic acid.

Impact of nanoparticle inclusion on bioethanol production process kinetic and inhibitor profile

“…Similarly, the degradation products depend on operating conditions and could be regulated by controlling the process parameters. In addition, the formation of organic metabolites also occasion by the amounts of enzymes and co-factors such as nickel and iron present, thus, from enzyme regulatory mechanisms, and the need to maintain a relatively steady intracellular pH [ 63 ]. Inclusion of metallic supplement in bioprocessing performs various functions such as enzyme activator, enzymes stabilisers, enzymes cofactor, growth factor and chelating of other compounds hence, reducing their toxicity [ 57 ].…”

Impact of buffering capacity on the acidification of wort by brewing-relevant lactic acid bacteria

“…The temperature of the proteolytic rest also corresponds to the activation of malt phosphatases ( T opt = 49–51°C), which release inorganic phosphorus mainly bound as phytic acid in grains . Both nitrogenous compounds (amino acids and peptides) and phosphates have long been considered as the most important buffering substances in wort . However, a recent study by Li et al questioned the relevant contribution of both free amino acids and phosphates to the overall BC.…”

Study on the buffering capacity of wort

“…There is little published research regarding the buffering capacity of wort and its effect on beer production in the literature. Of course, there is literature that indicates that loss of buffering substances during fermentation substantially affects the fall in pH , and that this is probably due to important buffering substances in wort . In the present study the effect of the buffering capacity of wort on beer production and the contribution of some constituents in wort to the buffering capacity of wort were investigated.…”

“…They inferred that the direct excretion of H + by yeast accounts for this discrepancy. There is another study suggesting that loss of wort buffering capacity during fermentation is an important reason for the fall in pH , and that amino nitrogen compounds and phosphate are the important buffering substances in wort and their assimilation illustrates the pH fall during beer fermentation.…”