food deterioration(decay) and its control ch. 7, pp.113 …karaali/lecture32004.pdf · 3 food decay...
TRANSCRIPT
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EP. O
F FO
OD
EN
GIN
EERIN
G1
Intr
oduc
tion
toFo
odScien
cean
dTe
chno
logy
FOOD D
ETER
IORA
TION(D
ecay
)
AND
ITS
CONTR
OL
Ch.
7, p
p.11
3-13
7
LECT
URE
3
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F FO
OD
EN
GIN
EERIN
G2
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS
FOR
ITS
PREV
ENTI
ON
All
food
sun
derg
ova
ryin
gde
gree
sof
det
erio
rati
ondu
ring
stor
age.
Det
erio
rati
onin
clud
elo
sses
in:
Org
anol
epti
c(ta
ste-
arom
a) d
esir
abili
ty
Nut
riti
onal
valu
e
Safe
ty
Aes
thet
icap
peal
Food
sm
aych
ange
in c
olor
, tex
ture
, fla
vor,
or
anot
her
qual
ity
attr
ibut
e.
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OD
EN
GIN
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G3
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
360
and
mor
eDried
seed
s1-
2Le
afy
vege
tables
360
and
mor
eDried
fruits
1-7
Fruits
360
and
mor
eDried
, sa
lted
, sm
oked
mea
tan
dfish
1-2
Mea
t, f
ish,
pou
ltry
Sto
rage
life(
days
) a
t ro
omte
mpe
ratu
re(2
1ºC)
Food
Prod
uct
Expe
cted
Sto
rage
Life
of
Plan
tan
dAnimal
Tissu
es
Slow
erra
tes
of d
eter
iora
tion
occu
rwi
thfo
ods
that
are
low
in m
oist
ure,
hig
hin
sug
ar, s
alt
orac
idor
with
food
sm
odif
ied
in o
ther
ways
.
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OD
EN
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G4
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Food
Scienc
e:Und
erst
andi
ngof
foo
dde
terior
ative
fact
ors
and
theo
rising
for
their
cont
rol
FOOD T
ECHNOLO
GY: Att
empt
sto
slow
down
dete
rior
ative
proc
esse
s
Form
ulat
eNew
Pro
duct
s:( C
hees
e, s
mok
edfish
, dr
ied
fruits
, fe
rmen
ted
food
s)
Dev
elop
pres
erva
tion
met
hods
Prolon
gst
orag
elif
e by
pack
aging
applicat
ions
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OD
EN
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G5
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
SHEL
F-LI
FE A
ND
DA
TIN
G O
F FO
OD
SSH
ELF-
LIFE
AN
D D
ATI
NG
OF
FOO
DS
•She
lf-li
fe:T
heti
me
it t
akes
a pr
oduc
tto
decl
ine
toan
un
acce
ptab
lele
vel.
It
is a
req
uire
dju
dgem
ent
that
mus
tbe
mad
eby
food
man
ufac
ture
ror
reta
iler.
It
has
beco
me
a wi
de-s
prea
dpr
acti
ceto
add
som
efo
rm o
f da
ting
syst
emto
reta
ilpa
ckag
esof
foo
dsto
give
an
indi
cati
onof
fre
shne
ssan
dsh
elf-
life
of p
rodu
cts
toco
nsum
ers.
