Hello, I’m Andrea Castillo and this is Seasonal, a newsletter that connects you to the Bay Area food system, one fruit and vegetable at a time. Seasonal comes out twice per month, and each post highlights the most interesting aspects of one seasonal fruit or vegetable grown and harvested around the Bay Area. Find me on Instagram at @seasonalbayarea or e-mail me at to share your feedback and suggestions, I’d love to hear from you. If you’d like to unsubscribe, click the gray unsubscribe link at the bottom of this post.

This week we nerd out on tomatoes (available June-October).

Social distancing has made it difficult to meet new people. But, through food, I managed to socialize more than I was expecting. I’ve been corresponding weekly with a couple dozen local farmers since April to share social media updates about who will bring what to the Tuesday and Saturday Berkeley farmers markets. Although I’m immersed in these farmers markets, it’s a digital immersion more than anything because I limit outings as much as I can. But I have my weaknesses and Elephant Heart plums got me out of the house and into Tuesday’s market. And that’s how I met my new friend, Efrén.

essential businesses

After picking up my special seasonal plums, I stopped by Efrén’s stand to get a bunch of cilantro. We had spoken on the phone a few times and texted at least twice a week during our weekly check-ins so I was excited to meet him in person. To my delight, the person who helped me at the stand turned out to be Efrén. I told him it was Andrea, from all the calls and text messages and he recognized me right away. We didn’t know what each other looked like, and the masks didn’t help, but my Colombian accent was a dead giveaway, and it was a blast to finally connect. We air hugged and chatted for a few minutes about our families and overall health: all were good. I also asked Efrén how business was going. Luckily, they’re doing very well. Summer for him can be slow, but people are traveling less and visiting his stand more often, so business is strong.

We wanted to keep socializing, but the line behind me was growing, so he asked if I wanted anything else. Although I had only stopped by for cilantro, I asked him what he’d recommend. His eyes lit up, he smiled—funny how you can still see a smile in spite of a mask, isn’t it?—and without hesitation said, “It’s peak tomato season, you have to try them! They’re so good!“ He picked a few for me, feeling each one for ripeness as he placed them in a paper bag. As I pulled out my wallet to pay, he waved it away, saying, “no, no, es cortesía de la casa.” It’s on the house.

Efrén’s kindness made my day. When I returned home and sliced one of his tomatoes, it blew my mind. It tasted incredible! The sweet, tangy, undeniable tomatoey goodness inspired me to explore a tomato dichotomy: how come tomatoes like Efrén’s explode with flavors while others disappoint our tastebuds?

flava flava

Efrén grows tomatoes for taste. Similar to wine, tomatoes have their own kind of terroir, and Efrén has a good handle on how to optimize the natural conditions in which he grows his tomatoes. Some variables like sunlight, temperature, and unexpected climate changes are out of his control. Others like tomato varieties, irrigation, and harvest methods he tweaks and leverages to build great flavor. But what exactly is tomato flavor? If we boil it down to its essence, it’s the balance between the basic flavor building blocks within tomatoes. To better understand how conditions farmers create encourage strong flavor, it’s worth taking a deep dive into the tomato and exploring three key flavor components: sugar, acid, and volatile aromatic compounds.

a balancing act

Americans love tomatoes—it’s the second-most consumed vegetable in the United States—and they value their sweetness. Side note: the tomato is a fruit, but we cook it like a vegetable and in the eyes of SCOTUS, it’s a vegetable. Anyway, the main sugars in the fresh tomatoes we eat today are fructose, the sweetest of all the common sugars, and glucose, the most common sugar in plants. Sugars make up about 4% of a ripe tomato and they are concentrated in the meaty part of the tomato known as the fruit wall. 

But a tomato with too much sugar and not enough acidity will taste bland and a good dose of tang from the acids in a tomato help create better flavor. The two main acids in a ripe tomato, citric and malic acid, provide that tasty zing. These two acids congregate in the jelly that holds the seeds together as well as the skin. Because citric and malic acids are non-volatile, they like to stick around even when cooked in heat—a reason many tomato sauce recipes that want sweetness call for no skin and no seeds. If a tomato sauce is too sweet for your preference or tastes like it’s missing something, adding back the seeds or skins can kick your sauce up a notch.

Another important acid in tomatoes that elevates flavor is glutamic acid, popularly known as MSG in its concentrated form. Compared to concentrations in other fruits, glutamic acid content is high in a tomato and, as Harold McGee explains in my go-to food-science reference book, it’s an important building block in the deliciousness of the tomato known as umami.

Even with a deliciousness bonus, sugars and acids need their third musketeer to add the finishing touches to tomato flavor. Sugars and acids work well for our sense of taste but our sense of smell is just as crucial to our overall tomato-eating experience. This is where volatile aromatic compounds come in.

