E: Food Engineering & Physical Properties Effect of D-Psicose Used as Sucrose Replacer on the Characteristics of Meringue Siwaporn O’Charoen, Shigeru Hayakawa, Yoshiki Matsumoto, and Masahiro Ogawa Abstract: Excessive intake of sugar-rich foods leads to metabolic syndrome. d-Psicose (Psi) not commonly found in nature, is noncalorie sweetener with a suppressive effect on the blood glucose level. Thus, Psi has the potential to be utilized as a sucrose (Suc) replacer in sugar-rich foods, including meringue-based confectionery (MBC). In this study, we investigated the effect of Psi on the physical and chemical properties of meringue. Meringue was made by whipping egg white and Suc (at a weight ratio of 1:1) and baking at 93 °C for 2 h. Thirty percent of the total weight of Suc was replaced with d-ketohexoses such as Psi, d-fructose, d-tagatose, and d-sorbose. The meringues containing d-ketohexoses had higher specific volume than the meringue not containing d-ketohexoses (Ct-meringue). Baking of meringue caused differences between Psi and the other d-ketohexose meringues. Meringue containing Psi (P30-meringue) had the highest breaking stress (7.00 × 10 5 N/m 2 ) and breaking strain (4.40%), resulting in the crunchiest texture. In addition, P30- meringue also had the highest antioxidant activity (491.84 μM TE/mg-mer ingue determined by ABTS method) and was the brownest due to a Maillard reaction occurring during baking. The replacement of Suc with Psi improved the characteristics of baked meringue. Thus, Psi was found to be useful in modifying the physical and chemical properties of MBC. Keywords: d-psicose, egg white protein, meringue, sucrose, sugar replacement Practical Application: d-Psicose, a noncalorie sweetener with a suppressive effect on the blood glucose level, can be utilized as a sucrose replacer in sugar-rich foods such as meringue-based confectionery (MBC). d-Psicose creates a cr unchy texture and enhances the antioxidant activity of baked meringue. Thus, d-psicose may be useful in modification of MBC. Introduction Meringue is a popular aerated confectionery made of egg white (EW) and sucrose (Suc). Meringue is also an important base ma- terial of many confectioneries such as souffl ´ es, macaroons, and angel food cake in which it provides most of the structural sup- port (Vega and Sanghvi 2012). EW provides a foamy structure, while Suc provides sweetness and stabilizes the foamy str ucture. Since Suc has a high calorie count (4 kcal/g), the excessive con- sumption of meringue and meringue-based confectionery (MBC) results in a high calorie intake. A high calorie intake can cause obe- sity, which is a risk factor for type 2 diabetes and coronary heart disease (Walker 1971; Roberts and Wright 2012; Song and others 2012). Elimination of Suc in meringue and MBC helps reduce the calorie count, but it will simultaneously cause a loss of sweetness and sponge texture of the MBC. Low- and noncalorie sweeteners have been used as substitutes for Suc. Recently, rare sugars, defined as “monosaccharides and their derivatives not commonly found in nature” by the Intl. Soci- ety of Rare Sugars have been introduced as alternative sweeteners (Levin 2002; Mu and others 2012). d-Psicose (Psi), the C-3 epimer of d-fructose (Fru), is a rare sugar having a sweetness equivalent to 70% of that of Suc but a much lower calorie count of approx- imately 0.39 kcal/g. Psi has a suppressive effect on blood glucose MS 20140657 Submitted 4/18/2014, Accepted 9/30/2014. Authors are with Dept. of Applied Biological Science, Faculty of Agriculture, Kagawa Univ., 2393 Ikenobe, Miki, Kagawa, 761-0795, Japan. Direct inquiries to author Hayakawa (E-mail: hayakawa@ag.kagawa-u.ac.jp). levels and an inhibitory effect on body fat accumulation (Mat- suo and others 2002; Chung and others 2012; Ochiai and others 2013). Psi has been approved as generally recognized as safe by the U.S. Food and Drug Administration (Mu and others 2012). An application for approval as food for specified health uses has been made to the Japanese