Dat
eof
man
ufac
ture
-“p
ack
date
”Dat
eth
epr
oduc
twa
sdisp
laye
d–
“display
date
”Dat
eby
which
the
prod
uct
shou
ldbe
sold
–“s
ellby
date
”La
stda
teof
max
imal
quality
–“b
est
used
byda
te”
Dat
ebe
yond
which
the
prod
uct
is n
o long
erac
cepa
table
–“u
seby
date
” or
“exp
irat
ion
date
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OD
EN
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G6
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
NM
AJO
R CA
USE
S OF
FOOD D
ETER
IORA
TIO
NM
AJO
R CA
USE
S OF
FOOD D
ETER
IORA
TIO
N
Maj
orfa
ctor
saf
fect
ing
food
dete
rior
atio
nin
clud
e:(1
)Gr
owth
and
acti
viti
esof
mic
roor
gani
sms
(bac
teri
a, y
east
and
mol
ds)
(2)
Act
ivit
ies
of f
ood
enzy
mes
and
othe
rch
emic
alre
acti
ons
with
info
odit
self
(3)
Infe
stat
ion
byin
sect
s, p
aras
ites
and
rode
nts
(4)
Inap
prop
riat
ete
mpe
ratu
res
for
a gi
ven
food
(5)
Eith
erth
ega
inor
loss
of m
oist
ure
(6)
Reac
tion
with
oxyg
en(7
)Li
ght
(8)
Phys
ical
stre
ssor
abus
e(9
)Ti
me
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OD
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3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
The
idea
l pre
serv
atio
nm
etho
dsh
ould
take
into
acco
unt
allo
f th
em
ajor
fact
ors
in f
ood
dete
rior
atio
n.
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OD
EN
GIN
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G8
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
1 BA
CTER
IA,
YEAST
S AND M
OLD
S1
BACT
ERIA
, YE
AST
S AND M
OLD
S
Ther
ear
eth
ousa
nds
of g
ener
aan
dsp
ecie
sof
m
icro
orga
nism
s(m
.o.)
Seve
ralh
undr
eds
are
asso
ciat
edwi
thfo
odpr
oduc
tsTh
eyca
n :
Caus
ea
dise
ase
Caus
efo
odsp
oila
geSo
me
m.o
. are
desi
rabl
ebe
caus
eth
eyar
eus
edto
mak
ean
dpr
eser
vefo
ods
(i.e.
Lac
tic
acid
prod
ucin
gba
cter
iaus
edto
mak
ech
eese
, sau
erkr
aut,
sau
sage
set
c. O
ther
sus
edfo
ral
coho
lpro
duct
ion
in m
akin
gwi
neor
beer
, fla
vor
prod
ucti
onin
oth
erfo
ods)
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OD
EN
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G9
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Mic
roor
gani
smm
ulti
plic
atio
non
or
in f
oods
freq
uent
lyis
the
maj
orca
use
of f
ood
dete
rior
atio
n.
Mic
roor
gani
smca
pabl
eof
spo
iling
food
are
foun
dev
eryw
here
: •in
the
soil,
wat
eran
dai
r,
•on
the
skin
sof
cat
tle
and
the
feat
hers
of p
oult
ry,
•in t
hein
test
ines
and
othe
rca
viti
esof
the
body
, •o
n th
esk
ins
and
peel
sof
fru
its
and
vege
tabl
es,
•on
the
hulls
of g
rain
and
the
shel
lsof
nut
s•o
n fo
odpr
oces
sing
equi
pmen
tth
atis
not
san
itiz
ed•o
n th
eha
nds,
ski
n an
dcl
othi
ngof
foo
d-ha
ndlin
gpe
rson
nel
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OD
EN
GIN
EERIN
G10
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Inne
arly
allc
ases
, the
pres
ence
of
spoi
lage
orga
nism
sin
foo
dsis
a r
esul
tof
cont
amin
atio
n.
Ther
efor
e, o
neof
the
maj
orst
rate
gies
in r
educ
ing
food
spoi
lage
due
tom
icro
orga
nism
sis
:
Tore
duce
cont
amin
atio
n
byen
suri
nggo
odsa
nita
tion
prac
tice
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OD
EN
GIN
EERIN
G11
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Bact
eria
(Fig
. 7.1,
2)
Sing
lece
lled
orga
nism
sCa
n be
cla
ssif
ied
acco
rdin
gto
shap
e
Sphe
rica
lsha
pes
“coc
ci”
Rod
shap
e
“bac
illi”
Spir
al f
orm
s“s
piri
llaan
dvi
brio
s”
All
bact
eria
asso
ciat
edwi
thfo
ods
are
smal
l.
One
toa
few
mic
rom
eter
s(µ
m) i
n le
ngth
.
