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Upcycling of Belgian endive (Cichorium intybus var. foliosum) by-products. Chemical composition and functional properties of dietary fibre root powders
Anna Twarogowska, Christof Van Poucke, Bart Van Droogenbroeck
PII: S0308-8146(20)31306-6 DOI: https://doi.org/10.1016/j.foodchem.2020.127444 Reference: FOCH 127444
To appear in: Food Chemistry
Received Date: 10 January 2020 Revised Date: 24 June 2020 Accepted Date: 26 June 2020
Please cite this article as: Twarogowska, A., Van Poucke, C., Van Droogenbroeck, B., Upcycling of Belgian endive (Cichorium intybus var. foliosum) by-products. Chemical composition and functional properties of dietary fibre root powders, Food Chemistry (2020), doi: https://doi.org/10.1016/j.foodchem.2020.127444
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1 Upcycling of Belgian endive (Cichorium intybus var.
2 foliosum) by-products. Chemical composition and functional
3 properties of dietary fibre root powders.
4 Anna TWAROGOWSKA*, Christof VAN POUCKE, Bart VAN DROOGENBROECK
5 ILVO (Flanders Research Institute for Agriculture, Fisheries and Food), Technology and
6 Food Science Unit, Brusselsesteenweg 370, BE-9090 Melle, Belgium;
7 [email protected], [email protected],
9 *Corresponding author; [email protected];
10 mobile: +32 494 40 26 23, Brusselsesteenweg 370, BE-9090 Melle, Belgium
11 Abstract
12 By-products of Belgian endive represent an interesting yet underutilised source of dietary
13 fibre (DF). Dietary fibre concentrates (DFC) that are low in sugar and neutral in taste are
14 sought by the food industry to increase DF content and improve texture in food products. The
15 aim was to set up a biorefinery process to produce DFC from forced roots of Belgian endive
16 (DFC-BE) and characterise the resulting product. As a control, non-treated forced roots
17 powder (FRP-BE) was tested. Water extraction significantly (p<0.05) decreased the content
18 of sugars, phenolic acids (PA) and sesquiterpene lactones (SL) in DFC-BE. In contrast, total
19 dietary fibre concentration (TDF) was higher in DFC-BE (81.82 g/ 100g DW) in comparison
20 to FRP-BE (49.04 g/100g DW). DFC-BE offers an excellent water holding capacity (WHC)
1
21 of 14.71 g water/g DW and a swelling capacity (SWC) of 23.46 mL water/g DW, suggesting
22 possible use as a functional food ingredient.
23 Keywords
24 Belgian endive, By-products, Hydration properties, Phenolic acids, Sesquiterpene lactones,
25 Dietary fibre, Dietary fibre concentrates, Biorefinery
26
27 1. Introduction
28 Rising challenges for food security and environmental issues have led to increasing interest in
29 bio-economy and more sustainable production. A circular economy and its goal of “zero
30 waste” is gaining attention. In the agri-food sector, which generates substantial amounts of
31 underutilised biomass fractions, this has spurred research into using these by-products and
32 waste fractions as raw material for new products and applications (Faustino et al., 2019). One
33 of the possible approaches for effective utilisation of biomass is the biorefinery concept,
34 which aims to obtain multiple products by applying cost-efficient fractionation technologies.
35 It focuses on the recovery of different types of valuable biomolecules which can be used, e.g.
36 as functional ingredients, food additives and nutraceuticals (Carciochi et al., 2017).
37 Besides the transition to bio-economy, a growing number of consumers are shifting their diets
38 to plant-based foods and clean labels, i.e. minimally processed, natural products. This trend is
39 forcing the food industry to look for new sources of natural ingredients (Aschemann-Witzel,
40 Varela, & Peschel, 2019).
41 In Europe, crops from the Cichorium genus (Asteraceae) are economically important,
42 especially in Belgium, the Netherlands, France, and Italy. The most valuable and well-known
43 leafy vegetables on the European market are Belgian endive (Cichorium intybus var.
2
44 foliosum), Radicchio rosso (Cichorium intybus var. foliosum) and endive (Cichorium endivia).
45 At the same time, industrial chicory (Cichorium intybus var. sativum) is grown for the
46 extraction of inulin (Barcaccia, Ghedina, & Lucchin, 2016). Unavoidably, food waste and by-
47 products are generated during the production of the edible Belgian endive crop. White
48 Belgian endive heads are forced during a 21 day period in the dark at 16-20°C. Each year in
49 the EU, approximately 300,000-400,000 tons of forced roots are produced but they currently
50 have no high-value use, often with a fate as compost or animal feed (Eurostat, 2020).
51 However, these forced roots are a very interesting feedstock for the biorefinery concept: they
52 are available year-round and they have an attractive chemical composition, being rich in
53 sugars, dietary fibres (DF) and bioactive compounds such as phenolic compounds (PC) and
54 sesquiterpenes lactones (SLs).
55 According to the European Food Safety Authority (2010), the recommended daily intake of
56 dietary fibres should be around 25-38 g/day for adults. Chemical composition of DF and its
57 preparation influences its functional properties, which are vital in food applications. The most
58 common properties are water holding capacity (WHC), oil holding capacity (OHC) and
59 swelling capacity (SWC) (Garcia-Amezquita, Tejada-Ortigoza, Serna-Saldivar, & Welti-
60 Chanes, 2018). The inclusion of DF with these qualities in food products can improve quality
61 parameters such as texture, viscosity and shelf-life (Elleuch et al., 2011).
62 Plants defence mechanism against predators is related to a bitter taste, which is associated
63 with the presence of phenols and terpenes (Drewnowski & Gomez-Carneros, 2000). A high
64 concentration of these compounds can significantly affect consumer acceptance of plant-
65 based foods. However, in some cases such as beer and tonic water, a bitter taste is appreciated
66 (Drewnowski & Gomez-Carneros, 2000).
