Chloroplasts as ingredients for food: a review

The chloroplast is best known for its role in photosynthesis, the process by which sunlight energy is converted into chemical energy in the form of sugar. Research conducted at the University of Nottingham (UK) over several years has revealed the nutritional composition of the chloroplast and the physical properties of its multicomponent membrane. These attributes qualify this globally ubiquitous organelle to be a natural ingredient in food products and to be an option to tackle specific nutrient deficiencies across the globe. Detailed studies of the biochemistry of photosynthesis require pure preparations of enzymatically active chloroplasts, requiring various stages of lab-scale extraction, separation and purification. Such an approach may be commercially viable for pharmaceutical applications, but not for food ingredients. It is against this background that we have developed a simple process to recover a chloroplast-rich fraction (CRF) that could be used in food products. After introducing the reader to the nature of chloroplasts, this review: presents the method we have developed to extract and stabilise a chloroplast-rich fraction; summarises the composition of chloroplast-rich fractions gleaned from spinach leaves and from the postharvest field residue 'pea vine haulm' (PVH); explores the impact of drying methods on the physical nature and composition of the CRF material; establishes the impact of heat-treatment on the quality of CRF material; presents the evidence for extensive galactolipid digestion processes in the human gastrointestinal (GI) tract; investigates the release of nutrients from CRF material during digestion; briefly covers the surface-active properties of the multicomponent membrane system/thylakoids/chloroplast membrane material (CMM).