new preservation methods for foods -...

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New preservation methods for foods

Prof. dr. ir. F. DevlieghereI. Vandekinderen, P. Ragaert,

L. Garcia GonzalezDepartment of Food Safety and Food Quality

Laboratory of Food Microbiology and Food Preservation

WAVFH-Flanders avondvoordracht 29 mei 2008Faculty of Bioscience Engineering – Department of Food Safety and Food Quality

Content

-Introduction-Alternatives for heat treatments

- High Hydrostatic Pressure (HHP)- Intense Light Pulses (ILP)- Liquid decontamination systems- Gaseous decontamination systems- High pressure carbon dioxide (HPCD)- Bacteriophages

-Active packaging systems

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Trends in the food industry

Conventional fresh ultra fresh

attractive, healthy and

without additives

Good shelf lifeand 100% safe

PRESERVATION TECHNIQUE


HIGH HYDROSTATIC PRESSURE (HHP)

3


High Hydrostatic Pressure Druk (HHP)

- Treatment > 100 MPa- Batch or semi-contineous- 0.10 tot 0.15 € per kg product- Limited number of food products


Some commercial HPD treated food products in Europe and U.S.A.

AGuacamole (U.S.A.)

Oesters (V.S.)

Versneden ham (Spanje)

Fruit juice (France)

Source Chris Michiels

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Most important disadvantages of HHP

- Cost- Batch- Adapted packaging configuration- Inactivation of vegetative cells butreduced inactivation of bacterial spores


Survival curves of B. stearothermophilus strain 1 (A) and strain 2 (B), B. coagulans (C), B. subtilis (D), B. licheniformis (E) and B. megaterium (F) through HHP at room temperature (Nakayama et al., 1996).

5


Use of HHP at increased temperatures toinactivate bacterial spores

(Devlieghere et al., 2004)


Use of HHP and nisine or an acid environment to inactivate bacterial spores

(Devlieghere et al., 2004)

6


Most important disadvantages of HHP

- Cost- Batch- Adapted packaging configuration-Inactivation of vegetative cells butreduced inactivation of bacterial spores-Selection for HHP- resistant vegetativegerms


Selection of HHP resistant strains of Escherichia coli by usingalternating cycli of exposure at HHP varying from 280MPa to450 MPa (Houben et al., 1997)

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Induction of pressure resistantvegetative bacteriaEscherichia coli (Houben et al., 1997)Listeria monocytogenes (Karatzas and Bennik, 2000) after single pressuretreatment of 400 MPa at 20 min.

CONSEQUENCES FOR THE FOOD INDUSTRY?


INTENSE LIGHT PULSES

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Inte

nsity

(µW

cm

-2–

nm) a

t 50

cm

(Hamamatsu, 1999)

Control unitManual mode: user’s choiceContinuous mode: 15 Hz

Treatment chamber

7 J linear Xenon flash lamp

UV-C

UV

9


Effect of the relative position between agar surface and lamp on the inactivation of Listeria monocytogenes by 50 flashes of ILP

0.1 0.9 1.0 0.3

0.2 5.8 6.0 0.6

0.0 0.4 0.4 0.1

43 cm

32 c

m

Distance lamp-agar: 6 cm

0.5 1.7 1.8 0.7

1.0 3.2 4.0 1.2

0.6 1.6 2.0 0.6

43 cm

32 c

m

Distance lamp-agar: 13 cm


Effect of food components on the microbial inactivation by 50 flashes of ILP

Listeria monocytogenes

0123456

Water Starch Proteins Oil

Inac

tivat

ion

(log

CFU

/cm

²) Photobacterium phosphoreum

012345


Inac

tivat

ion

(log

CFU

/cm

²)

Candida lambica

0

1

2


Inac

tivat

ion

(log

CFU

/cm

²)

Water: control , low level: 0.1 ml , high level: 1 ml (v/v).

Starch, proteins, oil: control: , low level: 1% , high level: 10% (v/v).

Error bars indicate SD.

