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Impact of type and particle size on the protein contents in wheat flour

November 2014

Authors:

Muhammad Hanif

The University of Agriculture, Peshawar

Mansoor Khan Khattak

The University of Agriculture, Peshawar

Shaiza Sheikh

The University of Agriculture, Peshawar

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Two main types of wheat flours that are fine and branded flours used in Khyber Pakhtunkhwa, Pakistan, were analysed for their particle size. Sieve analysis was carried out which gave eight samples of different particle sizes, divided into fractions and ranged from 63-100, 100-250, 250- 350 and larger than 350 µm. All the four sizes of the each flour type were analysed for their protein content, using Kjeldahl method by Kjeltec-1002 apparatus. The results showed that more proteins (11.8%) were recorded in fine flour as compared to (11.3%) in branded flour. Also it was observed that reducing the size from 350 µm to 63 µm caused 13% protein loss in branded wheat flour and 11% in fine flour. It was concluded that wheat flour with particle size smaller than 350-250 µm significantly lost its protein content. So it is recommended to grind wheat in such a way that the particle size remains greater than 250 µm.

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Hanif et al., 2014. Sci. Tech. and Dev. 33 (3): 107-109

* hanif_mechanization@yahoo.com

IMPACT OF TYPE AND PARTICLE SIZE ON THE PROTEIN

CONTENTS IN WHEAT FLOUR

MUHAMMAD HANIF*, MANSOOR KHAN KHATTAK, MASOOD-UR-RAHMAN, SHAIZA SHEIKH

SHER, HAFIZULLAH, SAQIB KHAN, MUHAMMAD SAEED, ABDULLAH KHAN AND

MUHAMMAD SAQLAIN

Department of Agricultural Mechanization, Faculty of Crop Production Sciences, University of Agriculture

Peshawar, Pakistan.

Abstract

Two main types of wheat flours that are fine and branded flours used in Khyber Pakhtunkhwa,

Pakistan, were analysed for their particle size. Sieve analysis was carried out which gave eight

samples of different particle sizes, divided into fractions and ranged from 63-100, 100-250, 250-

350 and larger than 350 µm. All the four sizes of the each flour type were analysed for their protein

content, using Kjeldahl method by Kjeltec-1002 apparatus. The results showed that more proteins

(11.8%) were recorded in fine flour as compared to (11.3%) in branded flour. Also it was observed

that reducing the size from 350 µm to 63 µm caused 13% protein loss in branded wheat flour and

11% in fine flour. It was concluded that wheat flour with particle size smaller than 350-250 µm

significantly lost its protein content. So it is recommended to grind wheat in such a way that the

particle size remains greater than 250 µm.

Keywords: Branded, Fine, Particle size, Proteins, Wheat flour.

Introduction

Milling requirements of more than 80%

countries for wheat is being done using conventional

Burr mill operated by engines or electric motors. For

grinding of wheat, flour mills fitted with cast iron

steel plates and emery stones have successfully

replaced the old traditional red stoned discs mills all

over the world, especially, in South Asia (Ramappa

et al., 2010). In Pakistan, beside Burr mills, which

are on large scale, small mills of conventional types

are still used in good number both in urban and rural

areas but the overall efficiency of these mills was

found to be very poor which results in low quality of

flour (Dorosh and Salam, 2008). In the past decade

technology has became very advanced by the

development of new mills for grinding of wheat

grains in which cast iron steel plates are present for

grinding and sharing on which the radial grooves of

different shapes running from the center of the plate

to the periphery have significantly improved the

milling performance of wheat and have improved

the quality of wheat flour (Banu, 2011).

The size of ground wheat flour is the most

important parameter judging the quality of the flour

as it is directly related with the protein content,

digestibility, N-balance as well as the cost. Fine

flour costs more due to uniform particle size as

compared to the branded flour (Majzoobi et al.,

2013). Sometimes milling of wheat in not done

efficiently which has a direct impact on the quality

as well as the cost of flour. Such inefficiencies arise

due to inability to produce uniform grinding of the

wheat grains and the time taken to crush the material

to the required size of the screen as in the mill. The

grade of grinding depends on the fineness within

each mill. The size of flour must be in the range of

250 µm and 360 µm to achieve high digestibility

from the cooked product (Yawatkar, 2010).

