Challenges Associated with Cleaning Plastic Food Packaging for Reuse
Abstract
:1. Introduction
2. Literature Review
3. Materials and Methods
3.1. Selection of Pack Form
3.2. Fouling Types and Fouling Deposition Method
3.3. Simulated Reuse
3.4. Cleaning Parameters
- Wash duration: Containers fouled with 2.00 g (±0.05) of food sample were cleaned for various wash durations with the standard 10 s rinse in the warewasher. For this test, the detergent (Jantex Pro Glass Wash Detergent 0.25% caustic soda, Bristol, UK) dose was set to 3 mL/L on the warewasher (i.e., 0.075% actual caustic soda concentration).
- Detergent dose: To investigate the influence of the detergent dose, containers were fouled and washed for various durations with 0 mL/L, 3 mL/L, and 6 mL/L of detergent. Detergent was only dispensed during the wash stage. The machine was drained before changing the detergent dose and run multiple times before use to ensure the correct dose of detergent was delivered.
- Fouling quantity: For orange juice, the quantity of fouling was determined by fouling a container before inverting it. It was found that when fouled with 2.00 g (±0.05) of orange juice, there was little to no dripping, therefore this quantity represented a realistic quantity of food residue. The same quantity was considered as an appropriate maximum amount of fouling for cream cheese. As the initial investigation with mayonnaise represented 0 RLU for the ATP reading, this fouling type was not studied further unless stated otherwise.
3.5. Cleanliness Assessment Method
3.6. Deformation and Material Properties
3.7. Analysis of Physio-Chemical Properties
- Tensile Testing: Before testing, the rPET packs were cut into small dumbbell shaped samples and equilibrated at 25 °C and 50% relative humidity. Tensile strength at yield and Young’s Modulus of the pack samples were measured using an Instron® 3366 universal testing system according to the ISO 527-2 standard testing parameters at a tensile rate of 80 mm/min. Measurements were performed on 6 samples across the area of the packs and the average results were recorded.
- Differential Scanning Calorimetry (DSC): The thermal characterisation of the packs was performed using TA instruments® Q200 DSC, New Castle, DE, USA. Approximately 5 mg of sample was heated from room temperature to 300 °C at a rate of 10 °C/min. Thermal transition values were determined using TA® Universal Analysis software, New Castle, DE, USA. Measurements were performed on 3 samples across the area of the packs and the average results were recorded.
- Fourier Transform Infrared (FTIR) Spectroscopy: FTIR spectroscopy was performed directly on small cut sections on the packs using a Shimadzu® IRTracer-100, Milton Keynes, UK, equipped with an attenuated total reflectance (ATR) attachment. Data was collected in the region of 400 to 4000 cm−1.
4. Results and Discussion
4.1. Cleaning Assurance Assessment Using ATP Swab Test
4.1.1. Orange Juice
4.1.2. Mayonnaise
4.1.3. Cream Cheese
4.2. Impact of Washing Procedure on the Pack Form
4.2.1. Wash Duration
4.2.2. Detergent Dose
4.2.3. Fouling Quantity
4.3. Pack Form Appearance under Simulated Reuse
4.3.1. Physical Deformation
4.3.2. Mechanical Deformation
4.3.3. Thermal (DSC) and Chemical (IR) Degradation
5. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Appendix A
Summary of Tensile Testing Data | ||||
---|---|---|---|---|
Number of Washes | Tensile Strength (MPa) | Young’s Modulus (MPa) | Yield Stress (MPa) | Strain at Yield (%) |
0 | 44.8 ± 8.9 | 1717 ± 277 | 49.4 ± 5.4 | 3.67 ± 0.21 |
5 | 57.0 ± 10.6 | 1984 ± 266 | 51.9 ± 7.2 | 3.89 ± 0.09 |
15 | 56.7 ± 11.2 | 2035 ± 344 | 57.6 ± 1.0 | 3.97 ± 0.07 |
20 | 61.1 ± 9.6 | 2076 ± 268 | 61.2 ± 1.0 | 4.17 ± 0.07 |
25 | 61.0 ± 3.9 | 2181 ± 145 | 61.3 ± 0.6 | 3.97 ± 0.01 |
