High methoxyl pectin from the soluble dietary fiber of passion fruit peel forms weak gel without the requirement of sugar addition

Passion fruit peel (PFP) is a by-product from the fruit processing industry, accounting for approximately 50 % of the fruit weight. It is well known for its health properties, although few studies evaluated its rheological properties. PFP polysaccharides (PFPP) contain a high methoxyl pectin (HMP), specifically a 70 % methylesterified homogalacturonan.

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forms weak gel without the requirement of sugar addition

Kahlile Youssef Abbouda, Marcello Iacominia, Fernanda Fogagnoli Simasb,* ,

Lucimara M.C Cordeiroa,*

a Department of Biochemistry and Molecular Biology, Federal University of Paraná, CP 19.046, CEP 81.531-980 Curitiba, PR, Brazil

b Department of Cell Biology, Federal University of Paraná, CEP 81.531-980 Curitiba, PR, Brazil

A R T I C L E I N F O

Keywords:

Passion fruit peel

Soluble dietary fibre

High methoxyl pectin

Rheological analysis

A B S T R A C T Passion fruit peel (PFP) is a by-product from the fruit processing industry, accounting for approximately 50 % of the fruit weight It is well known for its health properties, although few studies evaluated its rheological properties PFP polysaccharides (PFPP) contain a high methoxyl pectin (HMP), specifically a 70 % methyl-esterified homogalacturonan Flow behaviour analysis of PFPP (with or without sucrose) revealed a shear-thinning non-Newtonian behaviour Dynamic oscillatory tests showed a weak gel-like behaviour, even without sucrose addition Moreover, under simulated pasteurization process PFPP maintained its gel structure Taken together we demonstrated that PFPP has divergent behaviour from commercial HMP, since it does not require sucrose or low pH to form gel The present work reinforces the use of PFP as a source of soluble dietaryfibres and pectins, providing its alternative application as a rheological modifier in a wide range of products, including those with low sugar

1 Introduction

Passion fruit peel (PFP) is a by-product from the fruit processing

industry and it accounts for approximately 50 % of the fruit weight

Brazil is the largest passion fruit producer worldwide, responsible for

more than 80 % of the production, reaching approximatelyfive

hun-dred thousand tons of fruit in 2017 (Albuquerque et al., 2019;de Souza,

Jonathan, Saad, Schols, & Venema, 2018;Souza & Gerum, 2017) The

underutilization of these peels may represent an important

environ-mental issue However, it could also represent a good source of

bioac-tive components such as antioxidants, dietaryfibres and vitamins The

recovery of by-products holds great potential to be used as food

ad-ditives by the food industry, as well as functional food ingredients or

nutraceuticals to be used for the prevention or treatment of human

conditions (Albuquerque et al., 2019; Kowalska, Czajkowska,

Cichowska, & Lenart, 2017) Therefore, these (by) products represent a

potentially convenient resource to be explored and their transformation

on high-added value compounds may be conducted towards the

re-duction of their impact in the environment For most consumers, the

acceptability of industrialized products for daily use is improved when

natural ingredients are added instead of synthetic ones (Kowalska et al.,

2017)

Accordingly, PFP has been widely studied regarding its health-promoting properties, including its metabolic effects (reduction of the fasting blood glucose, triglycerides and glycated hemoglobin levels, reduction of homeostasis model assessment for insulin resistance index -HOMA IR and of the hepatic cholesterol levels), and action on the gastrointestinal tract (gastroprotection, reduction of faecal pH and in-crease in the faecal moisture) (Abboud et al., 2019;Corrêa et al., 2014;

de Queiroz et al., 2012;de Souza et al., 2018;Macagnan et al., 2015; Ramos et al., 2007) Furthermore, it contains dietaryfibre (DF), mainly pectin, which is considered a soluble dietaryfibre (SDF) SDF are un-digestible food compounds which comprises polysaccharides, such as pectins, β-glucans, gums and some hemicelluloses (Englyst, Liu, & Englyst, 2007)

