Factors Influencing Content and Availability of Lutein and Zeaxanthin in Distiller's Grains

Visual impairments are prevalent among aging populations, often leading to conditions such as cataracts and age-related macular degeneration. Lutein and zeaxanthin supplements have been touted for their protective properties within the retina. These carotenoids, which cannot be synthesized by humans, must be obtained through diet or supplements. Marigold flowers are the current primary commercial source for supplements, but the extraction process is solvent, land, and labor-intensive. An alternative source exists in bioethanol production, where dried distiller’s grains and solubles (DDGS) are produced in large quantities and contain significant levels of lutein and zeaxanthin. The present study investigated the optimal extraction conditions for these carotenoids from distiller’s grains using Soxhlet extraction and analyzed using RP-HPLC. Factors such as solvent type (ethanol, ethyl acetate, water), solids loading (30, 35, 40 mL/g), and grain moisture (wet or dry) were statistically examined. In addition to extraction conditions, DDGS from five Indiana bioethanol facilities were analyzed for yield variability using the predetermined optimal extraction conditions. The DDGS sources were compared using nonparametric ANOVA to evaluate the stability of yield across different facilities. It was determined that the combination of ethanol and dried grains (DDGS) was optimal for maximum extraction yield. Solid loading was statistically insignificant, while solvent and material type, along with their interaction, were significant in determining yield (α = 0.05). Lutein yield variability between the five facilities was statistically insignificant, indicating consistent lutein content regardless of sourcing. However, zeaxanthin content varied significantly, suggesting potential challenges in implementing DDGS into a large-scale supply chain. Bioethanol facilities follow standard operating procedures, but variations in production processes lead to differences in grain quality. Further research is needed to understand how each unit operation affects the biochemical properties of lutein and zeaxanthin and the feedstocks upstream of DDGS that may concentrate these carotenoids. These studies demonstrate the clear need for further research to optimize extraction processes and ensure consistent quality of lutein and zeaxanthin from DDGS, paving the way for a sustainable and scalable alternative to marigold-derived supplements.