Received: 27 November 2016
|
Revised: 17 May 2017
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Accepted: 3 June 2017
DOI: 10.1111/jfpp.13411
ORIGINAL ARTICLE
Extraction and characterization of pectin from pomelo peel and its impact on nutritional properties of carrot jam during storage Manik Chandra Roy1 | Majbaul Alam1 | Abu Saeid1 | Bijoy Chandra Das1 | Md. Biplob Mia1 | Md. Atikur Rahman1 | Jong Bang Eun2 | Maruf Ahmed1,2 1 Department of Food Processing and Preservation, Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh 2
Department of Food Science and Technology and BK 21 Plus Program, Graduate School of Chonnam National University, Gwanju, South Korea
Abstract Pectin was extracted using 0.1 N HCl at 90 8C for 120 min at pH 1.5 and 2.0 from pomelo peel and characterized in this study. Influence of various concentrations of extracted pomelo peel pectin on physicochemical, bioactive compounds, color, and sensory attributes of carrot jam during storage was also studied. Pectin extracted at pH 2.0 had higher ash content, equivalent weight, and total anhydrouronic acid content than that extracted at pH 1.0. Extracted pomelo peel pectin was categorized as high-methoxyl pectin based on the degree of esterification. The b-carotene
Correspondence Dr. Maruf Ahmed, Department of Food Processing and Preservation, Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh. Email:
[email protected]
and total phenol content were increased in jam after 90 days of storage. Ascorbic acid content decreased with increasing storage period. Jam prepared using commercial pectin had higher DE values than jam prepared using pomelo peel pectin. Physico-chemical properties were influenced by pectin concentrations and storage time. Overall acceptability was similar for all samples on the basis of sensory evaluation. The results showed that pomelo peel might be used as a rich source of pectin and pomelo peel pectin could be used as an alternative to commercial pectins for carrot jam preparation.
Practical applications Pectin is one of the main ingredients for jam and jelly making. Citrus fruits are main sources of pectin. Usually pomelo peels are discarded as waste materials. However, it could be a good source of pectin. In this article, pectin was extracted from pomelo peel and its application was observed as carrot jam during storage. Therefore, it can be concluded that extraction of pectin from pomelo peel might be used as an alternative to commercial pectin for carrot jam preparation.
1 | INTRODUCTION
nitric (Constenla, Ponce, & Lozano, 2002), and sulfuric acid (Garna et al., 2007), which are regarded as conventional acids for extraction
The most widely cultivated citrus fruits are the following: orange, lemon,
(Yapo, 2009). Sulfuric, hydrochloric, and nitric acids are cheap mineral
lime, mandarin, grape fruit, and pomelo. Citrus fruit pulp consists of 60–
acids. Among these, hydrochloric acid is recommended as the best sol-
65% peels, 30–35% segment, pulp, and 0–10% seeds (Afshar & Naser,
vent to extract pectin (Kalapathy & Proctor, 2001). High strength acid
2008). Citrus by-products are considered as rich sources of phytochemi-
has the ability to solubilize the protopectin from the albedo. Lower pec-
cals, pectin, and dietary fibers (Afshar & Naser, 2008). Pectin is the
tin yield was obtained after using water and oxalate as chelating agents,
methylated ester of polygalacturonic acid, which contains 1,4-linked
as compared with that obtained from acid extraction (Methacanon,
a-D-galacturonic acid residues (Mesbahi, Jamaliana, & Farahnaky, 2005).
Krongsin, & Gamonpilas, 2014). Hot acid extraction (HCl) of pectin
Pectin can be divided into two types based on the degree of esterifica-
yielded a high anhydrogalacturonic acid content and had a low degree
tion (DE): high-methoxyl pectin (DE > 50%) and low-methoxyl pectin
of methoxyl esterification (Yapo & Koffi, 2006). Kulkarni and Vijanand
(DE < 50%) (Mesbahi et al., 2005). The main sources for commercial pec-
(2010) and Methacanon et al. (2014) found that pectin yield was higher,
tin production are apple pomace and citrus peels (Mesbahi et al., 2005).
