Effect of technological processing and preservation method on amino acid content and protein quality in kale (Brassica oleracea L. var. acephala) leaves

Abstract

The aim of the investigation was to evaluate the level of amino acids and quality of protein in raw and processed kale leaves. In all samples the dominant amino acids in g kg⁻¹ raw matter were glutamic acid, aspartic acid and proline. In raw kale leaves the limiting amino acids were lysine, isoleucine and cystine with methionine, and in the remaining products also valine and leucine. Blanched kale leaves contained 88% of the amino acid content in raw leaves, 76% in cooked leaves, and 69-77% and 71-72% of initial levels in frozen and canned products, respectively. In raw, blanched and cooked leaves essential amino acids comprised 44%, 44% and 47%, respectively, of total amino acids; in frozen and canned leaves the proportions were 46% and 44%, respectively. The essential amino acid index was 97 for canned products, 100-109 for frozen leaves, and 117 for raw kale leaves. Raw and processed (blanched or cooked) kale leaves are a good source of amino acids.