## 2 Nutrition Profile of Hazelnuts, Almonds and Pistachios
### Almonds  
Nowadays, the USA is the leading producer of almonds, accounting for nearly 66% of worldwide production, primarily concentrated in California, followed by Spain [16].  
The lipids in almonds primarily consist of storage lipids, present as intracellular oil droplets in the cotyledon tissues of the kernels. These lipids are predominantly composed of mono- and polyunsaturated fatty acids. Generally, the lipid content of almonds ranges from 44% to 61%, influenced by factors such as local genotype selection, growing region, climatic conditions, and environmental interactions. Numerous studies report that mono-nunsaturated fatty acids predominate, accounting for 62-80% of the oil content, with over 90% composed of oleic acid and linoleic acid. The remaining less than 10% is composed of saturated fatty acids [17]. [PERSON] et al. (2021) reported that unsaturated fatty acids comprise oleic acid (58.1-71.3%), linoleic acid (15.7-29.9%), palmitoleic acid (0.20-0.62%), and vaccenic acid (0.77-2.17%). In contrast, saturated fatty acids are represented by palmitic acid (5-9.75%), stearic acid (1.0-2.4%), and arachidonic acid (0.07-0.1%) [18].  
Polyphenols are concentrated at the lipid-water interface. They are responsible for almond quality, nutritional properties, and increased shelf life. Gas chromatography-mass spectrometry (GC-MS) analysis has identified 0.312 g of polyphenols per 100 g of almonds. These polyphenols include phenolic acids, lignans, isoflavues, stilbenes, and a rich variety of proanthocyanidin polymers, tannins, ellagitannins, gallotannins, and ellagic acid. Different classes of flavonoids have been reported, ranging from 0.02% to  
\begin{table}
\begin{tabular}{l c c} \hline \hline
**Nutritional Value** & **g/100 g** & **References** \\ \hline Protein & 15 & [12] \\ \hline Carbohydrates & 6–26 & [14,15] \\ \hline Total fatty acids & 60–70 & [12] \\ \hline - Saturated fatty acids & 6.5 & [12] \\ \hline - Monounsaturated fatty acids & 75.8 & [14] \\ \hline Oleic acid & 75.6 & [14] \\ \hline - Polyunsaturated fatty acids & 8.1 & [14] \\ \hline Linoleic acid & 7.9 & [14] \\ \hline \hline \multicolumn{3}{c}{Micronutrients} \\ \hline Niacin & 1.45 mg/100 g & [12] \\ \hline Vitamin B1 & 0.276 mg/100 g & [12] \\ \hline Vitamin B2 & 0.052 mg/100 g & [12] \\ \hline Vitamin B6 & 0.501 mg/100 g & [12] \\ \hline Folic acid & 43 ug/100 g & [12] \\ \hline Ascorbic acid & 2.45 mg/100 g & [12] \\ \hline Retinol & 3.25 mg/100 g & [12] \\ \hline \(\alpha\)-tocopherol & 24.7 mg/100 g & [12] \\ \hline \(\gamma\)-tocopherol & 1.36 ug/100 g & [12] \\ \hline \(\delta\)-tocopherol & 1.78 mg/100 g & [12] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Nutritional value of hazelnuts.  
0.4%, including flavanols, anthocyanin, flavanones, and flavan-3-ols. Minor amounts of gallocatechin gallate, epicatechin gallate, and epicatechin glycoside are also present. Flavonols are the most abundant flavonoid class in almonds, ranging from 0.87% to 1.35%, with quercetin being the predominant flavonoid [19]. The protein content of almonds varies from 14% to 35.1% (\(w/w\)) depending on the cultivar. The two major protein fractions are albumins (21%) and globulins (74%). Almond kernels can be considered a high-quality protein source because their amino acid composition is extremely similar to the standard protein profile recommended by the FAO and WHO. Essential amino acids constitute approximately 30% of the total amino acid composition; specifically, almond kernels contain 3.14% threonine, 4% valine, 3.86% isoleucine, 7.47% leucine, and 3.47% lysine [20]. In 100 g of protein, [PERSON] et al. reported that the amino acid composition includes 0.601% threonine, 0.855% valine, 0.751% isoleucine, 1.473% leucine, and 0.568% lysine [19].  
Ultimately, almond kernels contain approximately 3.7 to 5.5% carbohydrates and 11.8% dietary fiber, including hemicellulose, cellulose, and lignin [14; 21].  
Table 2 summarizes the main nutritional values of hazelnuts.