Garlic is mainly consumed as a spice or condiment, giving flavor and aroma to other foods. And what gives garlic those wonderful aromas and flavors? Mainly, substances called “organosulfur compounds” that are stored in the bulbs.
Different garlic cultivars accumulate varying amounts and types of these compounds, resulting in garlics with different flavor intensity and aromas.
In addition to its use in adding flavor to foods, folk medicine has attributed a multitude of health benefits to garlic consumption for centuries. These range from treating heart disease to its use as an antiparasitic agent. It wasn’t until recently that some of these claims were backed up by scientific research. Among them are blood thinning, antihypertensive, antioxidant, and anti-cancer properties.
Most of these health-enhancing properties have been attributed, at least partially, to the same type of organosulfur compounds that account for garlic’s flavor. In addition, garlic contains phenolic compounds which seem to contribute to the antioxidant health effects. Research suggests that garlics with greater concentrations of these compounds will have greater health benefits.
As with many other vegetables, a quality trait in garlic is how well the crop stores after harvest, called postharvest conservation. This allows garlic growers and packers to store the garlics until a more convenient price is reached in the market. It also allows a longer shelf-life in the grocery store with reduced sprouting, dehydration, and softening of the bulbs.
Garlic cultivars vary in the expected length of their postharvest conservation. Research has shown that garlic – and other bulbous vegetables like onion – had better postharvest conservation as the water content in their bulbs decreased. So, if the bulbs have more solid content (and less water content) at harvest, their postharvest performance is better. Thus, because total solids content is easy to measure, this trait is often used to predict the postharvest quality of garlics and onions.
Garlic cultivars vary genetically in their ability to accumulate these compounds that influence the flavor, health-related properties, and postharvest conservation of garlic bulbs. Our team tested growing location and environment to find if they also influenced these attributes.
For our research project, we cultivated 12 Argentine garlic cultivars in four locations of Mendoza, Argentina, over two years. This is the main region for garlic production in Argentina. The locations vary in climatic and soil characteristics. Once we harvested the garlics at each location, we analyzed them for total organosulfur, phenolics, and solids content, as indicators of their flavor intensity, health-related properties, and postharvest quality.
We found that among all the cultivars and locations, the level of organosulfur compounds in the garlic bulbs varied more than fourfold. Most of this variation was due to the location and interactions between the cultivars and the locations. Only 30-40% of the variation was due to the genetic variation among the cultivars.
These results indicate that the growing conditions, and some interactions between cultivars and locations, are more important than the cultivar itself for flavor development and health-related properties associated with organosulfur compounds levels. Interestingly, we found substantial variation between Lujan de Cuyo and Santa Rosa. Lujan de Cuyo has colder temperatures, and soils containing greater organic matter and low salinity. Santa Rosa has higher temperatures, low organic matter and high soil salinity. This means that the Santa Rosa location is recommended for producing pungent garlics with high nutraceutical value. Lujan de Cuyo can be used to produce garlics with mild flavor.
Similar results were found for phenolics concentration. The results suggest that to produce garlics with high phenolic content and antioxidant activity, selecting the best location in combination with particular cultivars is perhaps more relevant than the cultivar itself.
Solids content – which influences the postharvest conservations – was the trait less influenced by the environment. A single garlic cultivar, called Castaño INTA, had the highest solids content across all the locations tested. Coincidently, this cultivar usually has the longest postharvest conservation among the Argentine garlic cultivars.
Altogether, our results indicate that garlic flavor, health-enhancing properties, and postharvest quality are strongly influenced by the growing conditions and their interactions with the cultivar. They are influence to a lesser extent by the cultivar itself. In conclusion, it is important to characterize these garlic attributes under different growing conditions to identify suitable cultivars and locations for specific production purposes (e.g., obtaining mild or pungent garlics, or garlics with high organosulfur and phenolic content to produce dietary supplements with high levels of phytochemicals). The identification of cultivars that consistently yield high levels of these compounds across different growing conditions is particularly valuable for garlic breeding programs. — By Pablo Cavagnaro and Karina Barboza, National Council of Scientific and Technical Research (CONICET) and the National Institute of Agricultural Technology (INTA), Argentina