What would be the wavelengths of the two photonsproduced when an electron and a positron, each with420 keV of kinetic energy, annihilate in a head-on collision?
Tuesday, March 8, 2016 NHM 253 Cereal Science - Grain Structure and Composition • Husk - protective outer coating - We do not eat this. - Husks can be stripped from grains and processed into ﬁber supplements. • Bran - protective coating of the endosperm - high in ﬁber, B vitamins, and minerals - We consume this if we consume whole grains. • Endosperm - where all the starch is located - serves as the basis of ﬂours • Germ - embryo of the plant; the part that sprouts - high in fat, vitamin E, and B vitamins - Classiﬁcation of Cereal Grains • Whole Grains - contain the entire grain kernel (bran, endosperm, and germ) - examples: oatmeal, bulgar, brown rice • Reﬁned Grains - grains that have been milled to remove the bran and the germ - ﬁner texture - increased shelf life • because: the germ (lipid portion) of the whole grain is the most easily oxidized - removes ﬁber, iron, and B vitamins - must be enriched - examples: white rice - Land Use for Cereal Production • 4 most abundantly grown: wheat, rice, corn, barley - Use of Cereal Grains 1 Tuesday, March 8, 2016 • Flour - wheat ﬂour is the most predominant choice (because of its protein content and ability to provide structure to baked goods) • Pasta • Breakfast cereal - primarily made from wheat, corn, and oats • Alcoholic beverages - made through fermentation of rice, barley, corn, or rye - Grains are used as food for the microorganisms responsible for fermentation. • Animal feed - for every 15 lbs of animal feed, 1 lb of beef is produced; for every 6 lbs of feed, 1 lb of pork is produced - Barley • Barley can be processed into malt. It is used primarily in the malt form for ﬂavorings, color additives, and in the manufacture of beer or whiskey. - Additional uses: soups and cereals, livestock feed • Processing Barley to Malt - Pearling - removal of the hull, bran, germ, and/or part of the endosperm • The endosperm is the only component left. - Sprouting - gently drying barley to stop germination and preserve enzymes responsible for converting starches to sugars (maltose) • should be below 110 degrees - Amylase enzymes (alpha and beta) break down starch to sugars such as maltose (glucose + glucose) and glucose • Malt becomes food for fermenting organisms. - Functions of Carbohydrates in Foods • sweetness • color (caramelization and Maillard browning) • moisture absorption • texture • thickening 2 Tuesday, March 8, 2016 - Grains to be avoided by individuals who have a sensitivity to gluten: • barley • rye • wheat • oats - Oats do not naturally contain gluten-forming proteins. However, oats may be processed in a facility that processes barley, wheat, or rye. • Gluten-free ﬂours do not have the same function as wheat (texture). - Complex Carbohydrates • Digestible polysaccharides are not sweet and they are not soluble in water. Complex starches are classiﬁed as: • - Amylopectin - bulky, branched structure • Less able to interact with water due to bulkiness of structure. - Amylose - linear molecule • Linear structure allows the molecule to interact with water easily. • Functional role: thicken and swell when heated with water - ex. cornstarch • Taste impact: dry, ﬂuffy mouthfeel - Responses of Starch in Food Systems • Dextrinization - breakdown of amylose and amylopectin molecules that results in shorter and sweeter glucose chains - Starches become sweeter in the presence of heat. - ex. white bread vs. toasted white bread (sweeter) - dextrose - glucose derived from starch - DE = dextrose equivalents • Gelatinization - cooking of starch granules causing water absorption resulting in the swelling and softening of granules 3 Tuesday, March 8, 2016 - water + heat + starch - uses: thickener in sauces or gravies; development of structure/texture in cakes or breads - Factors inﬂuencing gelatinization: • temperature - the higher the temperature, the faster the gelatinization rate • stirring - increases the rate of gelatinization • acidity and alkalinity of cooking medium - decrease the rate of gelatinization • sugar - decreases the rate of gelatinization - Sugar molecules will bind more readily to water. • Gel formation - upon cooling, some gelatinized starches will convert into a semi- solid paste or gel - dependent on the presence of amylose - Amylose molecules bind to each other, forming a gel. Water molecules that were bound between amylose molecules are released into the environment. - ex. yogurt • Retrogradation - the seepage of water out of an aging gel as a result of amylose reassociation; occurs with very cool temperatures under prolonged storage - opposite of gelatinization - also known as syneresis - negative attribute of food - component of staling (becoming stale) • sequence: gelatinization —> gel formation —> retrogradation • Some grains take longer to cook than others because: - size (how long does it take water to get to the center) - amount of processing (physical breakage that allows water to bind more readily) - presence of bran (whole grain products take longer to cook) - Pasta Basics 4 Tuesday, March 8, 2016 • Extrusion - process that takes a starch and gelatinizes it and then forms it into a shape by forcing through formed plates and then drying it - shapes pasta • Whole wheat pasta - incorporates bran and/or germ into dough prior to extrusion - ﬁrmer texture, stronger taste 5