Effects of a Ceramic Oven Coating on Baking Results

Research Article

Austin Food Sci. 2016; 1(1): 1002.

Effects of a Ceramic Oven Coating on Baking Results

Zettel V*, Hecker F and Hitzmann B

Department of Process Analytics and Cereal Science, University of Hohenheim, Germany

*Corresponding author: Zettel Viktoria, Department of Process Analytics and Cereal Science, Institute of Food Science and Biotechnology, University of Hohenheim, Germany

Received: January 22, 2016; Accepted: February 11, 2016; Published: February 15, 2016

Abstract

With the performed baking experiments it was investigated, if by coating internal surfaces of the oven chamber with an efficient ceramic will provide savings in energy costs or an improved product quality. The experiments were performed with bread rolls and rye-wheat-bread. All products were baked at same baking temperatures (conditions) in ovens with and without ceramic coating of internal surfaces of the oven chamber. The end of the baking process was determined based on the surface color by visual inspection. A significant reduction of baking time and a reduction of baking losses in the ceramiccoated oven chamber were determined. The volume yield was not significantly increased; presumably this is due to other parameters for the preparation of dough pieces, the final proof and baking. Since our own recipes and baking programs were used, the comparison with the data from the existing literature is not always given. The energy consumption could be reduced mostly through the baking time up to 36 %. The development of surface color of bread rolls differ from the 5th minute on. The color curve of baked bread rolls in the ceramiccoated oven chamber increased faster and, therefore, the final color was reached significantly earlier.

Keywords: Baking; Infrared radiation; Texture analysis; Retrogradation; Differential scanning calorimetry; Color

Introduction

During baking processes heat energy is transferred into baking products. This happens by conduction from the bottom of the oven, by convection through the air, condensation of steam and thermal radiation. Depending on the temperature of the emitter, principally heat radiation contains high amounts of infrared, visible and ultraviolet light [1-3]. At typical baking temperatures, the thermal radiation consists mainly of infrared radiation. It is in the wavelength range between 780 nm up to 1 mm. Since 2006 different baking ovens with a special ceramic coating of internal surfaces of the oven chamber are available on the market. It is a special ceramic coating that is said to increase the percentage of infrared heat during the baking process from 30 % to 90%. The special ceramic coating operates in the wavelength range between 3 μm and 6 μm. The coating is placed at the overhead wall of the oven. The inventing company wanted to create an infrared radiation, which is, depending on the application, adjusted to the absorption of water molecules and groups like -CH and -OH in baking goods. The maximum emission intensity of the ceramics is obtained between the temperatures of 100 °C to 750 °C. The radiation intensity depends on the wavelength and temperature. The connection could be described by Wien’s displacement rule. This law states, that for black bodies the wavelength for the maximum radiation is proportional to the bodies’ temperature. A piece of dough is consequently absorbing, emitting and reflecting electromagnetic radiation [2,4]. The penetration depth of near infrared radiation with a wavelength of 1 μm is about 4 mm - 6 mm [5]. Wade [6] determined that near infrared radiation with an emission maximum of λ = 1.2 μm is suitable to decrease baking times of cookies. Skjoldebrand and Andersson [7] compared infrared baking with baking of breads in conventional ovens and concluded that 6 min in an infrared oven are equal to 16 min in a conventional oven at 230 °C. Further work was carried out by Purlis [8] to optimize infrared heating in combination with natural thermal radiation and convection. The baking time could be reduced by the higher amount of applied infrared radiation. The big advantage of infrared radiation here is the low penetration depth, so the traditional baking process remains the same. Only a time reduction takes place without extensive baking losses and different characteristics in the resulting end product. The effects of baking time reduction on bread crumb properties were also investigated by Bosmans et al. [9].

