Food Packaging and Shelf Life

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FOOD PACKAGING AND SHELF LIFEIsmael Povea Garcerant Profesor, Programa Ingeniera de Alimentos Universidad de la Salle

Food Packaging and Shelf Life2

ObjectiveNext slides are devoted to food science and knowledge most relevant to food pacakging and their applications It discusses deterioration kinetics of foods and the role of packaging to

Retard food deteriorations Thereby extending the shelf life of food

The relationship between the shelf life of packaged foods and important variables realting to the food, package and environment

1. Basic Concepts3

1.1. Definitions of Shelf LifeIs the period of time from the production and packaging of a product to the p oint at which the product first beomes unacceptable under defined environmental coditions Shelf life is the period of time during wich the food retains acceptable characteristcis of flvoars, color, aroma, textura, nutritional value, and afety under definied environmental conditions. It also encompasses the time during wich a product may reasonably be expected to meet its label claims for specific atributes

1. Basic Concepts4

1.1. Definitions of Shelf Life

Increasing shlef lifeBetter barrier materials Using Packaging Technologies

MAP Oxygnen Absorbers

Reformulating the ingredients Different processing techniques or conditions Redisigning the distribution route

1. Basic Concepts5

1.2. Factors Affecting Shelf Life of Packaged FoodsFood

Shel Life of Package d Food

Package

Environment

2. Food Factors Affecting Shelf Life6

What are the major deterioration modes wich cause the end of product shelf life? What food products can benefit from packaging for improving shelf life? What quality indexes can be used to measure or quantify the rates of those deterioration modes? Below what levels the quality indexes ser no longer acceptable to the consumer?


2.1. Food Deterioration ModesChemical Microbiological Physical

See table 16.1. Food Packging Science and Technology. D.S. Lee. CRC 2006


2.2. Package Dependent versus Product Dependent Deteriorations

Package-dependent

Environmental factor that are controllable by the package

Oxygen Moisture Microbes Light

Product-dependent

Driven by intrinsic stability of the food

Aw

3. Kinetics of Food Deterioration9

Quantification fo quality changes and permeation of gas and vapor through the packaging materials can be described by the kinetic equations Kinetic equation ares useful for systematic determination and prediction of shelf life of packaged foods


3.1. Chemical Kinetics: Reaction Order and Rate Constant

Are use to describe the rate of disappearance (e.g. loss of nutrients or pigments)or generation of compounds in chemical reactions (e.g. hexanal from oxydation in food)n dB -k B dt = (1)

For zero order kineticdB dt = -k (2)

IntegratingB = B0-kt (3)



Quality deterioration of frozen foodsB0 B Slope = -k Bc

0

t B0 - B c k

ts

ts =

(4)



For the first order kineticdB dt = -k B (5)

IntegratingB = B0 e-k t

(6)



Vitamin C destructionB0 ln B Bc

ln B0

B

ln Bc

Slope = -k

0

t ln B0 / B c k

0

t

ts

t s=

(4)


3.2. Microbial Growth Model 3.3. Physical Changes 3.4 For the variable order Kinetics. Tempreature Dependence: Arrhenius and Shelf Life Plots

4. Environmental Factors Affecting Shelf Life15

4.1. Ambient Environment

Temperature is the most important variable

It can affect

Rates of food deterioration Barrier properties of packaging materials

Relative Humidity

Many products are moisture sensitiveHR=

PWPS

Gas composition Lighting condition


4.2. Physical EnvironmentCompression Shock Vibration Handling


4.3. Human EnvironmentManaging worehousing Transportation Retail purchase Consumer handling

5. Pacakage Factors Affecting Shelf Life18

5.1. Packaging Parameters Important to Shelf Life

PermeationFast Permeation-fast reaction Slow permeation-slow reaction Slow permeation-fast reaction Fast permeation-slow reaction

6. Shelf Life Studies19

7. Shelf Life Models20

Are mathematicals equations wich describe the relationship pf the food, package, and environment purposes

7.1. Shelf Life of Chemical and Microbial Deteriorations

KineticsFor zero order For first order

If there are changes of storage conditions with time, reaction rate constant, k value may be evaluated for each conditions by using Arrhenus Equation and then cumulated Quality changes may be obtained by stepwise calculation (order zero or first order) until total shelf life is reached where the quality level arrives at a critical value


Exercise. Kamman have reported that thiamin loss in a pasta product follows the first order reaction with rate constant of 1.99 x 10-4 day-1 at 25C and activation energy of 129 kJ mol-1. How long does it take for the retention of thiamin to reach 75% of the initial content at 25 and 35?


Exercise. Hourly growth of the naturally occuring bacteria, psudomonads on gilt-head seabream over to 15C, reported by Koutsoumanis and Nychas, can be represented by Belehradek equation, 1/2 = 0.0211 (T+10.65) and (1/)1/2 = 0.0133 (T+12.19) qhere T is temperature in C. Estimate the shelf life for psudomonads to multiply from initial level (104.45 cfu/g) to spoilage level (107.00 cfu/g) at 3 and 8C


7.2. Shelf Life Models of Constant H2O and O2 Driving ForcesMaximum allowable O2 Food products are no longer acceptable Maximum allowable H20 For moisture and Oxygen sensitive foods

Shelf life of moisture sensitive food =

Maximum allowable moisture WVTR

Shelf life of Oxygen sensitive food = WVTR= PW A ( ) PW,out PW, in L

Maximum allowable Oxygen OTR OTR = PO2 A( ) PO2,out PO2, in L


Exercise. Dried green tea is known to be highly sensitive to moisture increase and is tolerable to only 2% increase from initial moisture of 3.0% in wet basis. The 3.0% moisture content corresponds to equilibrium relative humidity of 16%. The green tea of 100 g is going to be package in a plastic pouch of 11 x 19 cm. If the package has a shelf life of 60 days at 30C and 80% relative humidity, what would be required water vapor permeance of (PW/L)?


Exercise. A certain spice is known to have the Oxygen tolerance limit of 50 ppm. Estimate the shelf life of the vacuum packed spice. Product weight is 250 g and initial Oxygen concentration inside the package is assumed as zero. The package surface area is 444 cm2. The package film has the structure of 40 m PET/ 10 m PVdC/ 15 m LDPE. O2 permeability coefficients of PET, PVdC and LDPE are 0.144, 0.035 and 36.1 cm3 (STP)m cm-2 day-1 atm-1, respectively.

BIBLIOGRAFIA26

DONG Sun Lee, Kit Yam, Pergiovanni Luciano. Food Packaging Science and Technolgy. CRC. 2007 ROBERTSON Gordon. Food Pacakging, Principles and Practice. 2007 ITENE. Memorias de Ciencia y Tecnloga de Envases, Emabalaje y Transporte. Valencia, 1998 http://www.blowmachines.com/images/injectblow.gif http://www.covalencecoatedproducts.com/docs/img/support/products /process-diagrams/PExtruCoat1.gif http://www.oshore.com/products/archived/images/thermoformed4.gif http://www.smcl.co.uk/content/images/thumb/vacuum%20metallizing %20process.jpg

Food Packaging and Shelf Life

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