Etude de l'acidité formée au cours de l'irradiation gamma de l'amidon de maïs

Study of γ Radioinduced Acidity in Corn Starch. Amounts of radioinduced acids and esters in corn starch have been measured in terms of different conditions of irradiation (dosis, dosis rate, temperature, atmosphere) and of starch characteristics (% water, impurities, kind of glucosidic link) and results have been compared to those given by heat sterilization. Subsequent development of acidity have been checked during the storage at ambient temperature.     

Identification et dosage des sucres de faible poids moléculaire formés au cours de l'irradiation de l'amidon de maïs

Sugars Formed During Irradiation of Maize Starch. Identification and Determination Sugars of low molecular weight formed during irradiation of maize starch were identified and determined by ion exchanger chromotography. The following sugars were found: one disaccharide (maltose), hexoses (glucose, mannose, galactose, fructose), pentoses (arabinose, xylose, ribose), and one tetrose (erythrose). There remains a slight uncertainty in the cases of mannose and erythrose. The influence of irradation conditions (dosis, atmosphere, temperature), of starch properties (bumidity, impurities, glucosidic bonds), and of storage conditions was examined. By the results it was made possible to propose a hypothesis on the kind of sugar formation and on the role of water in this process, which takes the observed differences into consideration satisfactorily. Irradiation effects have been compared to those given by heating.     

Technique de dilution isotopique pour le dosage de quelques produits carbonylés de faible poids moléculaire formés au cours de l'irradiation gamma de l'amidon de maïs marqué

Isotopic Dilution for Quantitative Determination of Some Low Molecular Weight Carbonyl Compounds Formed During Gamma Irradiation of Labelled Maïze U (¹⁴C) Starch . Gamma-induced glycolaldehyde, glyoxal, glyceraldehyde and hydroxymethylfurfural in maïze starch were quantitatively estimated by isotopic dilution from U (¹⁴C) starch. The experimental procedure was described and concentrations of individual compounds expressed as a function of dose (0 to 4.5 Mrad). The highest value was found for glycolaldehyde (9.1 μg/g/Mrad) with a few small traces of hydroxymethylfurfural.     

Evaluation des carbonyles formés au cours de I'irradiation gamma de I'amidon de maïs

Evaluation of Carbonyl Compounds Formed During Gamma Irradiation of Maize Starch . Changes in the levels of radioinduced carbonyl compounds were analysed as a function of irradiation conditions (dose, dose rate, temperature, atmosphere), starch properties (water content) and post irradiation treatments (storage, autoclaving). The percentages of identified and unknown carbonyl fractions were respectively 40 and 60 %. The half unknown fraction was linked on the radiodextrins (polysaccharides formed during irradiation of starch).     

Quelques composés volatils formés au cours de I'irradiation gamma de I'amidon de maïs

Some Volatile Compounds Formed During Gamma Irradiation of Corn Starch. Acetaldehyde, methanol, acetone, small amounts of methyl formate and various quantities of ethanol were found in ⁶⁰Co irradiated maize starch, using gas chromatography coupled with mass spectrometry. Influences of dose, temperature, atmosphere composition, water and impurities content, were investigated respectively for the first three substances. Irradiation effects were compared to heat treatment effects and concentration changes were followed during storage.     

Etude de la partie soluble dans l'eau des radiodextrines formées par irradiation gamma de l'amidon de maïs

Study of Water Soluble Dextrins Formed by Gamma Irradiation of Maize Starch . The respective influences of various irradiation parameters and of starch and its storage characteristics on the quantities of water soluble ridiodextrins are studied. The proposed theory takes into account the variations of the quantities and the sizes of the molecules as a function of irradiation dose and starch moisture. The dextrins are chemically characterized and a weight balance of water soluble already identified radiolysis products has been possible and therefore done.     

Etude des mécanismes de formation de quelques produits identifiés après irradiation gamma de l'amidon de maïs

Studies of the Formation Processes of Some Identified Radiolysis Products after Gamma Irradiation of Maize Starch . From the variations in the concentrations of different starch radiolysis products, studied as function of starch water content and of oxygen pressure, it has been possible to suggest different formation processes. The initied break of the C O C linkages as well as the further rearrangement of the radicals formed or their reactions with water and oxygen explain the observed rearrangements. Water generally has a protector effect, which can be interpreted as an inhibition of primary radical transformation. As for oxygen, its fixation on a carbon radical may account for the generally stimulating action of this gas.     

