Design and development of a portable aluminium insulated box for transportation of fresh fish

Introduction

In fish industry, high perishability rate of the raw material is recorded immediately after the harvesting of fishes. The waste of fish due to improper handling leads to income loss for fisherman, fish traders and contribute to food insecurity. In order to reduce these losses, using chilling method to extend the fish storage time on both onboard and at the shore (Atanda et al. 2022) [4] . The traditional containers such as bamboo basket and wooden boxes are used to transport the fresh fish from the landing centers to distant market (Rao et al. 1981) [16] . But those traditional materials are having some demerits such as less mechanical strength, less shelf life, difficult to keep clean and sanitized. The plastic insulated boxes can lead for accumulation of micro plastic on fish body (Shawyer and Pizzali, FAO. 2003) [19] . Ice is used to transport the harvested fish from the landing centers to market or processing units because ice is used as a chilling substance to keep the fish at low temperature to reduce the fish spoilage (Margeirsson et al. 2017) [11] . The insulated box widely used from the smallscale application to large scale applications such as events, and cold chain logistics. Different type of insulated boxes used to keep perishable foods or drink at low temperature. The conventional cool box is made from aluminium, can maintain the low temperature for 24 hours, this can be achieved by providing better insulation (Khairulmaini et al. 2020) [9] . The insulating material should be durable and waterproof. A good insulator will maintain the internal temperature of the box for a long time. Polyurethane foam is the cost-effective insulating material; it has low thermal conductivity and good mechanical properties (Atanda et al. 2022) [4] .

Materials and methods

Experimental design

The aluminium ice box was designed with locally available aluminium sheet and polyurethane foam. The inner and outer box was made by using an aluminium sheet with a thickness of 0.05cm. The dimension for inner box was 22cm(H)×22cm(W)×22cm(L) and for outer box was 25cm(H)×25cm(W)×25cm(L). The inner box was placed inside the outer box, and the insulating material polyurethane foam was fitted in between the boxes. The handle was fitted on the top of the box for handling and transportation.

Sample Preparation

Fresh Indian mackerel (Rastrelliger Kanagurta) fish of average total length and weight were 16.17 ± 0.25 cm and 70.14 ± 2.07 g, respectively was procured from Mirkarwada Landing Center, Ratnagiri. The fish was segregated, washed in fresh water and transferred to aluminium insulated box. Crushed ice and fish were used in the ratio of 1:1 (ice: fish). The aluminium insulated box was kept in the laboratory for 7 days of storage study. The ice was replenished once in 24 h after draining the melted water. The sample was drawn on each day of storage study for analysis. The sample was randomly dissected by hand to get their muscle and was subjected for biochemical, microbiological and sensory studies.

Performance test Temperature

The temperature was measured by using glass thermometer twice in a day. The thermometer was inserted inside the box and left for 2 minutes until a stable reading is obtained (Khairulmaini et al. 2020) [9] .

Heat transfer rate

Heat transfer rate per day was determined by measuring the surrounding and inside box temperature. Following formulae used to calculate the heat transfer rate of box (Shah and Dake. 2016) [18] .

𝑞𝑞 = 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝐿𝐿 ∕ 𝑘𝑘

Where, q = heat transfer rate in W/m/k A = height × length 𝐴𝐴T = temperature difference = surrounding temperatureinside temperature L= thickness of the insulating material K= thermal conductivity of material

Specific ice melting rate

The ice melting rate was estimated by the method described by (Nowsad et al. 2013) [14] . The crushed ice was completely filled inside the boxes. Before filling, the weight of the ice was taken. Melted water has been drained out at 24 h interval. The specific ice melting rate was calculated by the following formula: k = Amount of melted ice (l) Total amount of ice used (g) × 100

No-load test

The box was filled with 2 kg of crushed ice and placed the box in processing unit. How much hours required to complete melting of ice in which amount of ice was present after 24 hours of sampling was analyzed (Atanda et al.

