FE 376

FOOD QUALITY CONTROL

ANALYSIS OF WHEAT FLOUR 

Submitted to:     Emine ERÇELEBİ

Submitted by:      Ahmet DEMİRCAN

PURPOSE:

The aim of this experiment was to consider the standard content of flour by doing main analysis.

THEORY:

Wheat quality and methods in wheat quality determination is important. Determination of the quality of bakery products which have significant position in the food industry and nutrition is necessary from the point of product features and economic view. However, the choosing appropriate raw material according to that appropriate quality of wheat/flour/semolina is very important to produce products such as bread, biscuit etc. Beside that methods and analysis which are used to determine the quality must be applied exactly and results must be well evaluated by the aid of good qualified technical person and equipment. Nowadays the importance of technical person, equipment and methods for determination of quality is accepted by the consumers and producers.

Wheat is important than other grain. Because;

1- It is raised in large area due to fit different climate and earth condition.

2- high yield and easy agriculture

3- easy storage and high nutrition value

4- when wheat flour is contact with water, protein particles in flour form gluten (wet germ).No grain’s protein except wheat form wet germ.

Wheat Kernel

Wheat kernel contains some layers, germ, endosperm, aleuron layer, bran, outer kernel layer. The germ and bran are removed from the kernel when white flour is milled, even though they contain nearly all the fiber and B vitamins; they are removed because they also negate the elastic properties of the gluten, which is so vital to the texture and crumb of the bread.

The percentage of total product in any desired fraction of flour is called extraction. In other words, straight grade flour that is %72 of the total product is % 72 extraction flour. The composition of flour with various percent extractions is given:

Approximately composition of flour

Component	Flour (72%)	Flour (80%)	Whole meal (95-100)	Wheat Germ	Wheat Bran
Moisture (%)	13-15	13-14.5	13-14	9-12	14
Protein (%)	8-13	8-14	10-15	25-30	12-16
Fat (%)	0.9-1.4	1-1.6	1.5-2.5	8.5-11	3-4
Carbohydrate (%)	65-70	64-70	60-68	39-45	—
Fibre(%)	0.1-0.3	0.2-0.4	1.8-2.5	2-2.5	9-12
Ash (%)	0.3-0.5	0.6-0.9	1.2-2.0	4.0-4.5	4-6

Wheat that is between the bread and pastry types are used for cracker, doughnut, and all purpose flour. There are physical and chemical test of flour. These:

Physical Tests: including test weight, kernel hardness, gluten washing, density, internal infestation evaluation, thousand kernel weight, pearling index, granulation and particle size.

Chemical Tests: Moisture, ash, and protein tests are the most widely used on wheat. The kjeldahl protein test normally is made on al hard wheat. To report protein content on uniform moisture basis, the moisture lost is necessary. Miller and Johnson (1954) state that moisture is related to quality of wheat and flour in at least three ways:(1)flour yield varies inversely with moisture content (2)composition percentage are inversely related to percentages of moisture  present; and(3)deterioration of grain during storage may depend on the moisture relationships in the wheat kernel.

The ash test is significant as a way to determine flour grade. Since the ash content of bran is about 20 times that of endosperm; the ash test indicates how thoroughly bran and germ were separated from the kernel endosperm. There is considerable variation in the amount of mineral matter in wheat, depending on the class of wheat and the area it was grown; therefore, the ash test is often applied to wheat as well as to flour.

Color tests, such as the Pekar or the slick test, also are used to judge milling results or flour grade, and recently photo electric methods such as the Agtron for assessing flour color have come into use. Many attempts have been made to appraise wheat quality on the basis of the amino acid composition of wheat gluten. Determining the amino acid composition of wheat is no longer a tedious and expensive procedure, but pence 1950 failed to show essential differences in the amino acid content of 17 flours milled from different varieties and types of wheat.

Starch damage is a subject of recent concern to wheat processors and to the baker. The extent of starch damage alters flour characteristics and end use.

The amylase activity of wheat and flour are measured by the Falling Number test, Blish-Sandstedt method, and the amylograph. The description of those tests and other mentioned can be found in Cereal Laboratory methods (1962) and wheat and wheat technology.

Variental Differences in Gluten Quality: Many techniques have been developed to separate gluten from the other constituents of wheat flour. The washing-out process can be done by hand or mechanically. A quantitative test consist merely of weighing the gluten either wet or after being dried, but estimating gluten quality is a more difficult matter.

The measurement of gluten quality has been based on four general principles, namely; expansion by heat, recovery from compression, and gluten extension and gluten relaxation of gluten.

Although there is agreement that many properties of dough are due to the gluten component of flour, most cereal chemist in the United States prefer to study the properties of dough rather than to separate gluten and thus attempt to appraise quality. Regardless of the methods used, differences in gluten properties between classes and varieties of wheat are obvious

The production of flour affects quality of making bread. Therefore, before production of flour, suitable wheat must be selected firstly and analyzed in laboratory. Hence, produced flour is both high in quality and suitable for quality.

