The Effects of a Gum-Based Edible Coating on Apple Slices Characteristics During Infrared Heating

Document Type : Research Paper


1 Associate Professor, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran.

2 MSc Student, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran



Edible coatings used for food products before drying is a procedure that can certainly enhance the appearance and sensorial properties of dried food products. In this research study, it is aimed to determine the influences of some edible coatings, namely basil seeds gum and xanthan gum, on the colour and surface shrinkage of apple slices throughout drying time by infrared dryer. The colour parameters include a* (redness: green to red), b* (yellowness: blue to yellow), L* (lightness), and ∆E (total colour difference) were used to calculate colour changes during infrared heating. L* index values of untreated and treated apple slices with xanthan and basil seeds gums decreased from 85.90 to 38.19, from 81.38 to 46.76, and from 83.00 to 66.13, during infrared heating, respectively, however the ratio of the lightness index changes was lower for the treated samples. The redness of dried untreated and treated apple slices increased during the initial period of drying. The results illustrated that radiation power has a considerable effect on the colour parameters (P-value<0.05). As the radiation intensity increased from 150W to 250W, the lightness of apple slices reduced from 65.11 to 61.11. The lowest colour change value (19.06) was for the apple slices treated by basil seeds gum. Power equation, quadratic equation and sigmoidal equations (Gompertz, Logistic, Richards, Morgan-Mercer-Flodin (MMF) and Weibull) were used to fit the experimental drying data and the results illustrated that the MMF equation was the best equation to explain the colour change of untreated and treated apple slices (r>0.986). The lowest surface shrinkage change value was for the apple samples treated by basil seeds gum and dried in 375W (47.47%).


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