Protein hydrolysates contain mainly peptides and free amino acids. PHs can also contain carbohydrates and small amounts of mineral elements, phenols, phytohormones and other organic compounds.

Most Animal Derived PH's

Animal-derived PHs are usually produced through chemical hydrolysis with the use of acids(hydrochloric and sulfuric acid) at high temperatures (>121 C). because acid hydrolysis is very aggressive, the resulting product is composed of a large amount of free amino acids and to a lesser extent by soluble peptides. During the acid hydrolysis some of amino acids like tryptophan, cysteine, serine and threonine are partially or totally destroyed and many other amino acids are converted from the L-form to the D-form, thus losing their biological activity(Colla et al, 2015a).

Plant Derived PH's

Since plant-derived PHs are produced through a more gentile method (enzymatic hydrolysis using proteolytic enzymes and a temperature below 60 C), the resulting PHs contain higher peptides, free amino acids ratio, and proportion of L-amino acids in comparison with those obtained by chemical hydrolysis.

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