Authors: Shernett Brown and Kadane Coates ID# : 620043538 and 620058416Lecturer: Dr Donna Minott- Kates Course title: Food Processing LaboratoryCourse code: CHEM2511Date: November 26, 2013Name of department: Department of ChemistryInstitution: University of the West Indies, Mona, Jamaica

TABLE OF CONTENTSContent PageList of Figures 3Abstract 4Introduction 5-6Flour and Self Rising Flour 7Components of Flour 7Unit Operations in the Production of Self-Rising Flour 8-9Pre-Milling of Wheat 9-10Milling of Wheat 10- 11Post-Milling of Flour 12- 13Conclusion 13Reference List 14- 15

FIGURESFigures Page Figure 1. Diagram showing the different parts of a whole grain 8Figure 2. Showing the various steps within the pre-milling, milling and post-milling process. 9

ABSTRACTSelf rising flour is flour which contains mix spices, salt and leavening agents. This product is of great importance in the baking industry as it is of convenience to the consumers especially on a commercial an industrial level. Commercial bread production has grown exponentially over the years with an increase also in buns and rolls. The milling process is a means of preservation which entails the powdering of wheat or grain, along with any other materials such as roots and corns mainly. Wheat and other grains are high in fibers, proteins, oils and other essential vitamins and minerals. The endosperm is the portion of the grain normally used solely in self rising flour, as it is much lighter than the bran and germ which will aid in the rising of the dough. Pre-milling and post milling activities are important as they prepare and enhance the quality of the flour and is where the oxidizing and bleaching agents are added. Essential quality control tests are vital in ensuring that the consumers health is protected along with the organoleptic qualities. Packaging and storage is also key in extending the shelf life of the flour to prevent moisture and other unwanted elements from contaminating the final products.

INTRODUCTIONCereals are the edible seeds (kernel) or grains of the cultivated members of the grass family which all morphologically comprise three main parts1. These three main parts are the bran, the endosperm and the germ (See Figure 2). The bran is the thin outermost layer of the seed which is rich in cellulose and minerals namely iron, calcium and phosphorous. The endosperm, on the other hand is the largest inner part of the seed and is mostly comprised of starch along with protein, while the germ or the embryo of the grain makes up approximately 2% of the whole kernel and contains protein, and vitamins namely B and E along with minerals. Cereals are generally processed to improve their diversity, usage and storage in food production. Cereals are also chiefly processed however to extend their shelf life (preservation) because of their proclivity to be easily destroyed by pests, who normally target them as a source of food. The most common way cereals are processed to attain these advantageous properties is through milling, which is the mechanical grinding and pulverizing process in which these grains are converted to a powder. This resultant powder is commonly referred to as meal or flour2. The milling process can be categorized into three main components namely pre-milling, milling and post-milling. The most common type of cereal milled is wheat, which refers to the grains of grasses which belong to the family Poaceae and the genus Triticum3. The end product of milled wheat is termed wheat flour and generally comprises of the endosperm. The germ, which is the richest part of the grain is normally removed since it is responsible for spoilage of the grain through lipid oxidation (rancidity) because of its high fat content. Wheat flour is normally used for baking because it contains a high gluten content which normally ranges between 8 to 14%. Gluten is a collective term which refers to protein, which play an important role in baking by developing a thick, cohesive and elastic 3-D structure3. This 3-D structure is pivotal for allowing a dough or batter rise without collapsing and withstand heat. There are many types of wheat flour which include all purpose wheat flour, whole-wheat flour and enriched white flour. A common variation of all purpose or enriched white flour is self rising flour, which refers to refined wheat flour to which chemical leaving agents have been added to make it suitable for use in the creation of a dough or batter, which is subsequently subjected to frying or baking 4. These chemical leaving agents that are added to self rising flour are a formulated mixture of (a) weak acid(s) and a weak base which is commonly collectively referred to as baking powder 4. These chemical leavening agents in the presence of heat and moisture undergo a chemical acid-base neutralization reaction producing carbon dioxide as a byproduct. The weak acids used in a baking powder include tartaric acid, calcium acid phosphate, sodium acid phosphate and sodium aluminum sulfate, while the most commonly used wake base issodium bicarbonate. The carbon dioxide produced by the reaction between these weak acids and weak bases serves an important function in batters and doughs since it ensures that the final cooked product has a light and soft the texture there by enhancing its organoleptic appeal5. Self rising flour is normally used in to produce a variety of commercial and home based products namely quick breads such as Johnny Cakes, cakes, and pastries because it is highly convenient to have the raising agent already pre-mixed in the flour. In order to produce self rising flour which is fit to serve these functions it is important to understand the processes involved in the key stage of the milling process. Therefore the paper will explore in detail the unit operations of milling in order of pre-milling, milling and post milling.

