biochemical changes in plant food raw material and...
TRANSCRIPT
Biochemical changes in plant food raw material and products
a) Natural, in vivo, processes – tissue maturation and senescence
Cell wall and middle lamella structure degradation
Intracellular processes
b) Stress - cold, drought, injury, infection….
Oxidative burst
A ccumulation of phytoalexines, polyamines, phenolic
componds
Enzyme activation (PPO, LOX, PLases …)
c) Post harvest processes – tissue demage
Mechanical processing
Physiological processes – PCD, necrotization
Zrání a stárnutí pletiv
1. Iniciace
- Dosažení metabolického prahu
- Utlumení fotosynthesy
- Změny redox stavu buňky
- Signální dráhy
Iniciátory:
Vliv prostředí,vývojové vlivy (počátek
kvetení, tvorba plodů nebo semen),
hormony, patologické stavy
2. Reorganizace / degenerativní fáze
- Aktivace metabolických drah,
utlumení jiných
- autotrofní met. → heterotrofní
- detoxifikace
Akcelerátory a inhibitory:
Hormony, prostředí, vývoj
Terminální fáze
- akumulace antibiotik
- volné radikály
- eliminace metabolitů
- ztráta b. integrity, buněčná smrt
Autotrophic metab to
heterotrophic
Autotrophic metab. to
heterotrophic
Hormonal
regulation
Ethylene,
cytokinin
Maturation and senescence
Gene regulation SAG – senescence associated genes B. napus
Proteases, ubiqvitinylation factors, enzymes of Krebs cycle, PLD, gln synthase,
metalothionein, GST, catalase, cytP450, PR1, chitinase, ACC oxidase, NADH oxidase
Ethylene
Indukce synthesy pathogeny, poraněním
Hormonal regulation:
Ethylene signalling pathway
Cytokinin and its derivatives
riboside
riboside phosphate
Isopentenyl
aromate
glycosyl
Cis-, trans-
OE of IPT –
isopentenyltransferase
Delayed senescence
Changes in the cell wall texture in peach
Biochemical processes during ripening and senescence
Metabolism of pigments, phenolic compounds (PAL)
Protein metabolism
photosynthesis
Oxidative metabolism
lipids → saccharides (glyoxalate cycle)
ROS production
Metabolismus chlorofylu a ostatních barviv
Degradací chl se
„odhalí“ ostatní barviva
- karotenoidy
Synthesis of carotenoids
Protein degradation
Changes in basal metabolis
– peroxisomes conversion to glyoxysomes (lipids→sacharides)
Změny redox stavu buněk – produkce ROS
Membrane deterioration
Biochemical changes in plant food raw material and products
a) Natural, in vivo, processes – tissue maturation and senescence
Cell wall and middle lamella structure degradation
Intracellular processes
b) Stress - cold, drought, injury, infection….
Oxidative burst
A ccumulation of phytoalexines, polyamines, phenolic
componds
Enzyme activation (PPO, LOX, PLases …)
c) Post harvest processes – tissue demage
Mechanical processing
Physiological processes – PCD, necrotization
Abiotic stress
Buchanan, 2002
Biotic stress – patogens, herbivores
Tomatoes – frequent research subject
Affecting the texture of tomatoes (Lycopersicon esculentum)
PG in unripe fruits non-detectable, de novo synthesis, coded by 1 gene - 2 isoforms
(1% of mRNA in ripening fruits!!!!)
PE constituvely expressed, more isoforms, anti-PE2 tomatoes
Effect on pectins:
Tomato juice from antiPG tomatoes
Ethylene – influences ripening of fruits
Lycopersicon esculentum:
Antisense - ACC synthasa, ACC oxidasa
GMO - ACC deaminasa bakteriální
Biochemical changes in plant food raw material and products
a) Natural, in vivo, processes – tissue maturation and senescence
Cell wall and middle lamella structure degradation
Intracellular processes
b) Stress - cold, drought, injury, infection….
Oxidative burst
A ccumulation of phytoalexines, polyamines, phenolic
componds
Enzyme activation (PPO, LOX, PLases …)
c) Post harvest processes – tissue demage
Mechanical processing
Physiological processes – PCD, necrotization
Enzymes involved in the processing of plant raw materials
1. Changes in sensoric properties
- LOX, lipases, fosfolipases, proteases
2. Changes in texture and consistence
- pectolytic and celulolytic enzymes
3. Changes in colour
- Polyphenol oxidases, peroxidases
4. Decrease of nutritional value
- Ascorbate oxidase, ascorbate peroxidase, thiaminase…
Enzymatic browning
Animals
Crustacea Plants
(fruits, vegetables)
Reactionsce catalysed by polyphenol oxidase
Monophenoloxide reaction
Diphenol oxidase reaction
Enzymatic browning
Substrates of PPO - Products of phenylpropanoid pathway
Principle of enzyme browning
Oranžovo- hnědo-černé látky
Very complex process …..
Prevention of enzyme browning
1. Breeding of varieties with lower content of
phenolics
2. Inactivation of PPO – physical methods
- inhibition
3. Combined
Ad 2) physical methods
a) Temperature or pH change
b) Limitation of O2
- Packaging without O2 access
- Packagin in the inert atmosphere
- High sucrose content
Inhibition
a) Chelating agents
b) Anorganic ions - halides (NaCl. NaF)
c) Kompetitive inhibitors – benzoic acid,
cinnamic acid
d) Quinone reducing agents (askorbic acid,
HSO3-, thiols)