Food Bioprocess Technol (2014) 7:133–147 DOI 10.1007/s11947-013-1096-6
ORIGINAL PAPER
Response Surface Methodology Study for Optimization of Effects of Fiber Level, Frying Temperature, and Frying Time on Some Physicochemical, Textural, and Sensory Properties of Wheat Chips Enriched with Apple Fiber Ahmed Kayacier & Ferhat Yüksel & Safa Karaman
Received: 15 June 2012 / Accepted: 18 March 2013 / Published online: 18 April 2013 # Springer Science+Business Media New York 2013
Abstract In this study, wheat chips enriched with apple fiber were produced, and response surface methodology was used for the determination of the simultaneous effects of processing variables selected as fiber level (0–15 %), frying temperature (160–180 °C), and frying time (40–60 s) on some physicochemical, textural, and sensorial properties of chips. Ridge analysis was conducted to determine the optimum levels of processing variables. Predictive regression equations with high coefficient of determination (R2 ≥ 0.728) were constructed. Addition of apple fiber increased the dry matter; ash content; L, a, and b values of samples, while increase of frying temperature caused decrease of the hardness values. Overall acceptability of chips enriched with apple fiber decreased with the increase of frying temperature, but wheat chips enriched with apple fiber and fried at low temperatures received highest sensory score. Ridge analysis showed that maximum taste score would be attained at fiber level=15 %, frying temperature=170 °C and frying time=40 s. Keywords Wheat chips . Apple fiber . Response surface methodology . Optimization
Introduction Snacks are food products consumed between regular meals, and there are many different types of them including crackers, A. Kayacier (*) : F. Yüksel : S. Karaman Department of Food Engineering, Erciyes University, Engineering Faculty, 38039 Kayseri, Turkey e-mail:
[email protected] F. Yüksel Department of Food Engineering, Gumushane University, Engineering Faculty, 29100 Gumushane, Turkey
granola-type bars, chips, and cookies available in the marketplace. The current annual sale is approximately $30–35 billion in the world, and their consumption has been continuously increasing in many countries so that they became a considerable component of a human diet (Becker et al. 1986; Mc Charthy 2001; Pęksa et al. 2010). Development of new snacks is one of the most important driving forces of snack industry; hence, many studies related to development and enrichment of snack products especially of chips with some functional components such as plant extracts, dietary fiber, fruits, etc. have been conducted (Rababah et al. 2011; Mendonça et al. 2000; Izydorczyk et al. 2005; Onwulata et al. 2000). In recent years, there is a growing interest for dietary fiber usage in food formulations due to its positive health effects. Anderson et al. (1994) reported that dietary fibers play a very important function in human health. Several researchers have reported the importance of dietary fiber for health since 1970s (Eastwood 1974; Leveille 1975; Southgate 1975; Figureola et al. 2005). As it is known, overconsumption of foods with high fat and calories increases the risk of cardiovascular disease, some forms of diabetes, and suboptimal health (Knuckles et al. 1997). Consumption of high dietary fiber provides prevention, reduction, and treatment of some common diseases such as diverticular and coronary heart disease (Anderson et al. 1994; Gorinstein et al. 2001; VillanuevaSuarez et al. 2003; Figuerola et al. 2005). Dietary fibers are composed of non-starch polysaccharides including cellulose, hemicellulose, pectin, β-glucans, gums, and lignin, and their physiological effects in the human body are related to their physicochemical properties (Gallaher and Schneeman 2001; Lamghari et al. 2000). Dietary fibers are classified as “soluble dietary fiber (SDF)” and “insoluble dietary fiber (IDF)” (Gorinstein et al. 2001). It was reported that SDF/IDF ratio is very important for both physiological and functional characteristics of fibers. It is stated in the literature that dietary
