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Food Science
FOOD 2010
Massimo Marcone

Chapter 9 (p. 249 – 278): Understanding Fat, Sugar, Beverage, and Plant Product Processing 9.1 Processing of Fats and Oils - Lipids that have a relatively high melting point and are solid at room temperature are called fats - Lipids that have lower melting points and are liquid at room temperature are called oils - All food lipids are mixtures of triglycerides, usually with 2 or 3 different fatty acids attached to each triglyceride o Melt over a range of temperatures - Processing of fats means the removal or extraction of a fat or oil from its natural source, such as a kernel of corn, the carcass of a hog, or a cottonseed - Refining: refers to the removal of impurities from the extracted fat or oil o Oxidative stability of oils is generally improved by refining, as are colour and flavour o Toxicants are also removed during this process - Crude oil: when food lipid matter is obtained via pressing and rendering o Subjected to a number of commercial refining processes to remove compounds that may contribute especially to flavour and colour instability o RBD oil: crude oil that has undergone refining, bleaching, and deodorizing - Basic production methods: o Rendering – heating of fatty meat scraps in water o Pressing – mechanical squeezing of oil from oilseeds o Solvent extraction – separation of oil from cracked seeds using a nontoxic fat solvent such as hexane  Solvent is distilled off and recovered for reuse o Deodorization – application of steam heat in a vacuum chamber to strip away certain odor-causing low molecular weight compounds from oils o Degumming – first refining steps for oils such as soybean oil and others high in phospholipids o Neutralization – removes free fatty acids from a fat o Bleaching – refers to the removal of coloured substances from oil o Hydrogenization – process to saturate double bonds and make an oil more solid and more resistant to oxidative rancidity o Winterizing – refrigeration treatment of oils for a specific purpose o Plasticizing – softening a hard fat, which changes the fat’s consistency - Processing of specific fats: o Milkfat is a mixture of glycerides found in milk, milk products, and butter – processed by fractionation (to yield butter fractions of varying melting points)  Process generates solid and liquid phases that are easily separated by vacuum or pressure filtration o Interesterification: refers to the removal of fatty acids from the glycerol portion of food triglycerides, such as those occurring in large, and their subsequent recombination into numerous configurations  Contain a random distribution of the fatty acids within a glyceride molecule  Ester bonds break and reform during this reaction  Can change lard into one with a lower melting point, finer crustal size, more plastic, and smoother texture and mouthfeel  Also produces fats with reduced calories - Chemical and physical testing of fats: o Must be tested to gain information regarding specific food applications, to measure deterioration, to check performance vs. purchase expectations, and to examine physical properties o Iodine value: used to measure the degree of unsaturation of a fat or oil o Peroxide value (PV): used to measure lipid oxidation, and it too uses iodine o Acid value: measure of the number of free fatty acids present in a fat  Refers to the splitting of glycerides into component parts: glycerol and free fatty acids o Saponification value: test that gives the average molecular weight of the fatty acids in a fat  Molecular weight influences physical firmness  Potential to produce odour, with short-chain or low molecule weight fatty acids being most odorous o Smoke point: temperature at which smoke emanates continuously from the surface of a lipid heated under standard conditions  If higher temperatures – sample will flash and further burn 9.2 Sugar Processing - Most common sugar is sucrose – disaccharide found in almost all plants o Highest concentration in sugarcane and sugar beets - Cane sugar: refers to the sucrose product obtained from sugarcane and is generally produced in two stages o Manufacturing in cane-growing countries o Refining into food-grade products in sugar-consuming countries - Sugar beets are processed into white sugar in one stage - Extraction: o Cane is chopped into chips to expose the tissue and open the cell structure o Crushed cane proceeds through series of roll mills, where it is forced against a countercurrent of water (water of maceration) o Mixes with maceration water and combines into a dilute juice - Neutralization and clarification: o Mixed juice from the extraction mills is purified by addition of calcium hydroxide and heat - Concentration and crystallization: o Clarified juice is pumped to a series of devices called evaporators o Steam is used to concentrate the juice into evaporator syrup o Further evaporated under vacuum to achieve supersaturation o Crystallization: yield an “A” sugar, leaving behind a residual mother liquor known as A molasses o A molasses is concentrated to yield B variety, and low-grade B molasses is concentrated to yield C sugar o Left with molasses, known as blackstrap - Separation and drying: o Crystals and mother liquor are separated via