3
67 PC are present in the plant kingdom as a broad diversity of structures, from simple phenolic
68 acids to highly complex flavonoids. These bioactive compounds are known for their
69 antioxidant activity (Cheynier, 2012).
70 SLs are characteristic secondary metabolites for plants from the Asteraceae family. Besides
71 being responsible for the typical bitter taste of crops in the Cichorium genus, they also possess
72 a wide range of biological activities (anti-bacterial, anti-fungal, and anti-inflammatory). This
73 had led to their popularity as an active ingredient in traditional medicines to cure diarrhoea,
74 burns and influenza (Chadwick, Trewin, Gawthrop, & Wagstaff, 2013).
75 The aim of the present work was to set up a simple, cost-efficient biorefinery process to
76 prepare dietary fibre powders from forced roots of the Belgian endive and to assess their
77 potential as a fibre-rich functional food ingredient. The chemical composition, bioactive
78 compounds and dietary fibre profile of the obtained powders were characterised, and their
79 functional properties were evaluated. Additionally, sugars and short-chain carbohydrates,
80 phenolic acids and sesquiterpene lactones in the aqueous extracts were characterised to
81 estimate its potential for further valorisation in food and drink applications.
82 2. Material and Methods
83 2.1. Plant material
84 In total, 20 kg of forced roots of Belgian endive (Cichorium intybus var. foliosum), var.
85 ‘Sweet Lady’ were provided by NPW (National Proeftuin Voor Witloof, Herent, Belgium).
86 Sweet Lady was chosen as Belgian endive variety for this proof-of-concept study as this
87 relatively new variety which shows good quality and has a long production period.
88 2.2. Production of fibre rich powder from Belgian endive forced roots
4
89 Forced roots of Belgian endive were washed in cold water to remove remaining soil. Next, the
90 outer ends of the roots were removed at the top and bottom (±1 cm each end). Further, the
91 roots were cut into julienne form, about 5 cm long and 2.5 x 2.5 mm width, using a Robot
92 Coupe (CL50 Ultra, Mont-Sainte-Geneviève, France). The cut roots were soaked in water at
93 60 °C and stirred (120 rpm) at the ratio 1:4 (roots: water) during 3 h. Once per hour the water
94 was changed and collected for further analyses. After 3 h the roots were separated from the
95 water via a strainer and placed in a hot air oven (60 °C, 6-8h) to dried to a moisture content
96 below 10%. Dried samples were milled by using a ring sieve size 0.5 mm (Ultra centrifugal
97 mill ZM 200, RETSCH, Haan, Germany) to obtain dietary fibre preparations. Powders were
98 stored at room temperature in an aluminium coated plastic bags until further analysis.
99 The powder obtained after washing, cutting and drying the forced roots of Belgian endive
100 (without the soaking step) was called forced root powder (FRP-BE). The powder obtained
101 after an extra soaking step was called dietary fibre concentrate (DFC-BE) (see Figure 1.).
102 2.3. Chemical composition
103 2.3.1. Moisture, protein and ash content
104 Moisture content (MC) was measured by use of halogen moisture analyser (HB43-S, Mettler
105 Toledo, Schwerzenbach, Switzerland). Protein (N x 6.25) was quantified using the Kjeldahl
106 method (AOAC 960.52), and ash was determined after 20 h of incineration at 550 °C using
107 the AOAC 942.05 method (AOAC 1998).
108 2.3.2.Sugars and short-chain carbohydrates analysis
109 Sugars and short-chain carbohydrates were extracted as described by Muir et al. (2009) with
110 minor changes. Briefly, 100 mg of powder was placed into a 10 mL volumetric flask. Then 8
111 mL of hot (80 °C) distilled water was added. The volumetric flask was placed in the
5
112 ultrasonic bath and heated (80 °C) for 15 min. The sample was cooled down to room
113 temperature (25 °C), and volume was adjusted to 10 mL with distilled water. Next, the sample
114 was centrifuged for 10 min at 3000 g at room temperature. The supernatant was filtered
115 through a 0.22 µM sterile Millex filter (MERCK, Overijse, Belgium) and analysed using size
116 exclusion chromatography (SEC) by a Waters Acquity H-Class UPLC (Waters, Milford, MA,
117 USA) system with RI detector and external column oven. Two TSK gel G2500PWXL
118 columns (Tosoh Corporation, Tokyo, Japan) at 80 °C and guard column (Bio-Rad, Temse,
119 Belgium) were used. The analysis was performed under isocratic conditions, with distilled
120 water as a mobile phase. The flow rate was 0.5 mL/min, injected volume 10 µL, and one run
121 took 40 min. The quantification of each sugar was done by using the calibration curve of
122 standard sugars included: sucrose, fructose, glucose, raffinose, stachyose (acquired from