Out of the estimated 400 aromatic compounds in tomatoes, we can only smell and taste 15 to 20 of them. But they are mighty and a mere whisper of one of those compounds, like geranial, can change how we taste a tomato in spite of optimum levels of sugars and acids. These volatile aromatic compounds mingle in our noses and palates for a brief moment to join the complex process that creates our tomato taste experience. Their fleeting presence is powerful enough to create grassy, citrus, floral, pungent, malt, or chocolate notes that burst in divine tomatoness. We may owe a lot to these little volatile flavor ballerinas, but they are not well understood yet. The intricate, complex dance between sugars, acids, and aromas is choreographed not only by the internal mechanisms in the fruit, but also by the genetic variety of the tomato and a slew of external environmental factors as well.

very varied

Tasting and learning about tomato varieties sparked Efrén’s desire to farm for taste above all else. There are 7,000 tomato cultivars we can grow and their flavors vary enormously. When Efrén was growing up in Mexico, where tomatoes were first domesticated, he helped his father grow and harvest just one variety. The Roma. Tomato farmers in Mexico and in many tomato-growing countries throughout the world have a strong preference for growing plum, or processing, tomatoes like the Roma. Romas are in high demand: they are meaty, have fewer seeds than many other tomatoes, and make for great canned tomatoes and thick tomato-based sauces. Romas also store well, they do not damage easily, and are not too juicy. 

In Mexico, Romas are popular because the local palate demands them. Even though Roma tomatoes do have sugar, their sweetness is not as pronounced as it would be in other varieties. And this is important for Mexican cooks and eaters who don’t tolerate sweet tomato-based salsas, a staple of the Mexican diet. With its vegetal flavors, the Roma is a great fit and a frequent purchase at local markets. For Efrén and his dad, the choice in what variety to grow was obvious: they followed the basic principles of supply and demand economics and gave the people what they craved.

ugly… delicious!

After growing Romas for a few years, Efrén left Mexico, moved to the United States, worked for other farmers, and then started his own farm in the late 1990s in Hollister, California. Efrén called it Avalos Organic Farm and grew a variety of fruit and vegetables including tomatoes. In the beginning, he chose to plant the two tomato cultivars he was the most familiar with: Roma and Beefsteak (a larger tomato that is good for slicing and sandwiches). Sales were okay, but Efrén noticed his neighbors at farmers markets sold ugly tomatoes that customers loved.

Efrén was skeptical at first. The appearance alone was uninviting. Were those tomatoes even safe to eat? Curiosity got the best of him and Efrén decided to see what all the fuss was about. These funky-looking tomatoes were sweet. Too sweet! Why would Americans enjoy eating such a sweet tomato… and pay more for it? Efrén was stumped but intrigued. He learned that these sweet varieties were different kinds of heirloom tomatoes. Their seeds are passed down from generations and are bred for their flavor and sweetness on purpose. Efrén observed how local shoppers’ tastebuds had cast their vote for these sweet, lopsided tomatoes and decided to give his new audience what they desired. He took a leap of faith and opted to grow the bizarre heirlooms instead of the familiar Romas.

Efrén did not regret his choice. Sales were good, his farmers market clients became big fans, and he admits he also became a sweet tomato addict. After trying Efrén’s Cherokee Heirlooms and Early Girl tomatoes, I imagined how easy it would be to get hooked on them and asked him why they tasted so damn good. From his point of view, there are a couple of reasons, and developing a deep understanding of tomato varieties is essential. Tomatoes do not fit a one-size-fits-all farming model and each chosen variety should match the specific location where they will grow. With this in mind, Efrén chose cultivars that would do well in Hollister where it is dry and hot. Efrén also explains that every plant he grows has its secrets, and one of the secrets to his superb tomatoes is water.

One of Efrén’s delicious, fresh, hand-picked tomatoes, sprinkled with crunchy salt pyramids.

bless that stress

Ninety-five percent of a tomato is water, making it the fourth main flavor component in a tomato. Unlike sugars, acids, and volatile aromatic compounds, water doesn’t create flavor but rather dilutes or enhances it.

Young tomato plants crave water. Lots of it. Efrén quenches their thirst early on to help them grow and establish their roots. But when the plant produces fruit, Efrén resorts to a tough-love approach. He cuts back on irrigation, something he and his dad would never do in Mexico. While farming with his dad, Efrén learned that watering tomato plants throughout their life cycle yielded fruit that was gorgeous… but bland. Looks were important then, but Efrén is no longer in the eye-candy business. Instead, he leverages the lack of water to concentrate the sugars and acids in the fruit, yielding bolder flavors.

