Food manufacturers may practice one or more of the following in stealth mode.
1) Replacement of ingredients with non-noticeable alternatives. Using carabeef instead of beef for making corned beef is easy without the customer noticing. In fact, I never knew this technique until a person from a meat factory told me personally. Another example, the lack of pineapple in fruit mix can be masked by increasing the quantity of other fruits.
2) Decrease package contents slowly and gradually. This was what the cacao dealer suggested when we complained about the non-stop price increase. Gradually trim down the chocolate tablet size so we could still have income without increasing the retail price. Customers will notice it in due time but will never brought them in state of shock.
I have been observing many companies playing with this trick for a long time. Hotdogs are getting thinner and shorter. Chips and crackers in the same size packaging are getting fewer and lighter. Softdrinks head spaces are getting more spacier until such time that they switched to smaller bottles.
3) Adding fake.. or simply call it adulteration. Adding chicory to coffee, mixing melamine to powdered milk, or the totally fake egg. Some are perfectly safe while some bring dangers to life.
4) Method replacement. Ever heard of same two products produced via two entirely different method? That is soy sauce. It can be manufactured via natural fermentation and acid hydrolysis. The latter having lower cost and preferred my makers. Do you love cheese? Read the label carefully. The cheaper brand you might be getting is a substitute cheese or an imitation cheese. The two cheese alternatives have the same flavor as cheese but offers less nutritive value.