Evaporation Front Compared with Crust Thickness in Potato Deep‐Fat Frying

Abstract

Understanding the role of parameters that determine crust formation is of paramount importance since crust characteristics such as thickness and texture dictate the sensory perception of fried foods. This study aims to quantify the relationship between such parameters (that is, crust evolution and the propagation of the evaporation front inside the food) and to examine how frying conditions (oil temperature and frying duration) affect it. In addition, the present findings may be of particular value to deterministic modeling efforts on the coupled heat and mass transfer phenomena during deep-fat frying.

Effect of Potato Orientation on Evaporation Front Propagation and Crust Thickness Evolution during Deep‐Fat Frying

“…Figure 5 presents the estimated propagation of the evaporation front, δ ef , compared with time, for all the examined T in for θ= 0 o , 90 o , and 180 o . The evaporation front propagation data for θ= 0 o (Figure 5a) were first presented by Lioumbas and Karapantsios (2012) who estimated δ ef from knowledge of the exact location of the measuring thermocouples inside a potato. The evaporation front is designated as the location inside the potato where the temperature is 100 ± 0.5 °C.…”

“…Despite the fact that the illumination conditions during shooting and the image analysis procedure are identical, the crust exhibits darker colors, and so can be easier distinguished from the core, as T oil and frying duration increase. This is attributed to the formation of a more compact crust, which makes it difficult for light to pass through (Lioumbas and Karapantsios 2012). In this context, the lighter colored crust noticed for θ= 180 o , compared to those for θ= 0 o and 90 o , indicates also a less compact crust.…”

“…The thickness of the crust is determined by 2 individual methods (accurate down to ± 0.01 mm): (a) by image analysis of microphotographs and (b) by a digital electronic micrometer (SYLVAC). Details concerning the procedure followed for the crust thickness determination can be found elsewhere (Lioumbas and Karapantsios 2012). Crust is defined (for example, Ziaiifar and others 2010) as the top completely dry layer of a fried potato which exhibits different texture (color, rigidity, and coarseness) and structure (porosity and pore size) from the rest of the potato flesh (core).…”

“…The experimental setup and procedures are similar to those employed by Lioumbas and Karapantsios (2012). Only some basic features are presented here.…”

“…Recently, Lioumbas and Karapantsios (2012) constructed a special device in order to examine the relationship between crust thickness evolution and evaporation front propagation during deep-fat frying of single potato sticks having only their top surface exposed to hot oil. These authors combined temperature recordings at different locations inside the developing crust with independent crust thickness measurements.…”