INGENIEUR
INGENIEUR
and increased metabolic activity . Thermal imaging allows for the assessment of produce without causing further damage . This is crucial for maintaining the integrity and value of the produce throughout the supply chain . In addition , thermal imaging systems can quickly scan and analyse the produce in real-time , enabling the immediate identification and sorting of damaged items . Unlike visual inspections , thermal imaging provides objective , quantifiable data on the extent and location of physical damage , reducing reliance on subjective judgment .
Bruising is a common type of physical damage in fruits and vegetables , often resulting from impact during handling and transportation . Bruised areas typically exhibit different thermal properties compared to undamaged tissue . Thermal imaging can detect these differences , as bruised tissues often have altered metabolic activities leading to localised temperature variations . Thermal imaging can effectively identify surface defects such as cuts , abrasions , and punctures . These defects can disrupt the normal temperature distribution on the produce surface . By capturing high-resolution thermal images , it is possible to identify and quantify the extent of surface damage . This is particularly useful for quality control processes in packing houses and during transportation . Internal damage such as fractures or voids can significantly affect the quality of produce . Traditional inspection methods might miss such defects as they are often not visible externally . Thermal imaging , however , can detect internal damage based on the heat transfer properties of the agricultural produce . Damaged areas often exhibit different thermal conductivity and capacity , resulting in distinct thermal patterns that can be identified and analysed .
Thermal imaging has been successfully applied in various studies and industries to detect physical damage in a wide range of fruits and vegetables . The bruised areas on apples exhibit distinct thermal signatures due to changes in tissue properties and metabolic responses that are not visible to the naked eye ( see Figure 3 ). Citrus fruits such as oranges and lemons can suffer from handling damage that leads to internal bruising . Thermal imaging can detect these bruises early , allowing for better sorting and reducing spoilage during storage and transport . Thermal imaging
Figure 3 : The apple images using cold excitation thermal imaging ; ( A ) Thermal images ; ( B ) Thermal images after histogram equalisation ; and ( C ) The labelling for apple (‘ a ′) and bruises (‘ b ′). Courtesy : Lin et al . ( 2023 ).
has also been used to identify impact damage in potatoes that contribute to bruising and soft spots . This technology can help ensure that highquality potatoes are sent to market , improving consumer satisfaction .
The future of thermal imaging in assessing physical damage lies in the development of more sophisticated , user-friendly systems that can be seamlessly integrated into automated sorting and grading lines . Advances in image processing techniques and chemometrics can enhance the accuracy and speed of thermal image analysis , making it easier to identify and quantify physical damage . The ability of thermal imaging to provide rapid , real-time , and objective data makes it a valuable addition to traditional quality control methods . As technology advances and becomes more accessible , thermal imaging is poised to play a crucial role in ensuring the quality and longevity of produce , ultimately reducing postharvest losses and enhancing consumer satisfaction .
Challenges and Limitations
Thermal imaging has emerged as a promising technology for enhancing postharvest handling of agricultural produce . However , despite its
12 VOL 99 JULY - SEPTEMBER 2024