Changes in chloroplast pigments during the preparation of leaf protein

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Abstract
The nature and extent of the changes in the carotenoids and chlorophylls were determined at each stage of leaf protein (LP) preparation. Loss of carotenoids during pulping and pressing of the leaves is mainly enzymic and can be minimised by adding alkali and processing quickly. Carotenoids were more stable in the juice than in the fibre. When the protein was coagulated by heating the juice little carotene was destroyed but total xanthophyll decreased mostly due to violaxanthin being partly isomerised. With leaves rich in chlorophyllase, coagulating at 80 °C led to the conversion of chlorophylls to chlorophyllides. This reaction, and others that may be deleterious to the quality of the protein, did not occur at 100 °C suggesting a higher temperature of coagulation may be preferable. Washing with acid caused a marked colour change of LPs because of the conversion of chlorophylls to pheophytins and chlorophyllides to pheophorbides; xanthophyll decreased slightly but carotene was unaffected. No pigment changes occurred on freeze‐drying. During storage with air present carotene was less stable than xanthophyll; carotenoids were lost faster from acid‐washed LPs than from unwashed preparations.