123 MERCK, Overijse, Belgium). Sugar identification was performed based on retention times.
124 2.3.3. Determination of sesquiterpene lactones profile
125 Extraction and separation of sesquiterpene lactones were based on the method described by
126 Kips (2017) with minor changes. Briefly, after adding internal standard, santonin (74 µL,
127 10 µg/g) to 50 mg of powdered sample, the extraction was performed using 1.405 mL
128 deionised water + 0.1 % formic acid. The sample was shaken for 15 minutes at 30 °C at a
129 speed of 1300 rpm (Eppendorf thermomix comfort, Rotselaar, Belgium) and centrifuged (15
130 min, 20817 g). The supernatant was filtered through a 0.22 μM Millex filters (MERCK
131 Overijse, Belgium) and transferred to a vial for analysis. Separation of SLs was done by ultra-
132 high performance liquid chromatography (UHPLC) using an Acquity TM UPLC(Waters,
133 Milford, MA, USA), BEH C18 column (150 mm x 2.1 mm, 1.7 μm, Waters, Milford, MA,
134 USA). The mobile phase included deionised water + 0.1 % formic acid (solvent A) and
135 acetonitrile + 0.1 % formic acid (solvent B). The gradient started at 5% B for 5 min, then
136 increased in a linear fashion from 5% to 53% B in 20 min and remained constant at 53% for 6
137 1 min, and remained at 100% solvent B for 3 min. Next, the conditions were re-equilibrated to
138 the initial point of 5% solvent B for 4 min before the next injection. The column temperature
139 was 40 °C, the flow rate was 0.350 mL/ min, and the injection volume was 5 µL. High-
140 resolution mass spectrometry (HRMS) (Waters, Milford, MA, USA) was used for detection of
141 the SLs in positive electrospray (ESI+) MSE mode. Four compounds were quantified with
142 reference standards (acquired from Extrasynthese, Genay, France): lactucin (LC),
143 lactucopicrin (LP), dihydrolactucin (DHLC) and dihydrolactucopicrin (DHLP). For oxalates
144 and glycosides, no standards are commercially available, thus these compounds were profiled
145 based on relative peak areas. Data were recorded by MassLynxTM (v.4.1) while the
146 integration was performed with TargetLynxTM (v. 4.1) (Waters, Milford, MA, USA).
147 2.3.4. Phenolic compounds profile characterisation
148 Phenolic compounds were extracted from the sample using the protocol described by Kips
149 (2017). Briefly, 75 mg of the powder after adding an internal standard (daidzein, 1 μg/g) was
150 extracted with 5 mL of 100% methanol (MeOH) in a first step and with 5 mL MeOH: water
151 (20:80, v/v) in a second step. After 1 min vortexing and 15 min ultrasound-assisted extraction
152 (Transsonic Digital S, Elma, Germany) the sample was centrifuged (3000 g, 15 min), the
153 supernatant was collected and stored at 4 °C. After the second extraction cycle, both
154 supernatants were combined and filtered through a 0.22 μM Millex filter (MERCK, Overijse,
155 Belgium) into a vial. Analysis of the phenolic compounds was done using AcquityTM UPLC
156 (Waters, Milford, MA, USA) coupled to a XevoTM TQ-S tandem mass spectrometer (Waters,
157 Milford, MA, USA). The separation was done using a Waters UPLC BEH C18
158 chromatographic column (150 mm x 2.1 mm, 1.7 μm, Waters, Milford, MA, USA ). The
159 mobile phase included water + 0.1% formic acid (solvent A) and acetonitrile + 0.1% formic
160 acid (solvent B). The gradient increased in a linear fashion from 1% to 24% B (v/v) in 9.91
161 min, up to to 65% B at 18.51 min, and to 99% B at 18.76 min and was maintained at 99% B 7
162 up to 20.76 min. Afterwards, the initial conditions of 99% A were set from 20.88 min to 23
163 min before the next injection. The column temperature was kept at 40 °C, the flow rate was
164 196 µL/ min, and the injection volume was 5µL. The MS detector was operated in
165 electrospray negative (ESI- ) mode using multiple reaction monitoring (MRM) for detection.
166 Quantification was performed based on relative peak areas and using external standard curves
167 with reference standards: chlorogenic acid, chicoric acid, quinic acid, caffeic acid, 4-OH-
168 phenylacetic acid (all acquired from MERCK, Overijse, Belgium). Data recording was
169 performed by MassLynxTM (v.4.1) while the integration was done with TargetLynxTM (v.4.1)
170 (Waters, Milford, MA, USA).
171 2.3.5. Determination of dietary fibre composition by enzymatic-gravimetric method and
172 liquid chromatography
173 Total dietary fibre (TDF) content was determined by the AOAC Official Method 2017.16
174 (Mccleary, 2019). Briefly, 1g of the samples were treated during 4h at 37 °C with
175 amyloglucosidase and α-amylase. Next, protease was added, and samples were incubated at
176 60 °C for 30 min. For the measurement of insoluble dietary fibre (IDF), the samples were
177 filtrated, washed with ethanol and acetone, dried and weighed. One of the residues was
178 analysed for protein content by Kjeldahl method (Nx6.25) and the other one for ash after 5h
179 of incineration in the oven at 525 °C. The filtrates collected during filtration of IDF fractions
180 were mixed with 95% ethanol and left for precipitation. The soluble dietary fibres in water but
181 precipitated by alcohol (SDFP) were isolated by filtration and determined gravimetrically
182 after correction for any proteins and ash content. The liquid fraction from SDFP filtration was
183 concentrated and deionised by mixing equal amounts of Amberlite FPA53 (OH-) and
184 Ambersep 200 (H+) (Megazyme, Bray, Irland). The soluble dietary fibres in water and
185 alcohol (SDFS) content were assessed via size exclusion chromatography (SEC) using Waters
8
186 Acquity H-Class UPLC (Waters, Milford, MA, USA) system with RI detector and external
187 column oven. Two TSK gel G2500PWXL columns (Tosoh Corporation, Tokyo, Japan) at 80
188 °C and guard column cation and anion exchange (Bio-Rad, Temse, Belgium) were used.
189 Injection volume was 10 µL flow rate of 0.5 mL/min; one run took 60 min. Glucose
190 (Megazyme, Bray, Irland) was used for calibration and glycerol (Megazyme, Bray, Irland)
191 was the internal standard. SDFS fraction was determined by summing the areas of the peaks
192 corresponding to oligomers with degrees of polymerisation strictly higher than two. TDF was
193 the sum of IDF, SDFP and SDFS.
194 2.4. Functional properties
195 The water holding capacity, oil holding capacity and swelling capacity were determined
196 according to Robertson et al.(2000) with minor modifications.