Density

The Polyurethane foam (PUF) was cut into rectangular block. The weight of the block in air and water was Measured (Khairulmaini et al. 2020) [9] . The density of PUF was calculated by the following formula:

Where, 𝜌𝜌 𝑟𝑟 = density of foam in g/ 𝑐𝑐𝑐𝑐 3 𝑤𝑤 𝑎𝑎 = weight of the foam in air in g 𝑤𝑤 𝑤𝑤 = weight of the foam in water in g 𝜌𝜌 𝑤𝑤 = density of water in g/ 𝑐𝑐𝑐𝑐 3

Porosity

Porosity of the polyurethane foam (PUF) calculated by using bulk density and true density of PUF (Khairulmaini et al. 2020) [9] . The following formula used to calculate the porosity of PUF.

Where, 𝜀𝜀 = porosity of foam in % 𝜌𝜌𝜌𝜌 = bulk density of the foam in air in g/ 𝑐𝑐𝑐𝑐 3 𝜌𝜌 𝑟𝑟 = density of foam in g/ 𝑐𝑐𝑐𝑐 3

Quality evaluation of iced Indian mackerel Sensory evaluation

Sensory evaluation of the iced fish was carried out by a panel of 10 panellists by assessing attributes such as appearances, colour, odour and over all acceptability using "1 to 9" point hedonic scale. High score indicated the good quality. The individual scores from panellists were pooled and the average scores for each attribute were calculated (Chudasama et al. 2018) [5] .

Biochemical analysis Peroxide value (PV)

The peroxide value was expressed as milli equivalent of 𝐨𝐨 𝟐𝟐 / kg of fat. About 10 g of sample was macerated with 15 g of anhydrous sodium sulphate in a motor and pestle for the purpose of dehydration. After maceration, sample was extracted by using 30 ml of chloroform by standard method as per the method of AOAC (2005) [3] . Peroxide value as milli equivalent of O2 / Kg of fat was determined using formula:

Where, TV = Volume in ml of N/100 sodium thiosulphate used for titration N = Normality of sodium thiosulphate W = Weight of fat

Total Volatile Base Nitrogen (TVB-N)

A 10 g portion of the iced fish was homogenized with 20 ml of 20% trichloroacetic acid (TCA). The mixture was then filtered through Whatman No. 1 filter paper into a 50 ml volumetric flask. The extraction process was repeated and the filtrate was diluted to 50 ml with TCA. For analysis, 1 ml of N/70 sulfuric acid (H2SO4) and a drop of Tashiro's indicators were placed into the chamber of a Conway microdiffusion unit. In the outer chamber, 1 ml of the TCA extract was added and the unit was covered with a greased glass lid, leaving a small gap to introduce potassium carbonated (K2CO3). Then 1 ml of K2CO3 was gently added to the outer chamber and the unit was sealed completely. The setup was left at room temperature overnight. After incubation, the contents of the inner chamber were titrated against N/70 sodium hydroxide (NaOH) using a microburette until a color change was observed. A blank titration was carried out simultaneously using 1 ml of 2% TCA solution (Chudasama et al. 2018) [5] .

TVB-N (mg/100gm) = The sample was then ground and homogenized using a sterile motor and pestle as per the standard procedure by AOAC (2005) [3] .

Sterilization

Glasswares used for microbiological quality was sterilized as per the standard method of AOAC (2005) [3] .

Estimation of total plate count (TPC):

Serial dilution of the homogenate was prepared using physiological saline and 1 ml from each dilution was inoculated into sterile petri dishes containing Plate Count Agar (PCA) using the pour plate technique. The plates were incubated at 37 °𝐶𝐶 for 48 hours. After incubation, colonies that developed on the agar surface were counted. Only the plates yielding colony counts within the acceptable range of 30 to 300 were considered for analysis following the guidelines outlined by USFDA (2022). Total plate count (cfu/g) = Average counts of colonies × Dilution factor

Statistical analysis

All collected data were statistically analyzed using statistical tool available in SPSS version 27 (Amitha et al. 2019) [2] . The analysis was carried out in triplicate (n=3). Analysis of variance (One way -ANOVA) was performed to compare the storage days of aluminium insulated box during storage study. Significance of differences was defined at p<0.05.