Pectin is considered a traditional food ingredient and additive due

to its emulsifying, gelling, thickening as well as stabilising properties, thus it has been widely studied for its physical-chemical and rheological properties (Lopes da Silva & Rao, 2007) Despite its availability in a large number of plant species, commercial sources of pectin are limited

to citrus and apple pomace, both by-products of the juice industry (Chan, Choo, Young, & Loh, 2017;Kowalska et al., 2017) The search for feasible alternative sources of pectin is increasing, as also the pectin market, which is expected to grow and may reach 1370 million US$ by

https://doi.org/10.1016/j.carbpol.2020.116616

Received 21 March 2020; Received in revised form 5 June 2020; Accepted 5 June 2020

⁎Corresponding authors

E-mail addresses:ferfs@ufpr.br(F.F Simas),lucimaramcc@ufpr.br(L.M.C Cordeiro)

Available online 12 June 2020

0144-8617/ © 2020 Elsevier Ltd All rights reserved

T

the end of 2025 (www.marketwatch.com) An important factor to

choose novel sources of pectin is the yielding In this sensefinding new

sources of pectin from different by-products, with distinct chemical

properties, would broaden their application as food additives,

nu-traceuticals or even biofuels This may contributes to solve the problem

of waste management, which has been estimated in millions of tons

every year, and its consequent adverse impact in the environment

(Kowalska et al., 2017)

Homogalacturonan (HG) is the main component of pectins It

comprises the “smooth region” of pectic domains, and is a linear

homopolymer ofα-1,4-linked-D-galacturonic acid (GalpA) units that can

be methyl esterified at O-6 in different degrees This is indicated by the

degree of methyl esterification (DE), which is expressed as the

per-centage of the total number of galacturonic acid residues esterified with

a methoxyl group Depending on DE, pectins can be classified as the

High-Methoxyl (HMP, where DE > 50 %) and Low-Methoxyl (LMP,

where DE < 50 %) (Chan et al., 2017; Einhorn-Stoll, 2018; Yapo,

2011)

HMP are well known regarding their gelling properties, for so they

are widely exploited by different types of industries as a rheology

modifier and stabilizer, as well as in sugary products (Lopes da Silva &

Rao, 2007) HMP behave differently from LMP In order to form gel,

HMP requires low pH (< 3.5) conditions and high sugar concentrations

(> 55 %), while LMP require divalent ions, such as calcium, and wider

range of pH (2–6), but have no need for sugar addition (BeMiller, 2019;

Chan et al., 2017) The acidic pH promotes the decrease of electrostatic

repulsive forces among high methoxyl pectic chains by the protonation

of the carboxyl groups To decrease the water activity and boost

chain-chain interactions, large amount of sugar (i.e sucrose) are used with

HMP Lastly, HMP gel formation is governed by two main non-covalent

types of interactions: hydrophobic interactions between methoxyl

groups; and, hydrogen bonds set between secondary alcohol groups and

non-dissociated carboxyl (Oakenfull & Scott, 1984) For those reasons,

as well as to their ability to form spreadable gels, HMP is mainly

ap-plied to jellies, jams, preserves and marmalades (BeMiller, 2019)

There is limited information regarding the rheological properties of

passion fruit pectins Yapo and Koffi (2006) evaluated the gelling

ability and viscoelastic properties of a low methoxyl pectin extracted

from passion fruit peel from Ivory Coast, while Canteri et al (2010)

determined the reduced viscosity of an HMP obtained from different

portions of PFP (exocarp, mesocarp and endocarp) extracted with

0.05 mol/L nitric acid at 80 °C

We have chemically characterized a high methoxyl pectin (DE 70

%), extracted from passion fruit peel (Abboud et al., 2019), with Mw

53 kDa and composed mainly of galacturonic acid (92 %) It presented

higher DE and lower neutral monosaccharides amounts compared to

other sources of HMP (Barbieri et al., 2019; Colodel, Vriesmann, &

Petkowicz, 2019; Nascimento, Simas-Tosin, Iacomini, Gorin, &

Cordeiro, 2016) Since these structural characteristics are important for

the rheological properties of high methoxyl pectins (May, 1990;

