Beet tissue ensiling: An alternative for long-term storage of sugars in industrial beets for nonfood use

Abstract

Industrial beets have significant potential to compete against corn grain as an important source of sugars for nonfood industrial processes including microbial bioconversions. However, dependable, long-term storage techniques are necessary to extend processing campaigns and meet increasingly-important industry requirements such as carbon footprint reductions. This work evaluated the potential of industrial-beet tissue ensiling as an alternative for long-term sugar storage. Ground industrial-beet tissue was ensiled for 8 wk at 23 °C and various combinations of pH, moisture content (MC), and sugar:solids (SSR). The pH, MC, and SSR values ranged from 2.0 to 6.8, 50%–85%, and 38%–76%, respectively, according to a central composite rotatable design. Response surface methodology was used to model and illustrate effects of parameter combinations on beet sugar retention. MC and pH had statistically significant effects on sugar retention in beet tissue silage, whereas SSR had no significant effect. Only some combinations of pH ≤ 4.0 and MC ≤ 67.5% enabled the highest sugar retentions in ensiled tissue (≥ 90%). Moreover, tissue ensiled at pH ≤ 3.0 and MC ≤ 67.5% showed increases of ≤ 7% over initial sugars after 3 d of ensiling, suggesting that highly acidic conditions may partially hydrolyze beet tissue cellulose and/or hemicellulose during storage. In contrast, tissue ensiled at some combinations of pH < 6.5 and MC > 67.5% only achieved sugar retentions of < 30% at 8 wk. Sulfuric acid cost estimates (on a dry-sugar basis) to achieve effective pH (2.0–4.0) for sugar retentions ≥ 90% range from $4.9 Mg−1 to $18.6 Mg−1.