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fiber with a SDF/IDF ratio of 1:2 is generally suitable for its use as a food ingredient (Jaime et al. 2002; Figureola et al. 2005; Schneeman 1987). It was reported that fibers obtained from fruits and vegetables contain higher proportion of soluble dietary fiber compared to fibers derived from cereals (Herbafood 2002). In this regard, apple is very good fiber source because it has a well-balanced proportion between soluble and insoluble fractions (Gorinstein et al. 2001). In addition, apple fibers possess better quality compared to other dietary fibers since they contain important bioactive compounds such as flavonoids, polyphenols, and carotenes (Fernández-Ginés et al. 2003; Wolfe and Liu 2003). There are many studies related to use of apple fiber in food formulations in order to take advantages of dietary and functional properties of fiber (Figuerola et al. 2005; Carson et al. 1994; Chen et al. 1988a; Sudha et al. 2007; Vasantha Rupasinghe et al. 2008). However, sensory properties of foods affect the consumer preferences of a dietary fiber. For that reason, a dietary fiber added to a food formulation must perform a satisfactory manner as an ingredient (Jaime et al. 2002). According to the information obtained from literature, fiber enrichment influences both the overall quality of foods by changing their physiological characteristics and sensory properties of final product (Figuerola et al. 2005). Because of these reasons, processing variables must be optimized to produce an enriched with fiber product of high acceptance. Response Surface Methodology (RSM) is a very common and effective method to optimize the processing variables for the parameters studied (Hunter 1959; Bas and Boyacı 2007). RSM is commonly used for development, improvement, and optimization of a process. RSM can be applied effectively in the design, development, and formulation of a new product because it can define the effect of independent variables (linear, interaction, or quadratic) on the process with a constructed mathematical model (Bas and Boyacı 2007; Anjum et al. 1997; Myers and Montgomery 1995). The purpose of this study was to develop a new functional snack product produced using wheat flour and apple fiber and to study the effect of processing variables selected as fiber level (0–15 %), frying temperature (160–180 °C), and frying time (40–60 s) on some physicochemical, textural, and sensorial properties of final wheat chips enriched with apple fiber and to optimize the levels of processing variables aiming to find the optimum levels for studied parameters.
Material and Methods
Food Bioprocess Technol (2014) 7:133–147
dietary fiber (20 % soluble fiber), 5 % glucose, 6 % sucrose, and 12 % fructose] was provided by Herbafoods Ingredients GmbH (Werder (Havel), Germany). Water holding capacity (WHC) and oil holding capacity of apple fiber were 4 and 1.65 mL/g, respectively. L, a, and b values of apple fiber were 66.62, 13.27, and 27.11, respectively. Sunflower oil (Kristal, İzmir, Turkey) used for the frying is purchased from local market. Methods Preparation of Chips Figure 1 illustrates the process flow chart for the production of wheat chips enriched with apple fiber. At first, dry mixtures containing wheat flour and apple fiber at different proportions were prepared (100:0, 92.5:7.5; 85:15, respectively). After mixing the dry ingredients using a KitchenAid dough mixer (Professional 600, MI, USA) for 5 min, 50 mL tap water was added. Then, the resulted dough was kneaded using a dough mixer (KitchenAid Professional 600, MI, USA) for 10 min, covered with a plastic wrap, and rested for 30 min at room conditions for proper hydration. Afterwards, the thickness of dough was adjusted to 1 mm using a lab-scale sheeter (Rondo, Doge, Model:SS0615, Switzerland) and chips’ shape (6× 2 cm) was given by a mold. Then, chips were deep fried in a temperature-controlled fryer which contained 500 mL sunflower oil. Twelve pieces of chips were fried in each batch. Different frying temperature (170, 180, and 190 °C) and frying time values (40, 50, and 60 s) were selected as presented in the Table 1 for the optimization of processing variables. After frying process, the samples were cooled by resting them on a paper towel at room conditions. Physicochemical Properties of Wheat Chips Dry matter content, protein, oil, and ash contents of the samples were determined as outlined by official procedures (AOAC 2000). Dry matter content of the samples was determined by drying of samples at 105 °C for 4 h in a drying oven (Nüve FN 120, Ankara, Turkey). Ash content was determined by incineration of the samples at 550 °C for 4 h in a furnace (Protherm PLF 12015 Electrical Furnaces, Turkey). The color was measured using a colorimeter (Lovibond RT Series Reflectance Tintometer, England), and L (brightness), a (±red-green), and b (±yellow-blue) values were recorded. Oil content of chips was determined by using a Soxhlet extractor (Buchi B-811, Switzerland).
