HTM 2700 Lecture Notes - Lecture 4: Semipermeable Membrane, Plant Cell, Transparency And Translucency

• School: University of Guelph
• Department: Hospitality and Tourism Management
• Course: HTM 2700
• Professor: Alison Crerar

Document Summary

Acid (added or naturally occurring organic acids speeds up rate of protopectin. Sugar slows down protopectin solubilization by forming hydrogen bonds with solubilization protopectin. Increase in translucency during cooking fruit and veg. Oxygen gives raw fruits and vegetables opaque appearance. Cooking in a medium containing h2o, means some oxygen is replaced by water. If water is in the intercellular spaces it would be translucent (cooked) Refractive index is closer to a value of 1 (value of pure water) Plastids which contain fat soluble pigments (chlorophylls and carotenoids) and starch. In living cells (raw food) cell membrane is semi-permeable, allowing osmosis to occur. Cooking denatures cell membrane making it totally permeable, allowing diffusion to occur - anything can pass through. = unfolding of the original configuration (shape) of a protein molecule. Cause: heat (+ other things we will discuss later) Occurs in living cells = raw, uncooked, not dried foods. Results in increase or decrease in turgor pressure.