Novel bigels based on walnut oil oleogel and chitosan hydrogel: Preparation, characterization, and application as food spread

This study developed new biphasic gel systems containing a walnut oil-based oleogel and a chitosan hydrogel and evaluated the application on food spread. The effects of different oleogelators [γ-oryzanol/β-sitosterol (γ-ORY/β-SIT), candelilla wax/span 65 (CW/SA), and mono- and diglycerides of fatty acids] were explored. Rheological analysis showed that γ-ORY/β-SIT-based bigel had the strongest gel strength, but XRD confirmed that β' crystal form (d = 3.72 Å, 4.12 Å) was predominantly in the CW/SA-based bigel, which was more appropriate for application as spread. The characteristics of CW/SA-based bigel with different oleogel fractions (40-80 wt%) were investigated. The microscopic images indicated that the hydrogels were dispersed as small droplets in the oleogels after oleogel fraction reaching 60 %. The highest crystallinity was achieved when the oleogel fraction was 60 %, and its oil binding capacity was 96.49 %. Textural analysis showed that the CW/SA-based bigel (OG-60 %) had similar properties with commercial spread B, and can be used as a partial replacement for spread B. Replacing 75 % of the commercial spread B with the bigel was found to be optimal and displayed acceptable sensory features. This study developed a healthy bigel based on walnut oil and provided the in-depth information for bigels as an alternative to plastic fats.