Hear me out. There’s nothing innate to an object that makes it “food”. It’s an attribute we give to certain things that meet certain qualities, i.e. being digestible, nutritious, perhaps tasty or satisfying in some way, etc. We could really ingest just about anything, but we call the stuff that’s edible “food”. Does that make it a social construct?
You are halfway there. Those examples you gave define constructs but a lot of these things are not what philosophy uses to define social constructs. Scientific taxonomy constructs and linguistic constructs are things but they are fairly useless in discussion surrounding social constructs because while different cultures might draw the line differently around what exactly constitutes a “chair” vs say a “stool” or some such that’s more of just a linguistic boundry. Its basically always a thing you sit on.
Philosophy uses a bunch of different ideas labeled as different forms of construct to break down the idea of how different types of categorization or subjection happen… but when they start talking about “social” constructs they are specifically talking about categories of human interactions with something that have incredibly variable different potential contexts based on culture. It also requires things which are included or excluded from those category for not entirely practical reasons. Philosophy uses this to talk about how social categories are subjective creating or allieving tension between different cultural groups.
Food is actually a good example. There are a lot of things culturally considered food and non food items despite those items all having nutritional value and being safe to consume. In our increasingly cosmopolitan world a lot of expansion has happened to increase the size of the category. Like raw fish was not considered a food item by a lot of people when and where I was growing up. Now sashimi is everywhere and no one bats an eye. Digging for another example mice are technically edible but even raised and slaughtered cleanly very few would consider them valid as food. Whether what I put on your plate is deemed an disgusting insult or a delicious delicacy is really in the eye of the beholder and has caused a number of historical diplomatic and cultural issues around other cultures veiwing each other as inferior.
Just because something is a construct does not automatically make it a social construct.