Here are some other things that correlate with advent of the refrigeration (btw - people in Europe and Northern US had always had ample access to refrigeration

Here are some other things that correlate with advent of the refrigeration (btw - people in Europe and Northern US had always had ample access to refrigeration - in big parts half of the year in a cellar the temperature will be below 10 degrees C). Reduction in fermented foods - with fresh produce all year round - stuff like sourkraut becomes a flavor agent and not a staple. Ditto with all other kinds of lactobacilic pickling. The rise of the dry yeast, mighty kitchen aid at home and the industrial bread at scale - In the dry yeast the ratio of yeast to lactobacilli is different than in cake yeast (and cake yeast if often inferior compared to sourdough starter when it comes to bio variety) The mixer (and chorleywood) at scale allows for faster dough development - and usually the recipes for home are insane - something like 7g of dry yeast for 500 g of flour - it pumps it full of air fast (2h), but you have more gluten that is often not chopped enough by protease action and the bacteria. The traditional home bread making was overnight proof. Also the flours today are much stronger than before so we get more gluten with them. And because wheat gluten is very useful - it is often added in all kinds of processed foods. Top that with what I frankly consider abuse in both human and animal populations that probably are not terribly beneficial to people gut biome and variety. And all this starts at the same time the refrigeration got going. And industrial bread is roll of the dice - it may vary from really good to cardboard. But the cardboard seems to be way more popular.