Biochemisch‐technologische Studien über die Naßverarbeitung von Mais 3. Mitteilung. Die Milieubedingungen im Maiskorn während des Quellprozesses

Biochemical‐Technological Studies on Wet‐Processing of Maize. Part 3. The Medium Conditions in the Maize Grain During the Steeping Process.1 According to fundamental methodical examinations the destillation method with use of ground steeped corn is appropriate for the determination of SO 2 content in the interior of the maize grain.As a result of the high buffering capacity of a maize‐water suspension it is possible to judge pH‐conditions in the interior of the grain during the steeping process by the pH‐value determined in this medium.2 During steeping by the single tank process at first a considerable amount of SO 2 is absorbed by maize components (the maximum after 10 hrs). Later, desorption symptoms begin to show according to the initial SO 2 ‐concentration. The course of pH‐values in the maize steeping‐water gives reason to believe that at this stage SO 2 adheres to parts of the protein matrix that have become soluble. As a result of the entering SO 2 , there occurs an intensive pH‐decrease in the maize grain. Near the end of the process, values in both maize steeping‐water and maize grain get very close without reaching full identity. Initial SO 2 ‐values of 0,4 % and more inhibit lactic acid bacteria. 3 In a technological counter‐current process two steeping phases can be distinguished. During the first phase – from the beginning up to the 40th hour – the SO 2 content in the maize steeping water and in the steeping maize increases unnoticeably, but the formation of lactic acid takes place (maximum between 12th and 28th hour). At a certain steeping condition the produced lactic acid can enter the interior of the grain and cause a decrease of pH‐value. The second, shorter phase is characterized by intensive SO 2 increase and pH decrease in both maize steeping water and maize. The lactic acid content as well as its new formation are low. The proteindesintegrating effect of the steeping agent, the determining factor for the further processing of the maize, becomes effective at a late stage of the process. 4 The lactic bacteries as well as their products of metabolism can enter themselfs in the interior part of the grain, provided that the bacteria concentration in the aqueous medium is high and a certain level of maize stepping is reached. As the portion of the relatif bacterial activity in the grain liquid is 70 % in relation to the maize steeping water, a proteolytic activity of the bacterial enzymes is possible.