This video addresses a question from a SikhNet user asking about the concept of "Jhoot", and not sharing food with non-amritdhari's. He was wondering why some Sikhs practice this. I tried searching online to better understand the reason some practice this, but found very little. From what little I read online in forums the reasoning was mostly hygiene (sharing food that you have eaten with someone else).... and also some reasons given about "non-amritdharis" putting bad vibrations on the food.
Below is an informative audio recording excerpt from a Question & Answer session (Jan 18, 1984) in Singapore with SSS Harbhajan Singh Khalsa Yogiji. This audio is on the same topic of Eating Joota food of someone who is not Amritdhari and topic of Langar. When an Amritdhari is eating can we eat together with him?