Milling and Processing of Grains PDF

𝐰𝐞𝐢𝐠𝐡𝐭 𝐨𝐟 𝐟𝐥𝐨𝐮𝐫 Milling and processing of grains 𝐘𝐢𝐞𝐥𝐝 = × 𝟏𝟎𝟎 𝐰𝐞𝐢𝐠𝐡𝐭...

𝐰𝐞𝐢𝐠𝐡𝐭 𝐨𝐟 𝐟𝐥𝐨𝐮𝐫 Milling and processing of grains 𝐘𝐢𝐞𝐥𝐝 = × 𝟏𝟎𝟎 𝐰𝐞𝐢𝐠𝐡𝐭 𝐨𝐟 𝐫𝐚𝐰 𝐦𝐚𝐭𝐞𝐫𝐢𝐚𝐥 What is milling?  Transformation of raw material into a primary  Optimization of the process product for secondary processing o Achievement of optimal conditions within  Size reduction process processes in terms of process and economic  Milling is a process, involving the use of a milling performance machine to create a specific particle size o Optimization represents a major opportunity distribution from the bulk raw material to reduce energy costs and improve quality  Milling involves a progressive series of breakdown followed by sieving Changes during milling  Wheat milling is a complex process o Size reduction o Changes to starch, which can increase the enzyme activity Milling process o These changes are important in industrial applications ( eg. bread making)  Preparation of grains for milling o The extent of this change will depend on the o Removal of extraneous matter (stones, etc)  quality of grain Separators  parameters of milling o Removal of other impurities Aspirator o There may be changes to the proteins within o Removal of other cereals Disc separator the grains o Removal of metal contaminants Magnetic o During milling temperatures may reach 50– separator 60°C, which can denature the cereal’s o Washing / cleaning washer proteins o Conditioning o This can lead to a lower wet gluten yield,  Grinding bin which decreases the water absorption  Milling capacity of the flour  Control of moisture before store is very o To prevent this, excessive heating of the important milled material is avoided  If the moisture content increase beyond 15%, Determination of particle size there is a high risk of growing MOs  Reduce temperature before packing (to avoid o Flour is known to be a heterogeneous moisture condensation) mixture of particles of different densities and  Packing shapes  Store in a cool and dry place o Sieving, sedimentation, and photo extinction techniques have received most of the attention in the measuring of particle size distribution of flour 1 Nutritional consequences of milling  The gliadin and glutenine are responsible for the formation of the gluten during kneading  Fiber, vitamins and minerals tend to be  The gliadin and glutenine form a network of concentrated in the outer bran and aleurone molecules capable of holding the carbon dioxide layers of the grain gas that is a byproduct of fermentation  The final nutrient content will depend on the  It is this network of lace that causes the bread to extent to which these layers are removed during rise processing / milling  Generally, the more processed the grain, the lower the proportion of vitamins in the final flour  For example, white flour may have less than one third of the mineral and vitamin content of whole grains  Therefore vitamins and minerals are often added back after milling  Affect to phytochemicals o Milling may decrease some of the bioactive substances that are found in cereals Gluten allergy? o e.g.. Phenolic components A gluten allergy, also known as gluten intolerance or gluten sensitivity, is a condition where the immune system reacts adversely to gluten, a protein found in Quality of flour wheat, barley, rye, and sometimes oats. Advantages of Gluten Disadvantages of Gluten  Should be properly dried (Moisture content around 10%) Provides Elasticity: Helps Allergic Reactions: Causes  Should free from sands, stones, etc dough rise and maintain allergic reactions in people shape in baking. with gluten sensitivity or celiac  Free from MOs / Fungi disease.  Should not adulterate  Flour quality changes with machinery and milling Texture Improvement: Digestive Issues: Can cause Contributes to the chewy digestive problems such as techniques used texture of bread and pasta. bloating and discomfort in o Hammer mill, disc mill, roller mill, plate mill some individuals. o Wet milling or dry milling Versatile: Used widely in Inflammation: May contribute baking and food industry to inflammation in the body, for its functional particularly in those with properties. sensitivities. Nutrient Source: Contains Restricted Diet: Requires proteins and nutrients individuals with gluten beneficial to those who can intolerance to follow a strict tolerate it. gluten-free diet. Flavor Enhancer: Adds a Limited Food Choices: Limits characteristic flavor to food choices for individuals on baked goods. gluten-free diets, which can be challenging. 2 Glycemic Index (GI)  Starch and protein are less affected by processing as these nutrients are concentrated in the  GI is a measure of the rate at which endosperm of the grain carbohydrates in foods are converted to sugar  Due to the removal of fiber and enzymatic break components and how these foods affect down of proteins, milling will increase protein postprandial (after a meal) blood glucose digestibility responses  Some of the grain’s lipids, which are mainly  GI is used for classifying carbohydrate containing present in the germ and bran, are distributed foods during milling into other fractions  How foods affect to the blood glucose level?  Refined grains also have a higher Glycemic Index  The rate of digestion and absorption of (GI) than wholegrain products carbohydrates is influenced by a range of factors; o Nature of monosaccharides present Flour properties of concern to commercial o Nature of starch (Amylose and Amylopectin bakers content) 1. Water absorption o Cooking / processing 2. Mixing property o Other food components  Mixing time  Foods low on the GI scale tend to release glucose  Tolerance to mixing slowly and steadily 3. Ash content / flour colour  Foods high on the GI release glucose rapidly 4. Quantity and quality of proteins  The slow and steady release of glucose in low 5. Moisture content glycemic foods is helpful in keeping blood glucose 6. Bulk density under control. 