Materials Texture Analysis Wheat flour (moisture 14 %, protein 12 %, 0.55 % ash, and 35 % gluten) was obtained from Degirmencilik Flour Co. (Kayseri, Turkey). Apple fiber [10 % moisture, 60 % total
All the wheat chips samples prepared based on the process flow chart (Fig. 1) were subjected to the textural analysis at
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Fig. 1 Process flow chart for the production of wheat chips enriched with apple fiber
FUNCTIONAL WHEAT CHIPS PRODUCTION APPLE FIBER
WHEAT FLOUR
10% moisture 60% total dietary fiber (20% soluble) 5% glucose, 6% sucrose, 12% fructose
14% moisture 12% protein 0.55% ash (in dry matter) 35 % gluten
MIXING with wheat flour (WF) and apple fiber (AF) at the following proportions (AF:WF) 0:100 (w/w) 7.5:92.5 (w/w) 15:85 (w/w) HOMOGENIZATION by dough mixer for 5 min. WATER ADDITION 50 mL for making dough KNEADING for 10 min. RESTING for 30 min by covering of dough with stretch wrap at room conditions
SPREADING with a dough roll out machine (until 1 mm fineness) MOULDING using a mould FRYING in sunflower oil at different temperatures and times (according to the Table 1) COOLING by resting on paper napkin for equal period
WHEAT CHIPS ENRICHED WITH APPLE FIBER
room temperature using a Texture Analyzer (TA.XT Plus, Stable Micro System Ltd., Surrey, England) equipped with a Kramer shear cell attachment (HDP/KS-5). A 30-kg of load cell was used for the analysis. Three pieces of wheat chips (each approximately 3 g) were placed in the Kramer shear cell. To ensure maximum number of blades contacting to the samples, wheat chips were placed as perpendicular to the Kramer shear blades. The blades travelled at 5 cm/min. The fracture force (Newton) which is the maximum force required to break the sample was determined from the timedeformation curve. The analyses were conducted to be six replicates for each sample. Sensory Analysis Sensory analyses of samples were conducted by a panel consisting of ten members (faculty and graduate students of Erciyes University, Food Engineering Department) who have experience for sensory analysis of various food
products. Sensory analysis was conducted in a room with appropriate temperature in open sitting. Before conducting the analysis, the panel members were trained, and special information related to the wheat chips with apple fiber were given to them in the training course. The definitions in the sensory score sheet were explained to the panelist group. Panelists were asked to evaluate the samples according to the definition of each attribute. Wheat chips were served in plastic dishes labeled randomly with three digit numbers after production in a random order to the trained panelists who were requested to wash their palates by deionized water prior to proceeding to the next sample. All samples were evaluated in two sessions per day (one in the morning and one in the afternoon) in order to minimize the carryover effects. The samples were evaluated using a scaling method of descriptive attributes for taste (1=undesired, 7=desired), color (1=very brown, 7=desired yellowness), crispness (1=undesired texture, 7=desired texture), and overall acceptability (1=dislike, 7=like).
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Food Bioprocess Technol (2014) 7:133–147
Data Analysis and Modeling
Results and Discussion
A three-factor, three-level Box–Behnken experimental design (Box and Behnken 1960) with three replicates at the center point was used for the modeling of processing variables (fiber level, frying temperature, and frying time), and predictive regression models were constructed for some physicochemical, textural, and sensory parameters. As stated before, the three processing variables, levels and experimental design in terms of coded and uncoded are tabulated in Table 1. Second-order polynomial equation of function Xi as stated below was fitted for each response analyzed: 3 3 3 X X X3 X Y ¼ b0 þ bi Xi þ bii Xii2 þ bij Xi Xj ð1Þ
Physicochemical Properties
i¼1
i¼1
i¼1 i
