A functional cookie formulation containing oligofructose, dietary fibre and lower calorie, fat and sugar contents than conventional cookies was optimized using Response Surface Methodology (RSM). Instant N-Oil II was used as a fat replacer, while Raftilose ®P95 was used as a sugar substitute with the addition of fructose to enhance sweetness. Selection of the optimal formulation was based on caloric content. An optimized formulation, V1, was obtained from the model Y = 4927.70 – 152.34X1 – 155.42X3 + 104.20X32 + 151.71X33 – 95.08X34, where Instant N-Oil II replaced 30% of butter and 24.4%, w/w (30.5g) fructose replaced 40.0%, w/w (50.0g) sucrose. Two additional optimized formulations, S1 and S2, were proposed which contained the same ingredients as V1, but both contained 19.0%, w/w (23.8g) Raftilose ®P95. Also, S2 had a higher fat replacement level (42%). A reference cookie prepared from a conventional recipe received significantly higher scores (P < 0.05) than the functional cookies V1, S1 and S2 in the sensory evaluation. However, when health benefits of the functional cookies were explained to the panel after the sensory evaluation had concluded, majority of the panelists stated that they would prefer S1, had they known of its health benefits. S1 contained 19.04% fat, 8.62% fructose and 0.74% sucrose, namely, significantly lower fat and sucrose levels and higher fructose content than the conventional cookie

Lee .L.Y,

Liew .S.L,

Tan .K.S,

UKM Journal Article Repository

Sains Malaysiana 40(9)(2011): 1007–1011  Optimization of a Functional Cookie Formulation by Using Response Surface Methodology(Pengoptimuman Formulasi Suatu Biskut Berfungsi dengan Kaedah Respons Permukaan)L.Y. LEE, K.S. TAN & S.L. LIEW*ABSTRACTA functional cookie formulation containing oligofructose, dietary fibre and lower calorie, fat and sugar contents than conventional cookies was optimized using Response Surface Methodology (RSM). Instant N-Oil II was used as a fat replacer, while Raftilose ®P95 was used as a sugar substitute with the addition of fructose to enhance sweetness. Selection of the optimal formulation was based on caloric content. An optimized formulation, V1, was obtained from the model Y = 4927.70 – 152.34X1 – 155.42X3 + 104.20X32 + 151.71X33 – 95.08X34, where Instant N-Oil II replaced 30% of butter and 24.4%, w/w (30.5g) fructose replaced 40.0%, w/w (50.0g) sucrose. Two additional optimized formulations, S1 and S2, were proposed which contained the same ingredients as V1, but both contained 19.0%, w/w (23.8g) Raftilose ®P95. Also, S2 had a higher fat replacement level (42%). A reference cookie prepared from a conventional recipe received significantly higher scores (P < 0.05) than the functional cookies V1, S1 and S2 in the sensory evaluation. However, when health benefits of the functional cookies were explained to the panel after the sensory evaluation had concluded, majority of the panelists stated that they would prefer S1, had they known of its health benefits. S1 contained 19.04% fat, 8.62% fructose and 0.74% sucrose, namely, significantly lower fat and sucrose levels and higher fructose content than the conventional cookie. Keywords: Functional food; optimization; response surface methodologyABSTRAKKaedah Respons Permukaan telah digunakan untuk mendapatkan formulasi optimum bagi menghasilkan biskut berfungsi yang mengandungi oligofruktosa, gentian diet dan kandungan kalori, lemak dan gula yang lebih rendah berbanding biskut biasa. Instant N-Oil II digunakan sebagai pengganti lemak dan Raftilose ®P95 digunakan sebagai pengganti gula. Fruktosa digunakan untuk meningkatkan rasa manis. Formulasi biskut optimum dipilih berdasarkan kandungan kalorinya. Formulasi optimum, V1 dihasilkan daripada model Y = 4927.70 – 152.34X1 – 155.42X3 + 104.20X32 + 151.71X33 – 95.08X34 dengan, Instant N-Oil II menggantikan 30% mentega dan 24.4%, b/b (30.5g) fruktosa menggantikan 40.0%, b/b (50.0 g) sukrosa. Dua formulasi tambahan