*3.1. Protein Profile*

Proteins are classified depending on their solubility in albumins (soluble in water and dilute solutions), globulins (classified into euglobulins—soluble in dilute solutions, acids and alkalis and insoluble in water, and pseudoglobulins—moderately soluble in these solutions), prolamins (soluble in solutions with 50–90% ethanol), glutelins (soluble in dilute acids and alkalis) and scleroproteins (insoluble in all mentioned solvents).

Saura et al. [15] found that the protein dominant fraction was that composed by globulins–albumins, with about 90% in all studied samples. On the other hand, glutelins accounted for between 4 and 11% of total proteins, while prolamins were found below 0.4% in all cases.

Within the protein profile, amandine is dominant, also known as the almond major protein (AMP), which represents 65% of total proteins of almond that can be extracted in aqueous medium [64]. This protein is the main component responsible for food allergies caused by almonds, due to the antigenic activity that it presents. It is an ideal marker to detect traces of almond in foods [24].

### *3.2. Free Amino Acids*

Together, free amino acids (AAs) represent a small quantity of total nitrogen matter (1%), which matches with the low content of non-protein nitrogen; consequently, the total amino acids content in almond kernel is a good approximation of the total protein content. The main free amino acids found in almond kernel are glutamic acid and aspartic acid (including glutamine and asparagine), followed by arginine. Phenylalanine, alanine, serine and threonine are also present although with lower quantities [15,65]. Amrein et al. [66] also found that aspargine was the main free amino acid in raw almond kernel (20–50% of total free amino acids).

The free amino acids fraction has been used for the characterization of almond cultivars [65,67]. These free amino acids are important due to their contribution to food taste and for being precursors of aromatic components and colored substances that are produced during the obtention, preparation and storage of food.

Esteban [18] found a higher content in almost all AAs in cultivars grown in northwest Spain compared to those grown in the southwest, which was related to the lower content of fats in the northwest cultivars.