centrifugation o Washing process is performed in an effort to produce high-purity raw sugar o Washed sugar dries and cools and is placed in bulk storage - Sugar refining: refers to the production of high-quality sugars from remelted raw cane sugars o Produces white sugar cubes, powdered and granulated white sugar, and light and dark brown sugars 9.3 Beverage Processing - Drinking (or potable) water: water that is intended for human consumption and sealed in bottles or other containers with no added ingredients, except optional antimicrobial agents - Bottled water: includes natural mineral waters, carbonated waters, and sweetened, flavoured waters that are typically carbonated o To ensure a safe product and to preserve the properties ascribed to the water, such as mineral content or flavour, up to the point of consumption - Ozone: an unstable, colourless gas that acts as a powerful oxidizer and a potent germicide o Controls the growth of bacteria in water o Does not leave a residual taste o Higher disinfection potential than chlorine - Soft drink beverages: o Soft drinks: non-alcoholic carbonated or noncarbonated beverages, usually containing a sweetening agent, edible acids, and natural or artificial flavours  Includes cola beverages, fruit-flavoured drinks, ginger ale, and root beer o Superchlorination: water is treated through this process to remove colour, chlorine, and any other tastes or odors that may be present  Water is exposed to a high concentration of chlorine and to a flocculant that removes microorganisms o Carbonation: the saturation of water with carbon dioxide under pressure in which the CO g2s dissolved in the water becomes carbonic acid  Water or the finished beverage mixture is chilled and cascaded in thin layers over a series of plates in an enclosure containing carbon dioxide gas under pressure - Special beverage categories: o Noncarbonated soft drinks: produced with much the same ingredients and techniques as those for carbonated soft drinks  Not protected from spoilage o Powdered soft drinks: made by blending flavouring material with such ingredients as dry acids, gums, and artificial colour o Nutraceutical beverages: drinks formulated with special functional ingredients that promote some aspect of health or reduce the risk of certain diseases 9.4 Processing of Cereal Grains - Conversion of cereal grains into food products or ingredients - Classified as dry fruits, derived from the seeds of plants in the grass family - Cereal: refers to any grain used for food - Grain: refers to a small hard seed produced by plants that are grasses - Barley, buckwheat, corn, millet, oats, rice, rye, sorghum, and wheat are grass plants that produce the common cereal grains - Milling – grinding of grain into a form that is easily incorporated into foods or cooked o Methods are dry and wet, depending on the particular grain - Wheat milling: o Hard and soft wheat describe the firmness of the kernels and relate to the strength of the gluten developed when doughs are made from milled flours o Strong gluten: higher protein content, elastic gluten suited to breadmaking o Weak gluten: low in protein, weak, fragile gluten producing a softer, more fragile dough for cakes and biscuits o Semolina: result of milling certain hard grains  Generally used to make pasta  Doughs made from it are strong but do not have the same level of elasticity o Wheat flour processing consists of grinding rollers, sieves, and purifiers - Breadmaking: o Bread: product of baking doughs from a mixture of flour, water, salt, yeast, and other ingredients o Patent flour: the purest flour, selected from the purest flour streams released in the mill  Very low mineral content, devoid of bran specks and other impurities o Basic breadmaking:  Flour, water, other ingredients (sugar, yeast, emulsifier)  Mixing (kneading) • Until the flour is converted into stiff dough, followed by baking the dough into a loaf • Want to produce dough that will rise easily and have eating properties desired by consumer • Must be extensible (relax/stress) and elastic, having strength to hold the • gases produced during fermentation, and stable to hold shape and cell structure • gluten is formed from two proteins present in flour: gliadin (stickiness) and glutenin (elasticity) • Natural flour lipids (glycolipids) bound to carbohydrate associate with gluten proteins in the dough matrix • After making, forms a crumb structure • Heating causes gluten proteins to strength and expand as the gas cells in the dough increase in volume • Overmixing reduces elasticity properties • Undermixing may create small, unmixed dough areas that will remain unrisen  Fermentation (29°C, 84°F for 4 hr) • Changes the dough to a smooth, extensible dough with good gas- holding properties • Each yeast cell forms a nucleus around which carbon dioxide bubbles form  Proofed dough  Sheeting, molding, and panning • Dough is sheeted after the first rise o Gentler process than mixing, less energy • Use an action roller system for sheeting – pair of rotating rollers shuttle back and forth over two separate belt conveyors • Dough is panned and returned to the fermentation cabinet  Baking (215°C, 419°F for 20 minutes) • Gas cells increase in size •
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