## 6 Effects of Roasting on Polyphenol Content
### Hazelnuts
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Nuts**} & \multirow{2}{*}{**Analytical Method**} & **Phenolic Content in Raw** & **Roasted Condition** & **Phenolic Content in** **Roasted Nuts** & **References** \\ \hline \multirow{4}{*}{Hazelnuts} & \(\begin{array}{c}\text{Folin-Ciocalteu}\\ \text{assay}\end{array}\) & 178–727 mg GAE/100 g & \begin{tabular}[]{c} Forced-air oven at \\ 140 \({}^{\circ}\)C for 30 min \\ \end{tabular} & 50–195 mg GAE/100 g & \\ \cline{2-5}  & \(\begin{array}{c}\text{Folin-Ciocalteu}\\ \text{assay}\end{array}\) & 150 mg GAE/100 g & \begin{tabular}[]{c} Conventional oven at \\ 180 \({}^{\circ}\)C for 20 min \\ \end{tabular} & 170 mg GAE/100 g & \\ \hline \multirow{4}{*}{Almonds} & \(\begin{array}{c}\text{Folin-Ciocalteu}\\ \text{assay}\end{array}\) & 750 mg GAE/100 g & \begin{tabular}[]{c} 200 \({}^{\circ}\)C for 5, 10, or \\ Gallic acid: 4 mg/100 g \\ \end{tabular} & 200 \({}^{\circ}\)C for 5, 10, or \\  & \(\begin{array}{c}\text{HPLC-PDA}\\ \text{Allords}\end{array}\) & \begin{tabular}[]{c} Total content: 480 mg/100 g \\ Gallic acid: 4 mg/100 g \\ \end{tabular} & 200 \({}^{\circ}\)C for 5, 10, or \\  & \(\begin{array}{c}\text{HPLC-PDA}\\ \text{Allords}\end{array}\) & \begin{tabular}[]{c} Total content: 420 mg/100 g \\ Gallic acid: 4 mg/100 g \\ \end{tabular} & 200 \({}^{\circ}\)C for 5, 10, or \\  & \(\begin{array}{c}\text{HPLC-PDA}\\ \text{Allords}\end{array}\) & \begin{tabular}[]{c} Total content: 420 mg/100 g \\ Gallic acid: 13 mg/100 g \\ Gentisic acid: 120 mg/100 g \\ \end{tabular} & 200 \({}^{\circ}\)C for 5, 10, or \\  & \(\begin{array}{c}\text{Folin-Ciocalteu}\\ \text{assay}\end{array}\) & 580 mg GAE/100 g & \begin{tabular}[]{c} Rotating drum \\ roaster at 110 \({}^{\circ}\)C for \\ 16 min \\ \end{tabular} & 840 mg GAE/100 g & \\ \hline \multirow{4}{*}{Pistachios} & \(\begin{array}{c}\text{Folin-Ciocalteu}\\ \text{assay}\end{array}\) & 480 mg GAE/100 g & \begin{tabular}[]{c} Unknown \\ (commercial samples) \\ \end{tabular} & 448 mg GAE/100 g & \\ \cline{2-5}  & \(\begin{array}{c}\text{Total content: 130 mg/100 g}\\ \text{Gallic acid: 13 mg/100 g}\\ \text{Gentisic acid: 120 mg/100 g}\end{array}\) & \begin{tabular}[]{c} Unknown \\ (commercial samples) \\ \end{tabular} & \begin{tabular}[]{c} Total content: 230 mg/100 g \\ Gallic acid: 1810 mg/100 g \\ Gentisic acid: 210 mg/100 g \\ \end{tabular} \\ \hline \multirow{4}{*}{Pistachios} & \(\begin{array}{c}\text{Total content: 26 mg/100 g}\\ \text{Protocatechuric acid:}\\ \text{HPLC-DAD}\end{array}\) & \begin{tabular}[]{c} Total content: \\ Single roasting at \\ 3 mg/100 g \\ Chlorogenic acid: 4 mg/100 g \\ 4 mg/100 g \\ \end{tabular} & 20 \({}^{\circ}\)C for 20 min and \\  & \(\begin{array}{c}\text{Second rooting at}\\ \text{Second rooting at}\\ \text{160 ${}^{\circ}$C for 22 min}\\ \text{Chlorogenic acid:}\\ \text{4-6 mg/100 g}\end{array}\) & 32–42 mg/100 g & \\ \hline \multirow{4}{*}{\begin{tabular}{c} Sodium \\ borohydride/chloranil \\ assay (SBC) \\ \end{tabular} } & 62.5 mg CE/100 g & \
\begin{tabular}[]{c} Unknown \\ (commercial samples) \\ \end{tabular} & 42.7 mg CE/100 g & \\ \cline{1-1} \cline{2-5}  & \(\begin{array}{c}\text{Folin-Ciocalteu}\\ \text{assay}\end{array}\) & 670 mg GAE/100 g &
\begin{tabular}[]{c} Rotating drum \\ roaster at 110 \({}^{\circ}\)C for \\ 16 min \\ \end{tabular} & 1050 mg GAE/100 g & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparison of the main polyphenolic compounds in three nuts in both raw and roasted conditions. GAE: Gallic acid equivalent; CE: Catechin equivalent. to the removal of the perisperm--the brown skin that envelops the seed. This leads to a decrease in antioxidant activity. It is well known that the perisperm is a significant source of polyphenols, containing levels over 40 times higher than the kernel [82]. [PERSON] et al. (2018) reported that removing the skin can decrease the amounts of phenolics by 59-79% compared to hazelnuts with skin.