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Liquid decontaminationmethods


Decontamination of fresh-cut produce

“ To treat produce by a process that is effective in destroying orsubstantially reducing the numbers of micro-organisms of public health concern, as well as other undesirablemicroorganisms, without adversely affecting the quality of the product or its safety for the consumer” (FDA, 1998)

6 prerequisites for an adequate decontamination process:

1. Reduction of the risk on food-borne infections and intoxications

2. Decrease of microbial spoilage

3. Maintaining the fresh-like character

4. Preservation of the nutritional value and the physiological processes

5. Maintaining the chemical safety

6. Economical feasibility

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Decontamination of fresh-cut produce

“ To treat produce by a process that is effective in destroying orsubstantially reducing the numbers of micro-organisms of public health concern, as well as other undesirablemicroorganisms, without adversely affecting the quality of the product or its safety for the consumer” (FDA, 1998)

6 prerequisites for an adequate decontamination process:

1. Reduction of the risk on food-borne infections and intoxications

2. Decrease of microbial spoilage

3. Maintaining the fresh-like character

4. Preservation of the nutritional value and the physiological processes

5. Maintaining the chemical safety

6. Economical feasibility


Tested decontamination agents

•Water = reference treatment•NaOCl (20 and 200 mg/L, pH 6.0)•Peroxyacetic acid (80 and 250 mg/L)•Neutral Electrolysed Oxidising water (NEW, 5 and 30 mg/L free chlorine)•Gaseous Chlorine dioxide

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Neutral Electrolysed Oxidising Water (NEW)

e A

I

+ -

V

Anode Cathode

Cl- Na+

OH- H+

M ox M red

Water as electrolyt

Direct currentLow voltage+ -

ELECTROLYSIS

CELL

Principle: generation and antimicrobial action

Creation of “free”oxidants

Mox:

• Oxygen radicals

(OH•, OOH•)

• Chlorine radicals

(Cl•)

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NEW: pilot installation (Ecodis 0.02)

Control unit

Cell withelectrodes

Tap afterelectrolysis

Tap beforeelectrolysis

Water inlet

Flow meter

Flow controlvalve




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ClO2 (g) treatment chamber

Treatmentchamber

Thermo-

hygrometer

Stripper

Gas sampling pump

Gas sampling

impinger formonitoring

[ClO2]

•Room temperature•RH = 90%•FClO2, g = 5,5 L/min•tstripping = 30s; tcontact= 10 min


Experimental set-up: case carrots

peeling, trimming, grating

100g in 1L desinfectant

5 min at room temperature undercontinuous agitation (120 tpm)

Removal of the excess of desinfectant + spin drying(1 min)

microbial, nutritional, sensorial, chemicalanalyses

NOTE: After rinsing with water (1 min, removal dirt), contact with chlorine dioxide gas like previously described

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Effect on microbial quality fresh-cut carrots

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

Water 1 min

Water 5 min

EOW 5 mg/L

EOW 30 mg/L

NaOCl 20 mg/L

NaOCl 200 mg/L

PAA 80 mg/L

PAA 250 mg/L

Chlorine dioxide

Mic

robi

al re

duct

ion

(log

cfu/

g)

a

cded

c

b

aa

a

a


Effect on microbial quality fresh-cut carrots

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

Water 1 min

Water 5 min

EOW 5 mg/L

EOW 30 mg/L

NaOCl 20 mg/L

NaOCl 200 mg/L

PAA 80 mg/L

PAA 250 mg/L

Chlorine dioxide

Mic

robi

al re

duct

ion

(log

cfu/

g)

a

cded

c

b

aa

a

a

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Effect on the microbial quality of fresh-cut carrots

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

Water 1 min

Water 5 min

EOW 5 mg/L

EOW 30 mg/L

NaOCl 20 mg/L

NaOCl 200 mg/L

PAA 80 mg/L

PAA 250 mg/L

Chlorine dioxide

Mic

robi

al re

duct

ion

(log

cfu/

g)

a

cded

c

b

aa

a

a


Effect on the nutritional quality of fresh-cutcarrots: carotenoid and total phenol content (1)

Decontamination treatment

ControlWater

NaOCl 20mg/L

NaOCl 200mg/L

Car

oten

oid

cont

ent (

µg/1

00g

fres

h w

eigh

t)

0

2000

4000

600010000

12000

14000

Phenol content (mg G

AE/100g fresh w

eight)

0

5

10

15

20

25


ControlWater

PAA 80mg/LPAA 250mg/L

Car

oten

oid

cont

ent (

µg/1

00g

fres

h w

eigh

t)

0

5000

15000

20000

25000

Phenol content (mg G

AE/100g fresh w

eight)

0

10

20

30

40

50

•Carotenoids: C30 RP-HPLC-DAD (α- and β-carotene most predominant in carrots)

•Total phenols: spectrophotometric Folin-Ciocalteu method

NaOCl PAAα-caroteneβ-carotenephenols

When compared to water, the use of NaOCl (20 and 200 mg/L) orPAA (80 and 250 mg/L) did not have a significant effect on the

carotenoid and the phenol content.