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OD
EN
GIN
EERIN
G12
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Yeas
tsSo
mew
hat
larg
erof
the
orde
rof
20
µm .
Mos
tof
the
mar
esp
heri
calo
rel
lipso
idal
.
Mol
ds(m
ould
s)(F
ig. 7
.3)
Larg
eran
dm
ore
com
plex
in s
truc
ture
Saccharomyces
cerevisiaeyeast
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OD
EN
GIN
EERIN
G13
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Som
eba
cter
ia, y
east
san
dal
lmol
dspr
oduc
esp
ores
, wh
ich
are
seed
like
pack
ets
and
whic
hun
der
prop
erco
ndit
ions
can
germ
inat
ein
tofu
ll-si
zed
cells
calle
d“v
eget
ativ
ece
lls”
Ster
iliza
tion
proc
esse
sar
ede
sign
edto
inac
tiva
teth
ese
high
lyre
sist
ant
bact
eria
lspo
res.
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F FO
OD
EN
GIN
EERIN
G14
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Bact
eria
, yea
sts
and
mol
dsca
n at
tack
allf
ood
cons
titu
ents
.Fe
rmen
t su
gars
and
hydr
olyz
est
arch
esan
dce
llulo
seH
ydro
lyze
fats
and
prod
uce
ranc
idit
yD
iges
tpr
otei
nsan
dpr
oduc
epu
trid
and
amm
onia
like
odor
s.Fo
rm a
cid
and
mak
efo
odso
urPr
oduc
ega
san
dm
ake
food
foam
yFo
rm p
igm
ents
and
disc
olor
food
sA
few
prod
uce
toxi
nsan
dca
use
food
pois
onin
g
2/24
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F FO
OD
EN
GIN
EERIN
G15
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Bact
eria
, yea
sts
and
mol
dslik
ewa
rman
dm
oist
cond
itio
ns.
Mos
tba
cter
iam
ulti
ply
best
at t
empe
ratu
res
betw
een
16-3
8ºC
......
.....m
esop
hilic
Dow
nto
free
zing
poin
tof
wat
er...
...ps
ychr
otro
phic
orps
ychr
ophi
lic
As
high
as 8
2 ºC
.....
.the
rmop
hilic
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OD
EN
GIN
EERIN
G16
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Som
eba
cter
iaan
dal
lmol
dsre
quir
eox
ygen
for
grow
th...
......
.aer
obic
Oth
erba
cter
iawi
llno
t gr
owun
less
oxyg
enis
abs
ent
......
...an
aero
bic
Oth
ers
can
grow
unde
rei
ther
aero
bic
oran
aero
bic
cond
itio
ns...
....f
acul
tati
ve
Food
-bor
npa
thog
ens
and
asso
ciat
edill
ness
esar
egi
ven
in T
able
7.2!
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OD
EN
GIN
EERIN
G17
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Bact
eria
mul
tipl
yby
cell
divi
sion
.
1 ba
cter
ia2
bact
eria
4 ba
cter
ia
Soon
in
expo
nent
ial
fash
ion
Und
erfa
vora
ble
cond
itio
nsba
cter
iaca
n do
uble
thei
rnu
mbe
rsev
ery
30 m
inut
e.M
ilkwi
than
init
ialb
acte
rial
coun
tof
100
.000
/ml (
befo
repa
steu
riza
tion
) can
rea
chto
25 m
illio
nin
24
h an
dov
er5
billi
on/m
l in
96 h
.
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OD
EN
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EERIN
G18
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
2 IN
SECT
S, P
ARA
SITE
S AND R
ODEN
TS2
INSE
CTS,
PARA
SITE
S AND R
ODEN
TS
Inse
cts
are
part
icul
arly
dest
ruct
ive
toce
real
grai
nsan
dto
frui
tsan
dve
geta
bles
both
in t
hefi
eld
and
duri
ngst
orag
e.
Whe
nin
sect
sea
tth
ayda
mag
eth
efo
odan
dop
enit
to
bact
eria
l, ye
ast
and
mol
din
fect
ion
caus
ing
furt
her
dest
ruct
ion.
