Sieving pdf

All measurements were repeated three times and the results were expressed as milligrams of gallic acid equivalent GAE per gram of sample fresh matter FM.

Foods , 10, 5 of 17 2. Antioxidant Activity The oilseed fraction extracts for the determination of antioxidant activity were pre- pared as described for TPC Section 2. Ascorbic acid was used for the calibration. All measurements were repeated three times and the results were expressed as milligrams of ascorbic acid equivalent AAE per gram of sample FM. The filtered solution PTFE 0. The absorbance of the reaction mixture was measured at nm after incubation at room temperature for 30 min.

Protein separation was carried out in duplicate using cooled dual vertical slab units SE Hoefer Inc. Protein detection was performed by using Coomassie Brilliant Blue R Data were subjected to analyses of variance using the two-way ANOVA method and the means were compared using the Fisher test.

Results and Discussion 3. Proximate Analysis of Oilseed Cake Flours The approximate compositions of all variants that were derived from the oil cake flours are given in Table 2. Significant differences were found for most of the variants. The crude protein content in the whole oilseed cake flour WF ranged widely from Except for pumpkin, the sieving process increased the crude protein content.

The size fractions with finer particles B reached a higher proportion of crude protein and these differences were statistically significant in most cases. The crude protein level of the fine fractions ranged from The highest differences between the A and B fractions were observed for species hemp, safflower, milk thistle and sunflower. Insignificant differences between the size fractions were found for poppy and pumpkin.

The significant increase in crude protein content in several species hemp, milk thistle, safflower and sunflower in the B fraction resulted from the different structures of their seeds, including the pericarp. Table 2. Composition analysis of oil cake flours from eight selected oil crops. The effect of size fractionation on crude protein content was limited for other species flax, poppy, pumpkin or rapeseed , which can be given in connection with the absence of pericarp.

This conclusion is well documented regarding carbohydrates content and their distribution between the size fractions for individual species. Carbohydrates contents, including fibre, were significantly lower in the group of flax, poppy, pumpkin and rapeseed and differences in carbohydrates content between the A and B fractions were more pronounced in the group of oilseed species with a pericarp. In contrast, we found a high content of carbohydrates in the flour of hemp, milk thistle and safflower, with a significant increase for the A fraction.

Differences in carbohydrates content were minimal and statistically insignificant for the flours of poppy and pumpkin. Foods , 10, 7 of 17 Dietary fibres are considered to be one of the major ingredients that are used to develop products with a functional purpose [9,27] and oilseed cake products with increasing content of this component can be added to new health benefit products.

Residual crude fat content in the WF fraction varied from 4. The amount of residual fat increased with decreasing flour particle size. The observed differences for the WF and A fractions were statistically significant, except for sunflower. The second exception was safflower flour, with the highest content of residual fat in the WP fraction and the lowest level in the B fraction.

The highest differences in fat content between the A and B fractions were determined for flax and rapeseed. A high content of residual fat in the B fraction appears to be problematic due to the application of this protein-rich source. On the one hand, the increased fat content of flax flour can be used as a substitute for animal fat sources e.

On the other hand, it is necessary to take into account the instability of flax fat components and the possible link to flour technological quality. Bochkarev et al. The instability of the fat component is also typical for hemp seed oil with a high content of polyunsaturated fatty acids PUFA [29]. The tested oilseed cake flours also differed regarding the ash content. The species with a pericarp hemp, milk thistle, safflower, sunflower exhibited higher differences in ash content between individual size fractions.

The lowest contents were determined in the A size fraction, and the highest level was found in the B fraction. This phenomenon was also observed for poppy and rapeseed flours; however, the differences between the fractions were minimal in comparison with the seed-coated species.

Ash content in pumpkin flour was specific in comparison with other species. The lowest content of ash 8. The ash content in the protein-rich fraction B ranged among the species from 5. For wheat flour [30], the technical quality of high-ash flour is lower because it is characterised by a darker colour and greater activity of proteolytic and amylolytic enzymes. However, in the case of oilseed cake flours, the results are unclear.