Results

Quality evaluation of iced Indian mackerel:

The quality parameters of the iced Indian mackerel such as sensory evaluation, biochemical analysis (PV, TVB-N) and microbial quality characteristics are shown in Table 3 and4. Values are presented as mean ± standard deviation (n=10). Statistical analysis was performed using one-way ANOVA followed by Turkey's HSD post hoc test to determine significant difference among the storage days. Means with different superscript letters within the same row indicate significant difference (p<0.05), while means sharing common superscripts are not significantly different. Sensory evaluation was conducted using a 9-point hedonic scale (9=like extremely; 1 = dislike extremely) Polyurethane foam is recognized for its exceptionally low thermal conductivity, typically ranging from 0.020 to 0.023 W/m•K, which is significantly lower than other conventional insulating materials (Manik et al., 2024; Shah and Dake, 2016) [10,18] . The incorporation of aluminium sheets as the inner and outer casing provides an additional thermal barrier. The aluminium surface acts as a radiant barrier, reflecting thermal radiation and reducing heat ingress. Similarly demonstrated that adding an aluminium foil radiant barrier to an insulated package improved its thermal performance by 46%, confirming the effectiveness of combining conductive insulation with a reflective surface (Wang et al., 2020) [22] . Similarly reported that an aluminium foil composite prototype achieved superior thermal resistance compared to conventional EPS foam boxes, further validating the design approach employed in the present study (Mwenya et al., 2024) [12] . The ice retention performance observed in the no-load test (4.14 ± 0.03 days) is consistent with findings by (Atanda et al., 2022) [4] , who reported that PUF insulated box-maintained ice for approximately 3 days at ambient temperature. The slightly longer ice retention observed in the present study may be attributed to the reflective properties of the aluminium casing, which reduces radiative heat gain. The density of the polyurethane foam used in the present study is 1.0289 g/cm³ and its porosity is 30.03%. Similarly reported that lower porosity in PUF foam contributes to a reduced heat transfer rate and enhanced thermal insulation performance (Khairulmaini et al., 2020) [9] .

Quality evaluation of iced Indian mackerel Sensory evaluation

The sensory quality of Indian mackerel stored in the aluminium insulated box was evaluated using a nine-point hedonic scale, where scores of 5 or above indicate acceptable quality for human consumption. The fish maintained acceptable sensory scores for all attributes (appearance, colour, odour, and overall acceptability) up to Day 6, with overall acceptability declining gradually from 9.46 ± 0.05 on Day 0 to 5.13 ± 0.08 on Day 6, and falling below the acceptability limit only on Day 7. This corresponds to a sensory shelf life of 7 days for fish stored under the experimental conditions. Similarly, the study of quality changes in physiochemical and sensory characteristics of iced fish reported that the sensory quality of Indian mackerel using the same nine-point hedonic scale and that fish stored under iced conditions maintained acceptable quality for up to 5 days (Chudasama et al., 2018) [5] . The extended shelf life observed in the present study (7 days) demonstrates the superior insulation provided by the aluminium PUF insulated box. The nine-point hedonic scale is a well-validated sensory evaluation tool in fish processing research, where scores of 5 or above indicate acceptable quality for human consumption (Nowsad, 2007) [13] .

Peroxide Value (PV)

The peroxide value, a key indicator of primary lipid oxidation, was monitored throughout the 7-day storage period. The aluminium insulated box effectively retarded the accumulation of primary oxidation products, with the PV increasing from an initial value of [21] . This slow progression of lipid oxidation is directly attributable to the stable lowtemperature environment maintained by the aluminium insulated box. Similar result was found in lower storage temperature directly controls spoilage in Indian mackerel, with fish at 4 °C showing significantly slower quality deterioration compared to those at higher temperatures (Humaid and Jamal, 2014) [7] .

