Is it permissible to take samples of food materials for analysis or as a reference without the supplier's knowledge or consent, and what should we do with samples that have exceeded the permissible retention period if that is not permissible?

Samples taken for analysis and the like are considered a trust (amanah). If the grace period for their retention by the relevant authorities expires and their owner or his agent does not come to retrieve them, and they do not authorize their disposal, and they cannot be contacted, then the way to deal with them is to give them away as charity on behalf of their owner. This is based on the analogy of deposits and trusts whose rightful owners are unknown. Sheikh al-Islam Ibn Taymiyyah indicated that funds whose rightful owners are unknown should be spent on public benefit, and that if it is impossible to return them to their owner, then the unknown is like the non-existent. He cited the hadith about lost property (Luqatah): "If you find its owner, return it to him; otherwise, it is Allah's property, which He gives to whom He wills."