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. 7. Mitteilung,Modellversuch zur Bestimmung hydrolytischer Reaktionen durch Maisenzyme während des technischen Maisquellprozesses

Biochemical-Technological Studies on Wet-Processing of Maize. Part 7: Model Test for the Determination of Hydrolytic Reactions by Maize Enzymes during the Technological Maize Steeping Process. In a model test enzymatic activity during the steeping process, which can be derived from the determined activity optima of maize enzymes in connection with the environmental conditions in the maize grain is confirmed. Amylolytic enzymes are qualified for degradation of maize starch only in the first steeping phase. Here, starch being closely linked to the endosperm protein is more stable than “isolated” maize starch. Proteases act throughout steeping time, but their activity decreases towards the end. It is supposed that during the steeping of maize degradation takes place mainly in the outer layers of the maize grain. It leads to a loosening of the linkage between endosperm and the germ on the one hand and the fruit hull on the other hand. These might facilitate the separation of the grain constituents. Proteolysis only plays a minor role for the dissolution of the protein matrix enclosing the starch granules.     

Zur Frage der Verwendung von Natriumdisulfit statt schwefliger Säure bei der Maisstärkeproduktion

Sodium disulphite (Na₂S₂O₅) has a less active effect on the extraction of corn colloids. The crude protein content of the colloids amounts to a total of 35%. On the Question of Using Sodium Disulphite instead of Sulphurous Acid in Corn Starch Production.

• 1 Comparative examinations have been carried out on the composition of extracts, which had been abtained by steeping of corn in sulphurous acid, sodium disulphite solution and water, respectively.
• 2 It was found that the presence of chemical reagents in the solution used for the steeping of corn, increases the diffusion of extractive substances (especially of the high-molecular ones) from the corn kernel into the steeping water. The most active reagent in this action is sulphurous acid because of its reducing properties and its faculty of increasing the permeability of the cell walls.
• 1 A certain difference in the effect of sulphurous acid and sodium disulphite solution on the colloidal matter of the corn kernel has been found. The highest total amount of colloidal matter extracted from the corn kernel occurred in the presence of sulphur dioxide. About 50% of the dry matter of the colloids (calculated as crude protein) consists of nitrogenous substances.

Test data show that some more high-molecular non-nitrogenous substances are extracted from the corn in the presence of sodium disulphite (= sodium pyrosulphite or sodium metabisulphite).

• 4 It has been found that the positive effect of lactic acid during evaporation of the extracts consists not only in the formation of soluble lactates, but also in the fact that the high molecular nitrogenous substances are degraded to low-molecular substances which do not precipitate during thickening of the extract.
• 5 Results of the technological testing of sodium disulphite showed that during the manufacturing of starch from corn it is possible to replace sulphur dioxide by this reagent in the steeping process according to the technological structure of the plant.

     

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.     

A Novel Enzyme Application for Corn Wet Milling

In corn wet milling the raw material is prepared by means of steeping. Steeping is required in order to:

• –obtain the valuable CSL (Corn Steep Liquor),
• –soften the kernel and break the cell walls.

SO₂ is added to the steepwater to inhibit bacterial growth. Depending on the type of corn, the steeping time in a semi-continuous steeping system varies from 36 to 60 h, which is substantially longer than all subsequent steps in the process. The corn comprises phytic acid, which to a large extent ends up in the CSL and constitutes an undesirable component. It has now been found that the problem caused by this phenomenon can be avoided by using phytic acid degrading enzymes during steeping. It has further been found, that by adding phytic acid degrading enzymes together with plant cell wall degrading enzymes to the steep liquor, the steeping time can be reduced considerably in a conventional steeping system and even further in a two stage steeping process, whereby the second steeping stage is carried out after course grinding. Also in case conventional steeping times are applied higher starch yields and lower energy consumption may be obtained.     

Schwefeldioxidaufnahme bei der Maisquellung. 2. Technologische Aspekte

Absorption of SO₂ During Swelling of Maize. Part 2. Technological Aspects . Investigations had been made by means of a modified method for practical starch extraction from maize kernels. Already after steeping in 0.8% sulfur dioxide in steeping water a final sulfur dioxide content in the starch lower than 8 mg/kg was observed. Studies in three german starch plants showed that the sulfur dioxide content of products from different process steps before the hydrocyclon station varied. After refining of raw milk this differences could not be observed any longer. Due to a further addition of sulfur dioxide during the refining steps the industrially produced starches contained much more sulfur dioxide than those extracted by the laboratory method. These results have been confirmed by processing industrially steeped maize in the laboratory without further addition of sulfur dioxide during the refining steps.     

