Indoor farmed lettuce tastes less bitter and more savory than soil-farmed lettuce

June 27, 2018

Clarifying how cultivation environment affects the way food tastes

RIKEN researchers in collaboration with Tsukuba University and Keystone Technologies compared two types of hydroponically cultivated leaf lettuce grown in a plant factory and grown in soil, using the same LED light intensity and the same type of liquid fertilizer. Using integrated metabolome analysis, the researchers were able to demonstrate for the first time how metabolite groups affect production in terms of taste and functionality, not just appearance.

Plant factory vegetables are grown hydroponically with liquid fertilizer but no soil. For the experiment, researchers grew two of the most commonly available types of leaf lettuce in both a commercial plant factory and in soil conditions. The same liquid fertilizer and light conditions were used. They subjected the lettuce to two types of high-performance mass spectrometers (GC-MS and LC-MS) and found that differences in their metabolite profiles were more closely related to differences in the cultivation environment, i.e., factory versus soil, than to differences between the cultivars or parts of the leaves tested. A more detailed analysis of metabolomic data revealed that amino acids (which are responsible for conferring a savory “umami” taste) accumulated more in the factory-grown lettuce than they did in the soil-grown lettuce, while sesquiterpene lactones (which confer a bitter taste) accumulated less.

Unlike laboratory studies that attempt to imitate cultivation conditions, this study focused on studying leaf lettuce that was cultivated in a real-world situation. It marks the first attempt to analyze quantitative and qualitative changes in metabolites and the findings will be useful when evaluating cultivation conditions for various agricultural products. Additionally, the metabolomic approach demonstrated in this research can be used as an index for customizing taste and functional ingredients of plant-factory vegetables.

First looking at metabolites and then investigating the cultivation conditions in detail is a reverse approach that can be expected to contribute to the development of high value–added agricultural production technologies.

Original article
Frontiers in Plant Science doi:10.3389/fpls.2018.00665
Y. Tamura, T. Mori, R. Nakabayashi, M. Kobayashi, K. Saito, S. Okazaki, N. Wang, M. Kusano,
"Metabolomic evaluation of the quality of leaf lettuce grown in practical plant factory to capture metabolite signature".
Miyako Kusano
Senior Visiting Scientist
Metabolomics Research Group