FLOUR AND SELF RISING FLOURFlour as is the powdery substance created when a dry grain is pulverized. This is referred to as the milling process. The most common varieties of flour are made from wheat although any grain can be made into flour, including rice, oats, corn or barley. Self rising flour as already mentioned is all purpose flour which has been blended in with salt, leavening agents such as baking powder and other spices that enhance the flavor. It is mainly used in the baking industry 6.THE COMPONENTS OF FLOURIn addition to the type of grain used, flour also varies depending on what part of the grain is retained during the milling process. This may include the endosperm, bran or germ. Endosperm:This is the starchy center of the grain, which contains carbohydrates, protein and a small amount of oil. Most simple white flours contain only this portion of the grain. Brain:The outer husk of the grain, known as bran, adds texture, color and fiber to flour. Bran gives whole grain flours their characteristic brown color and rough texture. Germ:The germ is the reproductive epicenter of the grain and is a concentrated source of nutrients. Flour that retains the germ during the milling process will contain more vitamins, minerals and fiber. Gluten:Glutenis a protein found naturally in the endosperm of wheat. It gives strength, elasticity and a characteristic chewy texture to yeast breads, pasta and pizza dough.6

Figure 1. showing the different parts of a whole grain7

UNIT OPERATIONS IN THE PRODUCTION OF SELF- RISING FLOUR

Grains receiving, storage and handling- manual and mechanical reaping and transportation from field to the factory or flour mill.

Grain cleaning the grains/wheat or whatever is to be pulverized is washed thoroughly with running water to remove dirt and other impurities.

Selection of wheat/grain - sorting of raw material based on size and color.

Milling the wheat/grain selected is milled or pulverized with a dry process to its powdered form.

Post milling treatments incorporation of maturing and bleaching agents and enrichment.

Packaging and storage - the end product is placed in containers that will protect and preserve the flour.

Figure 2. Showing the various steps within the pre-milling, milling and post-milling process8.

THE PRE-MILLING OF WHEATIn the pre-milling stage the wheat is received at the flour mill inspected and graded. Samples of wheat are taken for physical and chemical analysis. The wheat is graded based on several factors, the most important of which is the protein content 9. This generally is between 8 to 14% for self-rising flour. The wheat is stored in silos at regulated temperatures and humidity with wheat of the same grade until needed for milling. When ready for milling the wheat is then scoured, brushed and added to water. This water is then subsequently heated to temperatures of between 70-100 C. This process is called conditioning which makes it easier to separate the bran from the endosperm9. When this is complete the wheat undergoes a series of grinding operations which separates the bran from the endosperm, this process is called breaking 9.THE MILLING OF WHEATEssentially there are only two things that happen in a mill: grinding and separating. But that apparent simplicity belies the complicated nature of the modern milling process, as well as the degree of skill required to produce good flour of consistent quality from a variable supply of wheat.The process used to produce white flour in a modern roller mill is referred to as a gradual reduction. The endosperm is gradually reduced in particle size by running it between a series of pairs of rotating hardened steel rollers, either corrugated or smooth, and is separated from the bran and germ by running it over sieves. All pairs of rollers in a mill have one slow mill and one fast one. The rolls turn in opposite directions, toward each other, pulling the stock (material being ground) between them. The cut, depth, and spiral of the corrugation, together with the rotation differential, determine the aggressiveness of the milling at any particular step.10To begin with, a field of wheat is converted into a loaf of bread by breaking the grain open and grinding it in a process called milling, which is one of the common processes for making grains digestible and making their nutrients available to us. However, mainstream flour production, for the most part, takes the nutritious grain and turns it into nutritionally poor flour. To understand why this happens, we have to think about the structure of wheat, which is made up of the bran, the germ and the endosperm. The husk of the wheat grain, called the bran, contains some protein as well as many vitamins, minerals and other nutrients, including potassium, phosphorus, magnesium, calcium, niacin, phytic acid and dietary fiber. The germ is the embryo of the grain, containing proteins, fats, lipids, sugar and B vitamins. The endosperm contains a lot of the protein and carbohydrates to make flour. The aleurone layer between the germ and the endosperm contains essential amino acids. Since the endosperm contains most of the dry matter it is technically the only part of the grain needed to make flour. However, the majority of the nutrition is contained in the bran and the germ11. For self rising flour the endosperm is the portion of the grain which is used only as it is lighter and normally characteristic of a yellow colour. Bleaching agents such as chlorine dioxide, nitrogen peroxide, chlorine, benzoyl peroxide or acetone peroxide are used to give the flour its white colour. Aleavening agent(sometimes just calledleaveningorleaven) is a substance used in dough and batters that causes them to rise. In the presence of moisture, heat, acidity, or other triggers the leavening agent reacts to produce gas (often carbon dioxide) that becomes trapped as bubbles within the dough. When a dough or batter is baked, it sets and the holes left by the gas bubbles remain. This is what gives breads, cakes, and other baked goods their soft, sponge-like textures. For self rising flour these ingredients are already in cooperated 12.