197 2.4.1. Water holding capacity (WHC)
198 In total, 1g of dry sample powder was weighted in a 50 mL centrifuge tube, 30 mL of
199 deionised water was added to the tube, vortexed (10 s) and left for 18 h at room temperature
200 (20-25 °C). The next day the sample was centrifuged for 20 min at 3000g. After
201 centrifugation, the supernatant was decanted, and the tube was carefully inverted to drain off
202 the wet residue (10 min). The wet residue weight was recorded. Results were expressed as g
203 of water/g dry weight
204 WHC =
205 where W2 is the weight of residue (g) containing water and W1 is the weight of the powder.
206 2.4.2. Oil holding capacity (OHC)
9
207 In total, 1g of dry sample powder was weighted in a 50 mL centrifuge tube, 10 mL of corn oil
208 (Vandemoortele, Belgium) was added to the tube, vortexed (30 s) and left for 18 h at room
209 temperature (20-25 °C). The next day the sample was centrifuged for 20 min at 3000g. After
210 centrifugation, the supernatant was decanted, and the tube was carefully inverted to drain off
211 the wet residue (10 min). The wet residue weight was recorded. Results were expressed as g
212 of oil/g dry weight.
213 OHC =
214 where W2 is the weight of residue (g) containing oil and W1 is the weight of the powder.
215 2.4.3. Swelling capacity (SWC)
216 In total, 500 mg of dry sample powder weighted in a calibrated cylinder was hydrated in 15
217 mL of deionised water. After 18h incubation at room temperature (20-25 °C), the bed volume
218 was recorded and expressed as volume (mL) /g of the dry weight.
219 SWC =
220 2.5. Statistical analyses
221 All the analyses were performed in triplicate. Data were expressed as mean ± standard
222 deviation and reported on a dry weight basis. Homogeneity of variance across the group was
223 checked using Levene’s Test. Shapiro-Wilk’s test verified the normal distribution of the data.
224 Further data were statistically analysed using Welch’s Two-sample T-test to find significant
225 differences between treatments (p < 0.05). All analyses were done with R Statistics (version
226 3.5.1.).
227 3. Results and Discussion
228 3.1. Chemical composition
10
229 3.1.1. Moisture, protein and ash content
230 The results of the chemical composition of obtained powders are presented in Table 1. The
231 initial moisture content in the raw root sample was 81.80% ± 0.50, and in the sample after 3h
232 of soaking 94.16% ± 0.34. Moisture content increase is associated with the soaking process
233 and depends on temperature and time. The higher water temperature (60 °C) accelerated the
234 moisture uptake (Mukherjee, Chakraborty, & Dutta, 2019). After drying, the moisture was
235 6.06 ± 0.20 % for FRP-BE and 6.22 ± 0.16 for DFC-BE, ensuring microbiological and
236 physical powder stability. The primary purpose of powder form of the ingredient is the
237 convenient storage and to maintain its functionality until the time of use (Fitzpatrick & Ahrné,
238 2005).
239 The protein content of both samples was relatively low (Table 1) compared with other
240 vegetable fibre sources such as potato (4.20 g/100g DW) and pea (6.90 g/100g DW) (Huber,
241 Francio, Biasi, Mezzomo, & Ferreira, 2016).
242 The FRP-BE and DFC-BE showed a higher content of ash (around 5.50 g/100g DW, Table 1)
243 compared to potato and pea fibres which have an ash content of 2.07 g/100g DW and
244 2.97g/100g DW, respectively (Huber et al., 2016).
245 3.1.2. Sugars and short-chain carbohydrates analysis
246 Sucrose (19.21 ± 0.12 g/100 g DW) and fructose (15.88 ± 0.25 g/100 g DW) were the most
247 abundant sugars present in FRP-BE, where glucose was only minimally present (0.32 ±
248 0.03g/100 g DW). Stachyose and raffinose, which belongs to galacto-oligosaccharides (GOS)
249 were also detected at 1.82 ± 0.03 g/100 g DW and 4.78 ± 0.11 g/100 g DW, respectively. In
250 DFC-BE, the content of sugars was reduced by approximately 98.00% ± 2.50% (Figure 2).
251 Temperature and time are the main factors influencing the diffusion of sugars from a plant
252 matrix into the water due to disruption of the cell wall (Cazor, Deborde, Moing, Rolin, &
11
253 This, 2006). Analyses of the water obtained after each hour of extraction (1, 2, 3h) showed
254 that within the first hour of soaking at 60 °C already 80.00% of all sugars were diffused into
255 the water (data not shown). Reduction of fermentable oligo-, di-, monosaccharides and
256 polyols (FODMAPs) in food ingredients is desired because these compounds can cause
257 gastrointestinal problems. Especially problematic is a high concentration of free fructose,
258 which in excess to glucose leads to fructose malabsorption. Stachyose and raffinose are also
259 considered to be responsible for flatulence upon intake (Mukherjee et al., 2019). Fruits such
260 as mango, apple and pear, which are often used as a source of dietary fibre, present high
261 excess of fructose to glucose ratio and can thus cause abdominal discomfort for some
262 consumers (Muir et al., 2009). Similarly, in FRP-BE, fructose is present in much higher
263 concentration than glucose. However, in DFC-BE, the concentration of fructose is
264 significantly (p<0.001) lower than in FRP-BE and glucose is not present (see Figure 2).
265 Another beneficial aspect of extracting sugars from forced Belgian endive roots is that the
266 final product has a low caloric value. In addition, the current perception of the sugars by
267 consumers is quite negative; they consider high sugar content, even from natural sources, as
268 unhealthy (Aschemann-Witzel et al., 2019). Low caloric value and low concentration of
269 sugars can hence be used as positive selling points for DFC-BE as a functional food
270 ingredient.
