For a methodological approach to life cycle analysis and thinking see the website of 2.-0 LCA Consultants here.
This researcher has undertaken a number of fascinating studies into the GHG impacts of the food chain.
This database has LCA data for products and processes. In addition, it publishes the proceedings from its annual LCA conferences. The papers from the conference include LCAs of a very large range of foods, including bread, apples, milk, olive oil and tomatoes. In addition, there are papers looking at the issue of byproducts in the food sector, as well as those focusing more closely on methodological issues.
Food 21 is an interdisciplinary research program funded by the Foundation for Strategic Environmental Research (MISTRA), the largest funding body for environmental research in Sweden. The programme carries out research on a very wide range of food and environment related topics, some of them directly concerned with climate change issues. See the website; in particular the abstracts from the 2004 Food 21 Symposium are well worth examining.