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Which material is best for storing fresh foods and vegetables - Coggle…
Which material is best for storing fresh foods and vegetables
How do we measure 'best'
Material strength and durability
Is the material transparent enough for consumers to inspect the produce condition without opening the package? (aesthetic appeal)
Does the material have high tensile strength and flexibility to prevent tearing or puncturing when handled or transported
A tear or puncture will destroy the protective barrier, causing rapid moisture loss (wilting), entry of foreign pathogens, and physical bruising of the vegetable/food during transport
Best way to check 'durability'
Conduct a drop test from a fixed height (e.g., 1 meter) with a standardized mass inside each bag, or measure the force required to puncture the polymer film using a force gauge/spring balance
Independent Variable: Type of packaging material (LDPE, HDPE, PLA, and Paper).
Dependent Variable: Puncture resistance force (measured in Newtons using a force gauge/spring balance) or structural integrity after a standardized drop test.
Benefits:
Directly addresses the real-world supermarket requirement that packaging must protect food from physical damage, tearing, and breaking during transport.
Limitations
Does not measure food freshness or moisture loss directly; it only evaluates physical durability.
Drop testing can produce subjective or variable tear patterns depending on the exact angle of impact
Which thickness of 'LDPE' works best
Aim: To investigate how varying thickness of a single polymer material (LDPE film at 20micrometeres 40micrometeres and 60micrometeres) affects its moisture barrier efficiency and overall suitability for food storage.
Independent Variable: Thickness of the LDPE packaging film (20micrometeres 40micrometeres and 60micrometeres).
Dependent Variable: Percentage mass loss (%) of enclosed uniform cucumber slices over a 5-day storage period at 4°C.
Controlled Variables:
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Limitations :
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Price
How expensive is it to produce the polymer?
standard LDPE/HDPE vs. plant-based PLA
Does government subsidies or taxes on single-use plastics affect the manufacturing and retail cost of biodegradable PLA versus traditional LDPE/HDPE?
Is the packaging affordable enough for supermarkets to use in large quantities for everyday transport?
Cost of sourcing the polymers
Enviromental Factors (recycling)
Can traditional soft plastics (LDPE and HDPE) be easily recycled?
Do plant-based plastics (PLA) or paper break down naturally, or do they require industrial composting facilities?
What is the environmental impact of producing versus disposing of each material type?
Biodegradable packaging vs traditional
Aim: To investigate how quickly different packaging polymers (biodegradable PLA vs. conventional LDPE and paper) break down under simulated industrial composting or soil conditions.
Independent Variable: Type of packaging material (LDPE film, biodegradable PLA film, and brown paper).
Dependent Variable: Percentage mass loss (%) and physical disintegration of the material over a 4-week burial test period.
Controlled Variables:
Soil composition and moisture: All samples buried in the same container using identical garden soil with controlled moisture content.
Temperature and environment: Kept at a constant warm temperature ( 30°C, 20°C and 25°C which is soil’s typical natural temp) to accelerate microbial activity.
Initial surface area: All polymer samples cut to identical dimensions (e.g., 5cm5cm).
Benefits:
Directly evaluates the environmental criteria of "best" storage by looking at polymer landfill/composting impacts.
Limitations
Soil bacteria and microbial activity can be slightly uneven across different burial spots even in the same container.
Requires a long testing period (weeks) which
Soil bacteria and microbial activity can be slightly uneven across different burial spots even in the same container.
Freshness of the of the fruit/vegetable (how long it stays fresh for)
What is the best way to check freshness?
Monitor visual indicators like color changes, texture softening, and surface mold growth?
Test over a 5 to 7-day period to track how quickly the vegetable degrades over time
does the packaging allow for carbon dioxide and oxygen gas exchange
Use a balance to measure daily percentage mass loss (water evaporation)
Mass Loss % = (Initial Mass - Final Mass) / Initial Mass x 100
Aim: To investigate how different packaging materials (LDPE, HDPE, PLA, Paper, and an unwrapped control) affect the rate of water loss (transpiration) in fresh cucumber slices over a 5-day storage period at 4°C
Independent Variable: Type of packaging material (LDPE film, HDPE film, biodegradable PLA, paper bag, and open-air control).
