The Indian researchers, publishing their findings in the Journal of Food Engineering, said their two-dimensional (2D) CFD model for bread baked without a crust will facilitate a better understanding of the process.
They stress that there is huge potential for an efficient method of quality crustless bread production within the bread manufacturing industry but they argue that the technology behind the process needs to be properly documented.
The authors said that the commercial varieties of crustless bread available in markets such as the US, Span and Italy are typically created by the baker cutting the crusts off after baking.
However, a crustless bread range that had been produced during the baking process was launched under the brand Hovis by UK food group Premier Foods in 2005, targeting mothers.
Bread waste
The authors cite a consumer research survey conducted by the US based Sara Lee Group that revealed that 35 per cent of mothers remove the crusts from their children’s sandwiches, which wastes up to 45 per cent of the actual loaf: “Crustless bread could lead to significantly lower wastage of loaves as well as better financial return for the bakers,” state the researchers.
During baking, crust develops at the upper surface of the dough as maximum evaporation takes place from that surface.
Crustless bread making process involves the dough surface being sprayed with water intermittently at controlled temperature so that it does not get too hot and no crust forms, they said.
As a result of the water spraying, the thermo-physical properties of the crustless variety are different from conventional bread types, along with the heat and mass transfer that takes place during the process.
Modelling
The authors explain that any attempt to modify or alter the baking process requires an understanding of the physico-chemical changes involved in the process, and experimental and mathematical modelling approaches are often used for this purpose.
As a result they developed a 2D CFD model of bread during baking to simulate this heat and mass transfer and to ascertain the actual baking time of this type of bread.
The model “determines the temperature rise over time in the bread as well as the moisture concentration in the bread, which is defined as the mass of water per volume of bread.”
The method
The authors explained that cylindrical moisture boxes made of aluminium were used as baking containers, with each one containing 30 gram of dough. After full proofing, the boxes were placed below the water nozzles in the crustless bread baking oven, which was preheated to 168°C. Baking was done for 7, 14, 21, 25, and 30 minutes respectively.
They added that 2 ml water was sprayed on the dough at 8.60 minutes intervals, with three thermocouples placed at the top, centre, and bottom of the dough. The temperature corresponding to respective time of each thermocouple was noted by a temperature indicator.
After seven minutes, one loaf was removed from the oven for moisture concentration analysis and the oven door was immediately closed. The box was covered immediately to avoid moisture loss. Moisture content of crustless bread was determined by a digital infrared moisture analyzer, said the researchers.
Approximately one gram of bread sample from central portion of bread was dispersed uniformly on the plate and evaporation of moisture was carried out by setting the temperature of the infrared drying chamber of the instrument at 105°C, they continued.
Moisture content of the bread was displayed as percentage moisture in wet basis. Volume and total weight of the crustless bread were also measured at 0, 7, 14, 21, 25, and 30 min of baking time.
Results
The researchers noted that the moisture removal rate is higher during the first seven minutes of baking when surface temperature increases sharply.
They said that as time progresses, moisture removal rate becomes lower with a decrease in surface temperature deviation and also due to the incremental moisture replacement on the surface to prevent crust development:
“Surface moisture concentration decreased from 218.26 to 181.06 kg/m3 after seven minutes of baking .... After 14 and 21 minutes of baking surface moisture decreases to 165.07 and 156.05 kg/m3. At the end of baking surface moisture remains at 146.64 kg/m3.”
The researchers stated that at the end of the bread baking process the centre temperature of the bread increases to around 95°C, while that of top and bottom surfaces increases to between 102°C and 112°C.
The authors concluded that their CFD model is able to predict the pattern of temperature and moisture profile during the crustless bread baking process and could be used to optimise baking oven conditions or the efficiency of the process to obtain a better quality product.
Source: Journal of Food Engineering
Published online ahead of print: doi:10.1016/j.jfoodeng.2010.02.015
Title: Two-dimensional CFD modeling and simulation of crustless bread baking process
Authors: Arpita Mondal 1, A.K. Datta *