The joke is about how yogurt cartons and cottage cheese both have expiration dates, but the yogurt never goes bad.
It is considered funny because it plays on the idea of expiration dates and how some foods can last longer than their expiration dates suggest.
Yes, yogurt contains live and active cultures that act as preservatives and prevent the growth of harmful bacteria. Cottage cheese, on the other hand, does not contain these cultures and is more susceptible to spoilage.
Yes, this joke can be used to introduce the concept of preservatives and how they can extend the shelf life of certain foods. It can also be used to discuss the limitations of expiration dates and how they are just a guideline, rather than an exact science.
Yes, there are several examples such as honey, vinegar, and salt. These foods have properties that inhibit the growth of bacteria and can last for extended periods of time. However, it is always important to use your judgement and inspect the food before consuming it, even if it is past its expiration date.