Thakur, Singh, & Handa, 1997), the main objective of this work was to

evaluate the rheological properties of the high methoxyl pectin

ex-tracted from PFP aiming its application as a rheological modifier by the

industry in a wide range of products, including those with low sugar

2 Material and methods

2.1 Extraction of the passion fruit peel pectin (PFPP)

The high methoxyl pectin (PFPP) analysed here was previously

extracted and chemically characterized as homogalacturonan by

Abboud et al (2019) Briefly, passion fruit peel flour was submitted to

the standard enzymatic-gravimetric method (Lamothe, Srichuwong,

Reuhs, & Hamaker, 2015) and fraction containing soluble dietaryfibres,

which corresponded to 20 % of passion fruit peelfibres, was composed

of an HMP and corresponds to PFPP fraction employed in the present

study

2.2 Sample preparation and rheological analysis PFPP dispersions were prepared in ultrapure water at 2% and 4% (w/w) concentration being stirred overnight at room temperature Samples with sucrose were prepared according toVriesmann, Silveira and Petkowicz (2010) PFPP at 2% (w/w) and sucrose at 25 % or 50 % (w/w) were mixed and stirred overnight Then, the mixture was heated

at 92 °C for 15 min in a water bath, under stirring, after that it was cooled and its pH adjusted to 3.0 with a saturated solution of citric acid Lastly, these samples were hermetically sealed and stored at 4 °C for 1

or 2 days until analysis

A HAAKE MARS II rheometer was used to conduct analysis, at 20 °C with a cone-plate (C60/2◦TiL) measurement system with maximum gap

of 1 mm The temperature was controlled by a circulating water bath (DC5, Haake) coupled to a Peltier temperature control device (TC81, Haake) In order to allow the equilibrium of the temperature in the sample dispersions, they were placed on the rheometer plate for 300 s before all rheological analysis

Flow curves were assessed in the controlled shear rate (CR) mode through the application of increased shear rate (0.001 - 1000 s−1) for

300 s The shear stress (τ) and the apparent viscosity (η) were evaluated

as a function of shear rate and, the data offlow curves analysed and fitted according to the rheological models of Herschel–Bulkley

( 0 ˙ n)and Ostwald–de Waele(τ=Kγ˙ n), whereτ is the shear stress (Pa), K is the consistency index (Pa sn),γ˙ is the shear rate (s−1), n

is theflow behaviour index (dimensionless) and τ0is the yield stress (Pa) (Rao, 2007)

The frequency sweeps were carried out with controlled deformation mode using 1% strain in the 0.02–10 Hz range G’, which is the elastic modulus associated to the solid response of the material and, G” which

is the viscous modulus, corresponding to thefluid response of the ma-terial (Zhong & Daubert, 2013), were analysed

In order to study the behaviour of PFPP dispersions after they were submitted to pasteurization processes, which is a relevant procedure to food products, the rheometer plate was previously heated to 88 °C and PFPP dispersions were poured on the warm plate, resting for one minute The sensor was covered with a sample hood (POM 222–1903)

to prevent water evaporation Subsequently, the temperature decreased

to 4 °C at a rate of 2 °C per minute, at afixed frequency of 1 Hz and strain of 1%

The rheological and statistical parameter were obtained by the software RheoWin 4 Data Manager All the analyses were performed, at least, in three independent experiments Graphics show the mean va-lues and corresponding standard error of the mean (SEM)

2.3 Scanning electron microscopy (SEM) PFPP was analyzed by scanning electron microscopy (SEM) (Model VEGA3 LMU, Tescan, Kohoutovice, Czech Republic), equipped with a detector (SDD 80mm2) and AZ Tech Advanced software The electron micrographs were obtained at a 15-kV accelerating voltage The lyo-philized PFPP was posed on aluminum stubs with double-face tape Then, it was submitted to metallic coating with gold for 2 min with thickness of 10 nm, under argon atmosphere, using metallic coating equipment (Model SCD 030, Pfeiffer, Balzers, Liechtenstein) This pro-cedure was carried out at the Electron Microscopy Center at the Federal University of Paraná, Curitiba, Brazil

