Nutrient Strategies for Carotenoid Enrichment in Hydroponic Lettuce

Abstract

Vitamin A deficiency affects approximately 30% of children under 5 years old globally, with Bolivia showing persistent rates despite intervention efforts. High-altitude environments like La Paz present unique challenges for nutrient-rich crop production, mostly due to harsh growing conditions and limited infrastructure.
This study investigated wether targeted modifications of hydroponic substrates, coupled with foliar calcium chloride (CaCl2) applications, could enhance carotenoid content in lettuce while addressing common cultivation challenges including tip burn and biofilm formation. For this purpose, two lettuce cultivars (“Crespa” and “Starfighter”) were grown in horizontal hydroponic systems using original and reformulated nutrient solutions. This was coupled with a weekly foliar application of a 1% solution of CaCl2 on selected plants. Carotenoid content and additional measurements of antioxidants, phenolics and polyphenols were analyzed using spectrophotometry, while caffeic acid was quantified using HPLC.
The reformulated solution eliminated tip burn, reduced biofilm formation, and increased carotenoid content in all samples when compared to the original solution. “Starfighter” showed superior carotenoid accumulation, while “Crespa” showed a better phytochemical profile (of the measured compounds). The effects of foliar treatment regarding carotenoids are inconclusive and were cultivar specific, reducing carotenoid content in “Starfighter” but increasing it in “Crespa”. Foliar treatment doubled the content of caffeic acid in all samples.
Substrate modifications effectively enhanced both plant health and nutritional quality in high-altitude hydroponic systems. The reformulated solution presents a promising approach for addressing vitamin A deficiency through biofortified lettuce production, though foliar treatment protocols require further optimization and research.

Popular Abstract

One leaf at a time
Have you heard ‘work smarter not harder’ before? With hydroponics, the burdens fall off your shoulders, no more daily watering, no more fear of hail, snow, heat or drought. The hydroponic solution is made approximately once per month, the system washed inbetween batches, and clean, fresh lettuce is on the way! Now you can not only increase the growth rate and mitigate potential problems in your solution, you can also boost the nutrients!
Lettuce is one of the most widely consumed leafy greens, however, it’s not given enough importance. Hydroponic lettuce contains a fair amounts of carotenoids (precursor for Vitamin A synthesis) and antioxidants (functional compounds protecting our body). Currently, research is ongoing to fortify lettuce with micronutrients such as Iodine and Selenium, as well as other nutrients due to its versatility. However, the idea of maximizing the content of carotenoids is novel and is waiting to be explored.
Changes in the nutrient solution allows for an increase in carotenoid levels in all cultivars, but it is important to note that the effect these changes have vary from species to species. Antioxidants, phenolics, and flavonoids have shown negative correlation to carotenoids. The best performance both in terms of carotenoids and of growth rate was shown by cultivar ‘Starfighter’ from the reformulated solution. Meanwhile, caffeic acid has shown a twofold increase with the foliar application (spray) of calcium chloride. It is important to note that foliar application results were inconclusive in the carotenoids measured, raising the amount of carotenoids in ‘Crespa’, while decreasing those levels in ‘Starfighter’ (when comparing to a control group).
This research shows the potential of hydroponic lettuce, paving a road to more nutrient-dense foods. The importance in this research also lays in cultural-sensitive solution to a problem of vitamin A deficiency in Bolivia; no campaigns to eat more vegetables, just more nutrient-dense food. The potential of high altitude in La Paz is yet to be examined, however it is assumed it acts as an additional stressor due to hypobaria (low atmospheric pressure) and low oxygen levels.

• author: Cíbová Morato, Alexandra
• supervisor: Federico Gómez Galindo; J. Mauricio Peñarrieta
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLTM02 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Agriculture and Food Sciences
• keywords: hydroponics, lettuce, carotenoids, Bolivia, foliar, vitamin A, food engineering nutrition and food chemistry
• language: English
• id: 9200288
• date added to LUP: 2025-06-17 16:04:51
• date last changed: 2025-06-17 16:04:51