271 3.1.3. Determination of sesquiterpene lactones profile
272 Non-soaked samples (FRP-BE) showed a higher level of SLs compared to soaked ones (DFC-
273 BE) (Fig 3). From the four quantified compounds in FRP-BE, the most abundant SLs was
274 DHLC (476.69 ± 65.16 µg/g DW), followed by LC (43.52 ± 3.75 µg/g DW), LP (38.62 ±
275 2.38 µg/g DW) and DHLP (15.82 ± 0.84 µg/g DW). Treatment with hot water (60 °C, 3h)
276 could explain the lower level of SLs in DFC-BE, wherein DHLC was detected in the highest
277 concentration (49.66 ± 12.45 µg/g DW), followed by LC (18.87 ± 3.97 µg/g DW), DHLP 12
278 (0.34 ± 0.14 µg/g DW) and LP which was below limits of quantification (LOQ) (Figure 3a).
279 An analysis of the relationship of the bitter taste and SL level in Belgian endives (Peters &
280 Van Amerongen 1998) showed that extensive cooking reduces SL content. Wulfkuehler,
281 Gras, & Carle (2013) claimed that treatment in 40 °C for 2 min reduces SL content in leafy
282 crops of the closely related chicory (Cichorium intybus L. var. foliosum Hegi). The use of
283 warm water (≥40 °C) could, besides partial degradation of SLs, increases the damage to the
284 plant tissue, thereby leading to increased solubility and release of SL into the water
285 (Wulfkuehler et al., 2013). Graziani et al. (2015); Ferioli, Manco, & D’Antuono (2015) and
286 Kips (2017) reported that lactucin, lactucopicrin 8-deoxylactucin, their 11,13-dihydro
287 derivatives and oxalate and glycoside forms are present in Cichorium genus. Kips (2017)
288 claimed that the predominant form of SLs in crop and forced roots of Belgian endive were
289 oxalates, as confirmed by our analyses (Figure 3b). On the other hand, Ferioli, Manco, &
290 D’Antuono (2015) stated that glycosides are the main form of SLs in Cichorium intybus L. In
291 contrast, Giambanelli, D’Antuono, Ferioli, Frenich, & Romero-González (2018) reported that
292 the profile and concentration of specific SLs showed a relatively low level of LP (< 13.40%)
293 of total SLs in chicory. This is in agreement with our findings, while Graziani et al., (2015)
294 claimed that LP represented 50% of the total amount of SLs in chicory. These differences can
295 be related to the fact that the SLs quantity and profile depend on various factors, such as
296 species, cultivar, variety, matrix, growing conditions, storage time, processing conditions
297 (Peters & Van Amerongen, 1998; Wulfkuehler, Gras, & Carle, 2013; Ferioli et al., 2015;
298 Kips, 2017). Moreover, the general use of term Cichorium intybus L. in literature creates
299 confusion about which species, cultivars or varieties were analysed (Innocenti et al., 2005).
300 Logically, there has been a bigger interest in the edible, aerial parts of salad crops in the
301 Cichorium genus, Belgian endive heads (Cichorium intybus var. foliosum), Radicchio rosso
302 (Cichorium intybus var. foliosum) and Endive (Cichorium endivia) and in the roots of
13
303 industrial chicory (Cichorium intybus var. sativum), grown for inulin, as these are the crop
304 tissues representing the biggest economic value. This tendency, however, has led to a dearth
305 of information about the composition of forced roots of Belgian endive as an agricultural by-
306 product. Kips (2017) characterised SLs in chicons, non-forced and forced roots of Belgian
307 endive and demonstrated that forced roots were richer in SLs than chicons and unforced roots.
308 The best known attribute of Belgian endive is its unique taste, which is characterised by its
309 typical bitterness. The typical chicory flavour, bitter taste and its intensity are related to the
310 content of SLs (Peters & Van Amerongen, 1998). Perception of bitterness is influenced by the
311 bitter threshold for a specific compound. Van Beek et al. (1990) determined threshold values
312 for six different SLs. The lowest threshold values were set for DHLP (0.20 µg/g), and LP
313 (0.50µg/g) meaning, that even at low concentration of these compounds, the bitter taste is
314 noticeable. For DHLC and LC, threshold values were higher, 1.40 and 1.70µg/g, respectively.
315 The trace amount of DHLP (0.34 µg/g DW), LP below the LOQ and a general decrease of
316 other SLs in DFC-BE could explain the tasteless nature of the DFC-BE produced here. On the
317 other hand, the aqueous extract is rich in SLs such as 8-deoxyLC glycoside, LP (Figure 3c, d)
318 which contribute to bitter taste (Van Beek et al., 1990; Graziani et al., 2015). This confirms
319 the potential of this aqueous extract to be valorised as a source of bitter taste in drink
320 applications where it is desired.
321 3.1.4. Phenolic compounds profile characterisation
322 The leading group of phenolic compounds present in forced roots of Belgian endive
323 (Cichorium intybus var. foliosum) are phenolic acids (PA). In literature, the information about
324 the phenolic profile of Belgian endive is very scanty and mostly refers to aerial parts of the
325 plant. According to Innocenti et al. (2005), chicoric acid was the most abundant phenolic acid
326 present in the crop of Belgian endive, which represented 75% of total phenolic content. No
327 flavonoids were detected in this study. In forced roots, there were also no flavonoids found; 14
328 however, the phenolic compound most present was chlorogenic acid, which is in accordance
329 with data published by Kips, 2017. Figure 4. shows the profile and content of phenolic
330 compounds in FRP-BE and DFC-BE. There is a significant difference (p < 0.05) between the
331 concentration of phenolic compounds in the samples before and after soaking in the water at
332 60° C. In FRP-BE chlorogenic acid (2008.33 ± 225.91 µg/g DW) constituted 78% of all
333 detected and quantified phenolic compounds, followed by quinic acid (362.13 ± 69.45 µg/g
334 DW), chicoric acid (152.65 ± 5.44 µg/g DW), caffeic acid (30.71 ± 1.15 µg/g DW) and 4-OH-
335 phenylacetic acid (19.02 ± 1.91 µg/g DW). In roots after soaking (DFC-BE), the profile of
336 phenolic compounds changed, and the most abundant was quinic acid, with the highest
337 concentration 72.89 ± 3.03 µg/g DW, followed by chlorogenic acid (61.89 ± 4.07 µg/g DW),
338 4-OH-phenylacetic acid (14.38 ± 1.11 µg/g DW), chicoric acid (13.81 ± 0.65 µg/g DW) and
339 caffeic acid (below LOQ). During the soaking process, a significant (p<0.05) reduction of
340 each phenolic compound occurred (Figure 4). According to (Mukherjee et al., 2019) during
341 the first 2 h of soaking in 50 - 60°C, the decrease in total phenolic content in soybean meal is
342 the highest. In aqueous extracts from soaking after the first hour, the highest content of
343 phenolic acids was detected in this study. Chlorogenic acid was the most abundant, followed
344 by quinic and 4-OH-phenylacetic acid (data not shown). Thanks to the good thermal stability
345 of these compounds, recovery of bioactive phenolic acids from the aqueous extract is possible
346 (Innocenti et al., 2005). It brings the opportunity to valorise the water extract as a source of
347 antioxidants, relevant for product development with high antioxidant capacity.