Laurinen et al. (2000) studied the digestibility of

all cereal grains and studied that finely ground

cereals are dusty and they may induce respiratory

diseases. Moreover, small grist size is one of the

main causes of gastric lesions. They concluded that

the particle size of wheat flour of less than 150 µm

and larger than 350 µm adversely affects its protein

contents as well as its digestibility. Potkins et al.

(1989) and Alaviuhkola et al. (1993) reported that

coarse grinding of wheat flour having size more than

350 µm and less than 150 µm may impair essential

nutrients like proteins. Sauer et al. (1977) studied

that flour type and practical size have direct

correlation with the protein content of flour.

Nawaigwe et al. (2012) reported that finely ground

wheat flour is best for making biscuits, breads and

standard bakery cakes with high protein contents as

compared to coarsely ground and branded wheat

flour.

The aim of the experiments was to analyse the

particle size of the two main types of wheat flours

(i.e. fine and branded) used in Khyber Pakhtunkhwa

and to see the effect of the analysed particle sizes on

the protein content of each flour type.

108 Hanif et al., 2014. Sci. Tech. and Dev. 33 (3): 107-109

Materials and Methods

Sieve analysis: Retsch Vibratory Sieve Shaker

AS450 basic with 9 pans and a range of 20 µm to 25

mm with capacity of 3 kg was used in the

experiment. The analysis was done following the

procedure reported by AACC (2000).

Fineness modulus: It is defined as an empirical

figure obtained by adding the total percentage of the

sample of an aggregate retained on each of a

specified series of sieves, and dividing the sum by

100. The smaller the value of FM indicates the finer

size of grind of a material. FM for each flour sample

is calculated using the formula given by Ramappa et

al. (2010).

Experimental procedure: The two main flour

samples were collected from more than ten different

commercial flour mill bags available in the local

market. Both the flour types give 8 samples of

different practical size, divided into fractions,

ranging from 63-100, 100-250, 250-350 and larger

than 350 µm. All the eight samples were digested,

using sulphuric acid (concentrated, 95–98% ) with

catalyst and the nitrogen contained in the sample

was converted to ammonia; ammonium sulphate

being formed which was analysed, using Kjeldahl

method by Kjeltec 1002 apparatus following the

procedure of AOAC given by Williams (1984) to

find the crude proteins in each sample.

Statistical analysis: All the samples were taken as

treatments with flour type as a major factor and

flour size as a minor factor. Analysis of variance test

was applied to find out whether the data was

significantly different from each other or not. Mean

comparison was done after ANOVA test using

Duncan’s Multiple Range Test.

Results and Discussion

Particle size distribution

The granulometry profile of both the main flour

types is given in Table 1. Most of the particle sizes

lie in the range of 100 to 250 µm. Almost 70% of

the branded and 66% of fine flour lies in this range.

This shows that most of the flour of each type of

each mill has 60-70% flour size in the range of 100-

250µm. The results of particle size distribution are

in accordance with the sizes used in experiments by

Chiotelli and Meste (2002), Ramappa et al. (2010),

Blanchard et al. (2012) and Justin (2012).

The impact of type and particle size on the

protein content of both the flour types is shown in

Table 2. The analysis of variance showed that

protein content was significantly affected by particle

size distribution. The protein contents in both the

flour fractions differed as a function of the particle

size range. The smaller the size of particle, the lower

was the protein content of that flour. More proteins

at average of 11.8% were recorded in fine flour as

compared to 11.3% recorded in branded wheat flour.