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Effect on the nutritional quality of fresh-cutcarrots: carotenoid and total phenol content (2)

PAA

α-caroteneβ-carotenephenols

•When compared with water, NEW had no significant effect on the total

phenol and the α- and β-carotenecontent


Control Water ClO2Car

oten

oid

cont

ent (

µg/1

00g

fres

h w

eigh

t)

0

2000

4000

8000

10000

12000

14000

Tota

l phe

nol c

onte

nt (m

g G

AE/1

00g

fres

h w

eigh

t)

0

10

20

30


Control Water NEW 5mg/LNEW 30mg/L

Car

oten

oid

cont

ent (

µg/1

00g

fres

h w

eigh

t)

0

2000

4000

60008000

10000

12000

14000

16000

Tota

l phe

nol c

onte

nt (m

g G

AE/1

00g

fres

h w

eigh

t)

0

10

20

30

•No significant effect on the totalphenol content

•Significant decrease (10% in comparison with water treatment) of the α- and β-carotene content

•good penetration abilities?

ClO2NEW


Effect on the sensory quality of fresh-cut carrots•Significant difference between carrotstreated with a decontamination agent and water washed carrots?•Triangletest (18 panellists)•Samples offered in closed plastic boxes, after an incubation period of 3 h at 4°C

250 mg/L80 mg/L30 mg/L5 mg/L200 mg/L20 mg/LClO2PAANEWNaOCl

No significant difference(α = 0.05)

Significant difference (α = 0.05, a minimum of 10 out of 18 persons could distinguish the deviant sample )

Chlorine odour was not observed!Change in texture was observed after a treatment with PAA

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Gaseous decontaminationmethods- ClO2 (see previous part)- SONO-steam

Prof. Dr. ir. F. Devlieghere - 28/05/2008Faculty of Bioscience Engineering – Department of Food Safety and Food Quality

SonoSteam = combined action of ultrasound and steam

No ultrasound With ultrasound

•Laminar boundary layer: air layerclosest to the surface

•Restriction of vapour and heat exchange at the surface

•Lower inactivation efficiency

•Ultrasound induces molecularoscillations in the laminar layer

•Decrease of the restriction of vapourand heat exchange at the surface

•Steam reaches microstructures in the surface

•Higher inactivation efficiency

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SonoSteam: pilot installationPilot installation

•Water softener•Steam generator•Pump•Treatment chamber with nozzles•Steam exhaust

Treatment chamber (L= 46 cm, ø = 16 cm)•6 nozzles: production ultrasound + injectionsteam•3 nozzles: pressurized air (optional)•Grid


SonoSteam: effect on total count of fresh-cut vegetables

0

1

2

3

4

5

6

7

1 2 10 x 1Treatment time (s)

Mic

robi

al re

duct

ion

(log

cfu/

g) Soya sproutsLeeksIceberg lettuceWhite cabbage

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SonoSteam: effect on the microbialquality of cod fillets

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

1,60

1,80

2,00

2 10x1Treatment time (s)

Mic

robi

al re

duct

ion

(log

cfu/

g)Total aerobic and psychrophilic plate countH2S producing bacteriaLactic acid bacteriaBrochotrix thermosphactaPseudomonas


HIGH PRESSURE CARBON DIOXIDE (HPCD)

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HPCD-pasteurisation

High Pressure Carbon Dioxidesub- of superkritisch CO2

KLiquid

T (°C)

D (b

ar)

31.1-56.7

5.2

73.8

T

Solid

Gaseous

SupercriticalP > Pc (=73.8 bar)

T > Tc (= 31.1°C)

P < Pc and/or T < Tc

Liquid or gasSupercritical


HPCD-pasteurisation

Advantages: mild treatment conditions‣ THPCD < THT → no quality loss‣PHPCD < PHHP → lower cost

Disadvantage: posible extraction of ingredients

Batch / semi-batch / contineous implementation

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Experimental set-up: Batch

Cooler Pump

Water bath

Reactor

3. Decompression

1. Compressie

2. HPCD-treatment at cst P and T


HPCD-pasteurisation

Efficacy depends (omong others) of:

‣ Type of micro-organism

‣Composition of the food

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Type of microorganism

0

1

2

3

4

5

6

7

8

A. hyd

rophil

aE. c

oli

P. fluo

resce

ns

S. typh

imuri

um

Y. ente

rocoli

tica

A. acid

oterre

stris

E. faec

ium

B. cere

us

B. therm

osph

acta

I

L. sa

ke

L. mono

cytog

enes

S. aure

us

C. lambic

a

S. cere

visiae

Z. bail

ii

A. acid

oterre

stris

B. cere

us

A. nige

r

P. roqu

eforti

Microorganismen

Log 1

0 (N 0

/Ni)

Gram negatieven Gram positieven Gisten Sporen

HPCD-resistance : G- ≈ G+ < Yeasts < Spores

Relation HPCD-resistance & acid resistance?


