Two points: 1. Scopus returns 167 papers on "indigenous food preparation," many behind paywalls. However, this only includes literature with those key words, there is much more. Check ethnobiology, ethnobotany, ethnozoology, etc., where descriptions are sometimes casual but informative. This is an immense topic, not susceptable to easy summary. For Brazil, close to 1,000 papers would be relevant. More if the non-peer literature were searched.
2. One impression needs reinforcing, one correcting, at least for food consumption in Brazil in the 2002-3 and 2008-9 POFs. Native foods consumption declined overall, in spatial congruence with well-konwn land use changes. Rural areas with propulation spurts showed great declines in own-consumption. However, declines were quite minimal in the great cities, and somewhat offset by increasing away from home consumption of recipes including native foods. Native foods are higher priced than non-native across food groups. So there is hope, if sometimes forlorn due to disparities and macroeconomic distortions, that well-informed countries will increasingly be keeping current (with the past).
Links and resources:
Indigenous Peoples’ food systems: the many dimensions of culture, diversity and environment for nutrition and health
Comparative Assessment of Indigenous Methods of Sweet Potato Preservation among Smallholder FArmers: Case of Grass, Ash and Soil based Apporoaches in Zimbabwe
FSN Forum discussion: Looking back to effective rural practices ... Did we miss something?