Presence d'acide formique dans l'amidon de maïs irradié

Presence of Formic Acid in Irradiated Maize Starch. Formic acid occurs in relatively large amounts during gamma irradiation of maize starch (100 μg/g/Mrad, in oxygen). It represents the main part of radio-induced free acidity. We determined the influence of several parameters: irradiation conditions (dose, dose rate, temperature, surrounding gas), storage temperature, starch characteristics (moisture, impurities), heat treatment. A formation process is prosposed.     

Evolution de quelques caractéristiques des amidons extraits de grains de maïs normal et d'amylomaïs au cours de leur formation,

The Development of Some Characteristics of Starches extracted from Normal Corn and Amylomaize Grains during their Formation. Within the research work on the evolution of corn grains constituents with different amylose contents, during their development, a study has been carried on the starch content of corn grains, amylose content of starch grains, microscopical and submicroscopical aspects of starch grains and their crystalline organization marked by X rays diffraction. The quantity of starch synthetized for one corn grain is stated as all the more important as the amylose content of grain is lower. For amylomaizes, it is pointed out that the determination of amylose content of starch carried on at 2°C leads to higher values than at 20°C. The difference between the results might be ascribed to the presence of a glucidic fraction reacting as amylose and synthetized in a relatively important proportion at the beginning of corn grain formation, and later on becoming diluted with the other amylaceous components. The increasing stability of amylomaize starches when thermically treated might correlate with their amylose content.     

Artefacts au cours de la préparation de coupes de grains d'amidon. Etude par microscopie photonique et électronique

Artefacts During the Preparation of Sections of Starch Granules. Studies under Light and Electron Microscope. Dark bands which are usually observed in ultrathin sections of starch granules, „coloured”︁ or not, have been considered by some authors as marking the presence of protidic substances, by others as artefacts of sectioning, on account of the diversity of their shapes and the frequency of their appearance. Examinations under light microscope show that this phenomenon appears effectively, during the sectioning of the inclusion block, when the ultrathin section of starch comes into contact with the surface of water in the collecting tank and then swells. The examination under electron microscope of ultrathin sections shadowed with gold, allows us to show that these dark bands are the consequence of surface folding of the cut starch grains. The measurements of electron density show that there are folds like S or double folds like S, and that electron transmission across the sample follows a logarithmic rule. A discussion leads to think that these artefacts are the consequence of a defective permeation of starch with the inclusion material and the result of starch water affinity. We must definitely leave out that dark bands should be a manifestation of protidic material.     

Amidons Lintnérisés Etudes chromatographique et enzymatique des résidus insolubles provenant de l'hydrolyse chlorhydrique d'amidons de céréales,en particulier de maïs cireux

Lintnerized Starches. Chromatographic and Enzymatic Studies of Insoluble Residues from Acid Hydrolysis of Various Cereal Starches, Particularly Waxy Maize Starch . Native cereal starches, particularly waxy maize starch, have been carefully hydrolyzed at 35°C with hydrochloric acid (2,2-N) in heterogeneous phase. Observation of the course of hydrolysis as a function of time makes it possible to classify the starches according to their acid lability. The kinetic values distinctly reveal two phases, i.e. a fast hydrolysis of the amorphous fraction and a slower degradation of the crystalline starch grain fraction. This observation was confirmed by X-ray diffractometric patterns. The hydrolysis speed of acid resistant fractions seems to become slower as the apparent amylose ratio increases. The change in the macromolecular structure of the obtained granular residues or “lintnerized” starches as a function of time was examined after aqueous solubilization by means of gel chromatography using a calibrated Sephadex G-50 column. Lintnerization causes a decrease in the apparent DP of the chains of the starch residues and two subgroups with apparent DP 13 and 25 appear rapidly. These DP are unchanging with time of acid treatment. The chromatographic and enzymatic studies of lintnerized starches were performed directly and after successive enzymatic digests with pullulanase and ß-amylase. After debranching of solubilized residues with pullulanase and gel chromatography a linear chain subgroup of DP 15–20 appears. This one is in fact composed of two subgroups: one more important with a DP 13, the other broad distribution with a DP 15–25. The comparison with the subgroups observed before debranching shows that a main part of the initial subgroup of DP 25 could be considered as formed with singly branched chains. Furthermore a small proportion of pullulanase resistant ß-limit dextrins was obtained. The obtained results permits one to suggest a new model for the structure of waxy maize amylopectin. On the basis of this model the differences in structure existing between the various starches are discussed and the results are compared with those reported elsewhere for potato starch. A parallelism between crystalline patterns of native starches and the amylopectin structure, particularly its branching degree, is observed.     