telah dicadangkan berdasarkan model tersebut, iaitu S1 dan S2. Kedua-dua formulasi ini mengandungi ramuan yang sama seperti V1, tetapi juga mengandungi 19.0%, b/b (23.8 g) Raftilose ®P95. S2 juga mempunyai paras penggantian lemak yang lebih tinggi iaitu sebanyak 42%. Sampel biskut rujukan yang disediakan dengan menggunakan resipi biskut konvensional menerima skor yang lebih tinggi (P<0.05) dalam ujian penilaian sensori. Walau bagaimanapun, bila ciri-ciri positif biskut berfungsi dihuraikan kepada ahli panel selepas penilaian sensori selesai dijalankan, majoriti panel mengatakan bahawa mereka akan memilih biskut S1 setelah mengetahui ciri-ciri tersebut. Biskut S1 mengandungi 19.04% lemak, 8.62% fruktosa, 0.74% sukrosa serta mempunyai paras lemak dan sukrosa yang lebih rendah dan paras fruktosa yang lebih tinggi berbanding biskut formulasi rujukan yang dihasilkan daripada resipi konvensional.Kata kunci: Kaedah respons permukaan; makanan berfungsi; pengoptimuman INTRODUCTIONCurrent consumer interest in fat, sugar and caloric reduction has led to the development of alternative sweeteners, fat replacers and functional foods. Demand for functional foods amongst consumers is increasing due to greater awareness of health issues. Functional foods are foods that are similar to conventional foods, consumed as part of a regular diet and can demonstrate physiological benefits or reduce the risk of chronic diseases beyond basic nutritional functions. As such, functional foods contain specific ingredients that can enhance a specific physical or mental function (Fuller 1994; Mazza 1998). Foods typically targeted for fat and sugar reduction include baked products, frozen desserts, butter and margarine, meat products and snack foods. In recent years, oligofructose has gaining popularity due to its soluble dietary fibre content and prebiotic properties (Furrie et al. 2005). In fact, combinations of oligofructose and nutritive sweeteners such as fructose are increasingly 1008 being applied successfully in sugar-reduced food products (Tungland & Mayer 2002). In this study, the commercially-available Raftilose ®P95 was used as both sugar replacer and source of oligofructose. According to ORAFTI Food Ingredients, it possesses prebiotic characteristics and is a good source of dietary fibre. However, as it contributes only 30% sweetness compared with sucrose, fructose was added to enhance sweetness in this study. The food-grade maltodextrin, Instant N-Oil II which contributes only 1.2 kcal/g was used as a fat replacer. Response Surface Methodology (RSM) is a collection of statistical techniques for designing experiments, building models, evaluating the effects of the factors and searching for optimal conditions of factors for desirable responses (Myers 1976; Montgomery 1991). In this study, RSM was used to determine the optimum formulation for a functional cookie with lower fat and sucrose levels and higher fructose level compared to a conventional cookie by incorporating fat and sugar replacers. MATERIALS AND METHODSSTANDARD AND TEST COOKIE FORMULATIONSA reference butter cookie was obtained using a conventional cookie recipe with ingredients as shown in Table 1 (Chang 2002). Butter and castor sugar were mixed with a mixer (ELBA Model ECM948) at Speed 1 for 4 min and then at Speed 4 for another 4 min. Condensed milk and egg yolk were added followed by salt and vanilla essence. Low-gluten flour, cornflour and mixed cereals were then folded in. Cookies were shaped by hand into flattened balls weighing approximately 11 g each and baked at 160ºC for 25 min. A rotatable central composite design was applied to optimize the cookie formulation (Table 2). The experiment consisted of 8 factorial runs, 6 axial runs and 6 center runs. The 3 independent variables were Instant N-Oil II (X1, % w/w of butter replaced in the standard formulation), Raftilose ®P95 (X2, % w/w of flour used in the standard formulation) and fructose (X3, % w/w of flour used in the standard formulation). Each variable was set at 5 levels and a total of 20 experiments were designed whereby Formulation 15, namely the centre-point formulation, was repeated 6 times.  