348 3.1.5. Determination of dietary fibre composition by enzymatic-gravimetric method and
349 liquid chromatography
350 The profile and concentration of specific fractions of DF were different in both dietary fibre
351 powders (Table 2.). DFC-BE presented higher content of IDF, while in the FRP-BE, SDF
352 were the dominant group. The content of TDF in DFC-BE (81.82 g/100 g DW) allows to 15
353 classify it as a high dietary fibre powder (Larrauri, 1999). The soaking process had a major
354 impact on the DF profile. The higher content of IDF in DFC-BE may be associated with the
355 creation of insoluble complexes between polysaccharides and proteins or phenolic compounds
356 present in the cell wall. These new structures are determined as IDF (Rodríguez, Jiménez,
357 Fernández-Bolaños, Guillén, & Heredia, 2006). The concentration of low molecular weight
358 soluble dietary fibre (LMWSDF), such as fructans and other non- digestible oligosaccharides
359 (NOD) with polymerisation degree between 3-9, was significantly higher in FRP-BE than in
360 DFC-BE (p<0.001). Their solubilisation during the soaking process could explain their lower
361 concentration in DFC-BE (Zhu et al., 2016; Tobaruela et al., 2018). However, if the content of
362 high molecular weight soluble dietary fibre (HMWSDF) in both powders is compared, no
363 significant difference (p = 0.156) is noticed. Similar observation about SDFP content before
364 and after processing was presented in work of Tejada-Ortigoza, García-Amezquita, Serna-
365 Saldívar, & Welti-Chanes (2017).
366 The fibre composition of commercial fibre from oat, bamboo, potato, pea, apple and wheat
367 were characterised by Huber et al. (2016), and all had a comparable TDF content (54.50-
368 91.00 g/100g DW) to DFC-BE and FRP-BE (Table 2). In all these dietary fibre powders, the
369 IDFs were the most abundant group, with the highest concentration present in bamboo fibre
370 (91.00g/100 g DW) and the lowest IDF concentration in apple (43.20 g/100 g DW). The
371 soluble fraction ranged from 0.00 g/100 g DW in bamboo fibre to 11.30 g/100 g DW in apple.
372 The DFC-BE had similar content of SDF as potato fibre (6.70 g/100 g DW), but higher than
373 the wheat (0.70 g/100 g DW) and oat (2.00 g/100 g DW). Nonetheless, the lower content of
374 SDF and TDF in some commercial vegetable and fruit fibres can be related to the analytical
375 method used. The TDF profile of dietary fibre concentrates mentioned above were analysed
376 by use of AOAC 991.43 method (Huber et al. 2016), while in our study, the samples were
377 analysed with the improved method AOAC 2017.16. The main difference between these
16
378 methods is that AOAC 991.43 does not quantify LMWDFS and only focuses on the
379 determination of HMWSDF, thus IDF and SDFP. Therefore it mainly leads to the
380 underestimation of SDF and TDF concentration (Tobaruela et al., 2018). The AOAC 2017.16
381 method is a combination of enzymatic-gravimetric and high-pressure liquid chromatography
382 (HPLC) method. This method counts TDF content as a sum of IDF + SDF, where SDF is a
383 sum of SDFP (HMWDF; by gravimetry) and SDFS (LMWDF; by HPLC) (Mccleary, 2019).
384 As a consequence, the method applied here results in a more accurate description of dietary
385 fibre composition.
386 The correct characterisation of the DF profile is essential in the assessment of the potential of
387 fibre powder as a functional fibre ingredient. The functional fibres not only contribute to
388 health benefits but also have relevant technological properties (Li& Komarek, 2017)
389 3.2. Functional properties
390 Different processing conditions causing changes in the structure and composition of the fibres
391 lead to changes in their functionality. The suitability of dietary fibre concentrates as a
392 functional food ingredient or food additive in specific food products can be assessed by
393 analysing their functional properties. Technological properties of FRP and DFP, such as water
394 holding capacity (WHC), oil holding capacity (OHC) and swelling capacity (SWC) are
395 presented in Table 2.
396 3.2.1. Water holding capacity (WHC)
397 Water holding capacity refers to the ability of dietary fibre to retain water when exposed to an
398 application of external force such as centrifugation (Aguedo et al., 2012). WHC depends on
399 multiple factors: the chemical structure of fibres, source of the fibre and ratio between IDF
400 and SDF are the most important. The other features affecting hydration properties are
401 porosity, particle size, extraction conditions (Mora et al., 2013). The WHC results obtained
17
402 for DFC-BE were almost threefold higher than those for FRP-BE (Table 2). The difference in
403 the values obtained for FRP-BE and DFC-BE might be a result of changes in dietary fibre
404 profile that occurred after processing. Marín, Soler-Rivas, Benavente-García, Castillo, &
405 Pérez-Alvarez (2007) found a very high correlation (r2 = 0.998 ) between WHC and SDF.
406 However, in our study, FRP-BE, which has a higher content of SDF and ratio SDF:IDF, has
407 lower ability to hold water than DFC-BE. In DFC-BE, the ratio of SDF:IDF is 1:12.6, which
408 shows the dominance of IDF. In this case, the increase in WHC capacity might be related to
409 washing out of free sugars which increases the WHC according to Larrauri (1999). The high
410 content of insoluble fraction has a positive impact on improving hydration properties thanks
411 to the capillary structure of the fibre, which helps to retain water (Cepeda & Collado, 2014).
