Protein structure Flashcards
what is the isoelectric point?
the pH at which the net charge of the protein is zero. proteins are positively charged at pH values below their pI and negatively charged at pH values above their pI
how does addition of salt affect solubility of proteins?
it decreases their solubility
protein networks in cheese should be..
strong! if fat moves into the grain boundary weaker structure is achieved and the cheese may crack.
how should fat droplets behave in a good cheese?
fat droplets should coalesce to a small degree
what are five different techniques to elucidate microstructure?
macroscopy, light microscopy, CLSM (laser), scanning electron miscoscopy, transmission electron microscopy
how do protein gels behave at different pH?
below pI: breaks on touch, fragile gel. slightly below pI: similar to cottage cheese. slightly above pI: elastic gel which releases water upon pressure. 2-5 % protein needed to form gel. above pI: 10 % protein needed to form a gel, gel is very extendable
a simple definition of a finished gel is…
when the protein network is connected from one side to the other a.k.a. a continuous network
protein gels form during…
heating and solidify further during cooling
turbidity of protein solutions is an indication of
degree of aggregation
what type of water holding capacity is desired in food production?
the water should be hold in the product but released upon chewing to give a nice mouthfeel. if the water is not released upon chewing a rubbery texture is achieved.
what effect does homogenization have on milk protein?
protein is further attached to the fat globule surfaces since protein acts as stabilizers for the fat droplets
what happens with myofibrils in food processing?
myofibrils dissolve and overworking them dissolves them completely which gives an overly elastic structure and retainment of water when chewing