To set up a statistical model, we let Y denote caloric values measured as kcal/g and we determined coded factor levels as follows: X1 = (Instant N-Oil II – 30/11.9), X2 = (Raftilose ®P95 – 19/4.2) and X3 = (Fructose – 23/3). Table 3 shows the coded and actual levels of factors used in this study. Preliminary tests were conducted to obtain levels of factors that are capable of producing a cookie with acceptable characteristics, ie. crispy, non-soggy, non-TABLE 1. Composition of the reference butter cookie (Chang 2002)Component Weight (g) % w/w*ButterCastor sugar Condensed milkEgg yolkVanilla essenceSaltLow gluten flourCornflourMixed cereals75.050.09.08.01.00.5100.025.08.060.040.07.26.40.80.480.020.06.4*Percentage of each component is based on total weight of flour TABLE 2. Treatment combinations and responsesFormulation Factor Response, YbX1a (%, w/w) X2 (%, w/w) X3 (%, w/w)123456789101112131415e18.1c (-1)d18.1 (-1)18.1 (-1)18.1 (-1)41.9 (1)41.9 (1)41.9 (1)41.9 (1)50.0 (1.632)10.0 (-1.632)30.0 (0)30.0 (0)30.0 (0)30.0 (0)30.0 (0)14.8 (-1)14.8 (-1)23.2 (1)23.2 (1)14.8 (-1)14.8 (-1)23.2 (1)23.2 (1)19.0 (0)19.0 (0)26.0 (1.632)12.0 (-1.632)19.0 (0)19.0 (0)19.0 (0)20.0 (-1)26.0 (1)20.0 (-1)26.0 (1)20.0 (-1)26.0 (1)20.0 (-1)26.0 (1)23.0 (0)23.0 (0)23.0 (0)23.0 (0)28.0 (1.632)18.0 (-1.632)23.0 (0)504550955090510048084776481747714667522049744893492250014920a X1= Instant N-Oil II (%, w/w of fat replacement); X2, = Raftilose ®P95 (%, w/w of flour used in the standard formulation); X3 = fructose (%, w/w of flour used in the standard formulation)b cal/gc Actual levels of factorsd(-1.632), (-1), (0) (1), (1.632) are coded levels of factorse Formulation 15 was repeated 6 times  1009sticky. For each factor, a conventional level which was determined from these preliminary tests was set to zero as a coded level. Treatment combinations and observed responses are shown in Table 2. Test formulations were prepared by mixing Raftilose ®P95 and fructose with butter at Speed 1 for 2 min. Instant N-Oil II was used as a 30% solution in this study. Water was added to Instant N-Oil II at the ratio of fat replacer : water (30 : 70) and mixed with the sugar replacer and fructose at Speed 4 for 4 min. Subsequent steps involving addition of condensed milk, egg yolk, salt, vanilla essences and flours were similar to those of the standard formulation. ANALYTICAL DETERMINATIONSEnergy contents of the cookies were determined with IKA Calorimeter System C4000 and caloric values are expressed in cal/g. Sugars were determined using AOAC Method 997.20 and 982.14 (AOAC 1990). The fat content of the samples was determined by extraction with hexane using Soxhlet apparatus (Tecator Soxtec System HT 1043 Extraction Unit, Sweden).SENSORY EVALUATIONFifty panelists (ages 20–55) both male and female assessed the sensory attributes of cookie samples. A 7-point hedonic scale ranging from 1 to 7, where 1 = extremely dislike and 7 = extremely like was used to evaluate acceptability of sample (colour, sweetness, butter taste, crispiness, overall acceptability). Data were subjected to analysis of variance (ANOVA) using the SAS software and differences among means were compared using Duncan’s Multiple Range test. A significance level of 0.05 was chosen. Information about the ingredients used in the functional cookies was revealed to the panelists after conclusion of the sensory evaluation exercise in order to evaluate the influence of health awareness on food selection by the panelists.ExPERIMENTAL DESIgN AND STATISTICAL ANALYSIS A central composite rotatable design was used to allocate treatment combinations in this experiment and the actual levels corresponding to the coded levels are shown in Table 3. In our regression model, the response variable was cal/g and