Colour change of bakery products influenced by used additions

This study deals with the effects of selected additions of vegetable origin on the colour of whole grain breads. The colour was assessed using model samples which were made of mixtures containing various wholemeal flour types (wheat, spelt, and rye flour) and increasing amounts of additions in the form of buckwheat, oat, and barley flour. The additions were 10, 20, 30, 40 and 50 per cent. Colour measurement was performed instrumentally, using an image analysis method which was modified for the purposes of this study. It was found out that, regardless of the flour/addition ratio, both factors in the form of wheat, spelt, and rye wholemeal flour, and barley, oat and buckwheat flour additions and their interactions exhibited a significant influence on the colour of the bakery products (P < 0.05). As far as dependence of colour on the flour/addition ratio is concerned, significant differences (P < 0.05) were found for the following combinations: mixture of wheat flour with buckwheat, barley, and oat; mixture of spelt flour with buckwheat and oat; and mixture of rye flour with buckwheat and barley. The proposed general regression model which was created using the data obtained in the experiment, showed colour variability of more than 95 per cent. Image analysis, whole grain breads, cereals, buckwheat, barley, oats The most important sensory characteristics of bakery products include overall appearance, colour, structure, and taste (Van Dyck et al. 2014). In the sensory assessment of whole grain breads, the primary characteristic is colour (Ziaiifar et al. 2008) which, in consumers’ minds, tends to be connected with texture, taste, food safety, elapsed time of storage, and also nutritional value (Moghaddam et al. 2014). The highest proportion of food cereals grown worldwide is used for bakery products (Perez-Nieto 2010). Nowadays, an increased consumers’ interest in whole grain breads leads to the search and implementation of new combinations of the commonly used cereals, including rye, barley, oats, corn, and also the non-grass pseudo-cereals, such as buckwheat (Liu and Scanlon 2003). In connection with introducing the new combinations of cereals and pseudo-cereals, a need arises to assess the sensory characteristics – especially colour – of products where these combinations are used. Although the perception of colour by the human eye is highly subjective, in sensory analysis it is considered to be a crucial aspect impacting consumers’ acceptance of the product (Zheng et al. 2005). Yet, no fixed range of values is available for sensory assessment of colour that would serve as an authoritative reference. However, sensory assessment cannot be applied in all instances of food assessment. The subjective nature of human visual perception (Scanlon and Zghal 2001) which is influenced by the evaluator’s general physical and mental condition, can skew the assessment results (Du and Sun 2004). An introduction of the image analysis method can represent a substitute for the vision-based ACTA VET. BRNO 2014, 83: S111–S120; doi:10.2754/avb201483S10S111 Address for correspondence: Mgr. Petra Caslavkova Food Production and Legislation Department Ministry of Agriculture of the Czech Republic Těsnov 17, 117 05 Prague 1, Czech Republic Phone: +420 725 240 552 Email: petra.caslavkova@seznam.cz http://www.vfu.cz/acta-vet/actavet.htm assessment, for the method is characterized by a high level of objectivity (Du and Sun 2004) and provides sets of relevant data. The main advantage of this method is its noninvasiveness in comparison with chemical analysis. Also, the objective nature of colour change assessment increases demand for this method among bakery producers who see it as a convenient final inspection procedure (Damez and Clerjon 2008; Girolami et al. 2013). Another benefit of image analysis lies in its high level of flexibility, reproducibility, a relatively low cost and in the scientifically advanced development of the method in the food industry (Gunasekaran 1996; Yam et al. 2004). Among the practical uses of the image analysis method in food processing is doughnut colour assessment (Abdullah et al. 2000; Velez-Ruiz and Sosa-Morales 2003), analysis of confectionery products as well as beer, nuts, and cereals (Gerrard et al. 1996), and also of pasta and rice (Locht et al. 1997). The method can also be used for the detection of changes in food structure (Davila et al. 2007) which was studied by Tao et al. (1995) for the purposes of assessment of fruits and vegetables. The objective of the present study was to adjust the method of image analysis for the assessment of bakery products colour as well as to develop a low-cost method which would be easily controllable and applicable. With the purpose to verify the method’s sensitivity and applicability, an experiment was designed whose aim was two-fold: to verify the applicability of the image analysis in bakery products assessment and to assess the influence additions used (buckwheat, oat, and barley flour) on the colour of samples of whole grain breads. When combined with wholemeal flour, the above additions can increase the nutritional value and increase the colour intensity of bakery products. Materials and Methods In the baking experiments the following raw materials were used: wholemeal wheat flour (PRO-BIO s.r.o, Czech Republic), wholemeal spelt flour (PRO-BIO s.r.o, Czech Republic), wholemeal rye flour (PRO-BIO s.r.o, Czech Republic), buckwheat (FOODISH, s.r.o, Czech Republic), oat (EMCO, s.r.o, Czech Republic), and barley (PENAM, s.r.o, Czech Republic). All raw materials were harvested and processed in 2012. Buckwheat, barley, and oat were milled to flour using a FOSS Cemotec TM 1090, Hoganas Sweden mill, with the same coarseness setting employed. Other additions used included baker’s yeast, vegetable sunflower oil, salt, and an appropriate amount of water.