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Unformatted text preview: © E.Garcia 2010 FST 1 – Main topics – Lecture 07 Proteins - 2
Protein reactions Denaturation (see summary lecture 06) Coagulation (see summary lecture 06) Hydrolysis: ‐ cleavage of peptide bond ‐ shortens polypeptide chain ‐ can be caused by acid and enzymes Enzymatic activity: ‐ possible only when protein is not denatured Enzymes in Foods Enzymes are biological catalysts MANY enzymes are important in Food Science ‐ some have detrimental effects, such as POLYPHENOL OXIDASES Cause enzymatic browning on the surface of fruits and vegetables ‐ others have a desirable effect, such as some uses of invertase invertase Sucrose Glucose + Fructose Food Quality
Nutritional quality Safety Sensory quality Food and Our Senses Sensory attributes of foods: ‐ appearance (color, size, shape, gloss, transparency, absence of defects, etc) ‐ taste ‐ smell ‐ texture / mouthfeel TASTE ‐ 5 basic tastes: ‐ Sweet (sugars) ‐ Sour (acids, such as citric acid) ‐ Bitter (caffeine, quinine) ‐ Salty (table salt, NaCl) ‐ Umami (MSG = monosodium glutamate) Relative Sweetness Sucrose (table sugar) is the reference sugar RELATIVE SWEETNESS is a measure of how sweet a specific substance is in relation to sucrose. Sucrose 100; Fructose 120; Glucose 70; Maltose 45; Corn syrup 30‐50 (McGee p.655) Umami (Japanese for “delicious taste”) is frequently described as “brothy”, savory. This taste is associated with the taste of glutamate (MSG). Taste Perception Taste can be detected throughout the tongue. Tongue has 4 types of PAPILLAE: Circumvallate, Folilate, Fungiform and Filiform. Tiny projections that give the top surface of the tongue its rough, “bumpy” appearance Within the papillae there are TASTE BUDS: onion‐shaped structures containing TASTE CELLS. Taste buds are located mainly on the tongue and soft palate. Only the Filiform papillae lack taste buds; these papillae are the most numerous papillae on the tongue. Food components dissolved in saliva reach the taste buds, and interact with taste cells. As a result, there are electrical changes in the taste cells, and signals are sent to the brain, which interprets them as the basic tastes. Readings 1. McGee p.269 (see figure and legend) 2. McGee p.270‐272 (Flavor) 3. McGee p.387 (Flavor is part Taste, mostly Smell) 4. McGee p.655 (The Complexities of Sweetness; see also box) 5. Taste Intensity (pdf file posted on the course web page) _____________
FYI (not for exam) Video http://www.youtube.com/watch?v=yHlAcASsf6U Note: the pool is filled with corn starch and water ...
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