Inse
cts
have
been
cont
rolle
din
sto
red
grai
n, f
ruit
and
spic
esby
the
use
of p
esti
cide
s, in
ert
atm
osph
eres
orco
ldte
mpe
ratu
res.
Use
of c
hem
ical
pest
icid
esm
ayha
vepo
ssib
leto
xic
effe
cts
and
max
imum
safe
leve
lssh
ould
be in
con
cern
.
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OD
EN
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G19
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
An
impo
rtan
tfo
od-b
orne
para
site
(Tri
chin
ella
) can
en
ter
hogs
(pig
s) e
atin
gun
cook
edfo
odwa
stes
Ifth
em
eat
is n
ot t
horo
ughl
yco
oked
, the
live
worm
can
infe
ctm
an.
Itis
als
opo
ssib
leto
dest
roy
it b
yfr
ozen
stor
age.
Infe
cted
wate
ran
dpo
orhy
gien
eal
sosp
read
para
site
.
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OD
EN
GIN
EERIN
G20
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
The
prob
lem
swi
thro
dent
sin
volv
eno
t on
lyth
equ
anti
tyof
foo
dth
eym
ayco
nsum
ebu
t al
soth
efi
lth
with
whic
hth
eyco
ntam
inat
efo
od.
Rode
ntur
ine
and
drop
ping
sha
rbor
seve
ral
kind
sof
dis
ease
-pro
duci
ngba
cter
ia, a
ndra
tssp
read
such
hum
andi
seas
esas
sal
mon
ello
sis,
ty
phus
feve
ret
c.
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F FO
OD
EN
GIN
EERIN
G21
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
3 FO
OD E
NZY
MES
3 FO
OD E
NZY
MES
Hea
lthy
unin
fect
edfo
odpl
ants
and
anim
als
have
thei
row
nen
zym
es, t
heac
tivi
tyof
whi
chsu
rviv
esha
rves
tan
dsl
augh
ter,
just
as m
icro
orga
nism
s’ en
zym
esth
atfe
rmen
t, r
anci
dify
and
putr
efy
food
s.
Unl
ess
thes
een
zym
esar
ein
acti
vate
dby
heat
, ch
emic
als,
rad
iati
onor
som
eot
her
mea
ns, t
hey
cont
inue
toca
taly
zech
emic
alre
acti
ons
with
info
ods
afte
rsl
augh
ter
and
harv
est.
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OD
EN
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G22
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
4 M
OIS
TURE
AND D
RYNES
S4
MOIS
TURE
AND D
RYNES
S
Exce
ssiv
em
oist
ure
pick
upor
loss
caus
esde
teri
orat
ive
chan
ges
in f
ood.
Moi
stur
eis
req
uire
dfo
rch
emic
alre
acti
ons
and
for
mic
roor
gani
smgr
owth
. Exc
essi
vem
oist
ure
acce
lera
teth
ese
type
sof
det
erio
rati
on.
Exce
ssiv
elo
ssof
moi
stur
eca
n ha
veaf
fect
son
ap
pear
ance
and
text
ure.
2/24
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G23
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
5 OXYG
EN5
OXYG
EN
20%
oxy
gen
in t
heai
ris
qui
tere
acti
vean
dca
uses
subs
tant
iald
eter
iora
tive
effe
cts
in m
any
food
s.
Des
truc
tive
effe
cts:
oCh
emic
alox
idat
ion
of n
utri
ents
(vit
amin
A a
ndC)
oCh
emic
alox
idat
ion
of F
ood
colo
rs
oCh
emic
alox
idat
ion
of F
lavo
rs
oCh
emic
alox
idat
ion
of O
ther
food
cons
titu
ents
oM
old
grow
th
2/24
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OD
EN
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G24
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Atm
osph
eric
oxyg
enis
exc
lude
dfr
omfo
ods
by:
Vacu
umde
aera
tion
Iner
tga
spu
rgin
g
Vacu
umpa
ckag
ing
Flus
hing
cont
aine
rswi
thni
trog
enor
carb
ondi
oxid
e(M
odif
ied
Atm
osph
ere
Pack
agin
g)
Add
ing
oxyg
ensc
aven
gers
(rem
oves
resi
dual
oxyg
enth
roug
hch
emic
alre
acti
on)
2/24
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OD
EN
GIN
EERIN
G25
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
6 LI
GHT
6 LI
GHT
Des
troy
sso
me
vita
min
s, n
otab
lyri
bofl
avin
, vit
amin
A
and
vita
min
C.