The flour production is made three different type of wheat;

·         Triticum durum: for macaroni

·         Triticum aestivum: for bread

·         Triticum compactum: for biscuit

 Some criterions very important for flour;

·         amount of protein and quality

·         amount of normal starch and damaging starch

·         moisture content

·         amount of aflatoxin

·        amount of alpha amylase

MATERIALS:

·         Bunsen burner

·         Porcelen cruise

·         Desiccator

·         Oven

·         Flour

·         Analytical scale

·         Beaker

·         Conical flask

·         Water bath

·         Filter paper

·         Phenolphthalein

·         Test tubes

·         2 % urea solution

·         0,05M NAOH  solution

PROCEDURE: 

• Determination of Ash in Wheat Flour

2 g of flour was weighed in to a well-dried porcelain evaporating dish.Then it was heated gently on a Bunsen burner and the dish was ashed at 550-570°C.After two hour the dish was transerred to a dessiccator,was cooled and weighed.Finally the total ash was calculated as a percentage of the sample.

• Determination of Crude Gluten  in Flour

25 g of flour and 19 ml of water was added in a mortar,the mixture was worked with a spatula.The dough was kneaded gently under a water tap for 10-15 min.The solid matter under water was placed.Finally it was compressed as dry as possible,was rolled into a ball,and the moist gluten was weighed and it was expressed as a percentage of flour.Also its color,toughness and elasticity were noted.Then it was dreid at 100°C to a constant weight,it was weighed and expressed as a percentage of flour.

• Determination of Acidity  in Wheat Flour

18 g of flour with 200 ml of CO2-free water was shaken in a conical flask.Then it was placed in a water bath at 40 °C for 0,5 h with the flask loosely stoppered.100 ml clear filtrate with 0,05 M NaOH solution was filtrated and titrated by using phenolphthalein as an indicator.:It was calculated as a lactic acid or KH2PO4.

• Detection of soy flour in wheat flour

0,5 g sample with 5 ml of 2 % urea solution was mixed in a test tube.A strip of red litmus paper was immersed in the liquid.The test tube was stoppered and heat in a water bath held at 40 °C for 0,5 h.If soy flour is present in more than traces ,the litmus paper will turn to blue.

• Mositure Content of Wheat Flour

• 2 g of sample was weighed out accurately into a pre-dried nickel or steel dish ,spreading the sample as thinly as possiblke over the base of the dish.The dish was put and  the contents was maintaned at 105°C,and was dried for 2h.Then it was removed ,was cooled in a dessicators and was weighed.drying was continued until a constatn wight had been reached.FinallyThe moisture content was calculated from the weight loss of the sample.

 RESULT AND CALCULATION:

 Moisture content of wheat flour:[(2-(57,6-55,874))/2]*100: 13,7 %

Ash content of wheat flour  : [(27,4152-27,3852)/2]*100 : 1,5 %      

              % wet gluten [(7,54)/[25*(100-13,7)]]*100 : 0,35 %

          % acidity(KH2PO4 in dry matter): [(1,36*1,4)/(18*(100-13,7))]*100:0,13 %

          % acidity (lactc acid in dry matter):[(0,9*1,4)/(18*(100-13,7))]*100:0,08 %

DISCUSSION:

In this experiment, we made moisture, ash, crude gluten, detection of soy flour and acidity analysis of different types of flours. We should compare our samples with TS 4500.

But we should understand and learn limitation of quality standards and Why is important for human health. For instance; the moisture content of flour is an important point for us. Our sample is suitable for moisture content according to TS 4500 because it should not be over limit %14.5.

The reason of moisture content can be many such as climate, wet and temperature of warehouse or rain harvest. More wet amount cause a problem during milling.

One other way of quality determination is ash of sample. Obtained result by at the end of experiment is 0.85%. The percentage amount of Bran is higher with compare to normal flour. Because inorganic matter diffuses quickly into Bran, then they diffuse inside wheat particles. So, inorganic matter exists in low amount at center of wheat particles. Ash content of bran mixed is suitable for TS 4500 because maximum value is 0.85 for “under semolina flour”.

Also an important quality analysis is gluten amount determination of flour and bran. If gluten amount of flour is high sufficient, this is very well. Because this effect swelling of bread during fermentation of yeast in it. At the end of reactions CO₂ gases is produced during fermentation. In this event, gluten service to hold to coming out CO₂ gases. Dry gluten result of sample, according TS 4500 it should not be under 9%. Our result is much higher than this value.

The other important parameter is detection of soy flour. We analyzed the flour, and there was no change in color at litmus paper. So we can say that this flour does not contain soy flour which is illegal in Turkey.