uht theory lth
DESCRIPTION
UHT Theory LTHTRANSCRIPT
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Tetra PakUHT technology Seminar
LTH
PSD.TPD&B.BP.1.01, AA10
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Presented by Andrzej Holanowski, PhDSenior Dairy Technologist
Tetra Pak Dairy & Beverage Systems AB
Lund, Sweden
PSD.TPD&B.BP.1.01, AA10
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Aseptic processing
Aseptic environment
SterilisationSterilisation
Filling &sealing
Aseptically packagedproduct
Conta
inerProduct
PSD.TPD&B.BP.2.04, AA10
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SterilisationA process applied to a product with the object of destroying all micro-organisms (by heat treatment at a temperature exceeding 100C)SterileCondition in which living cells are absent or killedSteriliserEquipment used for sterilisation: autoclave, hydrostatic steriliser or aseptic processing plantCommercial sterilityProduct which is free from micro-organisms that can grow and contribute to its deterioration (Not absolutely sterile)
UHT definitions
AsepticConditions to prevent bacteriological contamination
PSD.TPD&B.BP.2.01, AA10
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High-acid pH 4.5milk products, tea, coffee, liquid food products containing vegetables
Long-life products
PSD.TPD&B.BP.2.07, AA10
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UHT what do we need to achieve ?
PSD.TPD&B.BP.2.01, AA10
In low acid foods (specifically milk):Required bacteriological effect expressed as:- Reduction of Clostridium botulinum spores to the level of 10-12
or 1 of initial 1012 survives - public health requirement (12D reduction or Fo= 3 process)
- Reduction of thermophilic spores by minimum 9D (B*>1) guarantying commercially sterile product
Minimised chemical changes expressed as:- Decomposition of thamin (vit. B1) less than 3% (C*
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UHT what do we need to achieve ?
PSD.TPD&B.BP.2.01, AA10
In low acid foods (specifically milk):Biochemical stability expressed as:- Maximal reduction of enzymatic activities in the heat treated
product
Physical and chemical stability:- No phase separation (fat, proteins, serum)
- No sedimentation
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Raw milk quality
for processability:pH 6.65-6.80alcohol stability >75%total Count of bacteriafor sterility level:limit of heat resistant spores
PSD.TPD&B.BP.2.17, AA10
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Classification of bacteria by temperature preference
Psychrophilic
Thermophilic
Mesophilic
Psychrotrophic
45 C
20 C
7 C
PSD.TPD&B.BP.2.18, AA10
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Bacterial formation of spores
No. TP70:68, 9311BM
1
2
3
4
5
6
1 Viable bacterium2 Nuclear content gathered
(at bad growing conditions)3 A thick wall is formed around
the nucleus (the spore)4 The cell decomposes and the
spore is liberated5 The spore is free6 At favourable conditions the
membrane of the spore bursts and a new cell will be formed
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The commercially sterile product must: Keep without deterioration, stable and
good commercial value during storage Free from micro-organisms and toxins
harmful to the health of consumers Free from any micro-organisms liable to
proliferate during storage
Commercial sterility
PSD.TPD&B.BP.2.03, AA10
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UHTUHT
Heat treatment>135C and >1 s
(Council directive 92/46/EEC)--------------------Lactulose*50 mg/l
(*IDF and ECC suggestions)
SterileSterile
Lactulose*>600 mg/l or
-Lactoglobulin*
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PretreatmentThermisation 6365C/15 sec Preliminary heatingPasteurisation 63C/30 min Pasteur's method
rare today (batch pasteurisation)
Heat treatments definitions
Heat treatment Chilled distributed productsHTST pasteurisation 7275C/15 sec MilkHTST pasteurisation 8590C/25 sec CreamHTST pasteurisation 90120C/25 sec Fermented productsUltra pasteurisation 125138C/24 sec Cold storageAmbient distributed productsUHT 135150C/415 sec Ambient storageConventional sterilisation approx. 116C/20 min Ambient storage
HTST = high temperature short time, UHT = ultra high temperature PSD.TPD&B.BP.2.06, AA10
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Definition of D-valueD-value (decimal reduction time) is the time at a specific temperature necessary to reduce the number of micro-organisms to 1/10 of the original value
Micro-organismsD121 C
B. cereus 2.3 sec.Cl. botulinum. 12.25 sec.B. stearothermophilus 408 sec.
N
D
time, t
104
103
102
101
100
10-1
105
10-2
temperature = constant
N
u
m
b
e
r
o
f
m
i
c
r
o
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o
r
g
a
n
i
s
m
s
PSD.TPD&B.BP.2.09, AA10
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Type of micro-organismvegetative bacteria (high) viruses (medium) endospores (law)Medium surrounding micro-organismspH, water activity (aw), concentration and type of food components i.e.(simple carbohydrates, fats, chemical ions, type of acid and )
Rate of thermal death of micro-organisms at high temperatures depends on:
PSD.TPD&B.BP.2.01, AA10
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Absolute sterility not possible
Logarithmic destructionTime/temperature would be
too drasticNot possible to prove
by random testingNot possible to prove sterility
(prove absence)
B
a
c
t
e
r
i
a
Timet
N
PSD.TPD&B.BP.2.02, AA10
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Definition of z-valuez-value is the increase in temperature, necessary to obtain thesame lethal action or the same effect in 1/10 of time
Temperature dependancez-value [C]
B. stearothermophilus 10.5Colour changes 29.0Losses of vitamin B1 31.2Losses of lysine 30.9
time, t [s]
temperature
103
102
101
100
10-1
z
PSD.TPD&B.BP.2.10, AA10
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Definition of F-value
t = heating time, secondsT = heating temperature, Cz = the increase in temperature necessary
to obtain the same effect in one tenth of the time.