412 Fuentes-Alventosa et al., (2009) also observed an increase in WHC of asparagus by-products
413 after extraction with water for 90 min at 60 °C in comparison to gentle treatment with water
414 (1 min, 20-25 °C). They also claimed that the choice of drying system - oven-drying (60 °C)
415 versus freeze-drying - did not influence the WHC. It might explain the lack of increase of
416 WHC in FRP-BE despite thermal treatment such as drying at 60 °C.
417 FRP-BE with 5.02 g water/g DW presented similar WHC as commercially available dietary
418 fibres as mentioned above, which ranged between 3.20-5.30 g water/g DW (Huber et al.,
419 2016). On the other hand, DFC-BE with 14.71 g water/g DW showed similar WHC to fruit
420 fibres from mango (11.00 g water/g DW) and peach (12.10 g water/g DW), but lower than
421 dietary fibre concentrate from vegetable such as carrot (18.60 g water/g DW) and asparagus
422 (20.03 g water/g DW). The high WHC of DFC-BE suggests that it can be used as a functional
423 fibre in order to improve viscosity, texture and mouthfeel of some formulated food, as well as
424 in the prevention of syneresis (Elleuch et al., 2011; Fuentes-Alventosa et al., 2009).
425 3.2.2. Oil holding capacity (OHC)
18
426 Oil holding capacity alongside water holding capacity is a vital technological property. OHC,
427 like other technological properties, depends on the structure of the fibre. The fibre surface
428 properties, its hydrophobic nature, porosity and charge density of the fibre determinate how
429 much oil can be hold (Mora et al., 2013). OHC has a positive impact on the stability of high-
430 fat food and minimises oil/fat loss during processing which can improve the taste and
431 mouthfeel of food (Benitez et al., 2019). The FRP-BE and DFC-BE had an OHC of 2.50 g
432 oil/g DW and 2.98 g oil/g DW, respectively (Table 2). From the commercially available
433 dietary fibre powders characterised by Huber et al. (2016), the bamboo (4.62 g oil/g DW) and
434 wheat (4.38 g oil/g DW) presented highest OHC values, higher than OHC of DFC-BE and
435 FRP-BE. However, fruit-based fibre concentrates have lower OHC such as orange (1.27 g
436 oil/g DW), peach (1.07 g oil/g DW) and apple (1.47 g oil/g DW) (Mora et al., 2013; Huber et
437 al., 2016).
438 3.2.3. Swelling capacity (SWC)
439 The swelling capacity of DFC-BE (23.46 mL water/g DW) was almost twofold higher than
440 FRP-BE (12.80 mL water/g DW). The FRP has similar SWC as commercial fibres from pea
441 and wheat (15.90 and 12.90 mL water/g DW, respectively) but higher than oat, bamboo,
442 potato and apple whose SWC range from 5.70 up to 9.50 mL water/g DW (Huber et al.,
443 2016). DFC-BE possesses an SWC comparable with coconut (20.00 mL water/g DW) and
444 onion bagasse (21.00 mL water/g DW) (Tejada-Ortigoza, Garcia-Amezquita, Serna-Saldívar,
445 & Welti-Chanes, 2016; Huber et al., 2016). SWC as hydration capacity depends on chemical
446 structure, porosity, processing parameters, the affiliation between molecules (Resende,
447 Franca, & Oliveira, 2019). Primarily the composition of polysaccharides and their
448 configuration in the cell wall influences the SWC. The insoluble fibre fraction entraps water
449 by creating a hydrophilic matrix (Benitez et al., 2019)
19
450 Excellent hydration properties of obtained DFC-BE suggest their potential as a functional
451 fibre in order to reduce calories, improve texture, replace volume and improve stability of the
452 food. Besides the technological advantages, hydration properties are also associated with the
453 physiological effects such as increasing faecal volume and decreasing the time of
454 gastrointestinal transit as well as hypoglycemic and hypolipidemic effects (Figuerola,
455 Hurtado, Estévez, Chiffelle, & Asenjo, 2005; Tejada-Ortigoza et al., 2016; Benitez et al.,
456 2019).
457 4. Conclusions
458 Both of the dietary fibre powders (FRP-BE and DFC-BE) obtained from the forced roots of
459 Belgian endive presented chemical and technological characteristics which allow their use as
460 dietary fibre ingredient in different food formulations. The technological properties of FRP-
461 BE and DFC-BE were similar and in some cases, better than other dietary fibre powders
462 produced from other agro-food by-products. Nevertheless, DFC-BE seems to be more suitable
463 for a broader range of food applications than FRP-BE thanks to its neutral taste, lower caloric
464 value, higher content of TDF and excellent hydration properties which enhance the potential
465 positive physiological effects on human health. Application of dietary fibre powders produced
466 from forced roots into food product formulations (bakery, hybrid meat, snacks) could enrich
467 them in fibre, stimulating fibre intake and minimising the gap between current consumer fibre
468 consumption and dietary recommendations. Low sugar content and potential health benefits
469 meet the demands of the consumers looking for clean labels and less artificial ingredients.
470 Moreover, this prospective utilisation of by-products could have a positive impact on the
471 environment and promote a circular economy and sustainability.
