My experience with food waste is that it is primarily an combination of liability, lack of incentives, and very slightly infrastructure/organization.

Businesses and individuals worry about the liability; what if I /give/ someone food (presumably in good faith) and then they turn on me and sue me for some form of payout. (Political, laws)

The incentives part, how can you provide incentive for someone to give away food that is still good, but nearing the end of being good, to those who need it in a timely manor so that it reaches those with need. How can you encourage the correct kind of food being donated? (Probably political arena taxes and tax credits to manage this; yes both, you have to punish undesired behavior too.)

The infrastructure largely exists in most places, but communicating that to the public (awareness) and making the public's interaction with that structure easy (here's the one area Tech could help; aside from raw funds) are the issues.