Dynamic steam

Dynamicsteamvacuumdefrosting
rn a massager
t
ood manufacturersmust from
now on manage great quantities of
material while taking into account
the same time internal and external
constraints:
. Qualitative constraints (physical
deterioration of tissues, enzymatic
and microbiological alterations),
. Economic constraints (material
cost, labour, space, energy,
water...),
. Food safety constraints (HACCP),
. Environmentalconstraints
(effluents,cleaning water...).
These requirements lead food
manufacturers to seek eflicient,
consistent and safe solutions from
food equipment manufacturers. The
steam - vacuum dynamic defrosting
system in a massager(Picture 1)
answers these requirements.
Physicalconsiderations
Defrosting is defined as a process
which transforms the frozen
aqueous fraction to liquid water.
85% of the energy input is used to
convert the ice into water in quasi
isothermal conditions at around -1"C
--<
iI
I
(dependingon food composition).
During defrosting from -20oC to
+4C,70,5o/o of the energy is needed
to get from -2OoCto-1"C, 85% of
the energy to convert the ice at -1"C
into water at -1oC and 4,57o of the
energy allow to get from water at
-1oCto +4oC.
When defrosting is carried out by
contact of food with a defrosting
media (air, water...), the physical
mechanisms are almost exclusively
convective and diffusive. Defrosting
time can be predicted by Planck's
law equation (table 1). Several
important elements may be deduced
from Planck's law in order to
acceleratedefrosting (table 2):
During steam - vacuum dynamic
defrosting in a massager,low
pressure food grade steam is injected
directly into the vacuum massager
in contact with the frozen products.
This technology was patented.
While condensing,steam provides
the energy which is necessary to
optimally defrost the products. The
rotation of the vesselfacilitates the
homogenization of the temperatures
and acceleratesseparation of meat
nieceswithin the frozen blocks.
The increasinguse of
frozenfood materials
in manyfood industry
factorieshas madethe
defrostingprocessa
key phaseof the food
manufactudngprocess
writes FRANCOIS
DEUMIER*.
probe
Picture2: \Mreless
The quantityof steam
injecteddepends
1
on the mass
. of frozen
Picture3: Weightsensor
food and also on the initial and linal
temperatures. It generally represents
between 6-lOV, of the frozen food
weight.
Injecting steam under vacuum
allows an efficient transfer of latent
heat, a progressive warming of the
product and prevents the cooking of
food surface (table 3).
Picturel: Defrosting
massager
with loadingsystems.
Table1: Planck's law
Dslrosling tirc ae otlfl diffielt to @hulEte EEcdy be@
ol $e €dability ol food thmophy$rEl prcpsrti€s and hêat exôange betreen
læd sMls and delræling media @l8nt Th€ bads ol €lculalion follorc a Blalirehip d€tined by ths follùing eq@tion.
t:
e:
p:
ô
e . o l ( - 1+ - l e \
t=Lt
Lr \2h 87)
o
t^1
L,
=n:
defrcsling time of the prcducl (s)
pfodæt's lhick6
(m) podrct's dangly (kg.m)
latent h€at ol Ès tusion (L = $o 0m J-kst')
the dne@@ b€lren inilÈllmzs p,od61tmp€Etuæ
and @ling media
tmpsÉturo (C)
int€rtaciat h€at lans{s @flici€nt product/@ting media (W.m''?.Ki)
prcdrcit'slhmal @ndudiviiy (W.m'.K')
Table 2: Process parameter adjustment for faster defiosting plocesses
Inc.ease
detrostlrE
temp€EtuG (ÂT)
Red@ prcduci thij<n6
lmÉ.êô
-:::.--,
w'Nwurrt
d
^ï*
\^'
t|res
surtæ
@ffici$û (h)
m€dia
(e)
'b.r
- -""-'
h@i IrarEter
Wihin the limit ot produc{ salety and the maintena@
proporties.
Ve,y importânt effæt, ths inprcremerd iEæ
ol ib tæhrclogiæl
and organolepiic
q@dEti€lly.
Themdd|dælivityof
watsislorerthanthatotics-Gp€divdy0.553and2.2O
W.m-l.K-1 with
0 C. The defrested suttæ of â product ændrc1s h æt moE slowly than the frczen surlace dæs.
Prcæ$ algorihms are adapted lo optimis this factor.
Reæwal of the boundary layer by relaliw mffimt
ctw$
ot the fæd and the ddrcstirg
m€dia.
detrosiing medaawith good themal propsniæ (e.g. stem).
Generally, the lower the specific
dimension of the product (e.g.
radius, thickness..),the shorter
the processingtime. It is thus
benelicial to work with IQF products
or to reduce the block size before
defrosting.
With purely diffusive methods
(e.g.defrosting in cold room), if
the product specificdimension (e.g.
radius, thickness...)is multiplied by
N, defrosting time is multiplied by N'?
(application of Fourrier's secondlax
and Planck's law). This phenomenon
is lessin a massagerbecausecertain
not-diffusion mechanisms are also
involved (e.g.effect of vacuum,
rotary movement, progressive
dislocation of the blocks throughout
the defrosting process,Iatent heat
transfer when steam condenses...).