Det
erio
rate
sm
any
food
colo
rs.
Milk
in b
ottl
esex
pose
dto
the
sun
deve
lops
“sun
light
” fl
avor
due
tolig
ht-in
duce
dfa
tox
idat
ion
and
chan
ges
in
the
prot
ein
Sens
itiv
efo
ods
can
be p
rote
cted
from
light
byop
aque
pack
agin
gor
byin
corp
orat
ing
com
poun
dsin
togl
ass
and
tran
pare
ntfi
lms
that
scre
enou
tlig
htof
spe
cifi
cwa
vele
ngth
s.
2/24
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OD
EN
GIN
EERIN
G26
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N7
TIM
E7
TIM
E
Aft
erslau
ghte
r, h
arve
stor
food
man
ufac
ture
ther
eis a
tim
e wh
enth
equ
ality
of f
ood
is t
hehigh
est.
Inman
ypr
oduc
tsth
isqu
ality
peak
can
be p
asse
din t
hefield
in a
day
ortw
o, o
raf
ter
harv
est
in a
mat
ter
of h
ours
.
the
grow
thof
micro
orga
nism
s,
dest
ruct
ion
byinse
cts,
action
of f
ood
enzy
mes
,
none
nzym
atic
inte
ract
ion
of f
ood
cons
titu
ents
,
loss
of f
lavo
rvo
latiles
the
effe
cts
of h
eat,
cold,
moist
ure,
oxy
gen
and
light
allpr
ogre
sswi
thtime
...
2/24
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EP. O
F FO
OD
EN
GIN
EERIN
G27
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
For
the
maj
orit
yof
foo
dsqu
alit
yde
crea
ses
with
tim
e. M
ajor
goal
sof
foo
d-ha
ndlin
gan
dpr
eser
vati
onpr
acti
ces
are
toca
ptur
ean
dm
aint
ain
firm
ness
.
Exce
ptio
ns: W
ine,
Sau
sage
s, C
hees
es, O
ther
ferm
ente
dfo
ods
Ade
quat
epr
oces
sing
, pac
kagi
ng, a
ndst
orag
em
aypr
olon
gth
esh
elf-
life
of f
oods
cons
ider
ably
but
cann
otex
tend
it in
defi
nite
ly.
quality
time
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OD
EN
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G28
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
SOM
E PR
INCI
PLES
OF
FOO
D P
RESE
RVA
TIO
NSO
ME
PRIN
CIPL
ES O
F FO
OD
PRE
SERV
ATI
ON
Iffo
ods
are
tobe
kep
ton
lyfo
rsh
ort
peri
ods
of
tim
e, t
hen
ther
ear
etw
ove
rysi
mpl
eru
les:
(1)K
eep
food
aliv
eas
long
as p
ossi
ble;
kill
the
anim
alor
plan
tju
stbe
fore
it is
to
be u
sed.
(2)I
fth
efo
odm
ust
be k
illed
, cle
anit
, cov
erit
, and
cool
it a
s qu
ickl
yas
pos
sibl
e. T
hese
will
only
dela
yde
teri
orat
ion
for
a sh
ort
tim
e.