POST -MILLING OF WHEATAfter milling of wheat flour has taken place the flour produced normally has a yellowish tint, therefore one of the first steps in post milling is the bleaching of the flour, in which a bleaching agent is added to the flour. A bleaching agent can be defined as a food additive added to whiten and lighten the appearance of food and to also aid in the development of gluten13. Common bleaching agents which are normally added in this step may include peroxides such as calcium peroxide, chlorine, chlorine dioxide, bromates, nitrogen dioxide or azodicarbanamide. After the flour has been bleached by law it is normally subjected to enrichment this is because when wheat is milled, some of the nutrients are lost, therefore various nutrients are added to flour to enrich and even fortify it 14. The various nutrients and mineral salts in a powdered form are then added to flour at this stage which include thiamin, riboflavin, nicotinic acid and iron salts. Calcium carbonate may also be added for fortification at this stage. In order to actually produce the self rising flour, after it has been enriched a formulated mixture of weak acids and weak bases are added as described previously, in the introduction, are added 15. The amount of leavening agents and their proportions are normally left to good manufacturing practices (GMP) but the amount added does not normally exceed 2.5% of the net weight of the final product. Powdered salt or spices may also be added to the self rising flour after this. When this is complete in order to improve the shelf life of packaged self rising flour irradiation is sometimes employed as a preservative technique 16. This is because when commercially produced self rising flour can become infested with insects especially those which are offspring of insect eggs found in the flour hence the flour is irradiated with a 40 krad in a 60Co gamma irradiator. Apart from killing pests irradiation of the flour also helps to reduce the microbial load of the flour 16. Another key step after the treatment of the flour and preparation of the actual self rising flour is the packaging of the self rising flour. The flour is normally packed into cloth, plastic or paper bags with predetermined weights between 2 to100 lbs and then tied or sealed. During packaging, the flour can possibly be contaminated with microorganisms causing quality deterioration17. This can generally be avoided by upright positioning of the packaging material. Subsequently, the packaged self rising floor is then stored in a cool environment generally the flour is stored in air conditioned rooms temperature and relative humidity must be below 20 C and 65% respectively17. Both the temperature and relative humidity are recorded regularly and corrective actions are taken whenever deviations occur. This is done in order to inhibit the development of microbes. Storage may be generally up to two months to ensure maturation. Most cases before being released on the market the flour is subjected to quality assurance tests especially of its protein content 17.

CONCLUSIONBased on the findings it is important that each unit operation carried effectively in each stage of the milling process to ensure a safe product and that the self rising flour meets desirable qualities based on its commercial and home uses in baking. Correct milling procedures are pivotal in ensuring the self rising flour is of the appropriate particle size, that there is proper separations of the bran and germ from the endosperm and ensuring that an appropriate protein content is present in the final self rising flour product.

REFERENCES1. Potter N., and Hotchkiss, J. Food Science, 5th ed.; Aspen Publishers: Gaithersburg, Maryland, USA, 1998; pp. 205-220.2. Kent, N. L. Technology of Cereals: With Special Reference to Wheat. Pergamon Press, 1999. pp. 201-203. 3. Kent, N. L. Technology of Cereals: With Special Reference to Wheat. Pergamon Press, 1999. pg. 204. 4. Besant, Lloyd. Grains: Production, Processing, Marketing. Chicago Board of Trade, 1982. pp 192-194.5. Heldman, D and Hartwell, R. Principles of Food Processing, 2nd ed; Aspen Publishers: Gaithersburg, Maryland, USA, 1998; pg.190.6. Moncel Bethany, A Guide to Flour: Flour Components http://foodreference.about.com/od/Ingredients/a/A-Guide-To-Flour.htm ( accessed Nov 20, 2013)7. Healthy Living 101: Understanding Whole Grainshttp://www.fitday.com/fitness-articles/nutrition/healthy-living-101-understanding-whole-grains.html#b (accessed Nov 23, 2013).8. How Flour is Milled.http://www.namamillers.org/wp-content/uploads/2012/10/how-flour-milled.jpg (accessed Nov 27, 2013).9. Potter N., and Hotchkiss, J. Food Science, 5th ed.; Aspen Publishers: Gaithersburg, Maryland, USA, 1998; pp. 221-224.10. Leonard Thom, The Milling Processhttp://www.theartisan.net/The_Milling_Process.htm (accessed Nov 20, 2013)11. Wight Heather and originally published by HumJournal| JAN 25, 2011 The history and processes of milling http://www.resilience.org/stories/2011-01-25/history-and-processes-milling (accessed Nov 24, 2013) 12. Besant, Lloyd. Grains: Production, Processing, Marketing. Chicago Board of Trade, 1982.13. Fellows, P. Food Processing Technology: Principles and Practice, 2nd ed; Woodhead Publishing : Cambridge, England, 2000; pp. 325-330.14. The Chemistry of Baking. http://nzic.org.nz/ChemProcesses/food/6D.pdf ( accessed Nov 27,2013)15. Besant, Lloyd. Grains: Production, Processing, Marketing. Chicago Board of Trade, 1982. pp 303-305.16. Besant, Lloyd. Grains: Production, Processing, Marketing. Chicago Board of Trade, 1982. pp 207-208.17. Heldman, D and Hartwell, R. Principles of Food Processing, 2nd ed; Aspen Publishers: Gaithersburg, Maryland, USA, 1998; pg.195-197

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