Unit 7 - flavor formation by enzymes and microorganisms Flashcards
flavor generated by enzymes
aldehyde, ketone, esters, OH, terpene, terpenoid, S containing compounds, aromatic volatile compounds
origin
can be form volatile precursors. before harvest or due to disruption of cell tissue or by enzymes during fermentation
dynamic processes
biogenesis and synthesis = process depends on plant, variety, environment, maturation and fruiting
other components of flavors
some chemicals are odorless and tasteless
some metabolic by products
secondary metabolites
environment stress biosynthesize 2nd metabolites like antioxidants
metabolism levels
primary = growth and development = aa, nucleic acid, carbs (thermally generated) secondary = interaction of individual with its environment which results in flavor, fragrance, pigments, sweet, Pharma, pesticide
fruits flavor origin
ripening period
vegetable flavor origin
flavor form sulphur compounds and cellular disruption
action of lipoxygenase on linoleum and linolenic acid to produce volatile carbonyl and alcohol similar to ripening in fruits
veg: aldehyde for esters, aa, fatty acids
aldehydes are under 5C = develop off flavors
alkenols = 5 to 10 C = desirable flavors = fresh veg
cis trans 2 hexenals = green leaf
cis 2 nonenal = melon like odor of cucumber
aliphatic aldehyde form ester which are hydrolyzed by esterase + enzymatic oxidation
aa into alpha kept acid by transaminase and enzyme decarboxylation = flavor aldehyde
triglyceride hydrolyzed by lipase produce free fatty lipoxygenase + lyase produce aldehyde
sulfur in which plants
alliaceous and cruciferous
sulfur origin
cysteine sulfide and thioglucoside
sulfur volatiles
cysteine sulfide in allicaneous plants which produce disulfide
glucosinate cruciferous plants which produce isothiocyanate
alliaceous plants
main precursors are S substitues I-cysteine sulfoxide which produce thiosulfinate
heating of thio converts it into disulfide = cooked flavor
garlic = thiallyl compound which when chopped Allin (major thio) is converted to allicin by allinase
allicin = unstable + decompose = strong flavor/smell
allinase in chopped onion yields lacrimator propanethiol S-oxide
method of cooking of garlic and onion five different flavors. if water present it forms di-, tri- poly- sulphide from thio. if very little water present = allium in lipids = many poly sulfur compounds formed
skin in garlic inhibit garlic allinase
onion allinase is sensitive to acid
cruciferous vegetables
pungent taste caused by isothiocyanate = released by enzyme thioglucoside
tissue of plant need disruption to bring substrate close to the end = flavor
mustard, horse radish = sinigrin
yellow mustard = sinalbin
sinalbin and sinigrin are both types of thioglucosides which can be hydrolyzed to give tyrosinase which produce isothiocyanate
important = need water for activation
non volatile flavor compound causing pungency
chilipepper
black pepper
ginger
chilipepper = capsaicinoid = phenol + amide linkage + fatty acid and all 3 are needed to stimulate nerve to be perceived as hot
dose of capsaicinoid decrease sensitivity of individual at fq usage = adapt = cause pb in reproduction of sensory test
caps affect thermo regulation = body temperature decrease with small dose = eat in warm countries so perspiration doesn’t happen (hypothermia)
large dose can cause desensitization = allows over heat