Understanding Colour Intensity and Retention in Capsicum Fruit and Products as a Means of Improving Product Quality

In the UK and the rest of Europe the consumption of sweet and hot pepper (Capsicum annuum) products is growing rapidly driving the consumers' demand for quality and supply. Like tomato fruit and its products, pepper products are becoming important components of a balanced diet supplying essential and health promoting nutrients. Colour intensity, variation and retention are important traits in these products, impacting on nutritional quality as well as conveying aesthetic quality and perceived freshness to the consumer. Capsicum is not routinely grown on a commercial scale within the UK. Instead global and UK based companies such as Syngenta mostly develop and produce varieties abroad in order to supply UK retailers and consumers. A key aspect of this process is the significant variation and retention of colour in these products, which can vary dramatically with the genotype, upon drying, processing and transportation. Thus understanding colour and its retention in pepper products will have an important bearing on the development of germplasm with improved consumer traits. The predominant class of compounds responsible for the colour of Capsicum fruit are carotenoid pigments. The proposed project will utilise a diverse colour panel of Capsicum genotypes generated by Syngenta. Quantitative metabolite profiling will be carried out to determine the carotenoids present, in fresh fruit, harvested, dried/processed and transported products. Determination of carotenoid content in relation to colour intensity (ASTA value) will enable (i) the relationship between colour intensity and retention with carotenoid content to be evaluated and (ii) identify those genotypes with the most intense and altered pigmentation as well as providing an assessment of pigment retention. Selected genotypes showing desired or perturbed colour traits will then be subjected to detailed analysis in order to provide a greater understanding of the underlying biochemical and molecular mechanisms associated with colour intensity and retention in Capsicum. To achieve these aims it is proposed to perform, (i) targeted analysis on the carotenoid biosynthetic pathway at the gene, transcript, protein/enzyme and metabolite level, (ii) ascertain if the degradation of colour during the production chain is enzymatic or non-enzymatic in nature, (iii) use cell biology and traditional biochemical methods to determine mechanisms of sequestration and their bearing on carotenoid accumulation e.g. plastid numbers, size and stability as well as sub-plastid organelle structures such as globule formation, and (vii) use integrated metabolomic (GC-MS and LC-MS) and transcriptomic (Syngenta array) approaches to ascertain holistic changes in metabolism associated with colour intensity and retention. This programme of activities is synergistic to the on-going funded activities of the academic partner. The academic laboratory has over two decades of experience working on the biosynthesis, regulation and genetic intervention of nutritional and industrial carotenoids/isoprenoids. This work has mainly been carried out in Solanaceae, such as tomato. Syngenta Ltd., is one of the World's largest enterprises in the agricultural sector with an internationally renowned research station based in the UK. Its global fruit and vegetable produce section is a vibrant activity in the company with several new varieties introduced into the market place in recent years. Syngenta and Royal Holloway have been involved in long-term collaborative efforts focussing on carotenoid biosynthesis and its bearing on quality traits in tomato. Thus the proposed project is a timely and novel opportunity to build on the expertise of the academic and industrial partnership as well as research council investments made in tomato to develop resources and exploit knowledge in another related fruit crop.