The idea is for the customers to be able to comment on the quality of supermarket food products via a dedicated app by scanning a product's bar code and typing in some remarks or/and voting on the general quality level.
The cases when you buy a certain food product at the supermarket and there's something wrong with it are not rare in my experience. You can't always evaluate the quality before buying and just leave it lying there if there's something wrong. In any case, such products shouldn't be there in the first place.
Examples: the product has gone bad from the taste even though the expiry date is still valid; the dough of a pastry product is raw, not baked well; in a prepacked bag containing many fruits/vegetables some began to rot, etc.
There's not much you can do in those cases, except from complaining to the staff at the store, which people rarely do, cause they either leave the product at the store if noticed on time or if noticed only at home, they usually don't bother to come back and complain about it unless they get a serious food poisoning.
If nobody complains about the flaws of a certain product, the store might not even notice that there is a problem with a certain item and keep the situation as it is. So having such a review system would be beneficial for both the customers and the shops to increase the quality of their products.
You'd open a dedicated app and scan the barcode of a product with your smartphone, then a window would open for you to rate/type a review of that specific product. You could also upload pictures. You could do this both while still being at the store and after you've already bought the product.
If you already bought something and are dissatisfied with the quality, you could scan the receipt of the total shopping and the app would show you the list of products that are in the receipt for you to choose the one (or a few) you want to review. Scanning a receipt would also let the system register the precise buying time which is indicated in it. Otherwise, the users could indicate the approximate time of buying themselves.
The system could be used to review any product present in the supermarket, not only the food products, but it's less likely that there will be problems with non-food products, therefore food products should be the main focus of such a review system.