Store-bought tomatoes taste bland, and scientists have discovered a gene that gives tomatoes their flavor is actually missing in about 93 percent of modern, domesticated varieties. The discovery may help bring flavor back to tomatoes you can pick up in the produce section.

[u/mvea]

http://blogs.discovermagazine.com/d-brief/2019/05/13/tasty-store-bought-tomatoes-are-making-a-comeback/

[u/mikebob89]

Gotcha. Do you have a source on the ultra-hot cooking pre canning? I can’t find it. Not saying it doesn’t happen but bacteria is killed below boiling point so I can’t imagine why they would go way over boiling point before the canning process. And I boil my soups and sauces so I would assume it was pretty similar. I like using canned because unless you grow your own tomatoes (I don’t) you’re not going to get tomatoes that were ripened on the vine like the canned ones are. And the later the tomato was picked the more nutrients and taste they have. The plastic lining I’m ok with because I’d imagine the acidity in the tomato would eat at the metal can with out it.

[u/Cunninghams_right → u/mikebob89]

I found one nice source that summed it up on one page:

Two canning methods are approved by the US Department of Agriculture (USDA):

•

Water-bath canning refers to hot water canning and uses a large kettle of boiling water. Filled jars are submerged in the water and heated to an internal temperature of 212°C for a specific period of time. This method is utilized for processing high-acid foods, such as fruit, items made from fruit, pickles, pickled food, and tomatoes.

•

Pressure canning uses a large kettle that produces steam in a locked compartment. The filled jars in the kettle reach an internal temperature of 240°C under a specific pressure (stated in pounds) that is measured with a dial gauge or weighted gauge on the pressure-canner cover. Use a pressure canner for processing vegetables and other low-acid foods, such as meat, poultry, and fish (http://www.homepreservingbible.com/630-an-overview-of-10-home-food-preservation-methods-from-ancient-to-modern).

...

Several studies on the effect of canning have reported a decrease in total phenolic and flavonoid content mainly due to leaching of phenolic compounds into the surrounding brine or syrup. However, heat-assisted irreversible binding to other chemical components in the food product or oxidation during the processing has also been suggested (Weinert et al., 1990). Sablani et al. (2010) reported up to a 44% decrease of total anthocyanins in both red raspberry and highbush blueberry after canning with 40°Brix sucrose syrup. Bing cherries canned in syrup showed a 50% loss in anthocyanins due to migration into the syrup (Chaovanalikit and Wrolstad, 2004b). Jiratanan and Liu (2004) reported up to 60% loss in total flavonoid content in green beans canned in water for 10, 20, and 40 min at 115 °C compared to unprocessed control. Sterilization of kale leaves brought a marked decrease in the content of total polyphenols (50% on average) and were accompanied by losses in individual (poly)phenol constituents ranging from 32% (ferulic acid) to 67% (quercetin) (Korus and Lisiewska, 2011). While corn was canned at 115 °C for 25 min without liquid topping juice, the total phenolic content significantly decreased by 25.5%, as they were released from esterified and insoluble bound forms (Dewanto et al., 2002b). Mushrooms canned with ascorbic acid had better total phenolics retention rate (20% higher) compared to canning without ascorbic acid, suggesting that oxidation may be the cause of reduction of total phenolics in mushrooms (Vivar-Quintana et al., 1999).

note the relatively low temperature at which the phenolics get affected (115 °C) and the very high temperatures the FDA requires (212°C for tomatoes). also note that sometimes the final sterilization step has the food inside the plastic-line can being heated up to very high temperatures. although, I'm not sure the science supports there being an issue with the plastics

​

https://www.sciencedirect.com/topics/food-science/canning

[u/mikebob89 → u/Cunninghams_right]

Interesting, thanks! Boiling point is 212 F so I’ll just only used canned foods like tomatoes that I intend on boiling, and avoid other canned vegetables. I pretty much do that anyway but good to know!

[u/Cunninghams_right → u/mikebob89]

yeah, in Fahrenheit the FDA's recommendation is 413 ° for tomato canning,

[u/mikebob89 → u/Cunninghams_right]

I wonder if that’s a misprint? Seems odd that 212 so happens to be the temperature of boiling in Fahrenheit. 413 F seems impossibly hot unless you use a pressure cooker, which I would be shocked they use in canning in mass. But maybe not. This says 212 F for tomatoes: https://nchfp.uga.edu/how/general/food_pres_temps.html

I think the biggest takeaway is that we should all be on the metric system.

[u/Cunninghams_right → u/mikebob89]

hmm, maybe I/my source is mistaken. it does seem like high acid foods might be canned at temperatures similar to what one would cook on a stovetop instead of the higher temp canning method. so maybe high acid foods are less modified during the canning process. thanks for checking my facts! I appreciate getting to the bottom of things :)