Ministry of Health, Labour, and Wel- fare (Hishiike and others 2013). Psi is expensive because of the difficulty in mass production. However, the price of Psi has been reduced by the utilization of recombinant enzymes in the produc- tion (Takeshita and others 2000; Izumori 2006). Because of the confirmed health benefits and the lowered price, Psi has a high potential for use as a Suc replacer in MBC. The characteristics of meringue are related to its microstructure which relies on a structure building process (foam formation) and a structure disruption process (foam drainage). These processes are regulated by the foaming capacity of EW proteins (EWP) and the foam stability brought by the addition of sugar and other ingre- dients (Licciardello and others 2012). There is very limited in- formation of the effects of Psi on the characteristics of meringue. Therefore, we investigate the characteristics of meringue con- taining Psi. The effects of Psi were compared with the other 3 d-ketohexoses, Fru, d-tagatose (Tag), and d-sorbose (Sor). Materials and Methods Materials and chemicals Psi was obtained from Izumoring Co., Ltd. ( Kagawa, Japan). Tag, Fru, and Sor were obtained from the Kagawa Rare Sugar Re- search Center. 2,2’-Azinobis (3-ethlybenzothiazoline-6-sulfonic C 2014 Institute of Food Technologists R doi: 10.1111/1750-3841.12699 Vol. 79, Nr. 12, 2014 r Journal of Food Science E2463 Further reproduction without permission is prohibited E: Food Engineering & Physical Properties Effect of D-psicose on meringue . . . acid) (ABTS) was purchased from Wako Pure Chemical Industries Ltd. (Osaka, Japan). 1,1-Diphenyl-2-picrylhydrazyl (DPPH) was purchased from Nacalai Tesque Inc. (Kyoto, Japan). Fresh chicken egg and Suc were obtained from a local supermarket. All other chemicals were analytical grade. Preparation of meringue Meringue was prepared as follows: EW (50 g) was whisked to soft peaks by using a hand mixer (SHM-10H, Shinwa Trad- ing Co., Ltd., Tottori, Japan) at a speed setting of 3 for 2 min. Then, mixed sugars (0%, 10%, 20%, 30%, 40%, and 50% [w/w] d-ketohexose/[Suc + d-ketohexose]) (50 g) were gradually added while whipping for 13 min. The foams were then placed into circular-shaped silicone mold (dia 35 mm with 20 mm height) and leveled off using a spatula. Then, the foams were baked at 93 °C for 2 h in an oven (SCOB-4.5MP, Nichiwa Electric Corp., Osaka, Japan). The control meringue (Ct-meringue) was the meringue that did not contain d-ketohexoses for sucrose replacement. Determination of foaming capacity EW–sugar solutions were prepared by carefully dissolving mixed sugars (50 g) into EW (50 g) to avoid foam formation. Then, the foaming capacity was determined according to the method described by Phillips and others (1990). EW–sugar solutions were poured into a 30 mL measuring cup and weighed. Then, the EW– sugar solutions were whipped at a speed setting of 3 for 15 min using the hand mixer. The resultant foam samples were transferred back into a 30 mL measuring cup. Then, the foam was leveled off using a spatula and weighed. The percent overrun was calculated using the following equation: Overrun (%) =  ( weight of egg white − sugar solution (g) − weight of whipped foam (g) ) weight of whipped foam (g)  ×100 Microstructural observation of meringue Baked meringues were cut into small pieces (10 mm width × 10 mm length × 2 mm height) using a razor blade. Then, the small pieces of meringue were mounted on aluminum stubs (Nisshin EM Corp., Tokyo, Japan) with electrically conducting carbon tape (Nisshin EM Corp.) and dried using a vacuum freeze dryer. The dried pieces of meringues were coated with gold using a metal coater (smart coater, JEOL Ltd., Tokyo, Japan) and observed using a scanning electron microscope (JCM-6000, JEOL Ltd.) operated at 15 kV. The size of the observed meringue air bubbles was measured manually on image of baked meringues. Determination of rheological properties Breaking stress and strain of baked meringue were determined by penetration test using a Rheoner RE-3305 creep