The determined ash content in the analysed flours was in accordance with the results of other authors. Similarly, the high content of ash in poppy flour was in agreement with Yilmaz and Emir [31], who specified that the high ash level in poppy was caused by the K, P, Mg and Ca contents. This represents an additional potential in increasing the health and nutritional benefits of oilseed cake flours and their products. Electrophoretic bands covering the apparent 5— kDa range were found for all analysed samples, with visible protein pattern variability between individual species and size fractions.

The increase in protein pattern intensities between the A and B fractions were evident, especially for hemp, milk thistle and safflower. These observations correlated with the data that were related to the change in crude protein content between the A and B size fractions that were obtained for individual species Table 2. The detected protein zones were therefore identical to those reported by other authors [14,32].

The protein band of about 50 kDa that was found in all size fractions of flaxseed flour could be described as one of five subunits of globulin linin. The detected protein were therefore identical to those reported by other authors [14,32]. The protein b Foods , 10, about 50 kDa that was found in all size fractions of flaxseed flour could 8 of 17be descri one of five subunits of globulin linin. The 11—12S polypeptide subunits of this protei molecular weights of Subunitfraction, where protein bands of the alpha subunit were visible.

Figure 1. The protein The protein profiles that were profiles detected that wereother within detected specieswithin could other species be similarly could be sim charac- terised into the globulin and albumin protein groups with various manifestations.

The difference etbetween al. Similar particularly in th subunits. Similar differences between the A and B differences between the A and B fractions were visible for milk thistle. Li et al.

This information is largely in agreement with our is larg range of 16— kDa were the dominant protein fractions. Thealpha and beta. B fraction. Zones of cruciferin of cruciferin area of subunits alphaof subunits and beta alpha and and napin beta area and of napin area of 2S albumin 2S albumin were found in were found in the rap the rapeseed SDS-PAGE profiles. The 11S helianthinin and 2S albumin, which were reported previously for this species [35], are clearly visible in the zones of subunits alpha, beta helianthinin and 2S albumin albumin fraction.

A somewhat higher intensity of protein bands was found in the B fraction. However, we also found significant protein bands in the zone of subunits alpha and beta, with values of molecular weight of 30—36 and 15—19 kDa, respectively. Via the reduction of disulphide bonds, the two subunits were each separated into two polypeptide chains with molecular weights of around 36 and 22 kDa.

Functional Characteristics of Oilseed Cake Flours Table 3 shows the functional properties of oilseed cake flours in a relation to their species origins and particle size distributions after flour sieving.

The values of WS were increased for all evaluated variants with increasing fineness of the flour. The highest WS values were thus achieved for the B fraction for all evaluated species. In contrast, the A fraction had a decrease in solubility compared with the B fraction and for milk thistle, rapeseed, sunflower and the WF fraction with statistical significance.

The highest value of WS The B fraction was characterised as a protein-rich fraction that had a rapeseed protein content of The WS value was thus species-specific, given by the level and structure of the globulin and albumin protein fraction and the content of minerals and soluble carbohydrates. Similarly, the dominant albumin protein fraction was described in milk thistle [30] and the increase in solubility of the B fraction in this species can be linked to this fact.

The solubility of flax was the second highest and achieved In contrast, the B fraction of hemp and safflower flours showed the lowest solubility, achieving Malomo et al. This suggests a reduction in protein solubility during protein isoelectric precipitation via protein complexation.

The protein-rich fraction that was obtained by sieving with a more native state of protein fraction was more appropriate from this perspective. The water-holding capacity values ranged within the evaluated set from 1. The second group with WHC values between 2. The highest WHC was observed for all size fractions of flax flour, ranging from 3. This was probably related to the content of flaxseed gum, which is a constituent of dietary fibre present in the flaxseed hull [43].

This flaxseed component has a function of a food hydrocolloid and significantly increases the WHC of foods, which is important for both the yield and texture of related products [44]. The obtained values of the WHC that correspond with the carbohydrates content are presented in Table 2. The WF and A fractions contained significantly higher amounts of carbohydrates in comparison with the protein-rich B fraction.

Similarly, the lowest WHC was obtained for the B fraction. The WF and A fractions with high WHC can therefore be used as a component of products where water binding is an important functional indicator. Water holding affects the texture, juiciness, taste of food formulations and, in particular, the shelf-life of bakery products [45].

