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 SO₂ 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 SO₂ is absorbed by maize components (the maximum after 10 hrs). Later, desorption symptoms begin to show according to the initial SO₂-concentration. The course of pH-values in the maize steeping-water gives reason to believe that at this stage SO₂ adheres to parts of the protein matrix that have become soluble. As a result of the entering SO₂, 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 SO₂-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 SO₂ 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 SO₂ 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.

     

Biochemisch-technologische Studien über die Naßverarbeitung von Mais 5. Mitteilung. Untersuchung des amylolytischen Enzymsystems des Maises

Biochemical-Technological Studies on Wet-Processing of Maize. Part 5. Examination of the Amylolytic Enzyme System of Maize. 1. Amylolytic activity of the enzyme preparations isolated from the ungerminated maize is limited to the pH-range from 3.0 to 8.4. Activity reaches its optimum at a pH of 5.2. 2. With starch dispersion the temperature optimum lies in the range of 50 °C, with non-gelatinized maize starch around 60 °C. 3. A rapid decrease of stability, noticed at 20 °C and pH-values between 3.5 and 4.7 is attributed to the proteolysis of the enzyme protein. At 50 °C the amylolytic enzymes in aqueous solutions are instable over the entire pH-range. 4. Complete inactivation is reached by means of SH-inhibitors (10⁻² M iodine acetic acid, 3·10⁻³ M p-chlorine mercury benzoic acid) respectively 10⁻⁴ M mercury dichloride. 5. SO_-2-contents of 0.01% increase activity distinctly, at 0.03% complete inactivation takes place because of the pH-shift to 3.4. With the influence of sulfite an activation is also found to take place at higher amounts.     

Biochemisch-technologische Studienüber die Naßverarbeitung von Mais 4. Mitteilung. Über die qualitative Zusammensetzung des Mais-Hydrolasensystems und Aktivität einzelner Enzyme bzw. Enzymgruppen

Biochemical-technological Studies on Wet-Processing of Maize. Part 4. On the Qualitative Composition of the Maize Hydrolase System and the Activity of Particular Enzymes Respectively Enzyme Groups. Enzyme preparations have been isolated from the maize meal by means of water extraction and following protein precipitation (ethanol, ammonium sulphate, acetone). Cleaning or concentration operations have been left out, in order to preserve the enzyme system of the maize in its totality By paper chromatographical studies on these preparations as well as special activity deter minations a- and β- amylase could be traced in the ungerminated as well as in the germinated maize and the presence of phosphorylase could be confirmed. For enzymatic handling of the non-gelatinized starch a- amylase is above all convenient, but slight degradation by β-amylase cannot be overlooked. By means of paper chromatography and reductometry β-fructofuranosidase, a-glucosidase, β-glucosidase could be clearly traced in the germinated and ungerminated maize. a-Galactosidase could be traced with some reservation. Matters in this group have in common the faculty for hydrolysis and synthesis of glucosidic bondings. Proteinase and lipase have been traced in all preparations, peptidase exclusively in those from germinated maize and their activities have been determined. Of all the maize sorts examined, hard maize shows higher activities with all enzyme species compared to dent maize.     

Einfluß einer mechanischen Bewegung des Maises während des Quellprozesses auf die Ausbeuten

The Influence on the Yields by Mechanical Movement of Corn during the Steeping Process. Using two different corn varieties, U. S. Yellow Corn No. 2 and Kenya White Maize, it was tried to find out — in comparison with the conventional corn steeping process, wether higher starch yields may be obtained by means of mechanical movement of corn during the steeping process with steeping time remaining unchanged, or if equal starch yields may be obtained at as shortened steeping time. Naturally, this requires at least equal quality properties of the obtained starches. Under this premise, respective conclusions have been drawn from the results of laboratory yield determinations and analytical tests. In connection with earlier results several criteria for further possibilities of development in the field are given.     

Untersuchung über Änderungen von Fleischproteinen während der Gefrierlagerung

Investigation of changes in meat proteins during frozen storage. The effect of freezing and frozen storage on proteins was investigated in case of pork L. dorsi muscle. After fresh pork was sliced (1 cm thickness), wrapped and frozen (2 different velocities) samples were taken (control, 48 h-, 2, 4 and 6 month-frozen storage) and changes in proteins investigated by DSC and SDS-PAGE. DSC-thermograms show 4 peaks corresponding to myosin (peak 1) and actin (peak 4). Peak 2 reflects the sarcoplasmic proteins and connective tissue contribution. Peak 3 is not defined. When measuring the enthalpies of the DSC-thermograms, it can be observed that the enthalpy ascribed to myosin decreases during frozen storage, while the enthalpy corresponding to actin is not affected. At the beginning of our experiments SDS-PAGE was supposed to be a proper method for the investigation of protein denaturation. Our results show no significant changes in the electropherograms during the whole period of frozen storage.     

Veränderungen der Eisenspezies während des Verarbeitungsprozesses von Sojabohnen zum fermentierten Produkt Tempeh

Change of iron-species during processing of soybeans to its fermented product Tempeh The change of distribution of iron-species and the iron availability during processing of soybean to its fermented product Tempeh were investigated. The results demonstrated that the distribution of iron in various iron-species in soybean remained unchanged during soaking. During cooking and steaming, the soluble part of iron decreased. The percentage of iron(III) and complexed iron-species increased at the expense of iron(II) species. During fermentation the soluble iron increased, the percentage of iron(III) species and complexed iron decreased where as iron(II) species increased again. Based on the determination of the soluble iron content after the extraction of the sample using simulated digestive juices (gastric and intestinale juice), it can be established that the iron availability remained unchanged during soaking, decreased during cooking and steaming and increased through fermentation.