Dependent Variable: Percentage mass loss (%) of the cucumber slices over a 5-day period, calculated daily using an analytical balance.
Controlled Variables
Vegetable dimensions: All slices cut to the same 2.0cm thickness to ensure an identical surface-area-to-volume ratio across all trials.
Produce source: All slices cut from the same individual cucumber to guarantee identical initial moisture content and cellular structure.
Storage temperature: Maintained at a constant 4°C in the same refrigerator to keep transpiration rates steady.
Bag size and sealing method: All bags cut to identical dimensions and sealed using the exact same technique to standardise trapped air volume.
Benefits:
Using an analytical balance provides high-precision, continuous quantitative data rather than subjective visual estimates of freshness.
Directly measures water loss (transpiration), which is the primary driver of vegetable wilting and spoilage.Limitations:
Environmental exposure: Removing bags daily to weigh the slices exposes them briefly to room temperature and fluctuating room humidity, slightly altering evaporation rates.
Skin vs. flesh exposure: Variations in how much natural waxy skin is present on the outer edge of each slice can affect local evaporation rates if not strictly controlled.
Limitations:
Environmental exposure: Removing bags daily to weigh the slices exposes them briefly to room temperature and fluctuating room humidity, slightly altering evaporation rates.
Skin vs. flesh exposure: Variations in how much natural waxy skin is present on the outer edge of each slice can affect local evaporation rates if not strictly controlled.
What type of vegetable/food type is best suited for different investigatiosn
Which specific produce should be used for the lab test
Natural waxy cuticles provide a hydrophobic barrier that significantly slows down transpiration, whereas cut surfaces expose internal cell walls and accelerate water evaporation (national institute of health)
How does a natural skin/peel affect water loss compared to sliced vegetables
High-respiration produce (e.g., spinach, broccoli) rapidly consumes trapped oxygen and releases heat and carbon dioxide, creating condensation that speeds up bacterial decay. Low-respiration produce (e.g., carrots, apples) degrade much slower.
How fast the vegetable consumes oxygen and releases carbon dioxide and heat, which influences internal moisture buildup.
Cucumber or carrot slices (provides a uniform surface-area-to-volume ratio and consistent moisture loss)
What variables generally need to be controlled
Vegetable mass/weight/volume
MAking sure every slice is weighed to an exact starting mass (e.g., exactly 10.00 g) before sealing, rather than just relying on slice dimensions, so percentage mass loss can be accurately calculated from a uniform baseline.
Identically sized bags(/pacakging) for every test (to keep the volume of trapped air inside the packaging constant)
Using the exact same sealing technique for every bag (e.g., folding the top edge twice and securing with a standard length of tape) to prevent variable air gaps or leaks
Produce source (cut all slices from the exact same food/vegetable to ensure identical initial cellular structure and moisture content)
Environmental conditions and time (all at a constant temp and time)
Limiting and standardising the time each package is opened during daily measurements so that all the samples are exposed to the same room temperature and room humidity for the same duration.
Vegetable slice dimensions (keep thickness and surface area identical to ensure equal water loss rates)
What counts as 'fresh foods'
Raw produce that has not been cooked, frozen, or chemically preserved, meaning its tissue is still actively undergoing cellular respiration and transpiration
Grouping food into types (like leafy greens, juicy vegetables, and root veggies) because each one needs a different kind of plastic or packaging
Because fresh food is still "alive" and breathing, the packaging can't be totally sealed off. It needs to let the right amount of air and moisture pass through so the food doesn't rot.
Food that rapidly degrades due to natural enzymatic decay, moisture loss, and microbial growth (mold/bacteria) if environmental factors like temperature and humidity are not controlled
Possible materials to use/test
Low-Density Polyethylene (LDPE)
Standard flexible plastic film used for common grocery bags
High-Density Polyethylene (HDPE)
Firmer, rigid plastic used for sturdier bags or containers.
Biodegradable/Compostable Polymers (PLA)
Eco-friendly altenative
*Alternate materials as a control
*Paper bags or unwrapped (open air) controls.