Podcast
Questions and Answers
Which of the following is considered a nonperishable food?
Which of the following is considered a nonperishable food?
Nonperishable foods remain stable only as long as their packaging is intact.
Nonperishable foods remain stable only as long as their packaging is intact.
True
What factor can affect the bulk density of food powders?
What factor can affect the bulk density of food powders?
Processing and packaging
Low-moisture content unprocessed foods include ______ and ______.
Low-moisture content unprocessed foods include ______ and ______.
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Match the food preservation treatment with its description:
Match the food preservation treatment with its description:
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Which factor does NOT play a role in determining shelf life?
Which factor does NOT play a role in determining shelf life?
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All products that show changes in quality have exceeded their shelf life.
All products that show changes in quality have exceeded their shelf life.
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What is the definition of shelf life?
What is the definition of shelf life?
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The three factors controlling shelf life are product characteristics, properties of the package, and ________ conditions.
The three factors controlling shelf life are product characteristics, properties of the package, and ________ conditions.
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Match the following food types with their shelf life category:
Match the following food types with their shelf life category:
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Which change is NOT considered a quality factor that affects shelf life?
Which change is NOT considered a quality factor that affects shelf life?
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A loss of nutrition in a food product can determine when the shelf life has occurred.
A loss of nutrition in a food product can determine when the shelf life has occurred.
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Name one intrinsic factor that affects the shelf life of food.
Name one intrinsic factor that affects the shelf life of food.
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What is the effect of a large free space volume when food is packaged in an inert gas?
What is the effect of a large free space volume when food is packaged in an inert gas?
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Metal cans and glass containers are considered highly permeable to gases and moisture.
Metal cans and glass containers are considered highly permeable to gases and moisture.
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What are the important package properties that control shelf life?
What are the important package properties that control shelf life?
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The thermal conductivity of metallic materials is __________ due to the electron mobility in metallic bonds.
The thermal conductivity of metallic materials is __________ due to the electron mobility in metallic bonds.
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Match the following package materials with their permeability characteristics:
Match the following package materials with their permeability characteristics:
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Which of the following describes the lag and log phases of microbial growth?
Which of the following describes the lag and log phases of microbial growth?
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Free-flowing agglomerates or aggregates of milk and coffee are formed by treating individual particles to minimize __________.
Free-flowing agglomerates or aggregates of milk and coffee are formed by treating individual particles to minimize __________.
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Which insulating material is known to provide better insulation than solid board at the same thickness?
Which insulating material is known to provide better insulation than solid board at the same thickness?
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Organic materials like plastics have high thermal conductivity compared to metallic materials.
Organic materials like plastics have high thermal conductivity compared to metallic materials.
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The distribution environment has little influence on the shelf life of packaged foods.
The distribution environment has little influence on the shelf life of packaged foods.
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What is the primary factor that controls mass transfer across packaging?
What is the primary factor that controls mass transfer across packaging?
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Inadequate thermal insulation in packaging may cause products to reflect the temperature of their __________.
Inadequate thermal insulation in packaging may cause products to reflect the temperature of their __________.
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Match the factors contributing to shelf life with their descriptions:
Match the factors contributing to shelf life with their descriptions:
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What is a common consequence of increased microbial growth in packaged foods?
What is a common consequence of increased microbial growth in packaged foods?
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Water vapor transfer does not depend on the nature of the barrier material.
Water vapor transfer does not depend on the nature of the barrier material.
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What preservation methods can be employed against microbial growth?
What preservation methods can be employed against microbial growth?
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Study Notes
Shelf Life
- Shelf life is the time a product no longer meets expected quality standards for the consumer.
- Quality loss should happen without compromising safety.
- Safety is not the only factor in determining shelf life.
- Increased microbial growth can affect flavor and color without making the food unsafe.
- Nutritional claims can affect shelf life. A loss in nutrition might determine when shelf life ends.
- Shelf life is determined by changes in quality factors, including appearance, texture, and odor.
- Shelf life and product quality are strongly related.
Factors Controlling Shelf Life
- Product characteristics; formulation and processing; pH, water activity, enzymes, microorganisms, concentration of reactive compounds.
- Processing parameters can be controlled by selecting raw materials and ingredients.
- Packaging properties can significantly affect extrinsic factors & deterioration rates.
- Extrinsic factors are environmental factors during distribution and storage (temperature, relative humidity, light, total pressure, partial pressure of different gases, and mechanical stresses).
- Shelf life can be altered by changing composition, formulation, processing parameters, packaging, or the environment.
Product Characteristics
- Bulk Density: Packages of similar shapes with varying bulk densities will have different free space volumes.
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Packaging: Free space volume in packaging is important on the rate of oxidation. Large space volume acts as a "sink" to minimize oxygen effects.
- Large surface area and low food bulk density result in greater oxygen transmission.
- Concentration Effects: Chemical compounds in packaged food have little opportunity to move, leading to increasing differences in concentration as reactions proceed. Several deteriorative reactions may proceed simultaneously, creating a lag and log phase, resulting in different rate constants of microbial growth.
Package Properties
- Foods are classified based on the degree of protection required.
- Metal cans and glass containers are considered essentially impermeable
- Paper-based packages are permeable.
- Plastics provide varying degrees of protection, based on polymer type.
- Important properties include water vapor transfer and gas & odor transfer.
Thermal Properties
- Different thermal conductivities affect the heating/cooling rate in processing (e.g., pasteurization, sterilization).
- Metallic materials have high thermal conductivity due to electron mobility in metallic bonds.
- Organic materials (plastics and wood) have low conductivity due to their atomic and intermolecular bonds.
- Still air has very low thermal conductivity.
- Corrugated board and expanded polystyrene are better insulators than solid board and homogenous plastics.