candidates for explanatory variables were linear, interaction, quadratic, cubic and quartic terms of coded levels of the factors tested. The α-level at which every term in the selected model should be significant was set as 0.05. Optimum conditions were found through SAS data-step programming. Validation tests were conducted to determine and compare the caloric contents of the cookies prepared by using the optimized formulation, the reference cookie prepared from a conventional recipe and cookies of 2 different commercial brands.RESULTS AND DISCUSSIONDEVELOPINg A REgRESSION MODELA second-order polynomial regression model containing 3 linear, 3 quadratic and 3 interaction terms was employed by using the RSREg procedure of SAS/STAT. This model was found to be insignificant (P = 0.1040) with r2 = 0.6753 and coefficient of variation = 3.9747. Moreover, its lack of fit was significant (P < 0.0001). This indicates that it may be necessary to include higher order terms in the regression model as the second-order model is not able to represent the experimental data accurately. Since each factor had five levels, up to quartic terms could be included in the model (Box & Draper 1982).  Thus, variable selection techniques were used in attempts to find a better model. The maximum r2 improvement technique and forward variable selection technique were used to select good predictors from the following candidates for model terms:  X1, X2, X3, X1X2, X1X3, X2X3, X12, X22, X32, X13,  X23, X33, X14, X24, X34.As a result of the variable selection techniques used, the following functional form of this model was obtained:  Y = b0 + b1X1 + b3X3 + b33X32 + b333X33 + b3333X34 (1) This fourth-order subset model (Table 4) was significant (p<0.0001) and superior to the second-order full model as it had a larger r2 (0.9841>0.6753) and its number TABLE 3. Coded and actual levels of factors used in this studyFactor Actual factor level at coded factor level of:Symbol -1.682 -1 0 1 1.682Instant N-Oil II (%, w/w)aX110.0 18.1 30.0 41.9 50.0Raftilose®P95 (%, w/w)bX2 12.0 14.8 19.0 23.2 26.0Fructose (%, w/w)b X318.0 20.0 23.0 26.0 28.0a % (w/w) replacement of fat used in the standard formulationb % (w/w) of flour used in the standard formulation1010 of variables was also smaller (5<9). Its lack of fit was not significant (P = 0.8059) and it had a smaller coefficient of variation (0.5386 < 3.9747). The intercept, b0 was the estimated response at the center point (X1, X2, X3)=(0, 0, 0). The fourth-order model is as follows: Y = 4927.70 – 152.34X1 – 155.42X3 + 104.20X32  + 151.71X33 – 95.08X34     (2)FInDIng THE OPTIMuM POInT OF THE FACTORSThe response surface model could be written as:  Y = bo + f1(X1) + f3(X3)     (3)where,  f1(X1) = b1X1 and f3(X3) = f3(X3) + f33(X32) + f333(X33)  + f3333(X34) As f1(X1) is a linear function, it was not optimized but instead was set at its center point value of 30%. f3(X3) was optimized by differentiation. The effect of X2 was found to be insignificant and as such, Raftilose ®P95 was not included in the optimized formulation, V1, which consisted of (X1, X3) = (0, 0.46). These coded levels correspond to actual levels of X1 = 30% and X3 = 24.4%. The estimated optimal response corresponding to the optimum factor levels was 4889 cal/g. A validation test was conducted to determine the caloric contents of cookies produced from V1, reference cookies from a conventional recipe and 2 brands of commercial cookies. V1 cookies contained 5129 cal/g, which was significantly lower than the reference cookies (5348 cal/g) and commercial cookies (5339 cal/g and 5423 cal/g, respectively).  