Fermentation of liquid coproducts and liquid compound diets: Part 2. Effects on pH, acid-binding capacity, organic acids and ethanol during a 6-day storage period.

The effects of a 6-day storage period on changes in pH, acid-binding capacity, level of organic acids and ethanol of three liquid coproducts [liquid wheat starch (LWS), mashed potato steam peel (PSP) and cheese whey (CW)] and two liquid compound diets [liquid grower diet (LGD) and liquid finisher diet (LFD)] were studied. All products, except LWS, showed a significant decrease in pH and acid-binding capacity during storage. At the end of the storage period, all products reached a pH of between 3.5 and 3.9. In general, it can be concluded that the lactic acid content, and to a lesser extent the acetic acid content, increased dramatically during storage. In contrast, the ethanol content increased significantly in the liquid compound diets only. The pattern of changes in pH and organic acids during the 6-day storage period was different between the liquid coproducts and the liquid compound diets. At the start of storage, liquid coproducts are already in the 'middle' of the fermentation process, while liquid compound diets need approximately 24-36 h before fermentation begins. Consequently, in practice a different approach to obtain fermented diets is needed for liquid coproducts and liquid compound diets.