Effect of xylo‐oligosaccharides (XOS) addition on technological and sensory attributes of cookies

Abstract Xylo‐oligosaccharides (XOS) are nondigestible oligosaccharides (NDO) which are recently authorized as novel food ingredients in European Union. Present study introduces the effect of XOS on baking quality of cookies. Color measurements proved that XOS enhance the caramelization during baking. Texture profile, geometry, and baking loss of cookies showed little changes due to XOS addition indicating that XOS are easy to incorporate into baking products. Based on sensory evaluation by expert panel, it was observed that XOS increased the “baked character” of the cookies as indicated by the increased caramel flavor, darker color, and crispier texture. XOS addition also increased the sweet taste and global taste intensity of cookies suggesting that in bakery products XOS evolve a flavor enhancer role. XOS proved to be a promising new alternative to increase dietary fiber content of cereal‐based cookies.

These compounds are also noncariogenic as the bacteria of human oral microflora are not able to metabolize them (Vázquez et al., 1999).
A minimum daily XOS intake is required to achieve health effects: Effective dose of XOS as prebiotics has been suggested to be as low as 1 g per day (Mäkeläinen, Juntunen, & Hasselwander, 2009). Regular XOS consumption in Asia confirming that positive impact of XOS on human health is related to a daily dose of 1-4 g/person.
However, consuming more than 12 g XOS per day may result slight gastrointestinal effects in the case of sensitive consumers. These effects may be gastrointestinal discomfort, laxative effect, or flatulence are typical symptoms for high exposure to dietary fiber (Xiao, Ning, & Xu, 2012).
XOS are well known and widely used as a functional food ingredient or food supplement in Japan and China. In Japan, XOS are approved as food ingredients by Foods for Specified Health Uses (FOSHU) specifically foods that modify gastrointestinal conditions. In China, XOS have been commercialized since 2000 and have been used as a food supplement and as a functional compound in dairy products (Mäkeläinen et al., 2009). In Europe, XOS are a novel food ingredient and our research team has been working on having its use authorized based on suggestions of regulations (EC, 1997)  October 2018. Our previous study introduced the first steps of this work testing the rheological properties of XOS in aqueous media (Penksza, Juhász, Szabó-Nótin, & Sipos, 2020).
Since 1997, 32 product launches using XOS have been recorded by Mintel's global new products database (Mintel, 2008). The most typical products are dairy products, beverages, fruit juices, chewing gums, and healthcare products (dietary supplements). However, because of recent authorization of XOS limited information is available about its effect on quality of food products common in Europe such as bakery products, cookies, and breakfast cereals. Cookies are easy to dose because of well-defined size and weight and are suitable for precisely control the XOS intake. Previous study with arabinoxylan oligosaccharides (AXOS) enriched cookies showed that baking quality of cookies depends on whether AXOS are used as a flour or as a sugar replacer (Pareyt et al., 2011).
Aim of present study was to investigate effect of xylo-oligosaccharides addition on baking quality of cookies. Main objectives were to: 1. study changes of baking properties (baking loss, volume, color, texture), 2. ascertain the sensory profile of dietary fiber enriched modified cookies (flour or sugar was partly replaced by XOS), 3. evaluate the differences between available XOS products (powder and liquid forms, purity of 70 or 95%) when are used in cookies.

| Sample preparation
Cookie doughs were prepared according to the AACC-approved Method 10-50D (AACC, 1980). Three kinds of recipes were used in our experiments. The ingredients and formulas of the three kinds of recipes are introduced in Table 1 (sample code: S70P; S70L; S95P). XOS were used in 1.4% concentration level because of nutritional considerations.
Dough was prepared with one-stage mixing, in which margarine and flour were homogenized first during 5 min. Then, the other components were added and mixing was continued for 10 min. Dough was laminated (7 mm thickness), then cut with a circular cookie cutter (inner diameter 50 mm), and baked in an electrically heated rotary oven (Gierre, Milano, Italy) for 10 min at 205°C.

