1

Fronteras en el envasado de alimentos: envases activos e inteligentes

• Passive, Active, Sensing, and Smart Packaging• Sensing FilmsSensing Films• Absorbing Films• Flavor Improving Films• Gas and Vapor Management Films• Antimicrobial Films• In situ Processing Films• Bio-Active, Non-migrating Films

Tercer Simposio Internacional de Innovación y Desarrollo de AlimentosJ.H. Hotchkiss, Cornell University, USA

Passive versus Active Packaging

• Passive Packaging: Acts as a passive barrier to separate a product from its environment.

Enabling technology: meet product barrier– Enabling technology: meet product barrier requirements an acceptable cost.

• Active Packaging: Interacts directly with the product and/or its environment to improve one or more nutritional, quality or safety factors.

• Smart or Intelligent Packaging: Packaging whichSmart or Intelligent Packaging: Packaging which “senses” a situation and provides information such as quality, environment, location, safety, history, etc.

2

Microbial Sensing “Smart” Films

LASERDIFFRACTION PATTERN

ANTIBODY GRID

Removal of Unwanted Food Components

• Removal of aldehydes and amines from h dheadspace

• Immobilized Chelating Agents

3

Example: Active Control of Lipid Oxidation in Foods

Conventional control of lipid oxidation in foods:pAdditives

AntioxidantChelating agents

Barrier packaging/Nitrogen flushingActive control

Absorb products of oxidationAbsorb products of oxidation

Irreversible Removal of Amines and/or Aldehydes

• Incorporation of activated sites onto films• Formation of Schiff’s bases (imines) • R-NH2 + R’-C=O R-N=CH-R’

4

Removal of Metals from Beverages

Chelating agent

Fe2+

g g

Example: In situ Processing for Improved Flavor

• Nature makes foods such as citrus bitter to d f h ias a defense mechanism

• Enzymes exist which degrade the bitter compounds

5

Immobilization of Flavor-enhancing Enzymes into

Cellulose Ester Films• Debittering of citrus with naringinase• Debittering of citrus with naringinase

6

Loss of naringin from grapefruit juice after exposure to CA film containing naringinase at 7°C

Gas & Vapor Management

• CO2 , O2 , water vaporCO2 , O2 , water vapor • Ethylene• 1-MCP as an inhibitor of ethylene

receptors

7

Equations for optimal permeability & atmosphere

Al-Ati & Hotchkiss, 2004

8

Permeabilities and Permselectivity for Selected Produce to Give Opt Atmosphere(1 mil, 4°C, mL·mil/cm2.hr.atm)

P P CO /OPO2 PCO2 CO2/O2

Strberry 0.245 0.26 1.1Lettuce 0.049 0.47 9.5Broccoli 0.032 0.07 2.2Carrot 0.017 0.06 3.7Apple 0.017 0.10 6.3ppCelery 0.014 0.04 3.2Cabbage 0.008 0.03 3.0Grn Peppr 0.007 0.04 6.0

Release of MCP from Packaging Materials

CH2

HC = C – CH3

9

Release of MCP from LDPE film containing sliced apples

Antimicrobial Polymers: Potential Uses

• Packaging (food contact films)N k i f d t t f• Non-packaging food contact surfaces– tables, filler nozzles, conveyer belts

• Personal hygiene equipment– gloves, aprons, utensils

• Machinery surfacesy• Non-contact surfaces

– refrigeration systems, walls, floors, drains

10

Antimicrobial Polymers

Migrating: Incorporation and generation of volatile & nonvolatile antimicrobials in films

Non-migrating: Immobilization ofNon-migrating: Immobilization of antimicrobial agents to food packaging materials.

Example: Antimicrobial Enzymes in Films

• Immobilization of lysozyme in cellulosic ester films.

11

Films Containing Antibiotics or Antimycotics: Hydrolysis of

benzoic anhydride to benzoic acid

12

Inhibition of Penicillium spp. on cheese by LDPE containing benzoic anhydride

Nisin Impregnated Antimicrobial Film/Paper

Scanell et al 2000Hu et al 2000

13

Non-migrating “food additives”

When is a food additive not a “food additive?”