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OD
EN
GIN
EERIN
G29
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
PREV
ENTI
ON a
ndCO
NTR
OL
OF
FOOD
DEC
AY
PREV
ENTI
ON a
ndCO
NTR
OL
OF
FOOD
DEC
AY
Cont
rolli
ngba
cter
ia, y
east
san
dm
old:
Hea
tCo
ldD
ryin
gA
cid
Suga
ran
dsa
ltSm
oke
Air
Chem
ical
sRa
diat
ion
2/24
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4IT
U D
EP. O
F FO
OD
EN
GIN
EERIN
G30
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
HEA
T
Mos
tba
cter
ia, y
east
san
dm
olds
grow
best
in t
hete
mpe
ratu
rera
nge
of a
bout
16-3
8ºC.
Ther
mop
hile
sca
n gr
owin
the
rang
e66
-82
ºC.
Mos
tba
cter
iaar
eki
lled
in t
hera
nge
82-9
3 ºC
But
man
yba
cter
ials
pore
sar
eno
t de
stro
yed
even
at
100
ºC f
or30
min
.
Toen
sure
ster
ilisa
tion
( tot
alde
stru
ctio
nof
m
icro
orga
nism
sin
clud
ing
spor
es),
a te
mpe
ratu
reof
121
ºCm
ust
be m
aint
aine
dfo
r15
min
orlo
nger
.The
nst
erili
sed
prod
uct
will
last
over
a ye
aror
long
er.
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OD
EN
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G31
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Itm
aybe
nec
essa
ryto
empl
oyon
lysu
ffic
ient
heat
tode
stro
ydi
seas
e-pr
oduc
ing
orga
nism
sin
the
food
.
This
is d
one
in t
heca
seof
pas
teur
ized
milk
.
Mos
tof
the
bact
eria
and
allo
f th
edi
seas
e-ca
usin
gor
gani
sms
that
mig
htbe
pre
sent
in m
ilkar
ede
stro
yed
bypa
steu
riza
tion
at 6
3ºC
for
30 m
in,
but
the
milk
is n
ot s
teri
le. P
aste
uris
edm
ilksh
ould
be h
eld
in a
ref
rige
rato
ran
dco
nsum
edge
nera
llywi
thin
a fe
wda
ys.
2/24
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EP. O
F FO
OD
EN
GIN
EERIN
G32
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
COLD
Mos
tba
cter
ia, y
east
san
dm
olds
grow
best
at
tem
pera
ture
rang
e16
-38º
C.Ps
ychr
otro
phs
will
grow
down
to0
ºC a
ndbe
low.
At
tem
pera
ture
sbe
low
10 º
C gr
owth
is lo
wan
dbe
com
essl
ower
the
cold
erit
get
s.W
hen
the
wate
rin
foo
dis
com
plet
ely
froz
en, t
here
is n
o m
ulti
plic
atio
nof
mic
roor
gani
sms.
But
in s
ome
food
sal
lof
the
wate
ris
not
fro
zen
unti
la
tem
pera
ture
of -
10 º
C or
lowe
ris
rea
ched
, bec
ause
of d
isso
lved
suga
rsan
dot
her
cons
titu
ents
whic
hde
pres
sfr
eezi
ngpo
int.
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OD
EN
GIN
EERIN
G33
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
The
slow
ing
of m
icro
bial
acti
vity
with
decr
ease
dte
mpe
ratu
res
is t
hepr
inci
palb
ehin
dre
frig
erat
ion
and
free
zing
pres
erva
tion
.
Cold
stor
age
and
free
zing
fail
tost
erili
ze f
oods
.
Whe
nth
efo
odis
tak
enfr
omco
ldst
orag
ean
dth
awed
, the
surv
ivin
gm
icro
orga
nism
ofte
nre
sum
era
pid
grow
thsi
nce
the
food
may
be d
amag
edfr
omco
ldor
froz
enst
orag
e.
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OD
EN
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EERIN
G34
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
DRY
ING
Mic
roor
gani
sms
in a
hea
lthy
grow
ing
stat
em
ayco
ntai
nin
ex
cess
of 8
0 %
of
wate
r. T
hey
get
this
wate
rfr
omth
efo
odin
whi
chth
eygr
ow.