Compared to other fractions, the lowest protein

content as a total was observed in flours with

particle size 63 µm. There was a total of 31.1%

decrease recorded in proteins in branded flour when

its size reduced from 350 µm to 63 µm. Similarly

31.9% decrease was recorded in fine flour. These

results are in accordance with the findings of

Blanchard et al. (2012) who reported that wheat

flour with particle size smaller than 50 µm had

minimal proteins in it. The results are also in

agreement with those of Chiotelli and Meste (2002),

who reported that flour size smaller than 250 µm

resulted in significant decrease of protein content of

Table. 1. Granulometry profile of both flour types.

Sieve size

(µm)

Cumulative percent retained

Reported percent passing

Branded flour

Fine flour

Branded flour

Fine flour

350

22.5

18.6

77.5

81.4

250

27.2

33.9

50.3

47.5

100

42.7

35.4

7.6

12.1

6.2

13.8

1.4

17.9

Pan

1.1

18.6

Modulus of finesse for fine wheat flour = 2.7 and for branded wheat flour = 3.5

Table. 2. Impact of type and particle size on the protein content of wheat flour.

Particle size (µm)

Protein (%)

CD (%)

Branded flour

Fine flour

350

13.2a

14.1a

6.3

250

12.3b

12.7b

3.1

100

10.7b

10.8c

0.9

9.1c

9.6c

5.2

Mean

11.3b

11.8a

LSD = 0.13

Hanif et al., 2014. Sci. Tech. and Dev. 33 (3): 107-109

109

dough. Curic et al. (2002) also reported the same

results that particle size lower than 250 µm reduced

Gluten (protein) content of wheat flour. Majzoobi et

al. (2013) reported that good quality proteins like

albumin and globulins were destroyed due to

reduction in the particle size. Decreasing the size of

wheat flour directly decrease the proteins in it so it

is recommended for wheat flour to have particle size

within range of 450-750 µm.

Conclusion and Recommendation

The study concluded that wheat flour with

particle size lower than 350-250 µm has

significantly lost its protein content. Fine wheat

flour was found to have higher proteins than

branded flour. It is, therefore, recommended to grind

wheat in such a way that the particle size remains in

the range of 350-250 µm otherwise significant

protein loss would occur on grinding to very fine

size.

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Article

Oct 2001

The quantity and quality of gluten are considered the most important quality parameters of wheat flour, Gluten Index Method (GIM) is a rather new method for determining gluten quantity and quality in wheat semolina and flour. This study reports on values for flours obtained from the most important Croatian wheat cultivars. The gluten index value in the tested flour samples varied from 55.92 (Patria cultivar) to 99.60 % (Marija cultivar). This high variety was not only due to cultivar differences but also to different climate conditions (especially cultivars Žitarka and Sana). The determination of gluten quantity and quality by Gluten Index Method is compared with the determination by other methods. A significant positive linear correlation was observed between the values of gluten index and extensographic values of flour quality, i.e. between the gluten index and maximal resistance of dough to extensibility (r = 0.860), dough energy (r = 0.799) and dough resistance at 50 mm (r - 0.788). That indicates that the gluten index actually defines technological flour quality. The optimal gluten index values for bread production using Croatian wheat cultivars were between 75 and 90 %.

Study of the impact of wheat flour type, flour particle size and protein content in a cake-like dough: Proton mobility and rheological properties assessment

Article

Nov 2012

Apparent availabilities of amino acids in corn, wheat and barley for growing pigs

Article

Sep 1977
CAN VET J

The apparent ileal and fecal recoveries of amino acids in corn, wheat and barley were determined with barrows ranging in weight from 50 to 70 kg that were fitted with ileocecal re-entrant cannulas. Average ileal availabilities were 4–7% less than average fecal availabilities in the three cereal grains. Of the indispensable amino acids in the cereal grains, the recoveries of lysine and threonine were approximately equal in being the lowest at the end of the ileum, and they decreased from those in corn, to wheat and to those in barley. The recovery of lysine was the lowest in all cereal grains when determined by the fecal analysis method. The apparent fecal recoveries of amino acids in the cereal grains obtained from cannulated pigs were essentially similar to those obtained from non-cannulated pigs. Apparent ileal and fecal recoveries of amino acids in finely ground and cracked wheat were determined with eight barrows that weighed approximately 75 kg. The ileal recoveries of most amino acids were significantly higher (P <.05) in finely ground than in cracked wheat. On the other hand, differences in amino acid availabilities due to processing of wheat could not be detected by the use of the fecal analysis method.

