*6.4. Phytosterols and Stanols*

Phytosterols or plant sterols have a structure similar to cholesterol, while stanols are saturated sterols. They can be found in almond kernel, in free form or esterified with fatty acids [80]. β-sitosterol lowers cholesterol levels, enhances immunity and has anti-inflammatory, antipyretic and anti-carcinogenic effects (prostate essentially) [92].

Sterols are the most abundant class of compounds in the unsaponifiable matter. Desmethylsterols are the most commonly analyzed group, being β-sitosterol the main desmethylsterol with values of 95.5 % of total phytosterols [12], although with significant differences among genotypes [70,90,94]. As regards methylsterols, citrostadienol is the main compound, and regarding dimethylsterols, the total amount was around 30 μg/g [94].

β-sitosterol and campesterol are the dominant sterols in almond kernel. Δ5-Avenasterol, Δ7-Stigamasterol and stigmasterol are well represented in almond oils. Campestanol is the main stanol (Table 4). β-sitosterol is fundamentally found in almond kernel skin, while stigmasterol predominates in mesocarp [99].

Some studies have focused on the physiological phenomenon of phytosterols accumulation: biosynthesis and evolution, finding that the phytosterols amount depended on the harvest time [90,93]. Cherif et al. [90] found a relationship between the biosynthetic compounds of the glyceridic fraction of almond oil (mainly fatty acids) and those of the unsaponifiable fraction (particularly sterols). This relation may be established by 24-methylene cholesterol.

Ozcan et al. [87] compared varieties and extraction methods (cold press and Soxhlet methods). Both affected β-Sitosterol composition of the oil obtained. Neither extraction temperature nor extraction speed affected the total content of sterols in oils from the screw press, but higher temperatures caused a reduction in the content of Δ7-stigmasterol [12].