Effects of Steep Time and SO2 Concentration on Steepwater Profiles and Maize Milling Yields Using a Continuous Countercurrent Steep System

Effects of SO₂ concentration and steep time on maize steep profiles and wet milling results were studied using a continuous countercurrent steep system. Maize was steeped at 50 ± 2 °C at different SO₂ concentrations (target value at 1,000, 2,000 and 3,000 ppm) for different lengths of time (18, 24, 30 and 36 h). Steepwater profiles, including pH, SO₂ concentration, total acidity and steepwater solids content versus tank number for each combination of SO₂ level and steep time were generated. Three steeped maize samples for each condition were milled and average product yields were reported. Steeping, from the perspective of maize, can be viewed as a three-stage process including a lactic acid dominated stage, a SO₂ absorption stage and a SO₂ diffusion stage. From the perspective of steepwater, increasing SO₂ concentration increases the total dry solids increase rate and SO₂ decrease rate. Starch yield can be significantly increased by increasing either steep time or SO₂ concentration.     

Schwefeldioxidaufnahme bei der Maisquellung. 3. Einfluß auf die Mikroflora

Absorption of SO₂ During Swelling of Maize. 3. Influence on the Microflora. In order to gain insight into the micro-biological conditions during maize starch production the change in micro-biological germ content of the following products has been examined in three different plants: – Maize before entering the steep tanks and after the end of the steeping process, – Starch suspension before and after the hydrocyclone station as well as before entering the centrifuge, – Wet starch during its discharge from the centrifuge and before entering the drier, – Dry starch after discharge from the drier. It was shown that the number of microorganism remaining in the starch does not solely depend on piloting of the steeping process. Increase of germ number respectively infections at certain stages of production seem to be essential causes for micro-biological contamination of maize starch. Place and degree of this increase of germ number depend on the respective technological pattern.     

Einfluß von Schwefeldioxid auf die Lipide stärke-haltiger Lebensmittel: Mais

Influence of Sulfur Dioxide on the Lipids of Starch Containing: Maize. The present paper shows that sulfur dioxide retards the lipolytic activity during the steeping process of maize. The results show that the hydrolysis of phospholipase A (E.C. 3.1.1.4) which removes one fatty acid from the phospholipide is followed by the phospholipase B (E.C. 3.1.1.5). It is not worthy that the phospholipase A is more affected by SO₂ than phospholipase B. However, other lipides, e. g. galactosyldiglycerides and sterol-containing lipides, showed no observable changes in amount. It is of interest that a relative smaller amount of free fatty acids was extracted with petrolether from maize than the original amount extracted with the same solvent before the storage. Whereas the extracted amount with butanol water did not change markedly. On the basis of this findings it may be concluded that free fatty acids are adsorbed on the starch granules of the maize endosperm.     

EFFECT OF ALKALINE STEEPING ON WATER UPTAKE AND MALT QUALITY IN SORGHUM

Condensed tannin-free and high-tannin sorghum grain were steeped in dilute alkali and the effects on water uptake during steeping and final malt quality were determined. With the condensed tannin-free sorghum, steeping in dilute alkali led to increased water uptake during steeping and an improvement in malt quality in terms of diastatic power and free amino nitrogen. These effects are presumed to be due to the alkali opening up the pericarp cell wall structure of the grain, allowing more rapid water uptake. Best results were obtained by application of alkali early in steeping, presumably because the grain is less susceptible to alkali toxicity than later in steeping. Steeping high-tannin sorghum in dilute alkali did not improve malt quality. This appeared to be because water uptake was not increased to the same extent as with condensed tannin-free sorghum, as the alkali reacted with the tannins .     

Schwefeldioxidaufnahme bei der Maisquellung. 1. Verteilung in den Fraktionen

Absorption of SO₂ During Swelling of Maize. Part 1. Distribution in Fractions . It has been shown by means of S-35-labelled SO₂, that protein and germ take up most of SO₂ during the swelling of corn. The uptake by the maize kernels is only 6% from the amount solved in swelling water. The swelling process does not change the fatty acids composition of the total lipids of corn. There are only traces of sulfur in the extracted fats.     

