Squalene, fatty acids, and minor oil constituents in silflower (Silphium integrifolium) oils from nine varieties grown in Minnesota

Authors: Hwang, Hong-Sik; Liu, Sean; NIEHAUS, MAXIM - University Of Missouri; SCHIFFNER, SYDNEY - University Of Minnesota; SMITH, KEVIN - University Of Minnesota; Moser, Jill

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2025
Publication Date: 1/15/2026
Citation: Hwang, H-S., Liu, S.X., Niehaus, M., Schiffner, S., Smith, K.P., Winkler-Moser, J.K. 2026. Squalene, fatty acids, and minor oil constituents in silflower (Silphium integrifolium) oils from nine varieties grown in Minnesota. Industrial Crops and Products. https://doi.org/10.1016/j.indcrop.2025.122590.
DOI: https://doi.org/10.1016/j.indcrop.2025.122590

Interpretive Summary: The drought tolerant perennial silflower is native to the central United States and is currently being domesticated as a potential oilseed crop. However, there are still many challenges that need to be addressed before the crop can be adopted in the United States as an economically profitable cash crop. ARS scientists in Peoria, Illinois, collaborated with researchers from University of Minnesota to understand the effect of growing conditions such as temperature and precipitation on oil content and properties. Silflower seeds from different plant varieties grown at three different locations in the Midwestern United States in 2022 and 2023 were analyzed. The scientists found that several important economic traits (oil quality and yield) of silflower seeds differ with plant variety and environment (rainfalls and temperature variation). In addition, the team discovered that some varieties produced high concentrations of squalene (up to 4.9% in oil), a valuable ingredient used in consumer care products. The high squalene content is significantly higher than other commercial sources like olive oil, which typically contain less than 0.75% squalene. This research helps farmers to better manage their crop planting for expanded market diversification and stability; and it provides breeders with the necessary tools to develop new breeding lines with high oil quality and high squalene content.

Technical Abstract: Our previous study found that silflower (Silphium integrifolium Michx.) seed oil had a squalane content and great potential as a new edible oil. The current study aimed to examine the squalene level and other properties with thirty silflower oils from nine genotypes grown in three locations in Minnesota in 2022 and 2023. Oil contents of 30 different seeds determined by hexane extraction of unhulled seeds were 19.41–25.92%, and squalene levels in oils were 2.98-4.07%. Two major fatty acids, linoleic acid (C18:2) and oleic acid (C18:1), were 66.52-73.62% and 15.25-20.32%, respectively. Contents of a-tocopherol, total phenolics, chlorophyll, free fatty acid, and total polar compounds contents were 277.5-765.6 ug/g, 16.29-33.97 mg GAE/100g oil, 179.2 mg/kg - 977.6 mg/kg, 0.07%-0.53%, and 5.21-11.18%, respectively. Correlations between oil properties and growing conditions during two different growing seasons, P1 (90 days until flowering) and P2 (flowering to harvest), were analyzed. Oil content had a positive correlation with P1 temperature. Squalene content in oil was higher with lower P1 precipitation and higher P2 maximum temperature and precipitation. Oleic acid content increased, and linoleic acid content decreased when P2 temperature and precipitation were high. In general, a-tocopherol, total phenolics, free fatty acids, and total polar compounds negatively correlated with P1 temperature and precipitation while chlorophyll level had the opposite trend. This study provides more data on the properties of silflower oil and preliminary insight into the factors affecting these properties.