15A-24 |
Increased ester production in rum distillates using Propionibacterium thoenii and Clostridium propionicum stillage fermentations |
S. MAZA-GOMEZ1, W. H. Kampen2, and W. Prinyawiwatkul1. (1) Department of Food Science, Louisiana State University Agricultural Center, Baton Rouge, LA 70803-4200, (2) Audubon Sugar Institute, Louisiana State University Agricultural Center, Baton Rouge, LA 70803 Esters add a fruity-like aroma to rum. Yeast plays a central role in the aroma formation during rum fermentation, which is affected by bacterial contamination. Compounds produced by Propionibacterium thoenii and Clostridium propionicum affect rum aromas. This study (1) determined if additional esters and acids were produced by Propionibacterium thoenii and Clostridium propionicum without interfering with ethanolic-yeast fermentation, and (2) determined contributions of added fermented stillage to the rum aromas. Stillage with added-sugar was spontaneously fermented, filtered, sterilized, and inoculated with Propionibacterium thoenii or Clostridium propionicum. The resulting stillage was pH-adjusted to 8.0 and vacuum-evaporated. The sediment was rediluted with H2SO4 and high ethanolic distillates (“high wine”), and settled undisturbed. The filtered liquid was mixed with 10% normal yeast-fermented mash and distilled in glass-still. Acetic, propionic and butyric acids, ethyl-acetate, ethyl-propionate, and ethyl-butyrate were quantified using GC. Sterilization decreased propionic acid from 7,020 to 5,342mg/L in the initial stillage without affecting other analytes. After Clostridium propionicum fermentation trial, propionic acid was greater than acetic and butyric acids, and ethyl-butyrate. The highest %increase of acetic acid was observed. Although “high wine” contained some acids/esters, major contribution came from the Clostridium propionicum fermentation. After drying and re-diluting, 6,500mg/L ethyl-butyrate was produced. Transference of esters and acids to distillate was 50% and 20%, respectively. After Propionibacterium thoenii fermentation trial, propionic acid was greater than butyric and acetic acids. Major increment was found in butyric acid and ethyl-butyrate. Apart from ester formation, the reverse reaction (ester-deformation) may have occurred. Over 90% esters were transferred to the distillate, while acid transference was low. Bacterial fermentations produced final products with pleasant/sweet/fruity-like aroma, more noticeable in the distillates than in the only-yeast-fermentation distillates. Microbiologically acidifying the stillage and converting some acids into esters, incorporated into the final fermented mash for distilling, will improve rum aromas and shorten aging.
Session 15A, Biotechnology
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