7. Gelatinization temperature Glycemic Load (GL) 8. Fermentation tolerance 9. Oxidation requirement  The glycaemic load (GL) is an extension of the GI, 10. Damaged starch content taking into account the quantity of carbohydrates as well  The GL is obtained by multiplying the GI value by  Swelling power / water holding capacity of flour the carbohydrate content of the food. o Swelling power indicates the water holding  This provides with a more accurate picture of the capacity of Flour, which has generally been overall effect that the food product has on blood used to demonstrate differences between sugar levels various types of flours  Pasting properties of flour Fortification of flour o The level of amylase activity in grains  Products made from flour are important in the influences viscosity of starch, and thus diet pasting properties of their flours during  Nutritional losses during polishing, milling, etc processing  Flour can be fortified with minerals such as o Several factors (such as pH, temperature, calcium, iron, and vitamins such as thiamin and presence of minerals) can be used to control niacin in order to increase intake of these amylase activity and pasting properties of minerals and vitamins cereal flours and whole meals 3 Gelatinization of starch Important changes begin to occur at the presence of water and heat o Starch consists mainly of linear amylose and highly branched amylopectin and is stored as semi crystalline granules o Gelatinization is a irreversible process of breaking down the intermolecular bonds of starch molecules in the presence of water and heat o Starch granules are built of strands of starch called amylose and amylopectin o Amylose is a long linear molecule, often wrapped into a helix o Amylopectin is a branched molecule Retrogradation Retrogradation is a recrystallization process in which o The starch molecules are arranged in a disaggregated amylose and amylopectin molecules in starburst pattern, with hydrogen bonds gelatinized starches reassociate to form ordered holding the molecules in place structures o If add cold water to starch, the granules swell a little, but remain mostly unchanged 4   The mixograph curve suggests mixing time requirement, tolerance, and optimum water absorption  Depending on the dough strength of the flour, the curve will reach a maximum either as a well defined peak or as a plateau  After further mixing, a decrease in the mixing curve is recorded and the breakdown starts Alverograph Flour Performance Tests  Farinograph  Mixograph  Extensograph  Alveograph  Gluten Washing Tests  Alkaline Water Retention Capacity  Solvent Retention Capacity Profile Mixograph  An alveograph is a rheological tool to assess the baking performance of flours used in baked products (noodles, tortillas, biscuits, etc)  It is based on injecting air into a thinly stretched sheet of dough to form a bubble, simulating gas/carbon dioxide release and retention during dough fermentation and oven spring during baking  Bakers use alveograph data to gain an understanding of fluctuations in dough rheological changes by assessing o Tenacity o Elasticity o Baking strength o Resistance of dough to deformation o Extensibility 5 Extensograph Flour analyzing tests  Tests Exclusive to Wheat o Test Weight o Thousand Kernel Weight o Kernel Hardness o Flour Yield  Color Tests o Pekar Color (Slick) Test o Agtron Color Test  Basic Analyses  An extensograph is a tool used for measuring the o Moisture flour quality and stretching behavior of dough o Ash  Extensional properties, which determine the o Protein course of dough expansion during proofing and o pH baking, have a direct effect on o Enrichment Detection  Loaf volume o Semolina Granulation  Quality of texture of bread crumb o Test for water absorption power Farinograph: Measures the dough's resistance to mixing, indicating water absorption capacity and dough development Farinograph time, which helps predict baking performance. Mixograph: Assesses the dough's mixing characteristics, such as strength and stability, by measuring the resistance of the dough to mixing blades. Extensograph: Evaluates the dough's elasticity and extensibility, providing insights into how the dough will stretch and expand during fermentation and baking. Alveograph: Tests the dough's ability to expand and retain gas, measuring its strength and elasticity, which is crucial for understanding dough's behavior during fermentation and baking. Gluten Washing Tests: Determines the quantity and quality of  The farinograph is a recording dough mixer that gluten in flour by isolating gluten from the dough, providing measures and records the torque developed by information on its elasticity and cohesiveness. the action of the mixer blades on the dough Alkaline Water Retention Capacity (AWRC): Measures the during mixing flour’s ability to retain water in an alkaline environment,  It is used to estimate the water absorption of indicating the flour's ability to hold moisture and affect dough flours, the relative mixing time, the stability to consistency. overmixing, and rheological properties of the Solvent Retention Capacity (SRC) Profile: Assesses the flour's dough during mixing ability to retain different solvents, such as water, sodium carbonate, sucrose, and lactic acid, to understand its functionality related to protein, starch, and pentosan content. 6