Food Chem chp 7 Flashcards
What are homopolysaccharides
they are polysaccharides that contain only one same kind of repeating unit
what are heteropolysaccharides
they are polysaccharides that contain more than one kinds of repeating unit
what are the properties of polysaccharides
-they control the mobility of water in food systems
for eg. -decide the texture of food and shelf-life of food.
-control the functional properties of food
what are glycogen
glycogen is a multi-branched polysaccharide of glucose
-carbohydrate that is found in animal liver(can make up 5-6% of organ weight)
-got similar structural properties to amylopectin(both have alpha1,4 and 1,6b glycosidic linkages in their structure)
what are cellulose
cellulose are homopolysaccharides of glucose
-upon hydrolysis, glucose is obtained
-they give strength in plant tissues
-they are found in cell wall and plant fibers
-it is insoluble in water and resistant to enzyme also
what are pectins
-pectin is a polysaccharide obtained from the soft tissues in veggies and fruits, particularly citrus foods like lime peels and lemons
-they are found in cell wall of raw fruits
-they are made up of D-galacturonic acid
-used as fillings, stabilizers and source of dietary fiber
how many type of pectins are there
2 (MHP and LMP)
what is the diff between HMP and LMP
Pectin with more carboxyl group (>50%) in the methyl ester form are called high methods pectin (HMP)
pectin with less caborxyl group(<50%) in the methyl ester form are called low methods pectin(LMP)
There are various enzymes present in the cell wall and their function
they are -pectin methylesterases(involve in the de-esterification of pectin)
-polygalacturonases PG (involve in hydrolysis of pectin)
-pectate lyase
explain the ripening of fruits
1 pectin methylesterases enzyme in fruits cell wall causes de-esterification of methyl group present in pectin molecules to un-esterified carboxyl groups
2 PG polygalacturonases enzyme causes hydrolysis of pectin molecules
3 higher amount of LMPs are formed
4 by now, the structure of cell wall network is loosened and the fruit becomes softer
-food is ripened
Gel forming properties of pectin
-pectins are capable of cross-linking under optimal conditions to form pectin gels, the ratio of pectin-sugar-acid is critical for gel formation
-pH at 3,5
-pectin 1%
-sugar 65-70% are required for satisfactory gel formation
gelling of hmp and lmp
hmp can gel in the presence of acid and high sugar concentration
lmp can gel in the presence of divalent cations such as calcium ions. These pectin molecules form an egg box model with calcium ions with calcium ions.The strength of gel depend on the concentration of calcium ions used
what is alginate
-alginate is a polysaccharide widely distributed in the cell walls of brown algae
-is used to improve food texture like ice cream and pie fillings as an emulsifier, stabilizer thickened etc.
-absorb 200-330 times its own weight of water
-forms gel with divalent cations like Ca2+
What is alginate made up of?
mannuronic acid and guluronic acid
explain the gel formation of alginate
-aliginate can form gels in the presence of divalent Ca2+ ions.
-calcium ions crosslink with guluronic acid residues found in alginate
-the junction zones that form between alginate chains and divalent cations results in formation of egg box model
eg. gummy worms, made up of mostly alginate gels