HPCD-pasteurisation

Niche market: liquid food products‣ Fruit juices Tomatensaus‣Milk‣Egg products

⇒ Liquid whole egg (LWE)

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Shelf life of WLE

Natural flora HPCD (13 MPa – 10 min – 45°C – 50% filling – 400 rpm)

vs. HT (4 min – 65°C)

Storage for 5 weeks at 4°CMost important microbial parameters:‣Pseudomonas fluorescens‣Enterobacteriaceae‣ Total aerobic psychrotrophic count


Shelf life study on WLEPseudomonas fluorescens

0

1

2

3

4

0 7 14 21 28 35 42

Tijd (dagen)

Log 1

0 N

Onbehandeld Hittebehandeld HPCD behandeld

P. fluorescens

After pasteurisation < 100 cfu/g

After 5 weeks, 4°C < 1000 cfu/g

Enterobacteriaceae


after 5 weeks, 4°C < 100 cfu/g

Enterobacteriacaea

0

1

2

3

4

5

0 7 14 21 28 35 42

Tijd (dagen)

Log 1

0 N


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Bewaarstudie op VHE Totaal aeroob psychrofiel kiemgetal

0

1

23

4

5

0 7 14 21 28 35 42

Tijd (dagen)

Log 1

0 N


Aerobic psychrotrophic count


After 5 weeks, 4°C < 100.000 cfu/g

pH

5

6

7

8

9

3 4 5

Tijd (weken)

pH

Hittebehandeld HPCD behandeld

No pH difference betweenHPCD and heat treated LWE samples


Bacteriophages

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• Bacteriophages = bacterial virusses•Specific for a certain group of micro-organisms. E.g.

• Listeria monocytogenes, Campylobacter, Salmonella

Use of bacteriophages as a preservationtechnique

Thiel, 2004

Photo: Steven Hagens


Is listeriophage P100 useful to prevent proliferation of L.monocytogenes on vacuumpackaged CMP?

Challenge testing on CMP with and without P100Preliminary test on cooked chicken fillet

Time (days) LIS LIS + P100 (107 pfu/cm2)

0 1.00 1.00 7 2.46 2.04

14 4.62 1.85 21 4.32 1.00

Reduction in L. monocytogenes count of 3.32 log10(cfu/g)

Bacteriophages

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BacteriophagesCooked ham (vacuum packaged, 7°C)

• L. monocytogenes• L. monocytogenes + P100 (1 × 107 pfu/cm2)• L. monocytogenes + P100 (5 × 106 pfu/cm2)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 2 4 6 8 10Time(d)

L. m

onoc

ytog

enes

c

ount

(lo

g 10(

cfu/

g))


Active packaging

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Active & intelligent packaging (Def. EU 1935/2004)

•Active packaging: a way of packagingchanging the properties/conditions of the packaged food product‣Shelf life extension‣Remain/improve the condition of the foodproduct


Different kinds of active packaging

•Absorbing (scavenging)‣ O2, CO2, H2O, ethylene, aromas, UV,…

•Releasing‣ Ethanol, CO2, preservatives,…

•Removal og‣ Lactose, cholesterol,…

•Temperature control‣ ‘Self-heating’, isolating materials,…

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Choice of O2-absorber

•How much O2 present after packaging?‣ In head space (eg. flush vs vacuum)‣ In product (vb. poreous products)

•Permeability of packaging material•Relative humidity in packaging (activation)•Desired shelf life•Safety (e.g. ‘do not eat’, migration of oxidised products,…)•Economical


Examples O2-absorbers

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Example in cap of bottle/vessel


Ethylene absorbers

• Example of application: fresh(climacteric) fruits and vegeatbles

• Ethylene accelerates ripening and maturation of vegetables and fruits

sachets

foils pads

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Antimicrobial packaging

• Active compounds‣Ag2+-ions‣Chlorine dioxide‣Ethylalcohol‣Organic compounds e.g. triclosan‣Polymers e.g. chitosan‣Natural herbs


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