Author ORCID Identifier

https://orcid.org/0000-0001-6698-3351

Date Available

7-31-2024

Year of Publication

2024

Degree Name

Master of Science in Biosystems and Agricultural Engineering (MSBiosyAgE)

Document Type

Master's Thesis

College

Agriculture, Food and Environment

Department/School/Program

Biosystems and Agricultural Engineering

First Advisor

Tosin Olayemi Olanrewaju

Second Advisor

Dr. Akinbode A. Adedeji

Abstract

The Commonwealth of Kentucky accounts for over 95% of global bourbon production. A primary byproduct of bourbon production is stillage, which has a very high moisture content (91–94%) and high biochemical oxygen demand, making it challenging to manage. The recent expansion of the bourbon industry has heightened environmental concerns regarding the best methods to handle this byproduct. Dewatering and drying of stillage produce distillers' spent grains (DSG-B), which are rich in dietary fiber and protein and could serve as an excellent source of functional fiber in human nutrition.

This study examined the approach for dewatering, drying, inclusion of DSG-B as dietary fiber source in extruded-expanded products, and evaluated the life cycle and economic feasibility of the whole process. The first objective study evaluated the kinetics of moisture removal in bourbon distilling waste and investigated the effects of drying temperatures on the physicochemical properties of the resulting DSG-B. It evaluated the activation energy, moisture diffusivity, and proximate content of the DSG-B. The activation energy was determined to be 19.91 kJ/mol, and moisture diffusivity values were , and at 45 oC, 55 oC and 70 oC, respectively. There was no significant difference in the physicochemical properties of DSG-B samples dried at 45 oC and 70 oC. In the second objective, an assessment of the impact of DSG-B addition on the physicochemical properties of enriched food products, specifically expanded cereals, was conducted. The expanded cereals were produced using a lab scale twin screw extruder with a feed rate of 58 g/min, barrel temperature of 125 oC, moisture level of 16.5% and screw speed of 400 rpm. The level of DSG-B addition changed the physicochemical properties of the expanded cereals examined. The third objective evaluated the economic feasibility of producing enriched extruded-expanded food products using SuperPro Designer software. The results indicated that increasing stillage (feedstock) usage in the production decreased unit production cost. The financial analysis showed a gross profit margin of 25.06%, return on investment of 27.62% with a payback period of 3.62 years. The fourth objective evaluated the environmental sustainability of the production process through a life cycle assessment (LCA) modelled on OpenLCA software using Ecoinvent v3.10 database, experimental data, and ReCiPe 2016 impact categories. The climate change impact of producing the enriched expanded cereal was estimated to be 2.09 kgCO2 eq per kg expanded cereals.

The study investigated the thermal treatment of bourbon stillage and its impact on the physicochemical properties of the by-products. It also assessed the techno-economic feasibility and environmental impact of incorporating DSG-B into expanded cereal production. The results indicate that DSG-B can be effectively utilized to produce high-quality, cost-effective, and environmentally friendly expanded cereals with nutritional benefits for consumers.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2024.278

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