Ploteau et al. [10] investigated the baking of French baguette with lower temperatures, but higher infrared radiation within the same baking times compared to a conventional oven. The goal was to expose the dough to the same amount of energy. The validation of the hypothesis that the same amount of energy directed to the surface of the dough will lead to the same transformation within the dough roll remains to be done. But the energy consumption of the baking oven was reduced by 20 %. Beside temperature and wavelength the state of the material of the oven plays an important role in heat transfer with radiation. The infrared radiation is said to penetrate the dough piece in a better way and heat it from the inside faster than in conventional radiation ovens. The pasting and therefore the formation of a fine elastic crumb needed less time and more water is preserved in the baked good. This is obvious regarding the moisture content and therefore the freshness of the baked good. The second part of the baking process (browning, stabilization of the crust) is the same as in a conventional oven. The baking process is completed in less time, because of the faster heating and crumb formation and the raw material and valuable substances of the dough are gently treated. To achieve good baking results the manufacturer proposes a 30 °C higher baking temperature, depending on the baking good. This entails a completely different baking process compared to conventional ovens. Patel et al. [11] evaluated the effects of different baking processes on the bread firmness and starch properties in bread crumb. For this purpose they recorded the temperature profile inside the dough during baking. Higher heating rates, due to different oven systems, during the baking processes lead to higher crumb firmness after 15 days of storage. According to the manufacturer reductions in baking time between 20 % and 50 % can be achieved. However, Purlis [12] found out, that there is an internal resistance to heat transfer during the transformation from dough to bread. The end of the baking process, which is given by the complete transformation from dough to bread for instance, can be determined by the surface color development. This development has been studied by various authors [12,13]. Paquet-Durand et al. [14] worked on an on-line monitoring system which supplementary evaluated the volume development of bread rolls during the baking process. Higher baking yields can also be achieved using ceramic-coated oven chambers. Higher baking yields are due to higher masses of baked goods, which accompanies with higher moisture content. Higher moisture contents of baked goods are responsible for extended freshness. For the evaluation of the freshness of breads after storage or the amount of retrogradation differential scanning calorimetry and texture profile analysis are the most common methods [15-18].

With the performed baking experiments it was investigated, if a ceramic coating of internal surfaces of oven chambers will provide savings in energy costs or an improved product quality. The experiments were performed with bread rolls and rye-wheat-bread. To our knowledge no studies on this ceramic coating have been performed with the proposed products. All experiments discussed here were performed in a multiple deck oven with two conventional and two ovens with ceramic coating of internal surfaces. To evaluate the reduction of baking time comparing baking experiments, with wheat bread rolls and rye-wheat bread were performed at same temperatures. For a better comparison, the evolution of color formation was fitted to a function.

Materials and Methods

Materials

The experiments were carried out with commercial wheat flour (type 550: 0.51 % - 0.63 % mineral content in dry matter, Rettenmeier GmbH und Co. KG, Horba.N., Germany), commercial rye-flour (type 1150: 1.11 % - 1.3 % mineral content in dry matter, SchapfenMuhle GmbH & Co. KG, Ulm-Jungingen, Germany), water, commercial yeast (Omas Ur Hefe, Fala GmbH, Buhl, Germany), baking improver (MeisterMarken Ulmer Spatz, Bingen am Rhein, Germany), hydrogenated peanut fat (BAKO, Ladenburg, Germany), starter (rye StartGut®, IsernHager GmbH & Co. KG, Isernhagen, Germany) and salt (Sudsalz GmbH, Heilbronn, Germany).

Bread rolls

The dough was prepared with 61.5 g water, 4 g fresh yeast, 1 g peanut fat, 3.5 g baking improver and 2 g salt per 100 g wheat flour (type 550, corrected to 14 % moisture content). All ingredients were mixed and kneaded in a spiral mixer (Diosna laboratory kneaders). The dough was processed in the common way for bread rolls (Figure 1). Proofing took place in a proofing chamber (WachtelStamm Petit Computer Proofing Chamber, Wachtel GmbH & Co., Hilden, Germany) at 32 °C and relative moisture of 80 % for 60 min. The bread rolls were baked at 235 °C upper temperature and 225 °C lower temperature with 12 s of steam injection (the initial upper heat: 235 °C, the lower heat: 240 °C) in a multiple deck oven (Piccolo I, Wachtel GmbH & Co., Hilden, Germany). The flue of the oven chamber was opened after 90 % of baking time to drag out the moisture. The baking time was 20 min for the conventional oven (conv oven) and 15 min for the internal surface ceramic-coated oven chamber (cc oven).