3 Results and discussion 3.1 Steady-state shear properties of PFPP dispersions with or without sucrose

Flow behaviour analyses of PFPP dispersions at different

concentrations, with or without sucrose addition, were performed to

evaluate apparent viscosity in response to increasing shear rates

(Fig 1) The results for both, PFPP aqueous dispersions at 2 and 4% (w/

w) showed that the increasing concentrations of PFPP improved the

apparent viscosity of the solution Also, PFPP presented a characteristic

shear-thinning non-Newtonian behaviour, in which the viscosity

de-creases with increased shear rates This is considered a typical

beha-viour for polysaccharide systems, where the three-dimension network

of the molecules exhibit a tendency to align on the flow direction,

dissociate or assume another conformation thus, reducing viscosity

(Lapasin & Pricl, 1995;Schramm, 2006) Likewise, this outline was seen

in water solutions, at different concentrations, of HMP extracted from

alternative sources (other than citrus and apple pomace pectin) (Chan

et al., 2017;Schramm, 2006)

PFPP at 2% and 4% (w/w) exhibited apparent viscosity values of

20.9 and 118 Pa.s at 0.01 s−1, respectively These values were much

higher than those found for other HMP extracted from non-commercial

sources Nascimento et al (2016)found an apparent viscosity of

ap-proximately 0.2, 1.5 and 7 Pa.s at 0.01 s−1for an HMP from the pulp of

Solanum betaceum at 3%, 5% and 8% (w/w) respectively Likewise,

HMPs from Campomanesia xanthocarpa Berg fruit (Barbieri et al., 2019),

ponkan peel pectin (Citrus reticulata Blanco cv Ponkan) and from

commercial citrus pectin (Colodel et al., 2019), at concentration of 5%

(w/w) presented apparent viscosity values close to 10 Pa.s under shear

rate of 0.01 s−1 Pectin from cocoa pod husks had apparent viscosity

values even low, approximately 1 Pa.s at the same shear rate

(Vriesmann & Petkowicz, 2013) In this sense, it is important to

high-light that PFPP aqueous dispersions were 2–15 times more viscous than

other HMPs

The viscosity of aqueous HMP generally are improved by addition of

high amounts of co-solutes, such as sucrose Thus, we evaluatedflow

behaviour of PFPP at 2% added with sucrose (25 % and 50 % w/w)

(Fig 1) As expected, the apparent viscosity of PFPP at 2% was

im-proved by the addition of sucrose, although it was not observed the

same enhancement when the sucrose amount was doubled It is known

that sucrose decrease the water activity in aqueous dispersions of HMP

and further favour the junction zones establishment, increasing

hy-drophobic association between methoxyl groups from galacturonic

acids units (Thakur et al., 1997) However, in general, the viscosity

improvement with high amounts of sucrose (as 50 % w/w) can reach to

100,000 fold more than that observed without sucrose HMP from

So-lanum betaceum (at 3%; w/w) showed an enhancement in the apparent

viscosity at 0.01 s−1, from 0.2 Pa.s to near 20,000 Pa.s after addition of

50 % (w/w) sucrose (Nascimento et al., 2016) PFPP at 2% with 50 %

sucrose showed only a 9-fold increase in the apparent viscosity, from

21 Pa.s, at 0.01 s−1, to near 188 Pa.s (Fig 1) PFPP had lower Mw, low

amounts of neutral side chains and higher DE than HMP from S

betaceum Thus, it can be hypothesize that in the PFPP the junctions zones arising from hydrophobic non-covalent interactions can be formed in large amounts without sucrose and when this co-solute is added only minor of these interactions were newly established Fur-thermore, in that system the hydrogen bonds seems to be less decisive

in gel network, since sucrose could also facilitate this type of interaction (May, 2000;Thakur et al., 1997; Strӧm et al., 2014)