meter (Ya- maden Co., Ltd., Tokyo, Japan) equipped with a 3-mm-dia rod plunger and a 2 kgf load cell. The 20-mm height meringue was measured at a penetration speed of 1 mm/s. Stress and strain of baked meringue were calculated using the following equation: Stress (N/m 2 ) = F (N) A(mm 2 ) × 10 −6 A=π  a (mm) 2  2 Strain(%) =  H 0 (mm) − H(mm) H 0 (mm)  × 100 where F is a compressive force applied to baked meringue, A is the contact surface area before the plunger penetrates into baked meringue, a is the diameter of the rod plunger, H 0 is the original height of baked meringue, and H is the height of baked meringue after applying compressive force. Breaking stress and strain were obtained from the top of the 1st peak of stress against strain curve (see an example of stress–strain curve of baked meringue shown in Figure 1). Specific volume Specific volume (SV) of baked meringue was measured by the rapeseed displacement method (Sahin and Sumnu 2006). First, the bulk density of rapeseeds was determined. Rapeseeds were filled into a known-volume glass container through tapping and smoothing the surface. Then the glass container containing rape- seeds were weighed. The densities of the seeds (D s ) were calculated from the weight of rapeseeds (W s ) and the volume of rapeseeds placed in container (V s )asfollows: D s (g/cm 3 ) = W s (g) V s (cm 3 ) Baked meringue and rapeseeds were then placed together in container and weighed. The weight of only rapeseeds placed together with baked meringue (W sm ) was calculated as follows: W sm (g) = W t (g) − (W m (g) + W c (g)), where W t is the total weight of baked meringue and rapeseeds placed together in container, W m is the weight of baked meringue, and W c is the weight of the container. The volume of the rape- seeds placed together with baked meringue (V sm ) was calculated as follows: V sm (cm 3 ) = W sm (g) D s (g/cm 3 ) The volume of baked meringue (V m ) was calculated as follows: V m (cm 3 )=V c (cm 3 ) − V sm (cm 3 ) SV was calculated as follows: SV(cm 3 /g) = V m (cm 3 )/W m (g) Determination of thermal denaturation The thermal denaturation of EWP in the presence of mixed sugars was determined by differential scanning calorimetry (DSC; Micro DSC VII, Setaram Inc., Caluire, France). The samples were E2464 Journal of Food Science r Vol. 79, Nr. 12, 2014 E: Food Engineering & Physical Properties Effect of D-psicose on meringue . . . prepared by dissolving Suc (0.7 g) and d-ketohexoses (0.3 g) into EW (1.0 g). The sample (0.4 g) and deionized water (0.4 g) were placed in a sample pan and a reference pan, respectively. The pans were put into DSC vessels and heated at the heating rate of 0.5 °C/min from 25 to 120 °CinanN 2 atmosphere. The calori- metric data were analyzed using thermal analysis software from Setaram Inc. Determination of meringue color The color of baked meringue was determined using a colorime- ter (ND-300A, Nippon Denshoku Industries Co., Ltd., Tokyo, Japan). The color was evaluated using the Hunter L, a, b color scale. This color scale is based on 1 channel for luminance or lightness (L) and 2 color channels (a and b). The a-axis extends from green (−a)tored(+a)andtheb-axis from blue (−b)to yellow (+b). Each piece of meringue was rotated 90° 4 times and measured at each position. Determination of antioxidant activity Antioxidant activity of baked meringue was determined by measuring ABTS and DPPH radical scavenging activities of ethanol extract from baked meringue. Ethanol extract of baked meringue was prepared according to the method described by Sun and others (2008). Baked meringue (2.5 g) was suspended in 99.5% ethanol (10 mL) and homogenized at a speed setting of 7 for 1 min using a POLYTRON R PT 10–35 homogenizer (Kinematica AG, Luzern, Switzerland). The slurry sample was centrifuged at 10,000 × g and 4 °C for 20 min to remove the insoluble materials. The supernatant was collected and di- luted by 16 times using 99.5% ethanol. Then, the diluted baked meringue extract was used as a sample for determining antioxidant