Ifth
ewa
ter
is r
emov
edfr
omth
efo
od, w
ater
is a
lso
rem
oved
from
the
bact
eria
lcel
lsan
dm
ulti
plic
atio
nwi
llst
op.
“Wat
erac
tivi
ty” (
a w) o
f fo
ods
is r
elat
edto
both
wate
rco
nten
tof
foo
dan
dto
rela
tive
hum
idit
yof
env
iron
men
t.
Rela
tive
hum
idit
y:Th
era
tio
of t
hepa
rtia
lpre
ssur
eof
wat
erva
por
in t
heai
rto
the
vapo
rpr
essu
reof
pur
ewa
ter
at t
hesa
me
tem
pera
ture
.
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OD
EN
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EERIN
G35
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
At
the
usua
ltem
pera
ture
spe
rmit
ting
mic
robi
algr
owth
, mos
tba
cter
iare
quir
ea
wate
rac
tivi
tyin
the
rang
ea w
=0.9
-1.0
0.
Som
eye
asts
and
mol
dsm
aygr
owsl
owly
at a
wat
erac
tivi
tyas
low
as a
w=0.
65.
Part
ialo
rco
mpl
ete
dryi
ngof
foo
ddo
esno
t ki
llal
lm
icro
orga
nism
s. W
hen
the
food
is r
emoi
sten
edor
reco
nsti
tute
dba
cter
ialg
rowt
hm
ayre
sum
e.
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OD
EN
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G36
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
ACI
D
Suff
icie
ntst
reng
thof
aci
dity
affe
cts
bact
eria
lpro
tein
sas
it
den
atur
esfo
odpr
otei
nsan
dso
mic
roor
gani
sms
are
quit
ese
nsit
ive
toac
id. S
ome
m.o
. are
muc
hm
ore
sens
itiv
eth
anot
hers
; als
oac
idit
ypr
oduc
edby
one
orga
nism
duri
ngfe
rmen
tati
onof
ten
will
inhi
bit
grow
thof
ano
ther
type
of
orga
nism
. Acids
may
be p
rodu
ced
in f
oods
byad
ding
acid
-pr
oduc
ing
bact
erialcu
ltur
es(li
kelact
obac
illi).
Thi
sis
one
of
the
prin
cipl
esof
con
trol
led
ferm
enta
tion
as a
mea
nsof
pr
eser
ving
food
sag
ains
tgr
owth
of s
poila
geor
gani
sms.
Somet
imes
acid
smay
be d
irec
tly
adde
dto
food
s(C
itric
acid
and
phos
phor
icac
idto
soft
drinks
)
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OD
EN
GIN
EERIN
G37
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
SUGA
R &
SALT
Fruits
may
be pr
eser
ved
byplac
ing
them
in a
sug
arsy
rup:
jams
and
mar
melad
es.C
erta
inmea
tpr
oduc
tsar
epr
eser
ved
byplac
ing
them
in a
salt
brine.
Bact
eria, molds
and
yeas
tsco
ntain
cell
mem
bran
es.
The
semem
bran
esallow
wate
rto
pass
in a
ndou
tof
th
ece
lls. W
hen
they
are
plac
edin a
hea
vysu
gar
orsa
lt s
olut
ion,
wa
ter
in t
heir
cells
mov
esou
tth
roug
hth
emem
bran
e.Th
isis c
alled
the
proc
ess
of o
smos
is.
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F FO
OD
EN
GIN
EERIN
G38
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
Ten
denc
yto
equa
lise
wate
rco
ncen
trat
ion
inside
an
dou
tside
the
cell
caus
esde
hydr
ation
of c
ell, ca
lled
“plasm
olys
is”, w
hich
inte
rfer
eswi
thm.o
. multiplicat
ion.
Solution
shigh
in s
olut
e(i.e.
Salt
and
suga
r)
conc
entr
ation
have
high
osmot
icpr
essu
rean
dlow
wate
rac
tivity
(aw).
Yeas
tsan
dmolds
are
mor
eto
lera
ntth
anmos
tba
cter
ia. Th
isis w
hymolds
and
yeas
tsof
ten
are
foun
dgr
owing
on f
ruit
jam
and
baco
n, w
here
bact
eria
are
inhibi
ted.