Total Volatile Base-Nitrogen TVB-N is a widely used biochemical indicator of protein degradation in fish, reflecting the accumulation of volatile nitrogenous compounds produced by microbial activity and endogenous enzymes. In the present study, the aluminium insulated box was highly effective at retarding protein degradation, with the TVB-N value increasing from 6.36 ± 0.11 mg/100g on Day 0 to only 23.90 ± 0.36 mg/100g by Day 7, remaining well below the European Union regulatory limit of 35 mg/100g for fishery products. The TVB-N value observed on Day 7 in the present research of 23.90 mg/100g confirms that the fish remained well within acceptable limits even at the end of the storage period. Similarly, that chilled mackerel reached a TVB-N content of 37.34-37.57 mg N/100g precisely on the day the fish were rejected by a sensory panel (Day 7), thereby establishing 35 mg/100g as the spoilage limit for this species (Panguila et al., 2018) [15] . The iced marine fish species and reported that TVB-N values increased progressively with storage time, with fish reaching the rejection limit by Day 3 of storage (Al-Najada, 2019) [1] . The prolonged shelf life observed in the present study the fish remained well below the rejection limit on Day 7, demonstrates the superior temperature control achieved by the aluminium insulated box.

Total Plate Count (TPC)

Total Plate Count is the most widely used microbiological index for assessing the overall spoilage status of fresh fish.

According to the (ICMSF, 1986), plate counts below 5.5 × 10⁵ CFU/g are considered good quality, while counts at or above 10⁷ CFU/g are considered unacceptable. In the present study, the initial TPC of Indian mackerel was recorded as (2.77 ± 0.25) × 10² CFU/g on Day 0, similar result found in the initial TPC values of 10²-10³ CFU/g for freshly caught Indian mackerel procured directly from landing centres (Gopalakrishnan et al., 2016) [] . In the aluminium insulated box, the TPC increased progressively from (1.20 ± 0.10) × 10³ CFU/g on Day 1 to (9.43 ± 0.35) × 10⁴ CFU/g on Day 7, remaining below the ICMSF rejection limit throughout the entire 7-day storage period. This slow increase in bacterial population is a direct consequence of the stable, low-temperature environment maintained by the aluminium insulated box, which effectively suppressed the growth of spoilage microorganisms.

Conclusion:

In the present research after analysis of results and its comparison with the existing published literature, the aluminium insulated box with polyurethane foam insulation demonstrated significant potential to reduce post-harvest losses in tropical fisheries by extending fish shelf life by 2-3 times compared to conventional plastic boxes. The aluminium insulated box effectively retarded heat transfer, lipid oxidation, and microbial growth, extending the sensory shelf life 7 days. The study recommends that the aluminium insulated box should be promoted among small-scale fishers and fish traders as an affordable and effective cold chain solution. The results of this study provide a base for the future studies focusing on optimization of PUF-aluminium composite insulation, evaluation of long-term structural durability under repeated use, and field-scale validation of the aluminium insulated box in real-world fisheries supply chains, particularly under varying climatic conditions and handling practices.

Acknowledgement

AcknowledgementsThe author also extends their deep sense of gratitude to the Professor, Department of Fisheries Engineering, College of Fisheries, Ratnagiri, for their valuable guidance and Professor and Head, Department of Fish Processing Technology and Microbiology, College of Fisheries, Ratnagiri, for providing the necessary laboratory facilities to carry out this work. The first author wishes to express her heartfelt thanks to the Associate Dean and Major Advisors, College of Fisheries, Ratnagiri, for their constant support, encouragement throughout the course of the study.

