HTM 2700 Lecture Notes - Lecture 19: Isoelectric Point, Casein, Peptide

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

Document Summary

Week 7 lecture 19 monday, february 29, 2016. The point where the amino acid no longer has an electrical charge. The like charges of the protein are no longer repelling each other. Protein molecules are then attracted to each other and form h-bonds with each other creating larger molecules. Each protein has a different iep (ph value) where the negative charges are neutralized around the protein molecule. When proteins are no longer colloidally dispersed they precipitate out of colloidal dispersion. Sometimes this is something we want (ex. when making cheese) So(cid:373)eti(cid:373)es it is a (cid:858)culi(cid:374)ar(cid:455) catastrophe(cid:859) (cid:894)e(cid:454). curdled soft custard(cid:895) Proteins in food exist at a ph different from their iep. Therefore they exist as stable colloidal dispersions (ex. milk has a ph of 6. 5-6. 7: casein proteins in milk have an iep of ph 4. 6 (at around a ph of 4, your milk curdles) Ph least stable at their iep temperature: particularly increases due to cooking, also decreases (ex. freezing)