*4.3. Fiber*

Fiber is a heterogeneous mix of polysaccharides (cellulose, hemicelluloses, gums and mucilages and pectin substances) and non-polysaccharides (lignin, non-digestible proteins and other). Terms commonly used to define it are as follows: crude fiber, composed of cellulose (50–80%), hemicellulose (~20%) and lignin (10–50%); neutral detergent fiber (NDF), consisting of cellulose, hemicellulose and lignin; acid detergent fiber (ADF), consisting of cellulose and lignin; and acid detergent lignin (ADL) [73]. On the other side, dietary fiber can be defined as a group of components that are not digested by enzymes in the human gastro-intestinal tract, and as being mainly composed of cellulose, hemicellulose, lignin, pectin and non-digestible proteins.

The content in neutral detergent fiber, whose fundamental components are cellulose, lignin and hemicellulose, provides the value of dietary fiber, while acid detergent fiber, whose fundamental components are cellulose and lignin, provides the crude fiber value.

Barreira et al. [46] reported data of neutral detergent fiber between 2.9% and 3.2%, depending on the selected cultivar. However, dietary fiber content in almonds ranged from 3.3% to 16% (Table 1). Kodad [22] calculated a variation coe fficient of 9.81% for dietary fiber. Significant di fferences between selected cultivars, years and the interaction "genotype" × "year" have been found regarding dietary fiber content, which confirms the large variability of this character between genotypes and years. Yada et al. [9] found that the e ffect of harvest year on dietary fiber was highly significant ( *P* < 0.01), to the point of having blocked the observation of cultivar di fferences. In addition, some other agronomic treatments may have an e ffect on the content of dietary fiber. For example, when organic fertilizers were applied, higher fiber content was observed in the fruit than when an inorganic fertilizer was employed [57].

Crude fiber concentration in almond kernel also shows high variability. First references indicated low crude fiber contents, about 2% or 3% of dry matter [15,16], while other recent results reached contents of 5.81% [22], probably due to improvements in analytical techniques.

### **5. Mineral Fraction of Almond Kernel**
