Semester

Spring

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Kristen Matak

Committee Co-Chair

Jacek Jaczynski

Committee Member

Annette Freshour

Committee Member

Cangliang Shen

Abstract

Hemp seed cakes (HSC) are the byproduct of pressing hemp seeds for oil and are a significant agricultural waste product, with hundreds of tons produced annually. These nutrient-rich cakes have potential for sustainable applications in animal feed and food products. However, they could offer even greater value to the food industry through further extraction of the lipids and separation of the proteins they contain. Protein is a key nutritional component and companies are seeking cost-effective, time-efficient processes to concentrate protein from underutilized resources like HSC. Hexane (HEX) is a common solvent used in one-step defatting processes but may cause issue with consumers who want green processing in food products. Using alternative organic solvents such as ethanol (EtOH) may appeal to these consumers as EtOH is commonly found in beverages such as beer, wine, and liquor. Therefore, the first objective of the study was to determine the lipid extraction efficiency and proximate composition of HSC after one-step defatting by either HEX or EtOH. Each organic solvent was mixed separately with HSC in a 1:5 ratio (1:5 HSC: HEX or EtOH) for 18 hr. Lipid was separated from the remaining solid portion by Buchner funnel-assisted drying. Lipid reduction rate and proximate composition of the starting HSC and the HSC defatted using HEX or EtOH were determined. HEX achieved a greater lipid reduction rate (71.1%) than EtOH (18.7%) in defatted HSC. Both HEX and EtOH effectively removed lipids from the HSC; however, HEX-defatted HSC was more efficient, leaving only 3.29% lipid content after extraction, compared to 9.27% remaining with EtOH-defatted HSC following one-step defatting (P

The second objective of this study was to use a pH-shift process based on isoelectric solubilization and precipitation (ISP) to separate protein from HEX-defatted HSC. Proteins were solubilized using sodium hydroxide (NaOH), separated from remaining lipid and fibers, and precipitated using either glacial acetic acid (GAA) or hydrochloric acid (HCl). Proximate composition and protein recovery yield between the use of GAA and HCl were determined. There were no significant differences (P>0.05) in protein recovery yield between GAA and HCl, with an average of approximately 8% protein (protein-to-nitrogen conversion factor = 5.3) extracted from defatted hemp seed cake flour. Proximate composition of the extracted protein showed significant differences in concentrations of protein and lipids from the defatted HSC, regardless of precipitation acid, with the concentration of protein increased above 80% and the lipids reduced to less than 10% (NCF= 5.3). Results of this study confirmed that both HCl and GAA are effective at recovering protein from HSC using a pH-shift process. These protein isolates have potential in the food industry as a value-added ingredient to improve the nutrient profile of food products.

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