6 High Pressure

8/22/2019 6 High Pressure

1/10V.B. Alvarez/High pressure/10-2007

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




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


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




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


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




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


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




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


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



V.B. Alvarez/High presureproc./10-2007Source: Avure Technologies Inc., Kent, WA

Source: Avure Technologies Inc., Kent, WA

BATCH SYSTEMS SEMI-CONTINUOUS


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




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


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




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


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




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


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


10/10V B Alvarez/High pressure/10-2007


HIGH PRESSURE PROCESSING OF FOODS

Summary

HPP Background

Principle

Microbial effect

Productapplications


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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