Flow curves experimental data werefitted to rheological models, such as Ostwald de Waele and Herschel-Bulkley with high regression coefficients (R2) values (≥ 0.99) (Table 1)

These models are important since they may contribute to char-acterize flow behaviour of fluids on shear Chemical and physical properties offluids may influence flow behaviour affecting industrial systems productivity and improvement, as well as the orientation of equipment operation regarding heat transfer phenomenon, velocity and volumetricflow rates in channel and tube flows (Doran, 2013; Rao,

2007) The Ostwald-de Waele model, also referred as power law model, stipulate parameters offlow behaviour (n) and consistency (K) index, in which shear-thinningfluids present n < 1 (Rao, 2007) As shown in Table 1, all samples demonstratedflow behaviour (n values) lower than

1, indicating shear-thinning behavior Similarly, Herschel-Bulkley models also provide information on flow behaviour and consistency index, although with an extra parameter, the yield stress (τ0), in which non-Newtonian fluids demand finite stress (τ0), a necessary stress to fluid to start to flow Accordingly, these materials behave as rigid solids until the yield stress is exceeded and the materialflows as shear-thin-ningfluid, therefore samples presenting positive τ0values, willflow as power-law fluid (Alexandrou, McGilvreay, & Burgos, 2001) As re-presented in Table 1, τ0 values were increased as the sample con-centration increased, and the same occurred for the samples prepared with sucrose

3.2 Dynamic rheological properties of PFPP with or without sucrose One of the most important properties of pectins, as a raw material for the industry, is their capacity to form gel HMP dispersed in water usually demonstrated a liquid-like behaviour, where G” is higher than

G’ in the whole frequency range analysed (Barbieri et al., 2019; Nascimento et al., 2016; Vriesmann & Petkowicz, 2013; Vriesmann, Silveira, & Petkowicz, 2010) Interestingly, as seen inFig 2A, PFPP aqueous dispersion at 2 and 4% concentration (w/w), demonstrated weak gel-like behaviour, where the elastic modulus (G’) presented higher values than the viscous modulus (G”) in the whole frequency range analysed, although these moduli are somewhat frequency de-pendent As observed for other polysaccharides, the gel strength was concentration dependent, and PFPP gel at 2% presented lower strength than PFPP at 4% (Table 2) The dramatically increases on G’ and G” values in frequency sweep (up to 4 Hz) of PFPP at 2% (Fig 2A) could suggest that low concentrated weak gel system was less resistant and maybe at higher frequencies there is untangled in the gel network structure

A weak gel behaviour was also observed for 2% PFPP added with 25

Fig 1 Influence of shear rate (0.001 - 1000 s−1) on the apparent viscosity of

PFPP from passion fruit peel at 25 °C at different concentrations on water, with

or without sucrose

Table 1 Rheological parameter based on PFPPflow curves

2% 4% 25 % Sucrose 50 % Sucrose Ostwald de Waele K (Pa.s) 0.2132 2.148 1.971 4.303

r 2 0.9939 0.9936 0.9921 0.9943 Herschel-Bulkley τ 0 0.3971 1.859 2.243 4.406

K (Pa.s) 0.1220 1.308 1.072 2.669

r 2 0.9984 0.9971 0.9974 0.9976

% or 50 % of sucrose (Fig 2B,Table 2) Sucrose is a co-solute used to

promote gelation of HMPs, which generally are viscoelastic liquids in

the absence of a co-solute (May, 2000;Thakur et al., 1997) This

ex-pected behaviour was not observed here (Fig 2B), since although

su-crose increased the gel strength, it was not essential to gel network

establishment As described in the above section, it seems that sucrose

is not essential to establish in PFPP the junction zones arising from

hydrophobic non-covalent interactions necessary to gel network

for-mation Thus, PFPP showed a distinct feature, it forms weak gels in

water (G’ > G” in all the analysed frequency range) without require-ment of co-solutes or acidification.Barbieri et al (2019)also observed a gel-like behaviour for a pectin at 5% (w/v) aqueous dispersion from Campomanesia xanthocarpa Berg., however, the gel was weaker (G’ values around 1 Pa, from 0.03 to 1 Hz) than PFPP at 4% (w/w), which showed G’ values around 55 Pa in this frequency range