but methoxyl content and equivalent weight values were lower, at high
Pectin can generally be extracted using various acids: citric acid,
temperature and lower pH than the values observed at lower tempera-
oxalic (Koubala et al., 2008), hydrochloric (Kulkarni & Vijanand, 2010),
ture and higher pH. An increase in acid strength (that is, decreasing pH)
J Food Process Preserv. 2017;e13411. https://doi.org/10.1111/jfpp.13411
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C 2017 Wiley Periodicals, Inc. V
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plays an important role in increasing the content of galacturonic acid
thickness) with a sharp knife. Then, the slices were blended and
(Yapo, Robert, Etienne, Wathelet, & Paquot, 2007). Pectin quality
dried at 60 8C for 24 hr in a cabinet drier (Model-136–12, Seoul,
depends on extraction time, temperature, and pH. Pectin quality and
Korea), followed by grinding into powder using a blender (Jaipan
purity also depends on several factors: degree of esterification, anhy-
CM/L-7360065, Japan). The powder was sieved using a stainless
drogalacturonic acid, molecular weight, and ash content. Good quality
steel sieve (Sieve no. MIC-300) and packed in low-density polyeth-
pectin contains 65% anhydrogalacturonic acid and 10% ash.
ylene bags (thickness of 75 mm). The obtained powder was sealed
Pectin is used as a gelling agent in jams, jellies, medicines, sweets,
and stored at 6–10 8C until further use.
and as a stabilizer in fruit juices and milk-based beverages. Several researchers have prepared jam from various sources. Legua, Melgarejo, Martínez, Martínez, and Hern andez (2012) made jam from pomegran-
2.2 | Extraction of pectin
ate using high- and low-methoxyl pectin, and found that high-methoxyl
2.2.1 | Preliminary experimentation to find out optimum conditions
pectin resulted in a higher yield. Another study from Poiana, Alexa, and Mateescu (2012) reported that low-methoxyl pectin concentrations showed increased bioactive compounds for low sugar Bilberry jam. Pilizota et al. (2009) also produced strawberry jam using low and highmethoxyl pectin and revealed that low-methoxyl pectin could retain high amount of anthocyanin and total phenol than high methoxyl pectin. Colored carrot jams were produced using mild and common cooking methods (Renna et al., 2013). Pumpkin jams were processed using pectin extracted from lemon and orange fruit peels (Sulieman, Khodari, & Salia, 2013). Time and temperature had a great impact on the stabil-
Hydrochloric acid is recommended as the best solvent to extract pectin (Kalapathy & Proctor, 2001). Pectin extraction was performed using 0.1 N HCl solvent at different extraction temperatures (80, 90, and 100 8C), extraction times (60, 120 min), and pH (1.5, 2.0, and 2.5). The solution pH was adjusted with HCl and NaOH. For each condition, pomelo peel powder (30 parts extraction solvent and 1 part pomelo peel powder) was heated in a hot water bath. The heated extractant was filtered through a cheese cloth and pressed to recover the extract.
ity of apricot jam (Touati, Tarazona-Diaz, Aguayo, & Louaileche, 2014).
The pectin was precipitated by ethanol (95–98%) in the ratio of 1:2
Blackberry jam color and bioactive compounds were correlated with
(1 part extractant and 2 parts ethanol) and kept at room temperature
pectin type and dosage (Poiana, Munteanu, Bordean, Gligor, & Alexa,
overnight. The precipitated pectin was filtered through Whatman No.
2013).
1 and washed with 75% ethanol (v/v), 85% ethanol (v/v), and absolute
Carrots are commonly used as salad and cooked vegetables in
ethanol to remove the soluble impurities. Then, pectin was dried at
soups, stews, and curries and are also used for the preparation of
60 8C for 24 hr in a cabinet drier (Model-136–12, Seoul, Korea). Vari-
pickles and sweet dishes. They are an excellent source of beta-
ous conditions, such as extraction temperature (90 8C), extraction time
carotene, phenol, and vitamin C. Presence of phenolic compounds in
(120 min), and pH (1.5 and 2.0) were selected, based on the pectin
carrots contributes to their color, bitterness, and aroma (Zhang, Tan,
yield. We found both pH 1.5 and pH 2.0 resulted in higher yields than
Mckay, & Yan, 2005). It has been reported that different phytochemi-
that obtained at pH 2.5 (data not shown). Therefore, we were used
cals in carrots might be helpful to inhibit cancers, free radical scav-
both pH conditions for the extraction of pectin. In the preparation of
engers, high blood pressure, and also enhance the immune system
carrot jam, only pectin extracted at pH 2.0 was used due to higher yield
(Sharma, Karki, Thakur, & Attri, 2012). Phenolic compounds could be
than pectin extracted at pH 1.5 although the values were not signifi-
used as a good indicator to evaluate the quality of vegetables during
cantly different.
