Shelf-LifeBy Erica Pounds

Shelf Life

Analysis Type Shelf Life Length Date Coding

Microbiological changes

Short-life (up to 1 wk) “Use by”

Chemical changes Medium to Long (3 wks – 1 yr)

“Best Before”

Sensory changes Medium to Long (3 wks – 1 yr)

“Best Before”

Shelf-Life is defined as the time during which the food product will:a) Remain safe;b) Be certain to retain desired sensory, chemical, physical

and microbiological characteristics;c) Comply with any label declaration of nutritional data,

when stored under recommended conditions

Factors Affecting Shelf LifeExternal Conditions influencing shelf-life:• Raw material selection and quality• Product formulation and assembly• Processing environment• Processing and preservation techniques• Packaging• Storage and distribution• Consumer handling

Internal Changes influencing Shelf-Life:• Moisture loss and gain• Physical transfer of oxygen, water vapor, odors and flavors• Light induced changes• Chemical changes• Microbiological changes

Packaging• Barriers prevent moisture, gases, and light• Total barrier such as glass above 17 μm (total barrier to

moisture and all gasses)• Amber glass 2mm thick provides almost complete

barrier up to 450 nm•When a product contains fat an oxygen barrier is required for packaging• Use odor barrier to keep desirable odors and flavors

Microbial and Mold Growth• Water Activity – ability of moisture to migrate in food products. Major parameter for inhibiting microbial growth and molds

• Equilibrium relative humidity (ERH) – ERH of the environment is key to surface-growing organisms

Water Activity

AW < 0.86 (Pathogenic bacteria

can’t grow)

AW = 0.60 (Osmophilli

c yeasts can grow)

Sensory Changes (Lipid Oxidation)

Lipid Intermediate

Secondary Reaction Product

Oxidation Pathways

Oxidation

Auto-oxidation

Photo-oxidation I

Photo-oxidation

II

Off-Flavor

Triplet Oxygen

Singlet Oxygen

UVIonization

Radiation

Heat

Photo-Oxidation• Photo-oxidation uses light as a sensitizer with little or no induction period• Type I – excitation of lipids• Type II – excitation of oxygen

Auto-Oxidation•Autoxidation – spontaneous reaction of atmospheric oxygen with lipids

•Aldehydes commonly contribute to the off-flavors that develop during lipid oxidation

Decomposition Auto-oxidation Off-FlavorsSoybean Oil BeanyFish Oil Fishy flavorMilk Fat Creamy or Metallic

Flavor

Auto-Oxidation Induction Period“Antioxidants delay the development of off-flavors by

extending the induction period”

Measure of Oxidation•Visual• Oxidative deterioration may cause bleaching of foods

due to the reaction of pigments, especially caratenoids• Sensory Panel• Hexanal detection with age

•Qualitative• Monitor weight

•Quantitative• Headspace Analysis (Dynamic/Static)• Solid Phase Microextraction (SPME)• Peroxide Value (PV)• Para-anisidine value (absorbs at 350 nm)• Thiobarbituric acid value (absorbs at 532 – 535 nm)• Induction Period Tests

Types of Antioxidants

• Primary antioxidants – scavenges free radicals and are consumed during induction period, vitamin E (phenolic compounds)

• Secondary antioxidants – bind metal ions, scavenge oxygen, convert hydroperoxides to non-radical species, absorb UV radiation, or deactivate singlet oxygen, Citric Acid (sequestering agents) and ascorbic acid (reducing agents)

“Antioxidants are effective when added to fresh oils of good quality and are less effective in delaying oxidative rancidity

development when oxidation has already started”

US Regulations on Antioxidants“Antioxidants should satisfy several requirements before being accepted for incorporation into food products/ The antioxidant should be soluble in fats; it should not impart a foreign color, odor or flavor to the fat even on on long storage; it should be effective for at least one year at a temperature between 25 and 30C; it should be stable to

heat processing and protect the finished product, ; it should be easy to incorporate and it should be effective at

low concentrations. “

Plan•Cleaning• Use of metal chelating agents can be used to

prevent oxidation• Water activity – measuring and controlling provides

a means of monitoring and controlling pathogenic and spoilage bacteria

• Mixing• Check bulk flavorings with GC-MS for quality control• pH of all e-liquid should be at 6. Maximum

degradation of peroxides occurs in the pH region of 5.0 - 5.5

• Yeasts thrive between a pH of 4.5 – 5.5• Addition of antioxidants (antioxidants must not

exceed 0.02% by weight based on fat content of food)

• Bottling• Pumping introduces more oxygen• Opening and closing 5 gallon batches to bottle

introduces more oxygen in lipids and in headspace• Storage• Light and Temperature Control