activities. The diluted baked meringue extract (0.3 mL) was mixed with the ABTS working solution (2.7 mL). The absorbance at 734 nm was recorded after incubation for 1 min. The rel- ative antioxidant activity was calculated using the following equation: ABTS radical scavenging activity (%) =   Absorbance blank − Absorbance sample  Absorbance blank  × 100 The diluted baked meringue extract (0.5 mL) was also mixed with 0.125 mM DPPH in 99.5% ethanol (2.0 mL). After being left in the dark for 30 min, the absorbance of the samples was measured at 517 nm. The relative antioxidant activity was calculated using the following equation: DPPH radical scavenging activity (%) =   Absorbance blank − Absorbance sample  Absorbance blank  × 100 The ABTS and DPPH radical scavenging activities of meringues were expressed as micro molar of Trolox equivalents (TE) per milligram of baked meringue (μM TE/mg meringue). Statistical analysis Analysis of variance (ANOVA) was performed using the SPSS 15.0 statistical analysis system (SPSS Inc., Chicago, Ill., U.S.A.), and the Duncan multiple range test (P < 0.05) was used to deter- mine the statistical significance. Results and Discussion Preliminary preparation of Psi meringue The study was conducted in 2 steps. The 1st step was to deter- mine the Psi replacement ratio that yields meringue with desired properties. The 2nd step was to investigate the effect of Psi on physical and chemical properties of meringue. Meringues were initially prepared using Suc with a partial replacement with Psi (Psi replacement ratio, 0–50%). The meringues, where the Psi replacement ratio was 40% or more, showed undesirable qualities such as a wet surface and chewy texture. The Psi replacement Figure 1–An example of stress against strain curve of baked meringues. Vol. 79, Nr. 12, 2014 r Journal of Food Science E2465 E: Food Engineering & Physical Properties Effect of D-psicose on meringue . . . ratio had to be less than 30% to obtain a desirable dry surface. Therefore, meringues of which 30% Suc was replaced with Psi and other d-ketohexoses were employed in this study. Physical properties of Psi meringue Foamy structure is an important characteristic of meringue, so the foaming capacity of EW was determined in the presence of sugars (Figure 2). EWs having a replacement ratio of 30% had a higher percent overrun than EW containing only Suc (Ct). The meringues replaced with Psi (P30), Tag (T30), and Sor (S30) showed significantly higher percent overruns than that with Fru (F30). In general, lowering the interfacial tension of water phase of water–air system results in increasing foaming capacity of EWP (Foegeding and others 2006). Thus, Psi, Tag, and Sor may be superior to Fru in lowering the interfacial tension of EWP foam. Even though the reason why d-ketohexoses increase foaming capacity is not clear, we suppose that d-ketohexoses might bind to EWP through hydrogen bonding, leading to a change in sur- face hydrophobicity of EWP and the increase in foaming capacity (Sun and others 2008). Hydrogen bonding network of hydroxyl (OH) groups of saccharide and protein was affected by binding orientation and binding energy (Toone 1994). The orientation of OH groups of each ketohexose are different (Fukada and others 2010). The difference in orientation of OH groups contributes to the difference in hydrogen bonding o rientation and binding distance between D-ketohexoses and EWP. Thus, the position of OH groups of these sugars possibly has influence on the interaction between EWP and sugar. Physical properties of baked meringue containing Psi Meringue is subjected to heat treatment, namely baking, to set the foam structure by converting the foam from a liquid to a solid state. Baking induces water evaporation from meringue and EWP denaturation, leading to the formation of rigid structure of baked meringue. Additionally, baking of meringue causes a gas expansion of EW foam, resulting in an increase in the volume of meringue body. Figure 3 shows the SV of baked meringues pre- pared using the mixed sugars (30% (w/w) d-ketohexose/[Suc + d- ketoheoxse]). P30-, T30-, and S30-meringues had higher SV than F30-meringue and Ct-meringue. These results show that Psi, Tag, a b c c c 0 50 100 150 200 250 300 350 400 450 500 Ct F30 P30 T30 S30 Overrun (%) Figure 2–Percent overrun of EW-sugar solution containing 30% D- ketohexoses. Data are presented as mean ± SD (n = 6) and different superscript letters (a to c) show the significant difference (P < 0.05). and Sor have a higher expansion ratio of a gas in the foam network of meringue than Fru and Suc. Baked meringue was freeze-dried before observed by a scan- ning electron microscope (SEM) in order to completely eliminate moisture content of baked meringue. Freezing or freeze-drying might have only little impact on the structure of meringue be- cause of 2 reasons. The 1st reason is the absolutely low moisture content of baked meringue (2.5–4%). Water in structure of baked meringue could not form large ice crystal that destroys the baked meringue structure during freezing. In addition, the sublimation of only small amount of ice crystal could not cause shrinkage of baked meringue structure during freeze-drying. The 2nd reason is the hard and porous structure of baked meringue. In general, hard and porous structure in foods is stable and retards shrinkage during freezing or freeze-drying. The microstructure of baked meringue was observed by SEM and the air bubble size of the baked meringues was estimated from SEM images (Figure 4). Baked Ct-meringue had thin and rough meringue matrix and the largest-sized air bubbles (500 μm). In contrast, baked d-ketohexose meringues (F30, P30, T30, and S30) had thick and smooth meringue matrix and small-sized air bubbles (250, 125, 125 to 250, and 200 to 250 μm, respectively). However, we still think that there is no impact of freezing/freeze-drying on structure of baked meringue. We have 2 reasons supported our opinion. The difference in the gas expansion and microstructure of baked meringues may relate to thermal denaturation of EWP. Thus, ther- mal denaturation temperatures of EWP were determined by DSC (Table 1). EW showed 2 main endothermic peaks with peak tem- perature (T d ) at 64.51 and 78.00 °C, corresponding to the denat- uration of ovotransferrin and ovalbumin, respectively (Rossi and Schiraldi 1992). The T d values were increased by the addition of sugars by 9.8 to 11.2 °C and 11.9 to 13.0 °C for ovotransferrin and ovalbumin, respectively. The results imply that each sugar increased the heat stability of ovotransferrin and ovalbumin. The stabilizing effect of sugar for the 2 proteins was approximately 1 °C smaller in P30- and T30-EWs than in Ct-, F30-, and S30-EWs, suggest- ing that P30- and T30-meringues, compared to Ct-meringue, induced protein denaturation at ca. 1 °C lower temperature in the baking process. a a b b b 0 1 2 3 4 5 6 7 8 9 10 Ct F30 P30 T30 S30 Specific volume (cm 3 /g) Figure 3–SV of meringue prepared using sugar containing 30% D- ketohexoses. Data are presented as mean ± SD (n = 9) and different small superscript letters (a to b) show the significant difference (P < 0.05). E2466 Journal of Food Science r Vol. 79, Nr. 12, 2014 E: Food Engineering & Physical Properties Effect of D-psicose on meringue . . . The results of denaturation temperature indicate that EWP in Ct-meringue were denatured at the highest temperature. This suggests that it was the most difficult to form rigid structure of Ct-meringue. Thus, the foam structure of Ct-meringue may have collapsed because of disproportionation due to the increase in Laplace pressure and overexpansion of gas during baking. This foam collapse results in the low SV, the large-sized air bubble, and thin and rough meringue matrix of Ct-meringue. It was eas- ier to form rigid structure of F30- and S30-meringues than Ct- meringue, but more difficult than T30- and P30-meringues. This solid structure formation results in smoother and thicker meringue matrix compared to that of Ct-meringue. The results of denat- uration temperature also suggest that F30- and