Salted Veggies

Osmosis 

Mini experiment 4 – How to keep stuffed tomatoes from being soggy and runny?

Today and yesterday we discussed fruits and vegetables in class. A lot of vegetables consist of large amounts of water and they have unique characteristics that need to be considered before cooking them.
My last experiment explored the effects of salt on meat; today we will take a closer look at the effects of salt on vegetables. There will be two molecular processes that will be tested. The extraction of liquid from the vegetable through osmosis and the weakening of the pectin within the vegetable. 

Cook’s Illustrated explains that “When salt is applied to vegetables, it creates a higher ion concentration at the surface than exists deep within the cells. To equalize the concentration levels, the water within the cells is drawn out through the permeable cell walls. This is called osmosis, an important process in brining and marinating. (212).

Salt however, does not only extract water from vegetables. "Science of good cooking" also notes that, Much of the strength of pectin, the glue that holds the cells together, comes from the presence of calcium and magnesium ions within the molecules. These ions are part of the pectin structure, but they also act as links, holding the pectin molecules together. When raw vegetables are salted, or salt is added to the cooking water, the sodium ions in the salt replace the calcium and magnesium ions in the pectin. This causes the pectin - and therefore the cell walls  of vegetables - to weaken. 212

I decided to use a vegetable that consists of mostly water; the Tomato. Cook’s illustrated “The Science of Good Cooking” includes several recipes centered on tomatoes but the one that made my mouth water was the Stuffed Tomatoes with Goat cheese, olives and Oregano. Not only did this recipe sound delicious, it also required the tomatoes to be salted before they were stuffed and baked.  Stuffed tomatoes should not give off to much water to their filling as it takes away flavor.  The instructions of the recipe require the cored and seeded tomatoes to be salted on the inside and rest on paper towels for 30 minutes to drain the excess moisture. This process of the recipe is where I will perform my experiment.

Recipe
The recipe that I used can be found in Cook’s illustrated “The Science of Good Cooking”.
Some slight modifications that I made were using fresh Italian parsley instead of regular parsley and I

the ingredients 

used dried oregano leaves instead of fresh oregano.  The ingredients were:

- 3 Large Tomatoes, 1/8 inch sliced off stem end, cored, and seeded.
- ½ teaspoon salt
- ½ slice of white sandwich bread
- 2 table spoons olive oil
- ½ cup of goat cheese
- 1 ½ table spoons minced fresh Italian parsley
- 1 Garlic clove minced
- salt

Salting the tomato 

- pepper

I salted 1 of the tomatoes 30 before hand and let it dry. I stuffed the tomatoes with the mixture of garlic, olive oil, chopped black olives, parsley, goat cheese, crumbled bread, salt, and pepper.  In a 375 F oven I placed tomatoes on a baking dish covered with aluminum foil. The tomatoes were baked for 20 minutes until the top turned golden brown.

Goat cheese stuffing

The Experiment
As I mentioned earlier I will be testing the effects of salt on vegetables. Cook's illustrated pointed out how salt should extract liquid from the vegetable (tomato) but also make the tomato less . My hypothesis is that the tomato that is salted will disperse less liquid to the stuffing but will also be less stable. My independent variable was whether the tomato was salted or not and the dependent variable is both the liquid the tomato disperses while cooking and the structure and firmness of the tomato.
I standardized the cooking temperature and filling of the tomato by using the same ingredients for both and placing both tomatoes in the same oven dish. I also made sure I bought similar sized tomatoes and used the same procedure to core and seed the tomatoes.

Results

Tomatoes before they went in the oven (375 F)

The results of the tomatoes after 20 minutes of baking show that the unsalted tomato contained much more liquid than the salted tomato, but also that the salted tomato was less firm and more unstable.
I was able to support my two sided hypothesis through this experiment.

Unstable salted tomato on the left and
watery unsalted tomato on the right after 20 min. of cooking 

After 20 minutes of baking -	Salted	Unsalted
Most Liquid dispersed		X
Most unstable structure	X

  

Discussion
Both reactions that were predicted by "The Science of Good Cooking" did indeed happen. Some vegetables might react differently to salt than others, but for those vegetables that consist mostly of water salt has a duel effect on the structure of the fruit. More research can be done as to the question how to salt a vegetable without breaking down the pectin so it can remain its firm structure. It was clear however that the unsalted tomato was less flavorful as the water dulled the spices and the sharp taste of the goat cheese.

Dinner time The tomato was obviously only part of the main course. I decided to complement the sharp taste of the goat cheese with a piece of honey glazed, bacon wrapped, turkey tenderloin and some spanikopata.

Goat cheese stuffed tomato with bacon wrapped turkey tenderloin and spanikopata

More information on vegetables and  recipes can be found at Cook's Illustrated, The Science of Good cooking.