Extraction and characterisation of lemon, orange and grapefruit seeds press cake proteins

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E. Buket Karabiber
E. Yılmaz


citrus seeds, press cakes, protein, extraction, thermal property


The aim of this study was to characterise the proteins of lemon (Citrus limon var. Kütdiken), orange (Citrus sinensis var. Dörtyol) and grapefruit (Citrus paradisivar. Beyaz) seeds extracted from their defatted press cakes. The press cakes were collected from the cold oil pressing of the seeds which were pre-treated by different techniques. Ultrasound-assisted alkaline (pH=9.0) extraction and isoelectric point (pH=4.0) precipitation procedure yielded around 34.47-80.95% proteins. The extracted seed proteins were in good quality for colour and antioxidant capacity. The extracted-lyophilised proteins were more soluble at pH 11-12 and below 2. The viscosity of the protein dispersions ranged from 3.67 to 25.70 cP. Sixteen amino acids were quantified in the samples, while asparagine, cysteine, hydroxyproline and tryptophan were absent. Thermal denaturation temperature and enthalpy change of denaturation were reported for the first time. The gel electrophoresis indicated four distinct protein bands at around 10, 15-20, 20, and 25-37 kD. It was shown that while seed pretreatment prior to cold oil extraction caused protein yields to enhance, protein degradation especially, in naringinase and hesperidinase enzyme treated samples enhanced, as well. This study provides the evaluation of citrus seed proteins for the literature for the first time, and points out the possibility of utilisation of these proteins in food enrichments, animal feeding and non-food applications. More studies about applications of these seed proteins are expected.

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