The requirements and manufacturing procedure of complementary (weaning) foods is discussed. Nutritional requirements for infants (aged 6-12 months) include approx. 3 MJ energy and 14 g digestible protein per litre, of a semi-liquid porridge. Microbiological safety is enhanced by biological acidification (lactic acid fermentation) until pH ≤4.5. An evaluation of processing operations, e.g. soaking, germination, roasting, and fermentation is presented and their effect on safety and digestibility of the final product is discussed. Some scenarios are presented for complete processes to obtain shelf-stable, dry powdered formulas that meet the above requirements. Blends of cereals, rootcrops and proteinaceous legumes are prepared and subjected to lactic acid fermentation using a simple enrichment starter to ensure adequate acidification. Enzyme rich flour is used to reduce bulkiness. At small-scale production level, cooking and drying is best done by dry-toasting. Extrusion cooking is a promising technique that can be feasible at medium and larger-scale production levels.