Sensory evaluation of biscuits enriched with artichoke fiber‐rich powders (Cynara scolymus L.)

Abstract The artichoke by‐products from the canning industry are mainly used for silage, being minimally revaluated. The ways of extraction of by‐products of artichoke into fiber‐rich powders modify their industrial applications in biscuits, as the sensory evaluation may change compared with the reference fiber (Pea fiber, P) used with commercial biscuit. In this sensory study biscuits enriched with fiber‐rich powders of artichoke (W, Ca) are compared with biscuits with the same percentage of the reference fiber (P) and control biscuits without fiber (B). For most of the sensory attributes of the biscuits enriched with artichoke fiber‐rich powders were perceived similar to the biscuits with the commercial reference fiber (P). The good sensory behavior of the biscuits with artichoke fiber‐rich powders during two storage conditions applied may confirm that the artichoke by‐products would be a suitable substitute for pea fiber in oven‐baked products, like wholemeal biscuits with high‐fiber content.


| INTRODUCTION
Wholemeal biscuits with a high-fiber content constitute one of the rising sectors of the food industry in recent years, because of their possibilities of formulation and relatively low production costs. Consumer trends demand more natural products with better nutritional characteristics which can complement nutritional deficiencies, like the low fiber ingestion (Arrillaga & Martínez, 2006;Milte, Thorpe, Crawford, Ball, & McNaughton, 2015;Mongeau, Brassard, & Verdier, 1989).
The dietary fiber composition of the artichoke is high; singling out its high composition of inulin, which can be considered its most important industrial and functional composite and a prebiotic compound itself (Muzzarelli et al., 2012).
From an environmental perspective, the revaluation of vegetable by-products is also critical, since it increases the economic viability of waste minimization processes. Usually, those by-products (70% by weight are by-products of artichoke) are only used as animal feed, being minimum their economic revaluation. Assuming that the by-products have a composition similar to the edible part of the artichokes, these by-products can be a promising source of new value-added compounds such as phytochemicals and fiber (Ruiz-Cano et al., 2014).
However, there are no commercial products of food fiber-rich powders of artichoke yet, although it would be very interesting to study their possible industrial appliance. Thus, the aim of this study was to describe the biscuits enriched with artichoke fiber-rich powders, compared to biscuits formulated with commercial reference fiber (pea) and control biscuits without fiber. The shelf-life study of the biscuits was carried out by investigating the evolution of the sensorial qualities during storage at ambient (25°C) and accelerated (45°C) temperature.

| Ingredients and preparation of the biscuits
The biscuits were formulated in triplicate following the recipe of Whitley (1970) with slight modifications in the percentages of the ingredients since 4% (w/w) of plant fiber was added. The choice of this percentage of fiber was determined by an optimization study from which it was concluded that with 4% of plant fiber of both varieties (commercial reference fiber P and fiber-rich powders from artichoke Ca and W) obtained the maximum sensorial acceptability (data not shown). The commercial pea fiber (P) was obtained on the Spanish market of food additives and the two fiber-rich powders were produced in our laboratory by liquid extraction of artichoke by-products. Two different extraction liquids were used: distilled water (W) and a solution of 1% (w/w) of CaCl 2 . 5H 2 O (pH 6.5) (Ca).
In the control biscuits, the 4% (w/w) of fiber was replaced by wheat flour.
The dough was kneaded with a pilot mixer during 10 min at minimum speed. Subsequently, the dough was laminated to a thickness of 5 mm, using a manual sheet pasta machine. The round form of the biscuits was obtained manually, using a cutting cylinder (die) of 60 mm in diameter. After making eight evaporation holes in the dough with a fork, the biscuits were baked in an electrical convection oven at a temperature of 180 ± 10°C during 17 min ( Figure 1).
Afterwards, the biscuits were cooled at ambient temperature (18-20°C) and wrapped in heat-sealed bags of high-density polyethylene.
The biscuits were divided into two groups as a function of the storage conditions. As the control for each group of biscuits, the values were taken at time 0, which was the day after preparation.

| Storage
The wrapped biscuits were stored in two incubation chambers (Incudigit Selecta Spain), where temperature and humidity were kept constant.
One of the chambers simulated storage at room temperature (25°C, RH 55%), while the other simulated conditions of accelerated storage (45°C, RH 55%) (Yang et al., 2013), forcing the appearance of