EFFECTS ON THE ENDOGENOUS THIOLS AND DISULPHIDES OF STEEPING BARLEY IN SOLUTIONS OF DORMANCY-BREAKING SUBSTANCES

Conditions were optimised for overcoming dormancy by steeping barley in solutions of propyl mercaptan, British anti-lewisite (BAL), thiourea, 2-mercaptoethanol and bis-(2-hydroxyethyldisulphide). The ability of the last compound to break dormancy may have been due to the living tissues of the grain, which rapidly reduced it to a thiol. Dormant barley germinated more slowly than the mature when steeped in hydrogen peroxide (0.75%), but although the level of glutathione was lower in the embryos of mature grains than in those of dormant grains after 24 h steeping, while the level of cysteine was higher after 48 h steeping, the levels of oxidised glutathione and cystine were essentially the same. Steeping in solutions of BAL retarded the germination of mature grains and accelerated the germination of dormant grains so that germination with the two types of grain, after steeping in a solution of BAL, was nearly synchronous. There were no significant differences between the levels of the thiols and disulphides in the embryos of dormant and mature grains germinating after a steep in BAL. BAL evidently reduced all endogenous disulphides in the embryos. Decorticated grains took up BAL from solution and, when sufficient thiol had been present in the initial steep, released part of it into washing water. Part of the BAL was unaccounted for, evidently it had been metabolised by the grains. Results of staining sections of steeped grains with monobromobimane and viewing under ultraviolet light to locate thiols agreed with this conclusion. Analyses of micromalts prepared by steeping dormant and mature grains with and without BAL showed that BAL retarded the modification of mature grain but accelerated the modification of dormant grain without, however, improving the performance to give a malt equal in quality to that of water-steeped, mature grain.     

Verarbeitungstechnische Eigenschaften von Inlandmais. 3. Direktverzuckerung

Processing Properties of Local Maize. 3. Direct Saccharification. The corn grits obtained by dry degermination of 15 grades of corn grown in West Germany were subjected to direct enzymatic saccharification. In comparison with two overseas corn grades, the suitability for hydrolysis of the starch contained in the lowfat grit products has been investigated. Two-step enzymatic hydrolysis with bacterial alpha-amylase and glucoamylase was preceded by a steeping extraction with SO₂ water to remove undesired soluble corn components. Although from the technological point of view results cannot be regarded as optimum, it was demonstrated that the starch of domestic corn grades is as suitable for hydrolysis or even more suitable than overseas grades. It was also found that the lowfat products of the medium-early grades permit a larger starch turnover and, consequently, larger sugar yields than that of the medium-late grades although the average starch content of the latter was higher.     

The effects of processing methods on the levels of lysine, methionine and the general acceptability of ogi processed using starter cultures

Batches of ogi were produced from maize flour slurry, dehulled maize grains and whole maize grains using Saccharomyces cerevisiae and Lactobacillus brevis as starter cultures. Fermentation over time showed that dehulled maize grains inoculated with the starter cultures and processed whole maize grains requiring steeping led to higher acid production than fermentation with dry-milled maize slurry. Ogi from dehulled maize grains inoculated with starter cultures showed the highest levels of lysine and methionine. Steeping grains encouraged a stronger ogi aroma than fermentation of maize flour slurry alone. Lactobacillus brevis contributed most to the taste of ogi. Fermentation with starter cultures showed good prospects for improving the lysine and methionine levels of ogi.     

Über die Technologie der Verarbeitung von Maisgrits zu Stärke

On the Technology of Processing of Maize Grits to Starch. At the production of maize products of a low fat content, such as corn flakes or brewery grits, there results on principle a very fatty maize grit of a farinaceous structure in a quantity of 12 to 30 % which is hard to sell. From these waste grits there can be manufactured a quality starch, which complies with the quality designations with regard to protein, fat, ash, and viscosity. The process newly developed and applied for a patent was tested in an existing factory. By means of an intensive steeping the steeping time can be reduced to 1/4 to 1/3 of the normal maize steeping time. The steeping water is separated free of starch by means of a special decanter. The fat content of the steeped maize grit reduces thereby down to 1/8 of the original value. The steeped maize grit is ground and the resulting milk is treated further like in a normal starch factory, at which the separation of husks and germs is eliminated. The process enables maize mills to process also soft sorts of maize such as a German maize. In this case there results at the dry grinding a high yield of fine, fatty waste grits. Without further processing to starch the grinding of soft sorts of maize would, therefore, be uneconomical.     