Boiling oilseed flours increased their WHC, except for poppy flour; however, the trend of WHC that was observed for the unboiled variants also manifested itself in the boiled variants. The sample is placed on the top sieve. Dry and wet sieving Most sieving processes are carried out on dry materials.

However, there are many applications in which wet sieving cannot be avoided, e. As in dry sieving, a sieve stack is assembled on a sieve shaker. The sieving process is additionally supported by water from a spray nozzle located above the uppermost sieve. The sample is placed on the uppermost sieve in the form of a suspension.

Rinsing is carried out until the sieving liquid leaving the sieve stack outlet is no longer turbid with solid particles. In wet sieving, the sieving liquid must not alter the physical or chemical properties of the sample.

How can an optimal sieve analysis be carried out? Various preconditions must be fulfilled for a reproducible and meaningful sieve analysis and the settings must also be properly adapted to suit the particular problem. The most important criteria are briefly described below. Representative part-sample The most important requirement for a reproducible sieve analysis is to obtain a representative partial sample from the whole of the bulk material to be tested.

If this requirement is not fulfilled, then the results of the sieve analysis can only be applied to the particular part-sample. The amount of sample depends primarily on the maximum particle size, the number of sieves in the sieve stack and their openings.

The sieves must not be overloaded. For a sieve with a diameter of mm and 2 mm mesh the amount of sample should not exceed a volume of ml e. For a mesh of 0. Further information can be found in DIN 66 These standards describe the technical requirements for the sieves and methods for checking them.

The choice of test sieve diameter and mesh depends mainly on the amount of sample and its particle size distribution. The number of sieves and the steps between the nominal mesh openings should be selected so that as much as possible of the whole range of sizes contained in the sample is separated into fractions. The latter is particularly important if the test sieve is to be calibrated within the context of test agent monitoring.

Optimal sieving time and amplitude or speed The settings for the sieving time and the optimal amplitude or speed depend on the material to be sieved. National and international standards, internal regulations and standards normally provide detailed information about product-specific sieve analyses and their associated sieving parameters.

The instruction manual for the sieve shaker should also provide guidelines for this. This is done by first selecting a relatively short sieving time e. An initial approximate value for the amplitude can be obtained by observing the sample movements.

In the next step sieving is carried out with different sieving times at the amplitude or speed determined above. When the weight of the material passing through the sieve in one minute changes by less than 0. More From Rhon Dumrigue. Geoffrey Tolentino-Unida. Rard Tangangco Lozano. Godofredo Reyes Sr ES. Popular in Chemicals. Ja Six. Mayank Katiyar. Prince Ryan. Debra-Dreana Marshall-Stuart.

Thenmozhi Karan. Shamsul Azhar Mohd. Fabrice Bassama. Emily Segura. Irfan Omercausevic. Marco Aurelio Barbosa. Narayan Singhania. Paul Padilla. Morjhan MJ. Ramon Sanhueza. Michael Guinita. Horizontal sieve shakers are preferably used for needle-shaped, flat, long or fibrous samples.

Due to the horizontal sieving motion, hardly any particles change their orientation on the sieve. In a tap sieve shaker a horizontal, circular movement is superimposed by a vertical motion generated by a tapping impulse.

Tap sieve shakers are specified in various standards for particle size analysis. The number of comparisons between particles and sieve apertures is substantially lower in tap sieve shakers than in vibratory sieve shakers 2. On the other hand, the tapping motion gives the particles a greater impulse, therefore, with some materials, such as abrasives, the fraction of fine particles is usually higher.

With light materials such as talcum or flour however, the fraction of fine particles is lower. The air jet sieve is a sieving machine for single sieving, i. The sieve itself is not moved during the process. The material on the sieve is moved by a rotating jet of air: A vacuum cleaner which is connected to the sieving machine generates a vacuum inside the sieving chamber and sucks in fresh air through a rotating slit nozzle.

When passing the narrow slit of the nozzle the air stream is accelerated and blown against the sieve mesh, dispersing the particles. Above the mesh, the air jet is distributed over the complete sieve surface and is sucked in with low speed through the sieve mesh.