Japanese Quince Seeds as a Promising Rich Source of Proteins and Essential Amino Acids

The Japanese quince ( Chaenomeles japonica ) seeds (JQS) are generated in large amounts as a by-product in considerable quantities during industrial quince fruit processing. Due to economic, environmental, and nutritional reasons, the utilization of JQS as a protein source seems to be highly justified. Therefore, three cultivars were studied, 'Rasa', 'Rondo', and 'Darius' of JQS as a protein source during three harvesting years. The total protein content in JQS determined by the Kjeldahl method amounted from 24.6 to 33.2% and was significantly affected ( p ≤ 0.05) by the cultivar and harvesting year. The protein isolation was most effective in the pH range of 6–9, and their profile was mainly characterized by a molecular weight of 54.1–57.7 kDa and 70.0–77.6 kDa. The amino acids profile of JQS turned out to be valuable from a nutritional point of view due to the relatively high content of essential and relatively essential amino acids such as histidine (6–9%), leucine (11–12%), lysine (10–16%), phenylalanine (12–16%), glutamine/glutamic acid (7–15%), and tyrosine (9–13%). The initial analysis of JQS indicates that they can be a good source of proteins characterized by a favorable amino acid profile.