Distribution Environment
- Deterioration of packaged food quality is often related to mass and heat transfer through the package.
- Packaged foods can gain or lose moisture and reflect environmental temperature.
- Distribution environment significantly affects food deterioration rates.
- Mass transfer concerns include water vapor, oxygen, volatile aromas, and nitrogen/carbon dioxide.
- Differences in partial pressure of vapors/gases across the package barrier control the rate and extent of permeation. Transfer can occur through pinholes, seals, or cracks.
- Water vapor transfer depends on partial pressure differences and the barrier's nature.
- Heat transfer is important, as is the temperature product is exposed to during its journey.
Microbial Growth
- Increased microbial growth can lead to unsafe products due to foodborne pathogens and toxins.
- Microbial growth can change flavor, appearance, odor, and texture.
- Tests for microbial changes can be done, factoring environmental aspects, food products, and desired attributes.
- Methods for preserving include low pH, low/high temperatures, low water activity, increased solids, and decreased oxygen.
Chemical Changes
- Enzymes: Enzymatic reactions (proteolytic, lipolysis, browning) affect nutrition, flavor, and texture. Preservation factors include temperature, pH, and moisture.
- Lipid Oxidation: Exposure to oxygen leads to changes in flavor (rancidity), color, and texture, impacting nutritional value. Factors influencing oxidation include temperature, light, presence of metal ions (e.g., copper, iron), and moisture.
- Maillard Browning: Non-enzymatic browning from reactions between proteins and reducing sugars result in brown color and flavor changes (e.g., toasted, burnt). Temperature and water activity affect this process.
- Nutrient Loss: Temperature, light, water activity, and pH can cause nutrient loss. Nutritional content is important for food product quality.
Physical Changes
- Texture: Changes in texture are related to product quality. General causes include enzymatic reactions, moisture changes, and chemical reactions.
- Color: Color fading or changes over shelf life can be measured using a colorimeter or spectrophotometer.
- Moisture: Moisture changes can affect texture and appearance, including sensory changes like loss or gain. Moisture migration can occur between food components or the environment. Factors like clumping, loss of crispness, and crystallization in frozen foods are linked to moisture. Aw is related to microbial growth, browning, and chemical reactions.
Shelf Life Estimation
- There are at least three situations that necessitate shelf life estimation. Estimating shelf life of existing products, studying the effect of specific factors(storage temperature, package, and processing parameters) or food additives and determining the shelf life of prototypes or newly developed products.
Approaching Shelf Life Estimation
- Literature study: Using existing data from similar products.
- Turnover time: Based on average sales duration, assuming product acceptability remains for some time after average retail period.
- End point study: Purchasing random samples to test in the lab and estimating shelf life based on environmental exposures.
- Shelf life testing: Evaluating using accelerated testing, including elevated environmental conditions.
Selecting Criteria to Assess Shelf life
- Selecting suitable criteria for assessing shelf life depends on the specific product.
- Microbiological changes (total plate counts, specific microorganisms).
- Nutritional changes (e.g., vitamin C loss).
- Undesirable changes (color change, exudation, shrinkage, malodor).
- Change in functional properties (e.g., whipping, coloring, leavening).
- Undesirable textural changes (hardening, softening, staling).
Criteria For Shelf Life (Questions)
- Question 1: Relevant criteria for shelf life assessment: multiple, concomitant degradation. One characteristic's breakdown can accelerate others (e.g., artificial colors and off-flavors).
- Question 2: Acceptable loss of product quality before spoilage: consumer-based assessments of acceptable color, flavor, and texture loss, considerations of minimum nutrient requirements/violations based on labels, and microbiological count thresholds.
- Question 3: Conditions for shelf life testing: ideal (frozen/refrigerated) may not reflect real world consumer experiences; considering temperature fluctuations, transportation, improper storage, and handling during processing and distribution.
Conducting Shelf Life Testing
- Product Handling: Identifying future handling and storage conditions(temperature, humidity, light).
- Observing product changes (microbial, chemical, physical, nutrient loss).
- Based on sensory values, consider flavor, texture, color, and overall acceptability.
- Factors relating to packaging (moisture/gas/light barrier) and environmental exposures should be considered for accurate assessment.
Type of Tests
- Static Test: Observing product deterioration under a given set of environmental conditions.
- Accelerated Shelf Life Test (ASLT): Evaluating product under accelerated/elevated conditions(temperature increases to understand deterioration rates).
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Use/Abuse Test: Cycling the product through realistic environmental variables (temperature fluctuation during delivery and handling/storage).
- Including packaging stress, abusive handling (e.g., drop tests, temperature extremes).
Extending Shelf life
- Possible strategies include modifying formulation/processing/packaging, treating product to reduce pathogenic bacteria, and increasing severity of processing/pathogen elimination. This is to address unsafe levels or extend period for the product.
Marking Dates
- Date marking (use-by or best-before) begins at preparation/manufacturing.
- Best-before date indicates the period product remains marketable and retains intended qualities while held under specific conditions.
- Use-by date indicates the end of the estimated period in which the product should be used to maintain health/safety. Conditions of proper storage are essential.
- 'Use-by' dates are needed if product, for health reasons, must be consumed before a specific date because of potential nutrient, microbial, or toxic substance issues.
Summary of Shelf Life Determination
- Classifies methods into Direct (static) and indirect methods (accelerated, predictive models). Direct involves following product until spoilage, while indirect uses increased storage temperature to speed up degradation.
- Indirect (predictive models) use database information or apply mathematical models. Factors for considering shelf life include microorganisms, chemicals, and physical changes.
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Description
This quiz explores the concept of shelf life, focusing on various factors that affect product quality and safety. It delves into the importance of formulation, processing, and environmental influences on the longevity of products. Test your knowledge on how different characteristics impact shelf life.