Evolution de la microflore de deux échantillons d'amidon aprés irradiation gamma

Change of Microflora of Two Starch Samples by Gamma Irradiation. Starch is the basic component of a larger number of manufactured food commodities. The disinfection of such a powder by ⁶⁰Co is considered here. Gamma irradiation of two starch samples with various contamination admits of the assumption that, in most cases, good radio-pasteurization can be obtained with 300 krad. The radio-pasteurization doses (varying from 300 to 600 krad) are a function of the initial contamination. Irradiation effects are spectacular with moulds. Activation of spores of some Clostridium species leads us to recommend an irradiation level higher than 200 krad. The most resistant organisms to gamma irradiation are the aerobic and anaerobic sporulated bacteria. The thermophilic forms are the most important. Spores of Bacillus chiefly Bacillus licheniformis and Bacillus brevis are the most encountered bacteria. At room temperature stocking irradiated starch has little effect upon the number of revivable survivors.     

Dégradation in vitro de l'amidon par le suc pancréatique. Etude par microscopie électronique à transmission et à balayage

In vitro degradation of starch. Studies by transmission and scanning electron microscopy Starch granules of various botanical origins (potato, manioc, wheat, corn, waxy-maize, and amylomaize) were subjected to hydrolysis by piglet pancreatic juice. All starch granules are more or less damaged, however the kind of attack is particular for each starch species, i. e. one observes either exocorrosion alone, or accompanied by endocorrosion at preferential sites. In some cases randomly distributed pits appear. The present work shows various kinds of starch damage by means of photomicrographs, obtained by transmission and scanning microscopy and an attempt is made to relate the observations to the structure of each starch species.     

Contribution a l'étude de l'action du rayonnement gamma sur l'amidon. Partie 2. Évolution de certaines caractéristiques biochimiques du grain d'amidon en fonction des conditions d'irradiation

Studies on the action of γ-irradiation on starch. Part 2. Development of certain biochemical characteristics of the starch granule as a function of the irradiation conditions. Corn starch and potato starch were γ-irradiated at different hydrations with largely varying irradiation dosis. After having outlined before the development of certain physicochemical properties of the starch granule, we have now examined the aspect of the radio-chemical degradation of the units starch is composed off. The products generating 5 HMF, the COOH groups and the distribution of the modified anhydro-glucose units in the alcohol-soluble and the water-soluble fractions were determined. The results show that the amount of modified anhydro-glucose units, capable to form 5 HMF upon the action of acid, increases proportionnally to the irradiation dosis but independently on the water content of the irradiated sample. On the other hand, the development of the amount of COOH groups provides evidence for the important protecting role that the water plays in this kind of alteration. When the alcohol-soluble fraction is expressed as a function of the water-soluble fraction, but insoluble in alcohol, a linear relationship is obtained, which is independent on the irradiation dosis, on the hydration of the sample and the origin of the treated starch.     

Un test d'irradiation de l'amidon. Mode operatoire,application à différents amidons

Proof for Irradiation of Starch. Working Rules and Application to Various Starches . The test which is proposed for the proof of irradiation of starch is based on the determination of the malonaldehyde – which is formed by irradiation – by means of 2-thiobarbituric acid. The study was made on the alteration of the aldehyde content of 3 starches (maize starch, pregelatinized maize starch, potato starch) which had been irradiated with 400 Krad and stored at different temperatures. If water content of the sample, storage temperature and duration of storage are known, the original irradiation dose can be calculated by the obtained graphs. These calculations are of variable precision in the specific cases. It is possible to determine the irradiation of maize starch having been stored for three months at 25 °C, provided that the irradiation dose had been of at least 25 Krad.