Forty minutes west of Avalos Organic Farm, farmers grow crops in a cooler, wetter microclimate and some have decided to grow tomatoes with no irrigation. Farms like Dirty Girl and Happy Boy in Santa Cruz County use dry farming techniques for some of their tomatoes. Dry farming is a sustainable method that relies on pre-summer rains and on cooler summers that slow down water evaporation from the soil. Farmers who want to dry farm have to maintain healthy soils with ample organic matter so they can retain enough water to last through the summer. With the right soils and rains, there’s no additional use of city water or groundwater for growing crops like tomatoes. But dry farming only works for specific tomato varieties—it won’t work well for heirlooms. And because dry-farmed tomatoes need more physical space than irrigated ones to reach water deep down in the soil, there is less yield per acre. Still, similar to the water stress conditions Efrén creates for his tomatoes, the limited availability of water from dry farming typically results in sought-after tomatoes that pack plenty of flavor and command high prices.

timing is of the essence

Limiting how much water tomatoes access helps build great flavor, but the work doesn’t end there. For Efrén, knowing when to harvest tomatoes is also an important finishing touch in growing for taste. Efrén harvests tomatoes the opposite way he harvested them with his dad in Mexico. He and his dad needed firm tomatoes that would survive long hauls so they plucked Romas off the vine when they were not fully ripe yet. Tomatoes harvested this way are slow to ripen on their own so it’s a common commercial practice to gas them with ethylene gas and force the ripening process. Sadly, early harvesting and forced ripening leaves much to be desired when it comes to flavor.  

Tomatoes harvested early often ripen with low sugar and umami acid levels. Efrén knows that bland taste well, so he complements his water stress techniques by working with his family to hand-harvest the delicate, ripe fruit straight from the plant. By harvesting tomatoes this way, Efrén gives up hardiness and incurs higher labor costs. As a reward, however, his tomatoes build flavor even more, and he and his customers get to savor seriously good tomatoes.

cool like a… tomato?

As customers and tomato eaters, we can do our part to ensure the careful planning and hard work of farmers like Efrén do not go to waste. When we buy fresh tomatoes from the farmers market or local stores, there’s a simple action we can take to honor the flavor farmers and nature co-createeat them right away.

If you have no choice but to wait a few days, then there are a couple of options for how to store a tomato. If the tomato is not quite ripe, it should hang out on your countertop instead of the fridge. Similar to an eggplant, cold temperatures are a turn-off for not-quite-ripe tomatoes. And I mean that literally. When tomatoes go in refrigerators or cold warehouses they start to lose their aromatic compounds and flavor and their texture transforms from meaty to mealy

But ripe tomatoes seem to handle cold fridge temperatures much better. Mealiness or obvious loss of flavor does not necessarily afflict refrigerated ripe tomatoes, especially after taking them out of the fridge and eating them at room temperature. Whether in a fridge or on the counter, avoid stacking tomatoes on top of one another to maximize airflow. Another storage trick is to remove any stems and store them upside down, flat on a plate: they’ll remain juicy this way. 

joys of simple eating

Your efforts in proper tomato storage and a farmer’s hard work in growing flavorful tomatoes will pay off when you finally sit down to enjoy one of the greatest tastes of summer. During peak tomato season (i.e. right, right now), Efrén and I both love keeping it simple and eating raw tomatoes with salt sprinkled on top. I’ve been eating tomatoes with salt as a snack since I was a little kid, and now that I’ve discovered Maldon salt, it’s my favorite topping: these salt pyramids do not dissolve on juicy tomato slices and add a fun crunch to every bite. I’m interested in trying out Bryant Terry’s basil salt, not exactly a tomato recipe, but I can almost taste how fun that salt would be on a tomato. I’m also curious about Maureen Abood’s easy-to-make Lebanese salad, she has a clever approach to elevate tomatoes with another green herb: mint!

Thinking about the months ahead, I’m inspired by Sheela Prakash’s outside-the-box, non-sauce idea to preserve peak summer tomato flavor in butter. That tomato butter would be a treasure to have as fall rolls in. I’m savoring that butter already, especially slathered on a slice of King Arthur’s surprisingly consistent no-knead sourdough bread, a pandemic staple for my husband and me. 

built on flavor

We have about a month left to snack on, cook, and preserve one of the quintessential summer flavors. If you find excellent tomatoes this summer and have the opportunity to thank the farmer who grew them, do it! It’s not easy to choose to grow tomatoes for taste. Efrén explains that farming is a lot like gambling. Whether it’s irrigation methods, soil health management, contingency planning for unexpected changes in climate, or changes in demand in an already small market, they can all pose significant risks and opportunities to a farmer. But the risks and the 15 or 16-hour days are worth it. Efrén loves what he does. He has found local partners like Cosecha, Mandela Grocery Worker-Owned Cooperative, and Phat Beets, who buy the food he grows and allow others who can’t visit the farmers market to taste the love and care Efrén invests in his work. Efrén’s tomato journey goes beyond cultivating fantastic flavors. He also builds local communities, one ripe, delicious tomato at a time—and it’s a community I’m proud to be a part of.

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Andrea Castillo is a food nerd who always wants to know the what’s, how’s, when’s, and why’s of the food she eats.