Influence of simulated food and oral processing on carotenoid and chlorophyll in vitro bioaccessibility among six spinach genotypes.

Increasing the density of micronutrients and phytochemicals in vegetable foods through plant breeding and processing is of value for consumers. However, the extent to which interactions between genetics and processing (G × P) can be leveraged for green leafy vegetables to improve the delivery of such compounds is unknown. Using spinach as a model, a three-phase in vitro digestion method with and without simulated oral processing (mastication) and coupling to a Caco-2 human intestinal cell culture model was used to determine whether bioaccessibility and intestinal uptake of carotenoids and chlorophylls can be modified from six spinach genotypes, fresh or processed as blanched, sterilized, and juiced products. Carotenoid and chlorophyll bioaccessibility varied significantly with the genotype (p < 0.001) and processing treatment (p < 0.001), with processing having a more profound influence on the bioaccessibility, decreasing micellarization of phytochemicals from juiced (25.8-29.3%), to fresh (19.5-27.9%), to blanched (14.9-20.5%), and sterilized spinach (10.4-13.0%). Oral mastication had a significant influence on the carotenoid bioaccessible content of sterilized spinach (0.3-0.5 µmoles per g DW) as compared to fresh spinach (0.1-0.3 µmoles per g DW), most likely due to the additive effect of thermal processing and mastication on facilitating digestive breakdown of the spinach matrix. Caco-2 accumulation of carotenoid and chlorophyll was modestly but significantly (<0.001) lower in fresh spinach (2.4%) compared to other treatment samples (3.7-4.8%). These results suggest that the genotype, processing treatment, and genotype × processing (G × P) interaction may affect carotenoid and chlorophyll bioaccessibility in spinach and that food processing remains a dominant factor in modulating the bioavailability of these phytochemicals.

In Vitro Bioaccessibility of Carotenoids and Chlorophylls in a Diverse Collection of Spinach Accessions and Commercial Cultivars.

Spinach, a nutrient-dense, green-leafy vegetable, is a rich source of carotenoid and chlorophyll bioactives. While the content of bioactives is known to vary with the genotype, variation in bioaccessibility is unknown. Bioaccessibility was explored in 71 greenhouse-grown spinach genotypes in fall and spring 2018/2019. Spinach was phenotyped for its greenness, leaf texture, leaf shape, and SPAD chlorophyll content. Postharvest, spinach was washed, blanched, and homogenized prior to assessment of bioactive bioaccessibility using a novel high-throughput in vitro digestion model followed by high-performance liquid chromatography with a photodiode array detector analysis. There was a significant variation in the bioaccessible content for all bioactives (p < 0.05), except for chlorophyll b (p = 0.063) in spring-grown spinach. The correlation coefficients of bioaccessible contents between seasons reveal that lutein (r = 0.52) and ß-carotene (r = 0.55) were correlated to a greater extent than chlorophyll a (r = 0.38) and chlorophyll b (r = 0.19). The results suggest that carotenoid and chlorophyll bioaccessible contents may vary based on spinach genotypes and may be stable across seasons.