Two hours might not be nearly enough time to keep a lunch cold, once you take into consideration the occasion that you’re packing for. In an article for The Kitchn, Ayn-Monique Klahre said that her daughter had about four hours between leaving the house in the morning and opening up her lunch bag. That’s double the amount of time that the USDA warns could make perishable food unsafe.
The Kitchn also spoke with the International Food Information Council Foundation’s director of food technology communications, Dr. Tamika Sims, who explained that it’s completely possible to extend the life of your lunch with the proper planning. The key lies in having a cold source – no matter what box or bag you carry, you’ll need a completely frozen ice pack to go along with it. The more food you’re packing, the more cold sources you’ll need.
If you don’t have an ice pack, you can always DIY one at home by filling an old water bottle up and freezing it. As long as you add a cold source, you should expect your food to stay fresh for up to four hours – just in time for lunch.