processing and storage. In recent years, pomelo production has increased. Large numbers of pomelo peels are produced as a byproduct; these have not yet been used as a source of value added products. The extracted pectin from pomelo peel could be used as ingredient in jam production. Therefore, the objectives of this study were to characterize pomelo peel pectin, as well as produce carrot jam, using various concentrations of pomelo peel pectin and compare with commercial pectin by performing nutritional quality and sensory evaluation during storage.
2 | MATERIALS AND METHODS 2.1 | Sample collection and preparation of pomelo peel powder
2.2.2 | Preparation of jam Carrots were purchased from the local market of Dinajpur, Bangladesh. Raw carrots were washed, peeled, and cut into 2-cm thickness slices. Carrot slices were blanched in boiling water (1: 0.75) for 15 min and blended using a blender machine. Thereafter, 225 g pulp was mixed with sugar solution (275 g sugar dissolved in 200 ml boiling water). Sodium benzoate at the concentration of 0.05% of final volume of jam was added. Pectin (at concentration of 1% or 1.5%), which was diluted with boiled water (1 g in 35 ml), was added to the mixture. The pH of the mixture was adjusted to 3.0 6 0.2 by adding citric acid solution diluted with water (1 g in 10 ml). The mixture was cooked at 100 6 5 8C and stirred constantly until the TSS value reached 65–688 Brix. The prepared jams
Pomelo was purchased from the local market of Dinajpur, Bangla-
were poured into sterilized glass jars, cooled using cold water,
desh. The pomelos were washed carefully with tap water to remove
corked immediately, and stored at ambient temperature (30 6 2 8C)
dirt soil from the surface, peeled, and cut into slices (2–3 mm
until further use.
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2.3 | Characterization of pectin
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extracted with 20 ml of methanol and concentrated up to 10 ml by heating on a hot plate at 60 8C. The volume was readjusted to 20 ml
2.3.1 | Pectin yield
with methanol and filtered through Whatman no. 1 filter paper. There-
Pectin yield was calculated as follows: Pectin ðg=100 gÞ 5 Weight ðgÞ of dried pectin 3 100 Weight ðgÞ dried pomace powder taken for extraction
after, 1 ml sample and 0.2 ml of 10% Folin reagent were transferred to a test tube. Following 3 min incubation, 0.8 ml of 7.5% Na2CO3 was added and kept in dark for 1 hr at room temperature. Then, the absorbance was measured at 760 nm. The phenol content was determined using Gallic acid standard curve and was expressed as mg/g.
2.3.2 | Determination of equivalent weight Equivalent weight was determined using a previously reported method (Ranganna, 1995). Sample (0.5 g) was added to 250 ml conical flask and 5 ml ethanol was added. Then 1 g sodium chloride and 100 ml distilled water were added, followed by addition of 6 drops of phenol red and titration against 0.1 N NaOH. The end point was indicated by purple color. This neutralized solution was stored for determination of methoxyl content. Equivalent weight was calculated using the following
2.4.2 | Determination of beta-carotene Beta-carotene content of carrot jam was determined according to the method of Barros, Ferreira, Queiros, Ferreira, and Baptista (2007). One gram of jam was mixed with 10 ml of acetone : hexane mixture (4:6) and vortexed for 5 min. Then, the mixture was filtered through Whatman no. 1 filter paper and absorbance was measured at 453, 505, and 663 nm. b-carotene content was calculated according to the following equation: b2carotene ðmg=100 mlÞ 5 0:216 A663 2 0:304 A505 1 0:452 A453:
formula: Equivalent weight 5
Weight of sample 3 1; 000 ml of alkali 3 Normality of alkali
2.4.3 | Determination of vitamin C Vitamin C content was determined according to the method described
2.3.3 | Determination of total anhydrouronic acid content
by Adebayo (2010) with slight modification. Carrot jam (2 g) was mixed
Total anhydrouronic acid content (AUA) of pectin was obtained using
with 5 ml of 20% metaphosphoric acid solution and filtered through
the following formula (Devi et al., 2014):
Whatman no. 1 filter paper. The filtrate (1 ml) was added to a small
% of AUA 5
176 3 0:1z 3 100 176 3 0:1y 3 100 1 w 3 1; 000 w 3 1; 000
When molecular unit of AUA (1 unit) 5 176 g where, z 5 ml (titer) of NaOH from equivalent weight determination; y 5 ml (titer) of NaOH from methoxyl content determination; w 5 weight of sample.