Potential Non-migrating Functional “Additives”

• Anti-microbial • Enzymesy• Chelating agents• Anti-oxidants• Selective aroma sorbents/reactants• Colors• Surface energy modifiers• Sanitizers• Indicators (chemical & biological)• Film physical and chemical modifiers

14

Immobilized Functional Food Ingredients (Bio-active Packaging)

EEnzyme

Antioxidant Bulk Solution or Food S rface

Bulk Polymerw modified surface

Antimicrobial

Spacer Anchor

Active Agent

Surface

Covalent attachment of Bio-active Molecules to Polymers

Polymer surfaceFunctionalized Polymer surface

FunctionalizedPolymer surface

BiofunctionalizedPolymer surface

Goddard et al 2006

15

7.00

8.00/c

m2

Surface Protein Content of PE Film Before

and After Lactase Attachment

2.00

3.00

4.00

5.00

6.00

age

μg

prot

ein/

0.00

1.00

PE PE-COOH PE-NH2 PE-GL PE-LAC PE-LAC(SDS)

Film Sample

Ave

ra a baaa c

70%80%90%

100%

vity

(%)

Relative Activity of Free and Film-Attached Lactase

10%20%30%40%50%60%70%

elat

ive

Act

iv

0%4 5 6 7 8 9 10

pH Value

Re

Free Lactase Film-Attached Lactase

16

AFM view of modified surface of LDPE

Antimicrobial Peptides

• Occur widely in nature.• Typically 23 to 34 aa to 35-70 kDa proteins. • Amphipathic and highly basic (+ charge).• Helical structure.• Act at cell surface.• Permeabilize cell membrane.

17

Synthetic antimicrobial peptide

• 6K8L, leucine and lysine

• low hemolytic activity, strong antimicrobial activity

18

Changes in OD600nm of E. coli 0157:H7 in TSB with (�) or without (�) 50 μg/ml peptide 6K8L at 25°C

(b)

0.6

0.8

1

1.2

OD 6

00nm

0

0.2

0.4

0 20 40 60 80 100 120 140 160

Time (min)

19

Effect of peptide 6K8L on P. fluor., S. liquefac., S. typhy., E. coli survival in buffer at 25°C for 10 min.

A.

345678

og10

CFU

/ml

P.f luorescens

S. liquef sciens

S. t yphymurium

E. coli O157:H7

123

0 20 40 60

Peptide (ug/ml)

lo

Effect of peptide 6K8L on S. aureus, L. mono., and B. subtilis, K. marxianus in buffer at 25°C for 10 min.

B

34567

g 10 C

FU/m

l S. aureusL. monocytogenesB. subtilisK. marxianus

B.

123

0 20 40 60

Peptide (ug/ml)

log

20

Peptide Immobilization

• PS resin bead---spacer molecule---peptide

• 345 mg (0.2 mmol) peptide/g resin

• Surface modified polystyrene (SMPS)

Immobilization on PS Beads

Spacer Molecule

Peptide

Polymer BeadBead

21

Effect of 0, 6, 10, 20, 40 mg/ml of SMPS on E. coli 0157:H7 growth in TBS at 25°C. (�) PS control

6

8

10

12

Log 1

0 CFU

/ml

0

2

4

0 5 10 15 20

Time (h)

L

22

Concentration (mg/ml) of SMPS required to give a 3 log reduction in counts in buffer in 10, 30, or 60 min at 25°C

• ORGANISM 10 MIN 30 MIN 60 MIN.

• E. coli 0157:H7 8 5 4• S. typhimurium 18 17 8• S. liquefasciens 8 5 ND• P. fluorescens 7 5 3• B. subtltis 3 3 2• L monocytogenes 12 5 3• L.monocytogenes 12 5 3• S. aureus >60 57 50• K. marxiamus 16 9 8

Conclusions

• Surfaces can be reasonably made bioactive ith i l h i twith commercial chemistry.

• Bioactive materials can be covalently attached to surfaces with acceptable loss of activity.

• Active/smart packaging materials may be• Active/smart packaging materials may be useful in foods and biomedicine.

23

"Discovery is seeing what everyone has seen andeveryone has seen and

thinking what nobody has thought"

-- Albert Szent-Gyogyi