Rapid Inverse Method to Measure Thermal Diffusivity of Low‐Moisture Foods

• Published in: Journal of food science Vol. 82; no. 2; pp. 420 - 428
• Main Authors: Muramatsu, Yoshiki, Greiby, Ibrahim, Mishra, Dharmendra K., Dolan, Kirk D.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.02.2017
• Subjects: Algorithms; almonds; Arachis - chemistry; Arachis hypogaea; Butter; chocolate; Chocolate - analysis; corn meal; Devices; Diffusion; equipment design; Finite Element Analysis; finite‐difference method; Flour; Flour - analysis; Food; Food Analysis - methods; Food Handling - methods; Food processing; Food science; Foods; Fourier Analysis; Heat transfer; heat treatment; Hot Temperature; inverse problem; low‐moisture food; Mathematical models; Meals; methodology; Models, Theoretical; Moisture content; parameter estimation; peanut butter; prediction; Prunus dulcis; Prunus dulcis - chemistry; Temperature gradients; temperature profiles; Thermal diffusivity; Triticum - chemistry; Triticum aestivum; wheat flour; Zea mays - chemistry; finite-difference method; low-moisture food; inverse problem; parameter estimation; thermal diffusivity
• ISSN: 0022-1147; 1750-3841; 1750-3841
• DOI: 10.1111/1750-3841.13563

Thermal diffusivity is an important transport property needed in modeling and computations of transient heat transfer in basic food processing operations. In addition, the prediction of nutritional and microbial changes occurring in food during thermal processing requires knowledge of thermal diffusivity of foods. The objectives of this study were to develop a new nonisothermal and nonlinear determination method of thermal diffusivity and to measure the thermal diffusivity of low‐moisture foods using that new method. Thermal diffusivities of 5 kinds of low‐moisture foods (almond meal, corn meal, wheat flour, chocolate fudge, and peanut butter) were estimated using an inverse technique. Samples were canned and heated at the surface in a water bath at about 70 °C. The 1‐dimensional transient heat conduction problem for radial coordinates was solved with a finite‐difference model. The thermal diffusivity of each of the 5 samples was determined by the ordinary least squares and sequential estimation methods, respectively. Predicted and observed temperature matched well, with maximum residuals of 0.9 °C. The thermal diffusivity values of the samples ranged from 9.8 × 10−8 to 1.3 × 10−7 m2/s. The advantages of this method are that the device and the estimation method are simple, inexpensive, rapid, and can handle large spatial temperature gradients, such as those experienced during heating of low‐moisture foods. The results obtained in this study will be useful in the design of equipment and in calculations for the thermal processing of low‐moisture foods. Practical Application This work proposes a new nonisothermal and nonlinear determination method of thermal diffusivity. The thermal diffusivities of 5 kinds of low‐moisture foods were estimated by using this new method and an inverse technique. Advantages of this method include being simple, accurate, inexpensive, rapid, and requiring no special equipment. The method may be widely used to measure the thermal diffusivity of foods.