beaker and mixed with 10 ml distilled water. Then, 2 ml was transferred into a beaker, shaken with 2 drops of phenolphthalein solution, and titrated against 2,6-indophenol until pink color was developed. Vitamin C content was calculated according to the following equation: mg Dye factor3Titer value3volume made up 5 Vitamin C g Aliquot taken 3sample weight
2.3.4 | Determination of degree of esterification
2.4.4 | Determination of the color of prepared jam
The degree of esterification (DE) of pectin was measured on the basis
The color attributes (Haunter L*, a*, and b* values) were measured
of its methoxyl and AUA content, according to a report by Azad, Ali,
using a spectrophotometer (CM-2500d, Konica Minolta, Japan).
Akter, Rahman, and Ahmed (2014) and calculated from the following formula. % DE 5
176 3 %MeO 3 100 31 3 %AUA
2.3.5 | Physicochemical analysis of jam Moisture, crude protein, fat, and ash content were determined using official methods (AOAC, 2000). Titrable acidity was done according to a previously described method (Ashaye & Adeleke, 2009). Total soluble solids (TSS) of the carrot jam were determined by using a refractometer. Digital pH meter was used to determine the pH value of the sample.
2.4.5 | Storage studies of carrot jam All prepared jam was kept at room temperature and physicochemical, bioactive compounds, and sensory evaluation of prepared jam was conducted after 90 days.
2.4.6 | Sensory evaluation Sensory evaluation was performed on 90th day of storage. Fifteen members were selected from the University community. The samples were presented randomly. Panelists were facilitated to rinse their mouth with tap water between sample evaluations. Carrot jams were evaluated organoleptically for appearance, flavor, texture, and overall acceptability, according to the hedonic scale of nine points (9 5 like extremely to
2.4 | Determination of bioactive compound of prepared jam
1 5 dislike extremely), as reported by Basu and Shivare (2010).
2.4.1 | Determination of phenol content
2.5 | Statistical analyses
Total phenol was determined according to the method described by
All measurements were performed in duplicates for each of the sample.
Sulaeman et al. (2001) with slight modification. Carrot jam (1 g) was
Results were expressed as mean values with standard deviation.
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T A B LE 1
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Effect of pH on physico-chemical properties of pomelo
peel pectin
(Wang, Chen, & Lu, 2014). The highest value of DE in pomelo peel pec-
pH 1.5
pH 2.0
Yield (%)
16.073 6 0.651a
16.740 6 0.488a
5.501 6 0.027b
5.697 6 0.005a
540.04 6 11.89b
711.33 6 13.77a
AUA (%)
84.29 6 5.83a
85.57 6 4.96a
Degree of esterification (%)
61.19 6 2.83
b
70.79 6 1.77
L*
23.99 6 3.21
a
23.88 6 1.35a
Equivalent weight
Sotanaphun et al. (2012), who found DE values of 76.30 and 83.41% in pectin from fruit peel of Citrus maxima and apple pomace, respectively
Composition
Ash (%)
ET AL.
a
tin was found at pH 2. This might be due to increase in the deesterification of methoxyl groups of the chain (Pagan, Ibarz, Llorca, Pagan, & Barbosas-Canovas, 2001). Degrees of esterification were significantly different for both pH conditions. The equivalent weights of extracted pectin ranged from 540.04 to 711.33 (Table 1), which were lower than that of apple pomace pectin (833.33–1666.30, Kumar & Chauhan, 2010), but higher than that of cocoa husk pectin (510.68–645.19, Ramli & Asmawati, 2011). The
a*
3.76 6 0.46a
1.77 6 0.38b
pomelo pectin extracted at pH 2 showed significantly higher equivalent
b*
12.3 6 1.71a
8.99 6 1.27a
weight (711.33) than that of pectin extracted at pH 1.5 (368.0).