Two additional formulations, S1 and S2, were proposed which contained similar ingredients as V1 but also contained X2, Raftilose ®P95 at its centre-point level of 19.0%. In addition, S2 had a higher level of fat replacement, containing 41.9% of X1 (coded X1 value = 1). Table 5 shows the composition of formulation V1, S1 and S2. Cookies from four formulations, namely, the reference formulation, V1, S1 and S2 were evaluated by a sensory evaluation panel of 50 using a 7-point hedonic test. Highest sensory scores were recorded for the reference cookies from a conventional recipe in all attributes except colour. S1 and V1 received higher scores than S2. When the panelists were asked to choose between reference cookies and S1, they overwhelmingly chose the reference formulation, with only 5 panelists out of 50 choosing S1. However, when the properties of S1 were revealed to them after the sensory evaluation was concluded, 60% of the panelists stated that they would have made S1 their cookie of choice if they had known of its healthful properties. S1 contained significantly lower fat (19.04% <25.86%) and sucrose (0.74% <17.46%) than the reference cookies. It TABLE 4. Analysis of variance in the regression model selected through variable selectionSource of variation No. of degrees of freedom Sum of squares Mean square F value P valueModelResidualLack of fitPure errorTotal514861911426641847875861089211611422285331319.82948.251815.25173.150.5223<0.00010.8059  r2 = 0.9841 coefficient of variation = 0.5386TABLE 5. Composition of the 3 cookie formulations obtained from optimization of the factorsFormulation V1 S1 S2Weight (g) Weight (g) Weight (g)ButterInstant N-Oil IIAirRaftilose ®P95FructoseCondensed milkEgg yolkVanilla essenceSaltLow gluten flourCornflourMixed cereal52.56.815.7-30.59.08.01.00.525.0100.08.052.56.815.723.830.59.08.01.00.525.0100.08.043.69.422.023.830.59.08.01.00.525.0100.08.0Total 258.0 281.8 280.8  1011also contained fructose (8.62%) and oligofructose. This indicates that health awareness plays an important role in selection of food.CONCLUSIONUsing RSM, two functional cookie formulations were produced, namely, V1 and S1. In V1, which contained 24.4% fructose, 30% fat was replaced by 30% Instant N-Oil II solution. S1 contained 30% Instant N-Oil II, 19.0% Raftilose ®P95 and 24.4% fructose. The S1 cookie had lower levels of fat and sucrose compared with conventional butter cookies. It also contained fructose and oligofructose. REFERENCESAssociation of Official Analytical Chemists (AOAC) 1990. Official Methods of Analysis of the Association of official Analytical Chemists. Arlington: Association of Official Analytical Chemists, Inc.Box, g.E.P. & Draper, N.R. 1982. Measures of lack of fit for response surface designs and predictor variable transformations. Technometrics 24: 1-8.Chang, A. 2002. Baking Made Easy. Kuala Lumpur: Chang & Lam Trading.Fuller, g.W. 1994. New food product development: From concept to marketplace. Boca Raton, FL: CRC Press.Furrie, E., MacFarlane, S., Kennedy, A., Cummings, J.H., O’Neil, D.A. & MacFarlane, g.T. 2005. Synbiotic therapy (Bifidobacterium longum/Synergy 1) initiates resolution of inflammation in patients with active ulcerative colitis: a randomised controlled pilot trial. Gut 54: 242-249.Mazza, g. 1998. Functional Foods: Biochemical and Processing Aspects. Lancaster: Technomic Publishing Company.Montgomery, C.D. 1991. Design and Analysis of Experiments. New York: John Wiley and Sons, Inc.Myers, H.R. 1976. Response Surface Methodology. Michigan: Edwards Brothers.ORAFTI Active Food Ingredients. Nutritional Benefits: Nutritional properties of inulin and oligofructose. http://www.orafti.com (3 Aug 2005).Tungland, B.C. & Meyer, D. 2002. Non digestible oligo-and polysaccharides (dietary fiber): Their physiology and role in human health and food. Comprehensive Reviews in Food Science and Food Safety 1: 73-92.L.Y. Lee, K.S. Tan & S.L. Liew*Food Science ProgramSchool of Chemical Sciences & Food TechnologyFaculty of Sciences & TechnologyUniversiti Kebangsaan Malaysia43600 Bangi, SelangorMalaysia*Corresponding author; email: siew@ukm.myReceived: 16 June 2010Accepted: 19 October 2010

Optimization of a functional cookie formulation by using response surface methodology

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