Lipids
No description yet. This curated deck is ready for daily study.
Card preview (24)
what are fatty acids?
an aliphatic chain with a carboxylic acid group
what are unsaturated FA?
contain double bonds
how are saturated FA named?
based on the number of carbon atoms, with an ending of “oic” since FA contain a carboxylic group
oleic acid
18:1
linoleic acid
18:2 (omega-6)
linolenic acid
18:3 (omega-3)
arachidonic acid
20:4 (omega-6)
EPA eicosapentaenoic acid
20:5 (omega-3)
DHA docosahexaenoic acid
22:6 (omega-3)
how are double bonds, if there are several, normally found in FA?
C=C-C-C=C
what are some determinants of TAG melting points?
double bonds - symmetry on the glycerol molecule - trans/cis - polymorphic form (crystalline structure)
thermal stability of a lipid is characterized by:
smoke, flash and fire points
what are the three basic polymorphic crystal arrangements?
alpha, beta’ and beta
a melted TAG cooled rapidly will form the unstable…
alpha form!
slow heating of alpha crystals will cause
melting and resolidification into the beta-prim form. repeat this procedure to achieve the stable beta form.
the crystal form is dictated by..
FA composition and position in the TAG
solid fat content can give away information about…
emulsion stability, cloud point, melting behaviour, baking properties, spreadability
how many different polymorphic states can cocoa butter occur in?
six! melting points range from 17,3-36,4 deg C
what is conching?
stirring chocolate continuously for several hours at 50-55 deg C to get rid of undesirable flavours
what is tempering of chocolate?
cooling the chocolate to initiate crystallization, reheating and stirring to obtain very small crystals of desirable type
how is hydrogenation performed?
silica-bound Ni is used as catalyzator, it binds to and “eats up” the double bonds of UFA. after that, hydrogen replaces the Ni and a normal bond is formed.
what happens with hydrogenation if these is insufficient catalyzator, temperature or hydrogen?
double bonds may remain and there is a risk of forming trans fatty acids as the added hydrogen may leave its FA, creating a new double bond.
what are the two ways fats and oils deteriorate?
hydrolytic rancidity and oxidative rancidity
why are phospholipids surface active?
because of the polar phosphate group