Author ORCID Identifier

https://orcid.org/0009-0009-0001-1010

Semester

Summer

Date of Graduation

2025

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Division of Animal and Nutritional Sciences

Committee Chair

Kristen Matak

Committee Co-Chair

Jacek Jaczynski

Committee Member

Cangliang Shen

Committee Member

Janet Tou

Committee Member

Cassaundra Miller

Abstract

Commercial food processing creates side-streams that are often underutilized yet hold significant potential for valorization into value-added products for consumer use. This study investigated and compared potential protein recovery and lipid removal potential from buckwheat (BW; Fagopyrum esculentum Moench), brewer’s spent grain (BSG), and coffee silverskin (CSS) using a one-step solvent defatting and a pH-shift protein extraction method. The extraction efficiency yields of extracted protein from CSS were significantly lower than all other samples (p < 0.05). The defatted BW had the highest extracted protein content of all samples (p < 0.05). The sizes of the proteins in the starting materials were observed using LDS-PAGE. These sizes were consistent with published values and were mostly unchanged by defatting or the pH-shift process. The presence of 13S globulins and 2S albumins was confirmed under reducing conditions. Protein extracted from all native samples had lower total free essential amino acids than the starting materials. Native CSS and extracted protein followed this trend, but in defatted CSS and respective extracted protein samples, the extracted proteins had higher free essential amino acid content than the starting materials, sometimes of twofold or greater (p < 0.05). After defatting, the percentage of lipids recovered compared to the original lipid content of the samples was measured. The crude fat content of native and hexane-defatted BW flour was higher than BW flour defatted with ethanol (p < 0.05). The lipid extraction efficiency of all samples ranged from 4.6 ± 1.26%–43.20 ± 14.21%. The mass of the native and defatted starting materials were recorded at each step of processing, with reasonable losses assessed. The major non-polar lipid classes in each starting material were separated using thin-layer chromatography. All samples also displayed the presence of polar lipids. When comparing starting materials, BW and BSG was the most effective for protein extraction, and BSG has the most promise for lipid removal and potential for upcycling. All the examined starting materials show promise for use in food supplementation, especially as native flours. These products are plentiful and considered underutilized or side-stream products.

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