Fig 2 Frequency sweeps at 25 °C of PFPP aqueous dispersions with or without

sucrose Elastic modulus (G’) is represented with full symbols while viscous

modulus (G”) with open symbols (A) Frequency sweeps from PFPP at 2% and

4% (w/w) (B) Frequency sweeps from PFPP at 2% with 25 or 50 % sucrose (w/

w) (C) Comparison between the elastic modulus of all samples

Table 2

Elastic modulus obtained in dynamic oscillatory tests and ratio G’/G” of all samples, at different concentrations and frequencies

Fig 3 Viscoelastic evaluation of PFPP weak gels under cooling after pasteur-ization simulated method, with or without sucrose Elastic modulus (G’) and viscous modulus (G”) as a function of temperature (A) PFPP at 2% and 4% (w/ w) (B) PFPP at 2% with 25 or 50 % sucrose (w/w) (C) Comparison of elastic modulus (G’) of all samples

3.3 Viscoelastic behavior of PFPP samples under pasteurization-like process

As HMP may be used as a rheological modifier (additive) in food

and other products, it would be wise to evaluate its behaviour under

thermic treatments, such as pasteurization, which in turn is a widely

used procedure by the food and pharmaceutical industries, aiming

microbiological safety of products (Lewis & Heppell, 2000) HMPs

usually formed thermo-irreversible gels, since heating and cooling

processes may strongly affect the intra- and intermolecular interactions

that are important to maintain the HMP gel network (Lopes da Silva &

Rao, 2007)

Heating can be used in food products during the processing as a way

to prevent microorganism contamination in a pasteurization procedure

Thus, we submitted PFPP samples, with or without sucrose, to a

pas-teurization-like condition Samples were subjected to 88 °C, during one

minute and after that they were cooling down to 4 °C (at a rate of 2 °C/

min), and G’ and G” were analysed during the cooling process In this

experimental approach it was possible to see that during cooling from

88 °C to 4 °C the G’ modulus was higher than G” for all PFPP samples

(Fig 3), indicating that the weak-gel behavior was maintained over this

temperature range PFPP at 2% showed slight decrease in both moduli

from aprox 60 °C to 40 °C being stabilized from 40 °C to 4 °C We cannot

discard the hypothesis that at this concentration and under higher

temperatures there is a better condition for the interactions between

PFPP polymers chains, although the graph showin data from PFPP at

2% is very noisy due low precision of cone-plate system to determine

those low G’ and G” values An expected behavior, as reported by other

studies (May, 2000;Nascimento et al., 2016;Schramm, 2006;Silva &

Gonçalves, 1994; Simas-Tosin et al., 2010; Ström, Schuster, & Goh,

2014) were observed for PFPP at 4% and to PFPP at 2% with sucrose,

where G’ and G” slightly increased under cooling This behavior

prob-ably occurred due to formation of new intra- and inter-molecular

in-teractions stabilized by nonpermanent cross-links of gel networks after

cooling (Shaw & MacKnight, 2005;Thakur et al., 1997)

The differentiated rheological behaviour of PFPP may be related to

some structural and physical characteristics and/or method of

extrac-tion It can be observed that its monosaccharide composition presented

92 % of GalpA This is a high value when compared with those HMP

from other fruits, which showed values from 33.5%–84.5% (Barbieri

et al., 2019;Colodel et al., 2019;Min et al., 2011;Nascimento et al.,

2016;Vriesmann & Petkowicz, 2013) Also, the presence of rhamnose,

which was identified only in trace amounts in PFPP, was associated

with lower viscosity and weaker gels, as it may induce kinks in the

galacturonan structure, thus interfering in the macromolecular

orga-nization required to form a gel network (Oakenfull, 1991) It is also

reported that the presence of neutral side chains and the low molecular

weight pectin may weaken the gel strength once less junction zones

would be formed (BeMiller, 2019; Axelos & Thibault, 1991)

