## 2 Results and Discussions
### Bioactive Properties
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Bioactive Property** & **HOC** & **FHOC** \\ \hline Soluble protein content (mg BSA/g) & 256.8 \(\pm\) 3.3 & 279.5 \(\pm\) 4.0 \\ Total peptide content (mg tripton/g) & 32.35 \(\pm\) 7.76 & 462.37 \(\pm\) 8.34 \\  & 4.67 \(\pm\) 0.02 * & 16.17 \(\pm\) 0.31 * \\ Total phenolic content (mg GA/g) & 0.12 \(\pm\) 0.00 ** & 5.71 \(\pm\) 0.29 ** \\  & 1.61 \(\pm\) 0.02 *** & 11.30 \(\pm\) 0.39 *** \\ ABTS cation radical scavenging activity & 19.94 \(\pm\) 0.41 & 75.61 \(\pm\) 0.62 \\ (\(\mu\)g trolox/g) & 2.90 \(\pm\) 0.17 & 14.09 \(\pm\) 0.24 \\ OH radical scavenging activity (mg ascorbic acid/g) & 239 \(\pm\) 1 & 265 \(\pm\) 1 \\ \(\alpha\)-Amylase inhibition activity (\%) & N.D. & N.D. \\ \(\alpha\)-Glucosidase inhibition activity (mg & 10.49 \(\pm\) 0.12 & 182.11 \(\pm\) 2.61 \\ acarbose/g) & 1.79 \(\pm\) 0.07 & 1.02 \(\pm\) 0.16 \\ ACE inhibition activity (\%) & 40.58 \(\pm\) 0.77 & 40.73 \(\pm\) 1.76 \\ \hline \hline \end{tabular} Values are given as mean \(\pm\) standard deviation. * aqueous extract, ** methanolic extract, *** 80% methanolic extract (in water). N.D.: not detected. HOC: hazelnut oil cake, FHOC: fermented hazelnut oil cake, BSA: Bovine serum albumin, GA: Gallic acid, ABTS: 2,2’-azino-bis(3-ethylbenzothazoline-6-sulfonic acid, DPPH: 2,2-diphenyl-1-picrylhydrazyl, OH: Hydroxyl, ACE: Angiotensin converting enzyme, AChE: Acetylcholinesteraseterase.  
\end{table} 
Table 7: Bioactive properties of HOC and FHOC. [PERSON] et al. (2015), while preparing the hazelnut samples to be fermented, separated the dark colored and phenolic-rich membrane surrounding the hazelnut kernel ([PERSON], 2015). This process is estimated to significantly reduce the phenolic content of the raw material. As [PERSON] et al. (2007) stated, the highest phenolic compound content is in the membrane covering the hazelnut kernel ([PERSON], 2015). In terms of content, the membrane is followed by the brown hard shell outside the hazelnut (about 50% of the phenolic component of the membrane). In parallel with the phenolic content, the membrane also showed the highest antioxidant activity. Antioxidants such as ascorbic acid,tocopherol, and polyphenols can stabilize radicals by giving electrons or hydrogen atoms to free radicals from their hydroxyl groups. In addition, they can prevent the formation of free radicals through various reactions by chelating ions such as Fe\({}^{2+}\), Fe\({}^{3+}\), Cu\({}^{2+}\), and Cu\({}^{+}\) in the environment ([PERSON], 2015). Similarly, proteins, especially peptides, can show antioxidant activity through the various mechanisms. Studies have shown that bioactive peptides with antioxidant activity are generally composed of 3-6 amino acid units and have molecular weights less than 1 kDa. Approximately 1/3 of these antioxidant peptides are composed of glycine, proline and leucine amino acids. In addition to these, it was determined that histidine amino acid with imidazole ring showed strong antioxidant activity due to its ability to give proton. Tryptophan and proline amino acids with indole and pyrrolidine groups can function as hydrogen donors through their hydroxyl groups. Amino acids with excess electrons, such as glutamic acid and aspartic acid, also have the ability to bind free radicals. In addition to these properties, the amino acid sequence of the peptide has also been reported to have a significant effect on antioxidant activity ([PERSON], 2015; [PERSON], 2015). There is an increasing interest in the inhibitors developed or discovered for enzymes that catalyze certain reactions in metabolism and cause undesirable conditions in the body. In this study, the inhibition activities of \(\alpha\)-amylase, \(\alpha\)-glucosidase, angiotensin converting enzyme (ACE), and acetylcholine esterase (AChE) of hazelnut meal were determined by fermentation process.