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HIGH PRESSUREPROCESSING
OF FOODS
Valente B. Alvarez
Food Industries CenterDepartment of Food Scienceand technology
V.B. Alvarez/High presureproc./10-2007
HIGH PRESSURE PROCESSING OF FOODS
Contents
HPP Background
Principle
Microbial effect
Product applications
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One of the emerging technologies incommercial use for products like Juices,Seafood, Jam, Avocado, Oysters, Purees,Sauces and ready-to-eat meats.
Pasteurized and shelf stable high acid foodproducts
Pasteurized low acid products
Combination of elevated pressures and temperatures Microbial inactivation
Minimal thermal degradation Quality equivalent to that of fresh products
BackgroundBackground
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Isostatic Principle:
Pressure is transmitted in a uniform andquasi-instantaneous manner throughout thewhole sample.
Process time is independent of samplevolume
Le Chataliers Principle:
Under equilibrium conditions, a processassociated with a reduction in volume isfavored by an increase in pressure and viceversa.
Governing principlesGoverning principles
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KEY ADVANTAGES
Both particulate and pumpable foodProduct suited
Pressure transmitted uniformly andinstantaneously throughout the sample
Pressure application
Independent of product shape and sizeProcess time
Pressure accelerates traditional thermalinactivation kineticsReaction rate
Food will not undergo significant chemicalchanges due to pressure treatment itself
Quality impact
Opportunities for new process/productdevelopment (gelling, melting etc.) withimproved food functionality.
Influence phasetransition andfunctionality
Additional pH effectspH
Instant temperature increase andinstantaneous cooling
Adiabatic compressionheating anddecompression cooling
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Pressure creates no shear force and thepressurized food product remains uncrushed
Temperature
Time
Tm T2
Ts
P2P1
Ps Pf
tft2t1tsTf
Come-Up Hold ing Decompressi
on
Pressure
Typical HPP cycleTypical HPP cycle Source: Balasubramaniam, 2003Source: Balasubramaniam, 2003
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Typical process Product packaged in flexible container
Loaded in high pressure vessel filledwith pressure transmitting fluid (PTF)
Pressure transmitted from the pumpto the PTF and to the food throughthe package
Pressure held of 3-5 minutes
Chamber depressurized and cooledsampled taken out
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Packaging
Flexible packaging needed fortransferring pressure to the food At least one interface of the package
should be flexible
Minimize headspace Air has different compressibility than food
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HPP Parameters
Process Related Target process Pressure Process holding time Pressure-come up time (and decompression
time) Process Temperature Pressure transmitting fluid
Product Related product pH,
product composition
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Compression Heating of Some Foods
Substance (25C) Temperature change
T (C) per 100MPa
WaterMashed PotatoOrange JuiceTomato Salsa2% Fat Milk
Approx. 3.0
Salmon Approx. 3.2
Chicken fat Approx. 4.5
Water/Gycol
50%
From 4.8 to < 3.7 *
Beef Fat Approx. 6.3
Olive oil From 8.7 to < 6.3 *
Soy oil From 9.1 to < 6.2 ** Nonlinear behavior with lower
T at higher P
Source: Rasanayagam et. al., 2003Source: Rasanayagam et. al., 2003
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V.B. Alvarez/High presureproc./10-2007Source: Avure Technologies Inc., Kent, WA
Source: Avure Technologies Inc., Kent, WA
BATCH SYSTEMS SEMI-CONTINUOUS
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Microbial Inactivation
HPP induces changes in cell membranes, cell morphology,affect biochemical components and other geneticmechanisms (Patterson, 2005)
Extent of inactivation depends on
The type of microbe
Pressure used
Process temperature
Time of pressure treatment
pH and composition of food
HPP induces changes in cell membranes, cell morphology,affect biochemical components and other geneticmechanisms (Patterson, 2005)
Extent of inactivation depends on
The type of microbe
Pressure used
Process temperature
Time of pressure treatment
pH and composition of food
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Resistance to pressure treatment
Spores > vegetative bacteria
Gram positive > Gram negative
Smaller size > Larger size
Coccoidal shape > rod shape
Stationary phase cells > exponentialphase growth cells
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Structural and functional changesin vegetative microbe during HPP
Atmospheric pressure
Inhibition of protein synthesis; reduction in the
number of ribosomes
Reversible protein denaturation; compression of gas
vacuoles
Membrane damage; Signs of cell contents leakageIrreversible protein denaturation; Leakage of cell
contents
0.1
50
100
200300
Pressure influenced structural and functional changesPressure (MPa)
Source: Lado and Yousef, 2002Source: Lado and Yousef, 2002
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Protein denaturation by pressure
Primary structure (peptidebonds) remains intact
Secondary structures(hydrogen bonds) getruptured
Lower pressures producereversible denaturation
Higher pressures causeirreversible denaturation
Primary structure (peptidebonds) remains intact
Secondary structures(hydrogen bonds) getruptured
Lower pressures producereversible denaturation
Higher pressures causeirreversible denaturation
reversiblestate
reversiblestate
irreversiblestate
irreversiblestate
Heremans, 1998Heremans, 1998
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Effect of HPP on quality
Very little effect on low molecularweight compounds (flavor, vitamins,pigments)
Fresh like quality maintained
HPP products distributed and stored
refrigerated to maintain quality
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Other issues
No special labeling required
FDA regulations for thermal processingapply
HPP products cost 3-10 cents/pound morethan their thermal counterparts
Can be used in conjunction with othertechnologies
Active research on developing shelf stablelow acid foods using HPP
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High Pressure Milk ProcessingWork at OSU
Process that operates at highertemperature-pressure combinations, arebeing used synergistically to sterilize rawmilk.
Combination of pressure andtemperature
400 to 700MPa
90 and 105oC, for a few seconds
PET aseptically packaged
Processed milk analyses
Safety, overall chemical stability andshelf life
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HIGH PRESSURE PROCESSING OF FOODS
Summary
HPP Background
Principle
Microbial effect
Productapplications
V.B. Alvarez/High presureproc./10-2007
References
Balasubramaniam, V.M. (2003). High Pressure FoodPreservation. Encyclopedia of Agricultural, Food, andBiological Engineering, Marcel Dekker, Inc., 490-496.
Farkas, D., & Hoover, D. (2000). High pressure processing.In Special Supplement: Kinetics of Microbial Inactivation forAlternative Food Processing Technologies. Journal of FoodScience Supplement, 47-64.
Patterson, M.F. (2005). Microbiology of pressure-treatedfoods.Journal of Applied Microbiology, 98, 1400-1409.
Sizer, C., Balasubramaniam, V. M., & Ting, E. 2002.Validating high-pressure processes for low-acid foods. FoodTechnology, 56(2), 36-42.
Ting, E., Balasubramaniam, V. M., & Raghubeer, E. (2002).Determining thermal effects in high-pressure processing.Food Technology, 56 (2), 31-34.
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