Interest-ingly, PFPP molecular weight was lower (53 kDa) compared to other

HMP sources (> 100 kDa) and also demonstrated a homogeneous

elu-tion profile (HPSEC-MALLS), when compared to other HMP sources

(Barbieri et al., 2019;Colodel et al., 2019;Nascimento et al., 2016; Sousa, Nielsen, Armagan, Larsen, & Sørensen, 2015; Yoo, Fishman, Hotchkiss, & Lee, 2006).Min et al (2011)observed that the extraction methods may influence the rheological behaviour of pectins obtained from apple pomace PFPP was isolated by the enzymatic-gravimetric method, known to preserve the original chemical features of the iso-lated molecules The use of strong acids or high temperatures may be associated with alterations in the HMP structure (Adetunji, Adekunle, Orsat, & Raghavan, 2017;Lopes da Silva & Rao, 2007) Besides, the use

of strong acids is associated with environmental damage by producing hazardous contaminants Therefore, enzymatic methods are usually considered environmentally friendly and a potential alternative method (Adetunji et al., 2017;Min et al., 2011)

3.4 Scanning electron microscopy of PFPP sample The scanning electron microscopy of PFPP was also performed (Fig 4) It is possible to observe a delicate and smooth material Ac-cording toEinhorn-Stoll (2018)homogeneous surface of pectin parti-cles can promote water uptake and immobilization, moreover the au-thor argues that amorphous particles allow fast water permeation and reaching of hydrophilic groups, compared to crystalline ones As it can

be seen inFig 4, the whole structure resembles more amorphous, and that may explain PFPP behaviour when water was added, with fast uptake and swelling In sum, these images show that PFPP presents a porous homogeneous structure that may explain its high uptake and swelling in water

Finally, it is important to note that PFPP had similar yield (20 % yield) compared to the main sources of commercial pectin worldwide, i.e apple pomace and citrus pectin, which yields approximately 4–21 % and 9–33 %, respectively (Abboud et al., 2019; Chan et al., 2017) Taken together, all the results presented herein reinforce that passion fruit peel could be a novel source of commercial HMP, with dis-tinguished rheological properties

4 Conclusion PFPP extracted in this study, which is an HMP, demonstrated shear-thinning non-Newtonian rheological behaviour distinct from other HMPs, as no alteration in pH and addition of co-solute (sucrose) was required for PFPP in order to form weak gels Moreover, the addition of sucrose increased its apparent viscosity, however, not so intensively as observed for other HMPs, for which the addition of sucrose played a crucial role in gelation mechanism PFPP samples seems to maintain their weak gels profiles under pasteurization-like process, with or without sucrose addition

PFPP had a yield comparable to other commercial pectins, which in turn enhance its feasibility to use as an alternative source of HMP Moreover, there is a growing well-being trend among consumers and PFPP could fit well these demands since it didn’t require sugar or chemical alterations to form gel, besides its well-known health Fig 4 Scanning Electron Microscopy of PFPP (A) 100×, (B) 1000× and (C) 5000× magnifications

properties, prebiotic and DF potential Lastly, PFPP may be a feasible

option as a rheological modifier agent, with reduced environmental

impact and bioactive properties

CRediT authorship contribution statement

Kahlile Youssef Abboud: Investigation, Writing - original draft,

Visualization Marcello Iacomini: Supervision, Funding acquisition

Fernanda Fogagnoli Simas: Writing - review & editing, Supervision

Lucimara M.C Cordeiro: Writing - review & editing, Supervision,

Funding acquisition, Project administration

Acknowledgements

This research was supported by CNPq foundation (Process 404717/

2016-0 and 310332/2015-0) and by a fellowship granted to K Y

Abboud (Process 1564544) provided by CAPES The authors are

grateful to Electron Microscopy Center of the Federal University of

Paraná for the scanning electron microscopy experiments

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