S30-meringues should have higher SV than Ct-meringue. However, only S30- meringue, not F30-meringue, had higher SV than Ct-meringue. This may be due to the difference in air content (overrun) of F30- and S30-meringues. Since the air content of S30-meringue was higher than that of F30-meringue (Figure 2), gas expansion rate of S30-meringue is higher than that of F30-meringue, probably resulting in the higher SV of S30-meringue. On the other hand, T30- and P30-meringues formed the solid structure the most eas- ily. Thus, T30- and P30-meringues had small-sized air bubbles and thick and smooth meringue matrix. In addition, air bubbles of T30- and P30-meringues were smaller than that of S30- and F30-meringues. T30- and P30-meringues had high SV because they had more air content than Ct- and F30-meringues. Figure 4–SEM observation of baked meringue prepared using sugar containing 30% D-ketohexoses. Images were observed at the resolution 27 (left) and 150 (right). Vol. 79, Nr. 12, 2014 r Journal of Food Science E2467 E: Food Engineering & Physical Properties Effect of D-psicose on meringue . . . Table 1–Thermal denaturation temperatures of EW proteins in the presence of different sugars determined by DSC. Sample T d (°C) T onset (°C) T offset (°C) Peak 1 Peak 2 EW without sugar 64.51 ± 0.02 a 78.00 ± 0.01 a 61.39 ± 0.06 a 81.04 ± 0.10 a Ct-EW (Suc only) 75.73 ± 0.06 e 90.96 ± 0.03 d 72.92 ± 0.04 d 93.93 ± 0.13 c F30-EW 74.88 ± 0.33 cd 90.56 ± 0.43 cd 72.27 ± 0.14 c 93.89 ± 0.43 c P30-EW 74.34 ± 0.13 b 89.90 ± 0.37 b 71.39 ± 0.16 b 93.01 ± 0.16 b T30-EW 74.45 ± 0.58 bc 90.28 ± 0.10 bc 71.95 ± 0.67 c 93.13 ± 0.04 b S30-EW 75.13 ± 0.14 d 90.70 ± 0.17 cd 72.34 ± 0.08 c 93.75 ± 0.04 c Data are presented as mean ± SD (n = 3) and different small superscript letters (a to e) show the significant difference (P < 0.05). Table 2–Breaking stress and strain of baked meringue prepared using sugar containing 30% D-ketohexoses. Sample Breaking stress (10 5 N/m 2 ) Breaking strain (%) Ct-meringue 4.07 ± 0.99 a 3.09 ± 1.83 a F30-meringue 5.65 ± 1.27 bc 3.89 ± 1.36 ab P30-meringue 7.00 ± 1.00 d 4.40 ± 2.21 b T30-meringue 6.13 ± 1.08 c 3.38 ± 1.58 ab S30-meringue 5.28 ± 1.44 b 3.89 ± 1.56 ab Data are presented as mean ± SD (n = 24) and different small superscript letters (a to d) show the significant difference (P < 0.05). Breaking stress and strain of baked d-ketohexose meringues are shown in Table 2. The breaking stress and strain indicate hard- ness and retard the deformation of baked meringue, respectively. The baked d-ketohexose meringues (F30, P30, T30, and S30) had 30% to 72% higher breaking stress than the baked Ct-meringue. Particularly, the breaking stress of P30-meringue was outstand- ingly high, showing that the addition of Psi hardened the baked meringue. The high breaking stress of d-ketohexose meringues is closely related to the thick meringue matrix seen by scanning elec- tron microscopy (SEM) observation (Figure 4). The size of the air bubbles might also affect the hardness of the baked meringue. The results of the breaking stress suggest that the formation of small- sized air bubbles creates resulting hard meringue. A structure of baked meringue with large-size air bubble could fracture more easily than that with small-size air bubble when a compressive force is applied to meringue. For breaking strain, P30-meringue also showed the highest value. P30-meringue showed a higher breaking strain than Ct-, F30-, T30-, and S30-meringues, suggesting that Psi, compared to the other sugars including Suc, makes meringue harder to crum- ble. The overall results from the breaking test clearly shows that the 30% replacement of Suc with Psi in meringue causes a crunchy texture. It is of great interest that baking of meringue widens the difference in the physical properties between Psi and the other d-ketohexoses. Chemical properties of baked meringue containing Psi Maillard reaction (MR) is a spontaneous reaction between amino group of protein and carbonyl group of reducing sugar. MR begins with a condensation