30 | 63.3 ± 10.0 | 2127 ± 228 | 60.5 ± 3.6 | 4.02 ± 0.08 |
Appendix B
Cream Cheese—2 g of Fouling—3 mL/L of Detergent on Machine | |||
Wash Time (s) | Rinse Time (s) | ATP Test Result (RLU) | Observations after Wash |
0 | 10 | 290 | Visible fouling |
211 | Visible fouling | ||
155 | Visible fouling | ||
10 | 10 | 167 | Visible fouling |
207 | Visible fouling | ||
189 | Visible fouling | ||
20 | 10 | 249 | Visible fouling |
73 | Visible fouling | ||
189 | Visible fouling | ||
30 | 10 | 72 | Visible fouling |
40 | 10 | 22 | Visible fouling |
50 | 10 | 14 | Visible fouling |
60 | 10 | 13 | Visible fouling |
70 | 10 | 9 | Visible fouling |
80 | 10 | 2 | Visible fouling |
90 | 10 | 5 | Visible fouling |
102 (Standard wash) | 10 | 4 | Visible fouling |
Cream Cheese—2 g of Fouling—0 mL/L of Detergent on Machine | |||
Wash Time (s) | Rinse Time (s) | ATP Test Result (RLU) | Observations after Wash |
20 | 10 | 66 | |
30 | 10 | 83 | Visible fouling |
40 | 10 | 57 | Visible fouling |
50 | 10 | 26 | Visible fouling |
60 | 10 | 15 | Visible fouling |
70 | 10 | 12 | Visible fouling |
80 | 10 | 14 | Visible fouling |
90 | 10 | 20 | Visible fouling |
102 (Standard wash) | 10 | 13 | Visible fouling |
Cream Cheese—2 g of Fouling—6 mL/L of Detergent on Machine | |||
Wash Time (s) | Rinse Time (s) | ATP Test Result (RLU) | Observations after Wash |
20 | 10 | 42 | Visible fouling |
30 | 10 | 83 | Visible fouling |
40 | 10 | 57 | Visible fouling |
50 | 10 | 26 | Visible fouling |
60 | 10 | 15 | Visible fouling |
70 | 10 | 12 | Visible fouling |
80 | 10 | 14 | Visible fouling |
90 | 10 | 20 | Visible fouling |
102 (Standard wash) | 10 | 13 | No noticeable fouling |
Cream Cheese—1 g of Fouling—3 mL/L of Detergent on Machine | |||
Wash Time (s) | Rinse Time (s) | ATP Test Result (RLU) | Observations after Wash |
20 | 10 | 63 | Visible fouling |
30 | 10 | 32 | Visible fouling |
40 | 10 | 20 | Visible fouling |
50 | 10 | 8 | Visible fouling |
60 | 10 | 4 | Visible fouling |
70 | 10 | 4 | No noticeable fouling |
80 | 10 | 5 | No noticeable fouling |
90 | 10 | 3 | Visible fouling |
102 (Standard wash) | 10 | 7 | No noticeable fouling |
Appendix C
DSC Data | 0 | 5 | 15 | 20 | 25 | 30 |
Tg (°C) (±standard deviation) | 66.4 (±0.5) | 66.3 (±0.8) | 70.4 (±0.9) | 70.0 (±0.2) | 70.2 (±0.1) | 69.8 (±0.1) |
Tc (°C) (±standard deviation) | 125.9 (±0.5) | 124.5 (±2.9) | 124.3 (±2.0) | 124.5 (±0.5) | 124.1 (±0.4) | 123.4 (±0.3) |
Tm (±standard deviation) (°C) | 247.7 (±0.2) | 249.3 (±2.2) | 248.1 (±0.8) | 247.7 (±0.2) | 247.8 (±0.2) | 247.7 (±0.1) |
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Wash Time (s) | Rinse Time (s) | ATP Test Result (RLU) | Average (RLU) |
---|---|---|---|
20 | 10 | 4 | 4 |
10 | 10 | 6 | 6 |
0 | 10 | 4 | 2.67 |
2 | |||
2 | |||
0 | 7 | 7 | 16.33 |
16 | |||
26 | |||
0 | 5 | 322 | 398.67 |
155 | |||
719 |
Number of Standard Washes | Total Wash and Rinse Time (m:s) | Images | ||
---|---|---|---|---|
Top View | Bottom View | Side View | ||
0 | - | |||
5 | 8:30 wash 0:50 rinse | |||
10 | 17:00 wash 1:40 rinse | |||
15 | 25:30 wash 2:30 rinse | |||
20 | 34:00 wash 3:20 rinse | |||
25 | 42:30 wash 4:10 rinse | |||
30 | 51:00 wash 5:00 rinse |
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Nahar, S.; Sian, M.; Larder, R.; Hatton, F.L.; Woolley, E. Challenges Associated with Cleaning Plastic Food Packaging for Reuse. Waste 2023, 1, 21-39. https://doi.org/10.3390/waste1010003
Nahar S, Sian M, Larder R, Hatton FL, Woolley E. Challenges Associated with Cleaning Plastic Food Packaging for Reuse. Waste. 2023; 1(1):21-39. https://doi.org/10.3390/waste1010003
Chicago/Turabian StyleNahar, Samsun, Mala Sian, Ryan Larder, Fiona L. Hatton, and Elliot Woolley. 2023. "Challenges Associated with Cleaning Plastic Food Packaging for Reuse" Waste 1, no. 1: 21-39. https://doi.org/10.3390/waste1010003