References

1. Al-Najada AR. Assessment of total volatile basic nitrogen (TVB-N) and microbial contents of iced marine fish species. Int J Trend Sci Res Dev. 2019;4(1):29672.
2. Amitha CV, Raju JP, Lakshmisha IP. Evaluating specific ice melting rate (K) of indigenously developed fish vending and display unit and quality assessment of iced Indian mackerel (Rastrelliger kanagurta, Cuvier, 1816) stored in the unit. Life Sci Leafl. 2019;110:24-40.
3. AOAC. Official methods of analysis of the Association of Official Analytical Chemists International. 18th ed. Horwitz W, editor. Washington (DC): Association of Official Analytical Chemists; 2005.
4. Atanda SA, Anifowoshe AO, Oladeinde MO, Olumoh QA, Udefi IO, Pessu PO. Modification, fabrication and performance evaluation of insulated box for postharvest handling of fish. Arid Zone J Eng Technol Environ. 2022;18(4):741-50.
5. Chudasama BG, Dave TH, Bhola DV. Comparative study of quality changes in physicochemical and sensory characteristics of iced and refrigerated chilled stored Indian mackerel (Rastrelliger kanagurta). J Entomol Zool Stud. 2018;6(4):533-7.
6. Gopalakrishnan S, Sasidharan V, Sunder J, Mudavath M, Kumar RR. Effect of storage temperature on sensory and microbial quality of Rastrelliger kanagurta (Cuvier, 1816) from Andaman Coast. Adv Anim Vet Sci. 2016;4(9):468-75.
7. Humaid SA, Jamal MT. Effect of storage temperature on histamine formation and bacterial growth in whole three fish species (Rastrelliger kanagurta, Sardinella gibbosa and Lethrinus lenijan). Life Sci J. 2014;11(9):927-37.
8. International Commission on Microbiological Specifications for Foods. Microorganisms in foods 2: Sampling for microbiological analysis: Principles and specific applications. 2nd ed. Toronto: University of Toronto Press; 1986.
9. Khairulmaini M, Michael Z, Shah MAM, Zakaria MS, Abdullah B, Rashid AA. Improvement of insulation material for cool box application. IOP Conf Ser Mater Sci Eng. 2020;834:012019.
10. Manik P, Tuswan T, Prabowo A. Thermal insulation properties of materials for fishing vessel coolboxes. Mater Test. 2024;66(3):433-41.
11. Margeirsson B, Poroarson G, Guojonsson AH. Transport of chilled and superchilled rainbow trout in insulated containers and expanded polystyrene boxes: Trial shipment from Westfjords, Iceland to Slupsk, Poland. Reykjavik: BMargeirsson ehf., Matís, Skaginn 3X; 2017.
12. Mwenya J, Saengrayap R, Arwatchananukul S, Aunsri N, Kamyod C, Jakkaew P, et al. Thermal insulation box design for maintaining cool temperature and the postharvest quality of okra. Sci Hortic. 2024;332:113230. doi:10.1016/j.scienta.2024.113230.
13. Nowsad AKMA. Participatory training of trainers: A new approach applied in fish processing. Bangladesh: Bangladesh Fisheries Research Forum; 2007.
14. Nowsad A, Islam M, Shikha F. Development of a lowcost icebox for preservation and transportation of iced fish. Prog Agric. 2013;19:119-27.
15. Panguila EA, de Sousa MI, Esteves E, Figueira AC. Evaluation of the freshness and shelf-life of fresh and chilled mackerel (Scomber spp.) and horse mackerel (Trachurus spp.) marketed in Luanda (Angola) and Faro (Portugal). In: Mortal A, Aníbal J, Monteiro J, Sequeira C, Semião J, da Silva MM, et al., editors. INCREaSE. Cham: Springer; 2018. p. 168-81. doi:10.1007/978-3-319-70272-8_12.
16. Rao CCP, Saheb DIK, Gupta SS, Unnithan GR, Chari ST, Srinivasan R, et al. Comparative study of traditional and improved containers for transportation of fresh fish. 1981.
17. Shah S, Dake P. High insulation thermal box. Int J Mech Eng Technol. 2016;7(6):459-73.
18. Shawyer M, Medina Pizzali AF. The use of ice on small fishing vessels. FAO Fish Tech Pap No. 436. Rome: Food and Agriculture Organization; 2003.
19. Silver Spring (MD): USFDA; 2022 [cited 2026 Jul 6]. Available from: https://www.fda.gov/food/laboratorymethods-food/bacteriological-analytical-manual-bam
20. Viji P, Binsi PK, Visnuvinayagam S, Ravishankar CN, Venkateshwarlu G, Gopal TKS. Modified icing system containing mint leaf and citrus peel extracts: Effects on quality changes and shelf life of Indian mackerel. Indian J Fish. 2016;63(2):93-101.
21. Wang K, Yang L, Kucharek M. Investigation of the effect of thermal insulation materials on packaging performance. Packag Technol Sci. 2020;33(6):227-36.