Investigation of thermal Insulation box for preserving cold temperature and quality of Okra

Name: Mwenya, Jackson

keyword: Aluminium Foil

MeSH: Insulation (Heat) -- 307081

Classification :.DDC: e-Theses

; Browning

MeSH: Image analysis

MeSH: Transportation

MeSH: Aluminum

LCSH: Insulation (Heat) -- 307081

LCSH: Image analysis

LCSH: Transportation

LCSH: Aluminum

Abstract: Postharvest loss of okra is caused by its high respiration rate as well as temperature fluctuation throughout its supply chain due to inappropriate cold chain management. This causes significant water loss, discoloration and leads to a short shelf-life of okra. In Thailand, this work was the first to study thermal insulation box and phase change material (PCM) in cool chain management of okra under ambient temperature condition during simulated transportation. Firstly, characterization of material properties including thermal heat energy (Qx value), air permeability, water vapour transmission rate (WVTR), material thickness, and thermal conductivity were conducted. From the results, aluminum foil (ALF), Expanded polyethylene (EPE) and ALF composite materials exhibited the best performance in terms of high thermal conductivity, low thermal energy, low water vapour transmission rate as compared to expanded polystyrene (EPS) and corrugated fiberboard sheet (single wall). For thermal insulation box test, maximum insulation time (MIT) (h) and ice melt methods were conducted to determine thermal resistance. A composite prototype was designed as sandwich structure of ALF prototype with other materials in a middle layer. Five thermal insulation boxes were designed by combining different thermal insulation materials and layers including (1) foam box (FB) (positive control), (2) metalized foam sheet (MFS), (3) prototype A as a three layered composite of aluminum foil with expanded polyethylene (ALF+ EPE+ ALF), (4) prototype B as a four layered composite of ALF+ NW + EPE + ALF, and (5) regular slot container (RSC). For a box MIT test, Prototype A performed a greater MIT value (28.31 h) than FB (a positive control) (27.39 h), while Prototype B (27.25 h) exhibited comparable MIT value to that of FB (27.39 h) and RSC (negative control) exhibited the lowest MIT value (15.24 h). In the second experiment the efficiency of thermal insulation box on cool temperature preservation and postharvest quality of okra were investigated. Room cooling at 0°C for 2 h was applied in okra samples before packing in the box. The simulated transportation and shelf storage were conducted at 25°C for 24 h and at 12°C for 6 days, respectively. Performance of five thermal insulation boxes in maintaining cool temperature and okra quality during simulated transportation and shelf-storage had been investigated. Qualitative and quantitative including air and okra temperature levels, thermal image, carbon dioxide (CO2), oxygen (O2) levels, weight loss and color attributes via image analysis were conducted. From results prototype A exhibited lower air and okra temperature levels as well as a higher number of purple pixels of thermal image analysis than that of FB. No significant differences were observed in both air and okra temperature levels among the other three treatments. Both Prototypes A and B contained a higher CO2 level around 7% CO2 as compared to FB (3.36 % CO2). There was no significant difference in weight loss. In addition, there were no statistically significant in grayscale, total color difference, browning index and CIELAB among the five treatment boxes. In the third experiment, further investigations were conducted on nine treatments the selected best two prototypes (A and B) and the control FB, combined with either of the two types of PCMs (commercial gel pack: GP and ice water bottles: IB) or without PCM to improve cool temperature preservation and shelf-life of okra at 25°C for 48 h simulation transportation. The results showed that all three thermal insulation boxes with two types of PCM provided lower air and okra temperature levels as well as a higher purple color area than those of other three boxes without PCM treatments. All three FB treatments either with or without PCM exhibited the highest CO2 accumulation level around 15% CO2. The IB treatments caused a lower RH (%) level as compared to GP and without PCM. However, there was no significant difference in water loss (%) among nine treatments. Overall, nine treatments did not affect color attributes of okra in terms of CIELAB, gray scale, total color difference and browning index. Overall, from three experiments, Prototype A (ALF+EPE+ALF) is greatly recommended to apply for packed okra under simulated transportation with 5 supporting reasons; (1) high MIT value as indicating a long period of cool temperature, (2) less number of layers and package weight as compared to Prototype B (ALF+NW+EPE+ALF), (3) preserving cool air and okra temperature performance, 4) no high CO2 accumulation during both short and long journeys, (5) reducing water loss, and (6) less browning incidence after simulated transportation and shelf-storage for 6 days.

Mae Fah Luang University. Learning Resources and Educational Media Center

Address: CHIANG RAI

Email: library@mfu.ac.th

Name: Saowapa Chaiwong

Role: Advisor

Created: 2023

Modified: 2024-01-17

Issued: 2024-01-17

วิทยานิพนธ์/Thesis

application/pdf

CallNumber: e-Theses

eng

DegreeName: Master of Science

Level: Master's Degree

Descipline: Postharvest Technology and Innovation

Grantor: Mae Fah Luang University

©copyrights Mae Fah Luang University

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