## 2 Results and Discussions
### Functional Properties of HOC and FHOC
As a result, hydrophobic interactions increase, allowing proteins to interact with more oil molecules [2; 125]. An emulsion consists of two immiscible liquid systems where one of the liquids is dispersed as small spherical droplets into another liquid, formed by mechanical energy [126]. For a formation of a homogenic emulsion system, a small concentration of surfactant which is a compound has the ability to bind both hydrophilic and hydrophobic groups is needed. The stable emulsion systems are required for food formulations; therefore, the emulsion formation ability is one of the important technicolor factors of food components as flours, cakes, and protein to assess their usability in food production. In this study, the emulsion activity index (EAI) was measured for HOC and FHOC and the values were 42.32 \(\pm\) 2.18 and 36.74 \(\pm\) 1.42 m\({}^{2}\)/g, respectively. However, the fermentation process was not considerably affecting the EAI of FHOC, the emulsion stability of HOC and FHOC was significantly different from each other. The emulsion stability index (ESI) of HOC was 175 \(\pm\) 10 min after 60 min incubation at 25 \({}^{\circ}\)C while ESI of FHOC was 763 \(\pm\) 32 min (Figure 2). This ESI of HOC was considerably higher than the ESI of emulsion formed by defatted hazelnut cake in another study conducted by [PERSON] et al. (2015) [121]. They found the ESI value of their sample as 31.9 \(\pm\) 2.43% after ten minutes incubation while ESI of our sample was 31.70 \(\pm\) 4.47% after 15 min incubation. [PERSON] and [PERSON] (2021) reported that the 33 emulsions produced by different soybean meal had ESI values varied between 59.30 \(\pm\) 1.16 and 79.51\(\pm\) 1.6% after 30 min incubation where the ESI was 81.26 \(\pm\) 6.86% for the emulsion by HOC [123]. On the other hand, [PERSON] and [PERSON] (2021) determined increased ESI stability more than 100% for mustard, flaxseed, and soybean cake when the emulsions were heated at 80 \({}^{\circ}\)C for 30 min [61]. The similar method was applied by [PERSON] et al. (2021), who determined the emulsion stability of sample produced by sunflower oil cake was 27.92 \(\pm\) 0.57% [122]. The remarkable emulsion stability in FHOC might be attributed to the exposed hydrophobic groups or partially hydrolyzed proteins by metabolic activity of the microorganism. Moreover, more protein compounds were also produced during fermentation which might be contribute to emulsion stability of FHOC. The emulsion stability of the cakes was monitored for 1440 min and the stability measurements were also determined at 15 th, 30 th, 45 th, 60 th, 180 th, and 1440 th minutes of incubation. The decrease in emulsion stability of HOC was dramatic by time while the slight stability decrease was observed in emulsion formed by FHOC. After 1440 min (24 h) of incubation, 37.72% of stability emulsion formed by HOC was lost. In contrast, the emulsion formed by FHOC only lost 71.6% of its stability. Foam is defined as a system where the air is dispersed in a liquid and separated by a thin continuous liquid layer [121]. The foaming capacity (FC) is expressed as the formed foam volume in the tube by mechanical energy. The FC of HOC was 10.96 \(\pm\) 1.41 mL, which was almost two times more than the FC of hazelnut oil cake prepared at pH 9.5 and 5.0 by [PERSON] et al. (2015) [121].