Study on Enhanced Temperature Control and Quality Preservation in Food Cold Chains Utilizing Phase Change Materials = 식품 콜드체인 온도 제어 및 신선도 유지 향상을 위한 상변화물질 활용 연구

다국어 초록 (Multilingual Abstract)

The increasing demand for fresh food has highlighted the importance of cold chain systems. To overcome the limitations of traditional expanded polystyrene (EPS) box and coolant packaging and improve the quality of perishable products, there is a growing need for packaging solutions such as optimized packaging methods and novel phase change materials (PCMs). The conventional method often results in suboptimal temperature control due to the varying thermal properties of different foods. This study aimed to mitigate this problem using phase change materials as coolants to provide a stable temperature environment. To establish optimal cooling conditions, experiments were conducted using tofu. Tofu, characterized by its uniform dimensions and high specific heat and density, was selected as a model food for its suitability in monitoring temperature fluctuations. A portion of samples exhibited temperature stabilization above 10°C, despite the inclusion of ice packs. A new PCM with a stable phase change range between -4°C and -2°C was developed to address this limitation. The developed PCM extended the refrigeration temperature maintenance time by 35.59% and maintained an average temperature of 1.47°C lower than conventional ice packs during the refrigeration period. The results suggest that PCMs can be effectively employed to prevent quality degradation caused by improper temperature management and to establish efficient food distribution systems.

국문 초록 (Abstract)

최근 신선 식품의 수요 증가와 함께 콜드체인 시스템의 중요성이 더욱 부각되는 가운데, 기존 EPS 박스와 보냉재를 이용한 포장 방식의 한계를 극복하기 위하여 포장방법 최적화 및 새로운 상변화 물질 개발이 요구된다. 기존 방식은 식품의 종류에 따른 열 특성 차이로 인해 온도 유지 성능이 크게 달라져 식품의 품질 저하를 야기할 수 있다는 문제점을 가지고 있다. 이에 본 연구에서는 보냉재로서 새로운 상변화 물질(PCM)을 제시하여 안정적인 온도 유지를 통해 신선 식품의 품질 저하를 최소화하고자 하였다. 두부를 활용한 실험을 통해 최적의 보냉 조건을 확립하고, 이를 바탕으로 -4~-2℃에서 안정적으로 상변화하는 PCM을 개발하였다. 개발된 PCM은 기존 아이스팩 대비 냉장 온도 유지 시간이 35.59% 연장하였으며, 냉장시간 동안 두부 온도를 평균 1.47℃ 더 낮게 유지하여 우수한 냉장 성능을 보였다. 본 연구는 식품 콜드체인에 PCM을 활용하여 신선식품의 품질 감소 및 효율적인 식품 유통 시스템 구축에 기여할 것으로 기대된다.

목차 (Table of Contents)

• (Abstract) １
• Ⅰ. Introduction ３
• Ⅱ. Part 1: Investigation of Packaging Refrigeration Performance and Changes in Tofu Quality by Amount of Food and Ice-Water Phase Change Materials ６
• 1. Introduction ６
• 2. Materials and Methods １０
• 2.1. Methods １０
• 2.1.1. Quality characteristics evaluation for storage conditions １０
• 2.1.2. Measurement of changes in appearance and color １１
• 2.1.3. Measurement of textural properties １１
• 2.1.4. Turbidity measurement １２
• 2.1.5. pH measurement １２
• 2.1.6. Total aerobic bacteria counts (TAC) １２
• 2.2. Evaluation of cold storage application performance １２
• 2.2.1. Cooling time １３
• 2.2.2. Temperature inhomogeneity coefficient １３
• 2.2.3. Thermal behavior of cooling tofu １６
• 2.3. Statistical analysis １８
• 3. Results and discussion １８
• 3.1. Temperature variation in tofu and inside the container １８
• 3.2. Changes in quality characteristics ２０
• 3.2.1. Appearance and color ２０
• 3.2.2. Texture ２３
• 3.2.3. Turbidity ２５
• 3.2.4. pH ２６
• 3.2.5. Total aerobic bacteria counts (TAC) ２７
• 3.2.6. Correlations among quality characteristics ２９
• 3.3. Evaluation of cold storage application performance ３１
• 3.3.1. Effect of load weight on cold storage performance ３１
• 3.3.2. Changes in Turbidity ３５
• 3.3.3. Changes in pH ３７
• 3.3.4. Changes in total aerobic bacteria counts (TAC) ３９
• 4. Conclusion ４１
• Ⅲ. Part 2: Investigation of Eutectic Phase Change Materials for Temperature Stabilization in Refrigerated Food Logistics ４２
• 1. Introduction ４２
• 2. Materials and Methods ４６
• 2.1. Materials ４６
• 2.2. Methods ４７
• 2.2.1. Preparation of PCM ４７
• 2.2.1.1. Preparation of base solution PCM ４７
• 2.2.1.2. Preparation of base solution PCM with nucleating agents ４７
• 2.2.2. Characterization ４８
• 2.2.2.1. Measurement of cooling and heating temperature change ４８
• 2.2.2.2. Measurement of DSC ４８
• 2.2.2.3. Measurement of thermal conductivity ５１
• 2.2.2.4. Cycle stability ５１
• 2.2.3. Evaluation of cold storage application performance ５１
• 2.2.3.1. Cooling time ５２
• 2.2.3.2. Temperature inhomogeneity coefficient ５２
• 3. Results and discussion ５３
• 3.1. Screening of main energy storage agent ５３
• 3.1.1. Cooling and heating temperature variations by substance and ratio ５３
• 3.1.2. Static stability ５９
• 3.1.3. Thermophysical characterization of base PCMs ５９
• 3.2. Influence of adding nucleating agents ６４
• 3.2.1. Reduction of supercooling ６４
• 3.2.2. Change in thermal characterization ６６
• 3.3. Cycle stability ６９
• 3.4. Application of PCM in cold chain ７２
• 4. Conclusion ７５
• Ⅳ. References ７６
• Abstract (in Korean) ８３