Advantagesof the dynamic
steam- vacuumdefrostingin a
massager
- Various applications:this process
may be used for almost all kinds of
non-fragile products (table 4).
- Excellenttechnological properties
of the defrostedproducts: soluble
protein lossesin defrosting drip
lossesare very low or even zero.
In all cases,if drip lossesare not
absorbedduring defrosting (e.g.
vacuum packed frozen blocks), they
are completely recoverable for use in
the brine.
- High yield gains: the product
keepsits moisture and its proteins.
Injected steam is often absorbed by
the meat, in particular if adding a
little sodium chloride is allowed.
- Decreaseof effluents and of their
organic load: the product preserves
its water and proteins and generally
absorbswhole the condensedsteam.
- Fast process:as a consequence
of the processprinciple (direct
condensationof the steam onto the
product combined with the rotation
of the vessel),this processis 4 to 8
times faster than traditional methods
(4/8 hours instead of 24148 hours).
- Consistency:the line control
of temperature ensurescyclesare
consistent.Probeswith radio or
infra-red transmission (Picture 2)
allow continuous monitoring of the
temperature at the surface of the
product. In the same way the batch
weight which is measured by weight
sensors(Picture 3) providesperfect
control of the Iinal water content of
the defrostedproduct and constitutes
an important system security
control.
- Increasing food safety level: the
product remains conlined under
vacuum and also remains between
-2'C and +4C, lor only a very short
time, which reducesthe occurrence
of a bacterial "log phase" growth..
Picture4: Blockbreaker
Picture5: Doublejacketvessel
Picture6: Loadingconveyol
Table 3: Thermal properties of steam at low pressure
ro0
81
N
45
st
21
7
AM:PM- January/February
201I
Table 4: Some applications for the dynamic steam - vacuum defrosting process in a massager
Frozen
Defrosted
ina
LUTETIA
massager
- Productivity: this process
allows consolidation of processes
(defrosting,salting, cooking,
and cooling) in only one piece
of equipment. In addition the
equipment has a small and effective
'footprint'.
- For an even faster process: the
dislocation of the blocks using a
block breaker (Picture 4) allows a
time-savefrom 3O to 50% with a
greater homogeneity of temperature
in the batch.
- When you need to reduce water
addition in the product and/or an
excellent control of the temperature,
the massager is provided with double
jacket (Picture 5) fed with heat and
cold.
- For even higher productivity, fast
loading (Picture 6) and unloading
(Picture 7) devicescan be added to
the defrosting massager(e.g.Ioading
of the blocks with a conveyor,
unloading on a conveyor with a
hopper...).
Economicinterest
For example, a meat manufacturer
Table 5: Economic gain
One defrosdng
wdgh
(kg)
daily defrosts 5 tonnes of 15 kg
blocks of chicken fillets. With
traditional defrosting in a cool room,
the yield is about 94'/o. A Lutetia
type 5 defrosting massager can
defrost 22OO kg of frozen meat per
cycle of 8 hours with a defrosting
yield of about 106% (f 00% on the
initial matter + absorbed condensed
steam 6%). Economical calculations
are given in table 5.
Comparisonof Lutetiadynamic
steam- vacuumdefrostingin a
massagerwith the other methods
- Cold room: This method is slow
and generates water and protein
losses.
- Pulsated air: This method
generates water and protein losses.
- Defrosting in water: The product
loseshigh amounts of proteins.
This method consumes water and
generates abundant effluents,
presenting a strong load of organic
matters.
- Microwaves: Expensive in
investment, this fast method is
not adapted to thick products and
Picture7: Unloading
conveyor
presents the disadvantage of creating
hot spots.
- Ohmic heating: This fast method
requires the immersion in a liquid
and presents the same disadvantages
as the use of the microwaves.
Conclusions
Dynamic steam - vacuum
defrosting in a massager - a
technology developedby Lutetia - is
an interesting alternative compared
to the traditional methods. It is faster
and safer from a microbiological
point of view, with better
productivity, better yields and fewer
effluents. r
cyclê
Fpzen
2419
2ffi
Detusred
2 650
2 650
Savlngs
Mdl€r svirEa per cycle :
Wqking da]6 p€r !,6d
319 kg pâr qfde
Cyclæ psrday
2
.+oocyc-l€€/an
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i.€.:
Annualn6ât ævinga:
127600 kgr'ân
AM:PM - January/February201 I
* Françaîs
DewnienPhD([email protected])
is Food
Techrtology
Departmetû
Marngerfor Lutetiaarul
basedat theLutetiaR&D Center,Frarrce.
Lutetia
Irins
for the past30 gearsbeenmarrulacturirry
eqtùpmerû
industry.
for thefood-processirtg
GIobaIIy,
it l:ll.sinstalledover8,O0OslJstems
to
carrlJoutprocessitrg
operatiotts
sttchas defrosting,
utrfury,massagittg,
dryilry,cookittg,smokirtg
and
packaging,