I happen to work in a product that manages produce traceability, and I can confirm that it is quite within the realm of possibility to track produce in under 2 seconds with a simple web app and a relational database. We have been doing it for about 10 years.
To add, the produce supply chain is full of connectivity and digital literacy issues, so I would venture a guess that a blockchain implementation would generate a lot of attrition on the operations side of things. Another point of concern is performance since this is a fast moving supply chain due to the product short shelf life.
It was interesting to see how this audience thinks that blockchain somehow "solves" traceability when this has been going on in several different forms in a wide array of different industries with specific needs. They seem to also think that the right way to do it is with IoT and smart contracts, as if it were just a step away to push such a solution to an existing supply chain.
It keeps me up at night that one day a top-down decision will come that says we must a have a blockchain solution because market, or new competitors will bloom in the face of absurd amount of money being thrown at blockchain solutions and take market share. I imagine that 5 years from now, the winners of today's hype battles will be the losers when they have to maintain an overly complex inflexible solution for many years more.