Nixtamalisation of maize (Zea mays L) using a single screw cook-extrusion process on lime-treated grits

The tortilla flour market is expanding but present industrial production is lagging behind in the use of modern technologies to increase production and cut costs due to the maize steeping and drying operations. A process using a single-screw cook-extruder which eliminates the traditional steeping and drying operations was therefore explored. Lime (Ca(OH)₂) suspension was absorbed onto commercial maize grits (2 g lime kg^?1 maize) and the resulting meal conditioned to various moisture contents. These samples and one which had not been lime-treated were cook-extruded through a Brabender Do-corder extrusion cooker (Type 825602). The dry extrudate was milled through a 150 μm sieve and tortillas made from each sample. The tortillas prepared from the lime-treated grits conditioned to 472 g kg^?1 moisture compared favourably with that prepared from traditionally prepared masa flour when organoleptically assessed. Flour pasting properties (viscosity) and water absorption index were not significantly different (P < 0.05) from the traditionally prepared products. Enzyme susceptible starch index did not correlate well with dough quality.     

Role of Lactic Acid in Corn Steeping and Its Relation with Starch Isolation

Corn grains were steeped in fresh SO₂ solution (300 ppm), old SO₂ solution (100 ppm, 0.55 g lactic acid per 100 ml) and fresh SO₂ with chemically pure lactic acid (100 ppm SO₂ + 0.55 g lactic acid per 100 ml). The water absorption rate in all trials using old SO₂ or low SO₂ with lactic acid in the first stage of the steeping process was higher. The solubilization and diffusion of protein was stronger in corn grains steeped completely in old SO₂ or low fresh SO₂ with lactic acid. Such treatments gave the highest starch recovery with lowest protein content in the isolated starch. The low starch content in hulls and fibers confirms the important role of lactic acid in presence of a low concentration of SO₂ (0.01%).     

The influence of starch pasting properties and grain protein content on water uptake in barley

Steeping is the first operation of malting and its purpose is to increase the water content of the grain up to 43–46%; however, such a simple step encompasses several metabolic processes that affect germination and the final malt quality. The aim of this study was to evaluate the effect of initial grain protein (GP) content and starch pasting properties, measured using the Rapid Visco Analyser (RVA) on water uptake in different barley varieties. The partial least squares (PLS2) regression algorithm was used to compare the two data matrices, the independent block of variables X (RVA data and GP) and the dependent block Y (water uptake at different steeping times). The first two PLS2 loadings explained 65 and 23% of the total variation in water uptake in the barley samples. Water uptake at 1 and 2 h was poorly explained by the PLS2 models, while after 5 h the models explained more than 40% of the variability. The results from this study showed that, although a relationship between GP and water uptake exists, it is not universal for all the varieties, indicating that the relationship between GP and water uptake is varietal dependent. Copyright © 2014 The Institute of Brewing & Distilling     

Enzymatische Direktverzuckerung der Stärke in Zwischenprodukten der Maisstärkeindustrie

Enzymatic Direct Saccharification of the Starch of Intermediate Products of Maize Starch Industry . A new process for direct enzymatic saccharification of starch in wet-milled, degermed steeped maize is proposed. Utilization of this product instead of dry-degermed maize fractions is of advantage as maize germs are obtained in pure form about 50% fat in DS. Moreover, highest possible extraction of soluble maize components by the steeping process and simultaneous optimal loosening of the starch-gluten structure are achieved.     

Effect of steeping temperature on the quality of malt and Pito (an indigenous Ghanaian drink)

Pito is a traditional fermented beverage produced from malted sorghum or millet grains. Steeping is usually performed at 30°C. Limited information exists on the effect of temperature on the characteristics of the malted grains and the Pito. The aim of this work was to study the effect of varying the steeping temperature (30, 35 or 40°C) on the quality of malt and of the Pito brewed from Kadaga sorghum and to specifically determine the diastatic power, extract yield and attenuation limit of the malt. Total soluble solids, pH and alcohol content, as well as the sensory evaluation of the Pito brewed at both 40 and 30°C were assessed. Results from analysis showed that the 40°C malts had the highest diastatic power (88.1 SDU/g), extract yield (96.75% d.m.) and attenuation limit (78.95%). Pito produced from malt steeped at 40°C yielded a significantly higher alcohol content of 3.54 g/100 g, a total soluble solids of 4.34 and a pH of 3.57 and this Pito was preferred over the traditionally prepared Pito at the steeping temperature of 30°C. Therefore steeping sorghum at 40°C yields a quality malt and a quality Pito. This study should aid in the adoption of sorghum for brewing purposes. Copyright © 2015 The Institute of Brewing & Distilling