472 The green extraction process, with water as a solvent, creates the opportunity to aim for “zero
473 waste” production. The aqueous extracts rich in valuable SLs, PA, SDF and sugars could be
474 used in various applications. Bitter taste and potential high antioxidant activity due to the 20
475 presence of SLs and PA create the opportunity to utilise it in drinks where bitter taste is
476 appreciated such as tonic water, gin and beer. The presence of soluble fibres can also
477 positively influence the prebiotic potential of new food and drink applications. Possible
478 applications in cosmetic formulations as an anti-oxidant or ingredient with anti-microbial
479 activity could represent an alternative valorisation path.
480 Declaration of interest
481 The authors declare that they have no known competing financial interests or personal
482 relationships that could have appeared to influence the work reported in this paper.
483 Acknowledgments
484 The authors acknowledge financial support from the CichOpt project which is funded in the
485 frame of the ERA-NET FACCE SURPLUS; FACCE SURPLUS has received funding from
486 the European Union’s Horizon 2020 research and innovation programme under grant
487 agreement No 652615 and VLAIO, the Flemish agency for innovation and entrepreneurship.
488 We would like to thank the NPW for providing the plant material and Miriam Levenson for
489 English language editing.
490
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634
635
636 Credit Author Statement
637 Anna Twarogowska: Conceptualization, Methodology, Writing- Original draft preparation, 638 Investigation.
639 Christof Van Poucke: Supervision, Writing- Reviewing and Editing, Validation.
640 Bart Van Droogenbroeck: Conceptualization, Supervision, Writing- Reviewing and Editing
641 642 Declaration of interests
643
644 ☒ The authors declare that they have no known competing financial interests or personal 645 relationships that could have appeared to influence the work reported in this paper.
646
647 ☐The authors declare the following financial interests/personal relationships which may be 648 considered as potential competing interests: 649
650 651 652
653
654 655
25
656 657
658 Fig. 1. Scheme describing fibre rich powders preparation. Forced root powder (FRP-BE) and 659 dietary fibre concentrate (DFC-BE) 660
661
26
662 663 Fig. 2. Sugars and short-chain carbohydrates and their concentration (g/100 g DW) present in 664 forced roots powder (FRP-BE) and dietary fibre concentrate (DFC-BE). All data are given as 665 Mean ± SD (n=3) with significant difference ** (p< 0.01), ***(p<0.001)
666
667
668
669
670
671 672
27
673
674 Fig. 3. Profile of sesquiterpene lactones a) Four quantified sesquiterpene lactones: Lactucin 675 (LC), Dihydrolactucin (DHLC), Lactucopicrin (LP) and Dihydrolactucopicrin (DHLP) (µg/g 676 DW) in forced root powder (FRP-BE) and dietary fibre powder (DFC-BE). All data are given 677 as Mean ± SD (n=3) with significant difference ** (p<0.01), ***(p<0.001). b) Relative peak 678 areas (area compound/area internal standard) of the 16 measured SLs in FRP-BE and DFC- 679 BE, c) Four quantified sesquiterpene lactones; LC, DHLC, LP and DHLP (µg/ml) in the 680 aqueous extract from each hour of soaking d) Relative peak areas (area compound/area 681 internal standard) of the 16 measured SLs in the aqueous extract from each hour of soaking.
682
683
684
28
685
686 Fig. 4. Content of phenolic compounds (µg/g DW) in forced roots powder (FRP-BE) and 687 dietary fibre concentrate (DFC-BE). All data are given as Mean ± SD (n=3) with significant 688 difference *(p<0.05), ** (p< 0.01), ***(p<0.001)
689
690
691 Table 1. Chemical composition (g/ 100g DW) of forced roots powder (FRP-BE) and dietary 692 fibre concentrate (DFC-BE)
FRP-BE DFC-BE Moisture 6.06 ± 0.20a 6.22 ± 0.16a Ash 5.62 ± 0.18a 5.52 ± 0.02a Protein 1.44 ± 0.02a 1.13 ± 0.00b Total dietary fibre 49.04 ± 0.62a 81.82 ± 1.68b Insoluble dietary fibre 22.86 ± 2.09a 75.19 ± 1.12b Soluble dietary fibre 26.18 ± 2.07a 6.64 ± 1.12b Sugars (glucose, fructose, sucrose) 35.41 ± 0.40a 0.55 ± 0.02b 693
694 All data are given as Mean ± SD (n=3). Values in the same row with the same superscript are not 695 significantly different (p <0.05)
696
29
697
698
699 Table 2. Dietary fibre profile (g/100 g DW) analysed by AOAC Official Method 2017.16 700 Total Dietary Fiber in Foods and functional properties of forced roots powder (FRP-BE) and 701 dietary fibre concentrate (DFC-BE).
Dietary fibre profile Functional properties
IDF SDFP SDFS TDF WHC OHC SWC
g/100 g DW g H2O/g g oil/g mL H2O/g
FRP-BE 22.86±2.09a 4.81±0.75a 21.37±1.37a 49.04±0.62a 5.02±0.11a 2.50±0.04a 12.80±0.00a
DFC-BE 75.19±1.12b 5.91±0.80a 0.73±0.34b 81.82±1.68b 14.71±0.53b 2.98±0.10a 23.46±0.00b
702
703 All data are given as Mean ± SD (n = 3). Different letters in the same column indicate that 704 values are significantly different (p < 0.05). Insoluble dietary fibre (IDF), soluble dietary 705 fibre precipitate by alcohol (SDFP), soluble dietary fibres soluble in water and alcohol 706 (SDFS), total dietary fibre (TDF); water holding capacity (WHC), oil holding capacity 707 (OHC), swelling capacity (SWC)
708
709
710 Highlights 711 712 A dietary fibre concentrate (DFC-BE) from Belgian endive by-products was produced 713 and characterised 714 715 The obtained powder was tasteless, low in sugars and rich in insoluble dietary fibres 716 717 DFC-BE exhibited excellent hydration properties 718 719 DFC-BE presented potential as fibre rich functional ingredient 720 721
722
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