reaction of primary amino groups of protein with carbonyl group of sugar to form Schiff base products that are rearranged to Amadori/Heyn products. Amadori/Heyn products are degraded and then formed brown, water insolu- ble compounds known as melanoidins (Liu and others 2012). Melanoidins have the antioxidant activity due to their reduc- tone groups having reducing activity and metal chelating ability (Namiki 1988). Suc, a nonresucing sugar, can cause MR after hydrolysis of disaccharide (Hodge and Osman 1976). Thus, MR with Suc is difficult to occur compared to reducing sugar such as d-ketohexoses. It was considered that baked meringue would exhibit high antioxidant activities because of browning substances such as melanoidins generated by MR in baking process. Baked meringues containing 30% d-ketohexoses, especially Psi, had higher antioxi- dant activities than Ct-meringue as detected by ABTS (Figure 5a) and DPPH (Figure 5b) radical scavenging methods. Of all the meringue prepared, P30-meringue had the highest radical scav- enging activities. This is possibly due to that d-ketohexoses cause MR easily compared to Suc. Baking of meringue also generated color change (whitish to brownish). L-, a-,andb-values of meringue are shown in Table 3. Ct-meringue had the highest L-value whereas P30-meringue had the lowest one. This indicates that P30-meringue is darkest. The a b e d c 0 100 200 300 400 500 600 Ct F30 P30 T30 S30 ABTS radical scavenging activity (μM TE/mg meringue) A a b d d c 0 100 200 300 400 500 Ct F30 P30 T30 S30 DPPH radical scavenging activity (μM TE/mg meringue) B Figure 5–Antioxidant activities of baked meringue prepared using sugar containing 30% D-ketohexoses determined by ABTS (a) and DPPH (b) methods. Data are presented as mean ± SD (n = 3) and different small superscript letters (a to d) show the significant difference (P < 0.05). E2468 Journal of Food Science r Vol. 79, Nr. 12, 2014 E: Food Engineering & Physical Properties Effect of D-psicose on meringue . . . Table 3–−Color value of baked meringue prepared using sugar containing 30% D-ketohexoses. Sample L, a, b values Lab Ct-meringue 85.31 ± 0.48 a 1.46 ± 0.37 c 14.00 ± 0.32 c F30-meringue 83.88 ± 0.28 b 2.57 ± 0.28 b 16.87 ± 0.42 b P30-meringue 82.64 ± 0.27 c 3.20 ± 0.41 a 18.04 ± 0.24 a T30-meringue 83.93 ± 0.27 b 2.59 ± 0.37 b 18.06 ± 0.21 a S30-meringue 83.79 ± 0.28 b 2.42 ± 0.49 b 18.14 ± 0.27 a Data are presented as mean ± SD (n = 16) and different small superscript letters (a to c) show the significant difference (P < 0.05). a-value of all meringues was positive, which indicates that all meringues are tinged with red. P30-meringue had the highest a-value while Ct-meringue had the lowest one. The b-value of all meringues was positive, which indicates that all meringues are tinged with yellow. P30-meringue had much higher b-value than Ct-meringue. Overall, the results of L-, a-,andb-values indicate that meringues containing 30% d-ketohexoses were browner than Ct-meringue; especially P30-meringue was the brownest. This strong brownish color of baked P30-meringue will be responsible for the high antioxidant activity seen in P30-meringue. It also implies that MR proceeds fast with Psi compared to the other d-ketohexoses. Conclusion The replacement of Suc with d-ketohexoses caused increase in foaming capacity and decrease in heat denaturation tem- perature of EWP. These results seem to induce difference in microstructure and SV of baked meringues. Baked meringue containing d-ketohexoses had smaller size air bubble compared to the counterparts not containing d-ketohexoses. The different microstructures (e.g., air bubble size) of baked meringues led the different texture—the meringues having smaller size air bubble have crunchier texture. In addition, d-ketohexoses enhanced the antioxidant activity of baked meringues. Psi-meringue had the crunchiest texture and highest antioxidant activity. Thus, Psi may be helpful for modifying functional properties of baked meringue. 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