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OD
EN
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EERIN
G39
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
SMOKE
Inpr
eser
ving
food
ssu
chas
mea
tsan
dfi
shwi
thsm
oke
obta
ined
bybu
rnin
gwo
odth
epr
eser
vati
veac
tion
com
esfr
oma
com
bina
tion
of f
acto
rs:
Smok
eco
ntai
nspr
eser
vati
vech
emic
als
such
as s
mal
lam
ount
sof
for
mal
dehy
de
Hea
tas
soci
ated
with
smok
ede
stro
ysm
icro
orga
nism
sal
soth
roug
hdr
ying
the
food
.
Smok
eco
mbi
ned
with
othe
rpr
eser
vati
ves
is u
sed
toda
ym
ore
for
its
flav
orth
anfo
rit
spr
eser
vati
veac
tion
.
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OD
EN
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EERIN
G40
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
ATM
OSP
HER
E CO
MPO
SITI
ON
oTo
cont
rolo
rgan
ism
sth
atre
quir
eox
ygen
(aer
obic
s),
air
is r
emov
ed; o
n th
eot
her
hand
, for
orga
nism
sth
atca
nnot
tole
rate
oxyg
en(a
naer
obic
s),
air
is p
rovi
ded.
oWax
coat
ing
of c
hees
e
oOxy
gen-
impe
rmea
ble
skin
-tig
htpl
asti
cfi
lms
2/24
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OD
EN
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EERIN
G41
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
CHEM
ICALS
Man
ych
emic
als
will
kill
orin
hibi
tth
egr
owth
of
mic
roor
gani
sms,
but
mos
tof
the
sear
eno
t pe
rmit
ted
in
food
s.Pe
rmit
ted
chem
ical
sar
ecl
assi
fied
as
“ant
imic
robi
als”
und
erfo
odad
diti
vegr
oups
. Exa
mpl
es:
Sodi
umbe
nzoa
te
Sorb
icac
id
Sodi
uman
dca
lciu
mpr
opio
nate
Ethy
lfor
mat
e
Sulf
urdi
oxid
e
2/24
/200
4IT
U D
EP. O
F FO
OD
EN
GIN
EERIN
G42
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
NRA
DIA
TION
Mic
roor
gani
sms
are
inac
tiva
ted
tova
riou
sde
gree
sby
diff
eren
tki
nds
of r
adia
tion
:X-r
ays
Mic
rowa
ves
Ult
ravi
olet
light
Ioni
zing
radi
atio
ns
Each
of t
hese
are
a ty
peel
ectr
omag
neti
cra
diat
ion
whic
hdi
ffer
sin
wav
elen
gth
and
ener
gy. A
llm
aybe
use
dto
pres
erve
food
s. T
here
is n
o si
gnif
ican
tte
mpe
ratu
reri
sefr
om“io
nizi
ngra
diat
ion”
app
licat
ions
(irra
diat
ion)
, so
this
is
calle
d“c
old
ster
iliza
tion
” and
is p
rese
ntly
bein
gap
plie
dto
spic
es, p
oult
ry,
frui
tsan
dve
geta
bles
, por
k.
2/24
/200
4IT
U D
EP. O
F FO
OD
EN
GIN
EERIN
G43
3 FO
OD D
ECAY
AND T
RADIT
IONAL
MET
HODS F
OR
ITS
PREV
ENTIO
N
CONTR
OL
OF
ENZY
MES
AND O
THER
FACT
ORS
CONTR
OL
OF
ENZY
MES
AND O
THER
FACT
ORS
Prin
cipa
lmea
nsto
cont
rola
ndin
acti
vate
dam
agin
gfo
oden
zym
es:
Hea
t
Cold
Dry
ing
Cert
ain
chem
ical
s
Radi
atio
n
2/24
/200
4IT
U D
EP. O
F FO
OD
EN
GIN
EERIN
G44
END O
F LE
CTURE
3