Abstract
Concentrated, non-purified juice can be produced from industrial beets and stabilized to retain sugars and extend the processing campaigns of newly envisioned, nonfood fermentation industries. However, pre-storage juice concentration and acidification (to enable long-term sugar retention), and post-storage juice conditioning (to enable ethanol fermentation) could impact yeast (Saccharomyces cerevisiae) performance. In this work, ammonium and sodium salts were synthesized in diffuser juice acidified from pH 6.5 to 3.5 with one of three mineral acids—hydrochloric, sulfuric, or phosphoric—and partially neutralized to pH 4.8 with one of two bases—sodium hydroxide or ammonium hydroxide. Alternatively, juice was directly supplemented with salts in the quantities synthesized in situ. A follow-up experiment was conducted to confirm the effects detected on yeast fermentation of sugars in diffuser juice. This experiment involved concentrated, non-purified juice acidified from pH 6.4 to 3.5 with only sulfuric acid, and partially neutralized to pH 4.8 with either sodium hydroxide or ammonium hydroxide. In both experiments, the only effects detected on yeast fermentation were beneficial and resulted from ammonium salts, either synthesized or added to the juice. Ammonium-salt cations increased total Kjeldahl nitrogen (TKN) in diffuser juice by 40% to 60%, which almost doubled yeast ethanol production rates between 6 h and 12 h. Although ammonium cations increased TKN in concentrated juice by about 20%, this resulted only in slight improvements in ethanol production rates. Pre-storage acidification and post-storage partial neutralization of concentrated beet juice could be used to synthesize ammonium salts that can improve yeast fermentation rates.
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