Processing Grains

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A brief description of how grains can be processed.

Transcript of Processing Grains

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


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 take