(T 121.1)
Fo = 10t
60. z
Fo = 1 when heatedone minute at 121.1C PSD.TPD&B.BP.2.11, AA10
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Definition of B*-value
Assumption:Commercial sterility is achieved at B* = 1(heat treatment at 135 C for 10.1 sec., z = 10.5)= reduction of thermophilic spores = 109
B* = 10t10.1.
(T 135)
10.5
PSD.TPD&B.BP.2.12, AA10
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Definition of C*-value
C* = 1 = heat treatment at 135C for
30.5 sec. and z = 31.4C= 3% destruction of thiamine
C* = 10t30.5.
(T 135)
31.4
PSD.TPD&B.BP.2.13, AA10
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UHT treatmentTime-temperature combinations needed for destruction of spores
Temperature oC
Heating time or equivalent heating time, S Region of in-container sterilisation
A
B
2000
1000
1
400
200
100
4
40
2
110 120 130 140 150
10
20Mesophilic spores 30oC
Thermophilic spores 55oC
1% Destruction of lysine
90% Ps- Lipase de-activationno discolouration
UHTregion
3% Destruction of thiamine
90% Ps-protease inactivation
PSD.TPD&B.BP.2.08, AA10
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Bacteriological destruction
Chemical destruction
Enzyme inactivation
Temp, C110 120 130
10 3
104
10 5
10 6
Decimal reductiontime, sec
Heat effects
No. TP70:38, 9305BM
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Heat effects
Temperature Fo Time C*C minutes(z=10C)
seconds seconds(z=31.4 C)
121 6.0 360 4.23130 6.0 45 1.02135 6.0 14 0.46140 6.0 5 0.24141 8.3 5 0.25
PSD.TPD&B.BP.2.14, AA10
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PSD.TPD&B.PEH.6.09, AA10
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Batch sterilisation in containerContinuous processes
Time Minutes
Temp C Temp FTemp
Time Seconds
Temp F
DirectUHT
Indirect UHT
Pasteurisation
Continuous processes
150
100
50
300
200
100
PSD.TPD&B.BP.2.16, AA10
UHT Ultra High Temperature processes
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Shelf-life of milk
Subjective criteria: Taste Sedimentation Colour Fat separation Smell Viscosity Gelation
The time the product can be stored before the quality falls below an acceptable and minimum level
PSD.TPD&B.BP.2.19, AA10
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Factors influencing shelf-lifeQuality of raw product (chemical and microbiological)Pretreatment processType of aseptic processing system usedHomogenisation/deaerationPost heat treatment contaminationnon-sterileAseptic packagingBarrier properties of packaging material
PSD.TPD&B.BP.2.20, AA10
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PSD.TPD&B.BP.2.21, AA10
Main factors affecting the flavour of UHT milkMilk qualityType and severity of heat treatmentPackaging materialStorage temperature and time
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SulfurCooked
MetalStale
Rancid/Bitter
No. TP70:61, 9311BM
SulfurCooked
MetalStale
Rancid/Bitter
Optimum
Optimum
Off flavour
Sensoric changes in UHT milkDuration of storage (week)
5 C
25 C
Source: Blanc
2 4 6 8 10 12 14
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No. TP XX:XXX, JF06
Sensory Quality of UHT MilkHeated Flavour - four notesCooked, Sulfurous, Cabbagey
Various sulfur compoundsRich, Heated,UHT, Keton-like
Products of Maillard reactionCaramelized, Sterilized
Non-enzimatic browningScorched, Burned
Burn-on heating suffaces
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No. TP XX:XXX, JF06
Sensory Quality of UHT MilkHeated Flavour
The cooked flavour appears immediately after UHT treatment and is reduced during storage with rate dependant on availability of oxygen an temperature of storage.
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No. TP XX:XXX, JF06
Sensory Quality of UHT MilkStale and Oxidized flavour
Stale Aldehydes from autooxidation of fat
Oxidized, Flat Ketons, PropanalBland N-PentanalChalky N-HexanalCardbordy Brownning reactions
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No. TP XX:XXX, JF06
Sensory Quality of UHT MilkStale and Oxidized flavourStale and oxidized flavour develops during storage while the cooked flavour is disappearing.
It depends on a large number of different compounds.Aldehydes and ketons play the major role.
Formation of oxidised flavour is accelerated by high storage temperature.
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No. TP XX:XXX, JF06
Sensory Quality of UHT MilkOther off-flavours
Bitter flavour Proteolitic activities of plasmin and bacterial thermoresistant proteases.
Rancidity Lipolitic activities of native and bacterial lipases.
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Lactose and heat effectsLactulose
AcetaldehydeFormaldehydeFormic acidAcetic acidLactic acidTartaric acid
Maillard reactions productsbrown colourantioxydents
No. TP70:49, 9309BM
pH drop
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PSD.TPD&B.BP.2.22, AA10
Loss of vitamins in UHT milk
VitaminAscorbic acid
Folic acid
B12B6B2 (riboflavine)
Thiamine
A
D
E
UHT treatment
080
1020
030
020