| Geometry
After cooling to room temperature, cookies were weighed and their dimensions (height, diameter in cm) measured, and from these parameters, the volume was calculated: (V = r 2 *π*h). Baking loss (Bl) was determined using the following equation: where w 1 is the weight of cookie prior to baking, w 2 is the weight of cookie after baking.

| Color
Color of the surface of the baked cookies was measured with 9 parallels using a Konica Minolta CR400 chromameter. Results were expressed as CIE 1976 L*, a*, and b* values. L* is a measure of the brightness from black (0) to white (100), while a* describes the redgreen color (a*> 0 indicates redness, a* < 0 indicates greenness), and b* describes yellow-blue color (b*> 0 indicates yellowness, b* < 0 indicates blueness). To determine the total color difference between two samples using all the three coordinates, the following formula was used (CIE, 1976): (CIE, 2004)  (maximum deformation force during the first mastication cycle), and adhesive force (g·s) (force required to pull the compressing plunger away from the sample), cohesiveness (-), springiness (mm), gumminess (g), and chewiness (g·mm) were determined.

| Sensory analysis
Sensory evaluations were conducted at Szent István University, Sensory Evaluation Laboratory, which meets standard requirements (ISO 8589:2007

| Statistical methods
The sensory attributes of the cookies were evaluated separately. The mean values were compared by 2-way analysis of variance (ANOVA) when evaluating the sensory attributes of the products (α = 0.05).
Pair comparison was done by Tukey HSD post hoc test. These tests were carried out using XL-STAT software created by Addinsoft.
The performance monitoring of the panel was carried out according to the workflow of the PanelCheck ver 1.4.2 software using

| Results of the panel performance monitoring
After the 2-way ANOVA analysis, all sensory attributes were signifi-

| Color
Color has primarily importance in acceptability of cookies by consumers and an important parameter in determination of baking Note: The first column contains the mean of the panel for each attribute. The four following columns are, respectively: F statistics of discrimination (F-Prod), scaling heterogeneity (F-Scal) and disagreement (F-Disag), and repeatability (root-mean-squares of error, RMSE). Attributes are sorted from the most discriminative to the less discriminative (F-Prod) (panel limit = 0.05).
quality. Color of cookies was strongly influenced by XOS addition as proved by both the sensory evaluation and instrumental measurement (Table 3).

| Geometry and texture
Geometry is an important parameter in baking quality of cookies.
In general, increased volume of baking products is associated with their improved quality (Hoseney & Rogers, 1994;Pareyt et al., 2011).
Volume of cookie products is influenced by flour quality, gluten content, and quality of flour, water binding capacity of dough. The higher cookie is the better, and when volume is increased by diameter, it indicates the spread of the cookie. Baking loss refers to the moisture loss during baking: The higher water binding capacity of dough is related to lower baking loss.
XOS addition slightly affected the geometry of cookies (Table 4). Rheological properties of xylo-oligosaccharides were reported to be different from sucrose by the authors (Penksza et al., 2019). XOS has higher viscosity in aqueous solution than sucrose, especially at room temperature (at which dough formation was performed) because of higher water binding capacity. Thus, XOS may interact with starch in a competitive manner for water or modify protein-starch-water interaction during gluten network formation resulting in a more uneven cookie shape and more heterogeneous surface.

| Sensory attributes
Effect of XOS on sensory attributes of cookies has not been described previously; therefore, it was evaluated in detail ( Table 6).
The presence of XOS did not cause any off-taste or after-taste in cookies. Baking soda flavor and salt taste were not perceptible by panelists neither in control nor in XOS containing cookies.
Addition of XOS to cookies increased their global taste intensity (65.0 for control and 77.3-81.6 for XOS containing samples), TA B L E 4 Geometry and outlook of cookies with or without xylo-oligosaccharide (XOS) addition   and regarding the changes occurred in presence of XOS.

CO N FLI C T O F I NTE R E S T
The authors declare that they do not have any conflict of interest.