| Sensory analysis
The sensory evaluation was carried out in the tasting room of CITA-CTIC La Rioja. The sensory panel consisted of nine judges trained in the use of the sensory profiles method (Lawless & Heymann, 2010).
The panelists were trained with commercial biscuits and prototypes prepared in pilot plants, since the biscuits formulated with fiber-rich powder were also prepared in a pilot plant. By means of this training, a specific terminology for the sensory characteristics and ranges for each attribute was agreed upon. All the trained judges of the inter- Therefore, the absence of characteristic flavor and taste was rated below the standard value, while flavor and taste were rated above the standard value, up to very roasted or burnt as the upper end of the scale.
Color defined the degree of toasting and the outer ends of color went from bread crust of white tin loaf to toasted wholemeal bread.
Hardness was expressed as the resistance of the biscuit to breaking upon pressure of the front teeth during biting. For a hard biscuit, the strength needed for breaking would increase (the standard outer ends of texture went from the hardness of toasted bread rusks to that of wholemeal "grissini"-type rusks of 0.5 cm in diameter).
Appearance is related to the geometry and the structure of the biscuits, and the outer ends of appearance went from an irregular biscuit with an irregular surface produced by evaporation bubbles, to a very compact biscuit with a smooth surface.
Overall acceptability is a mixture of all of the sensory attributes

| Sensory samples
The samples tested during the sensory analysis were samples randomly selected from each of the three pilot plant batches. The three session of each replica of samples were performed with a time lapse of 2 days. Before the sensory analysis sessions, the samples were tempered for 30 min, at a temperature of the sensory analysis room (25°C). The presentation of the sample to the panelist was as follows: using white light, the four hold biscuits were presented together on a piece of white paper divided into four equal parts, in which the codes of the biscuit were printed randomly. The panelists were instructed to taste the samples clockwise starting from the upright quarter.

| Shelf-life test at room temperature
As can be observed in Figures 3 and 4, color and taste were the two sensory qualities for which all the groups of biscuits were significantly different (p < .001). With respect to color, as was expected, the biscuits without fiber (B) had a lighter color than the rest, followed by the pea biscuits (P), while the biscuits formulated with artichoke fiber-rich powders (W, Ca) were significantly darker, mainly due to the darker color of the artichoke fiber-rich powders (Figure 1).
Regarding the variable taste, it was observed that all the biscuits enriched with fiber had a more intense taste than the biscuits without fiber (B). When comparing the biscuits with artichoke fiber-rich powders (W, Ca) with the biscuits formulated with pea fiber, it was observed that their taste was similar.
With respect to the overall acceptability, biscuits B were more sim- Regarding the second principal component, taste is the sensory variable that produced the major differentiation of the groups, separating them in biscuits with pea fiber, biscuits with artichoke fiber-rich powders and biscuits without fiber.
When looking at the groups that were formed in the PCA-statis plot individually, it is observed that throughout the 4 months of storage at ambient temperature the groups of biscuits formulated with vegetal fibers remained grouped more closely. This is explained by a lack of significant variation in the sensory qualities and therefore, due to an effect of protection of the sensory qualities by the enrichment of the biscuits with vegetal fiber, or at least an effect of masking the changes in color and taste.

| Accelerated shelf-life test
As can be observed in Figures 6 and 7, during accelerated storage the score of the biscuits without fiber (B) significantly decreases for the sensory variables taste and flavor, diminishing their overall acceptability. This change in sensory perception is caused by the formation of aromatic compounds, of unpleasant taste and flavor, by-products of lipid oxidation (Talbot, 2010) like 2,4-decadienal y 2,4-heptadienal (Cheng & Bhat, 2016) and hexanal (Sakač et al., 2016).
With respect to color, only the color of biscuits B significantly increased during accelerated storage. This was partly because of the fact that the initial color of the biscuits B was lighter than that of the rest and therefore small variations in color were more perceptible by the panelist than in the biscuits with plant fiber, which were darker due to the color of the fiber.
When the sensory valuation of texture and appearance is ob- In conclusion, the evolution of the sensory qualities of the biscuits formulated with artichoke fiber-rich powders (W, Ca) was similar to that of the biscuits formulated with pea commercial reference fiber (P), and thus that its better sensory appreciation would be maintained throughout the accelerated storage.

| CONCLUSIONS
The sensory description of the biscuits with fiber showed that the variables taste and color were the sensory qualities that significantly differentiate them from the biscuits without fiber (B).
The taste of all biscuits enriched with fiber was appreciated as similar by the panelist. With respect to color, the use of both artichoke fiber-rich powders (Ca, W) modifies the color of the biscuits, making them darker than the biscuits formulated with pea fiber, due to its more neutral color. However, initially, the overall acceptability of the biscuits formulated with both artichoke fiber-rich powders was similar to that of the biscuits formulated with pea fiber (P).
When the biscuits were subjected to accelerate storage, significant changes in taste and color were produced in the biscuits without fiber (B), since color and taste in these biscuits are more neutral, and therefore small variations are more easily detected by the panelist. It was also demonstrated that the biscuits formulated with artichoke fiber-rich powders (Ca, W) had a similar behavior during storage to that of the biscuits formulated with the commercial reference fiber (P).
These results conclude that the utilization of fiber-rich powders from artichoke by-products (Ca, W) can be a viable alternative for the enrichment of biscuits as well as other oven-baked products and that it could be a suitable substitute for commercial pea fiber.