C-Therm Blog

TLS Application:Testing the Thermal Conductivity of Papayas in Determining Appropriate Freezing Time

Freezing is a widely used method of food preservation based on several advantages in terms of retention of food quality and ease of process.  The freezing time and freezing rate are the most important parameters in designing freezing systems.  The International Institute of Refrigeration (1986) defines various factors of freezing time in relation to both the product frozen and freezing equipment (Persson and Lohndal, 1993). The most important are:
·        Dimensions and shape of product, particularly thickness
·        Initial and final temperatures
·        Temperature of refrigerating medium
·        Surface heat transfer coefficient of product
·        Change in enthalpy
·        Thermal conductivity of product

 

Figure 1. Papaya fruit (Source: Prathyush Thomas) 

In this work – we summarize how to measure the thermal conductivity of papaya (Carica papaya) for such purposes.  The papaya fruit is a tropical fruit commonly cultivated in in India, Brazil, Indonesia, Nigeria, and Mexico. The C-Therm TCi Thermal Conductivity Analyzer configured with a Transient Line-Source (TLS) sensor to test the thermal conductivity of the fruit. 

Testing Results

 

                                 Figure 2. Thermal conductivity test results on papaya 

The sample was tested using the transient line-source method using a 15cm sensor and a 2.5 minute test time. The repeatability between different locations was 2.8%, suggesting there existed some regional variation in the thermal conductivity of the papaya. As fruits are complex solids composed water, carbohydrates, fatty acids, protein, minerals and vitamins, some degree of regional variation was to be expected.

Additional Resources:

Thermal conductivity and thermal diffusivity of papaya (Carica papaya L.) and cashew apple (Anacardium occidentale L.) Condutividade e difusividade térmica do mamão (Carica papaya L.) e do caju (Anacardium occidentale L.)

Freezing Point and Thermal Conductivity of Tropical Fruit Pulps: Mango and Papaya

Determination of thermal diffusivity in papaya pulp as a function of maturation stage

 

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