Effects of different grinding methods and particle size of barley and wheat on pig performance and digestibility

Article

Jan 2000
ANIM FEED SCI TECH

The effect of grinding method of barley and wheat on total tract digestibility of barley–soyabean meal and wheat–soyabean meal diet, N-balance (experiments 1 and 2) and pig performance (experiments 3 and 4) was studied. Cereals were ground by four mill types and there were two degrees of grinding fineness within each mill type. Mill types were a hammer mill (HM, sieve size 3 and 5mm), a crimping roller mill (RM1, gap between rolls 0.5 and 0.8mm), a flattening roller mill (RM2, gap between rolls 0.15 and 0.35mm) and a triple roller mill (RM3, gap between the 1st and 2nd roll 0.2 and 0.65mm, gap between the 2nd and 3rd roll was fixed at 0.65mm). Data were analysed in a nested design, mill type as the main treatment (all 4 mill types in experiments 1, 3 and 4, mill types HM, RM1 and RM2 in Experiment 2) and fineness of grinding (fine and coarse) as the subtreatment within each mill type.Digestibility and N-balance experiment with barley was conducted with eight castrated male pigs (25.9–91.9kg) in a 8×6 cyclic change-over design (Experiment 1) and with wheat, using 12 castrated male pigs (31.2–83.8kg) in two 6×6 Latin square design (Experiment 2). A growth experiment was conducted with 160 growing-finishing pigs (25.2–101.5kg) housed per pair (one female and one castrated male per pen, 10 pens per treatment) with barley (Experiment 3) and an other 160 pigs (25.2–100.3kg) with wheat using the same procedure (Experiment 4).RM1 depressed digestibility of crude protein (p

Effect of Small and Large Wheat Starch Granules on Thermomechanical Behavior of Starch

Article

Mar 2002

Cereal Chem. 79(2):286–293 The physicochemical properties of small-and large-granule wheat starches were investigated to reveal whether gelatinization properties and rheological behavior differ between size classes of wheat starch. All samples contained 60% water (w/w, wb). The starch granule size and shape were examined by scanning electron microscopy in the separated A-and B-type granule populations and in the whole wheat starch granule population. Differential scanning calorimetry (DSC) and electron spin resonance (ESR) analyses were performed in parallel with rheological measurements using dynamic mechanical thermal analysis (DMTA) to relate the viscoelastic changes to modifications in dynamic properties of aqueous solutions and structural disorganization of starch. The small (B-type) granules had slightly higher gelatinization temperature and lower gelatinization enthalpy than did the large (A-type) granules. Also, B-type granules had higher enthalpy for the amylose-lipid complex transition. Moreover, our results suggested that small granules have higher affinity for water at room temperature. It seems that there is a less ordered arrangement of the polysaccharide chains in the smaller granules when compared with the larger ones. These differences in functional properties of small and large granules suggested that the granule size distribution is an important parameter in the baking process.

Wheat Markets and Price Stabilisation in Pakistan: An Analysis of Policy Options

Article

Feb 2006
Pakistan Dev Rev

This article provides a quantitative analysis of the effects of Pakistan government domestic wheat procurement, sales, and trade policies on wheat supply, demand, prices, and overall inflation. Analysis of price multipliers indicates that increases in wheat procurement prices (one means of promoting domestic procurement) have relatively small effects on the overall consumer price index. Partial equilibrium analysis of wheat markets suggests that fluctuations in production, rather than market manipulation, are plausible explanations for price increases in recent years. Comparisons of domestic and international prices suggest that promoting private sector imports is one alternative for increasing supply and stabilising market prices, particularly in years of production shortfalls. Overall, this paper concludes that market forces play a dominant role in price determination in Pakistan, and that policies that promote the private sector wheat trade can both increase price stability and reduce fiscal costs.