Mean 6 SD (Three determinations). Mean values in the same row with different letters are significantly different (p < .05).
Changes in equivalent weight could be dependent on the amount of free acid (Ramli & Asmawati, 2011). Food Chemical Codex (1996) mentioned that total anhydrouronic
Statistical analysis was performed using the Statistical Software R (win-
acid content (AUA) indicates the purity of the extracted pectin, and its
dows version 3.2.2). Duncan test was performed to evaluate the signifi-
value should not be less than 65%. In this study, pectin extracted under
cance of difference between mean values at the level of p < .05.
both pH conditions (1.5 and 2) showed high values of AUA. The AUA contents in pectin extracted at pH 2 and pH 1.5 were not significantly
3 | RESULTS AND DISCUSSION
different, and showed values of 85.57 6 4.96% and 84.29 6 5.83%, respectively. These values were higher than those of apple pomace
3.1 | Effect of pH on various physicochemical properties of pectin Table 1 shows various physicochemical properties of pomelo peel pectin at different pH contents. The yields of pectin from pomelo peel at pH 1.5 and 2 were not significantly different, with values of 16.073 and 16.740%, respectively. These values were similar to those observed with ambarella peel pectin (10–13%) and mango peel pectin
pectin (59.52–70.50%, Kumar & Chauhan, 2010), commercial apple pectin (61.72%), and dragon fruit pectin (45.25–52.45%, Ismail, Ramli, Hani, & Meon, 2012). Low value of AUA means that extracted pectin might consist of high amount of proteins, starch, and sugars (Ismail et al., 2012). Purity of pectin or galacturonic acid content depended on pH, rather than temperature (Sotanaphun et al., 2012). The color of pomelo peel pectin powder in terms of L*, a*, and b*
(4.6–18.5%) extracted using deionized water (Koubala et al., 2008).
value were measured using a spectrophotometer, where, L*, a*, and b*
However, yield of pomelo peel pectin was higher than that reported by
value indicated lightness, redness, and yellowness, respectively. The
Yapo and Koffi (2006) for passion fruit pectin (7.5%) and lower than
visible color of pomelo peel pectin powder for both pH (1.5 and 2) was
golden apple pectin (22%, Rha et al., 2011). Mollea, Chiampo, and Conti
brown. The L values for pomelo peel pectin powder at pH 1.5 and pH
(2008) obtained higher yield at lower pH than higher pH. Koffi, Yapo,
2 were similar and recorded as 23.99 and 23.88, respectively (Table 1)
and Besson (2013) reported that the yield of pectin was strongly pH
indicating less lightness of powder. The L* value was lower (23.88 to
dependent when the other parameters (time, temperature, and solid to
23.99), while redness (3.76 and 1.77) and yellowness (12.3 and 8.99) to
liquid ratio) were kept constant. Usually pectin yield depends on the
the values observed by Masmoudi et al. (2010) for lemon pectin from
pectin source and extraction conditions (Rha et al., 2011). The ash con-
lemon by-products. The difference in L* values might be due to Mail-
tent of pomelo peel pectin was 5.501–5.697%, for both pH conditions.
lard reactions occurring during the extraction process.
Pectin extraction at pH 2 resulted in higher ash content, as compared with that from pectin extraction at pH 1.5. This observation was com-
3.2 | Chemical compositions of raw carrot
parable to that found by Azad et al. (2014), who reported that the ash content of lemon pomace pectin varied from 2.41 to 4.06%. Pectin
The present study showed the following properties of raw carrot: per-
purity and good gel formation could be dependent on low ash content
centage of moisture (90 6 0.17), ash (0.90 6 0.14), protein (0.67 6
(below 10%). Therefore, the ash content indicates that the pectin used
0.05), fat (0.20 6 0.01), titrable acidity (0.10 6 0.00), T.S.S (4.85 6
in this study was pure, and the extracted pectin might have gel-forming
0.07), vitamin C (79.5 6 0.03 mg/100 g), total phenol (81.73 6 3.27
ability.
mg/g), b-carotene (45 6 0.00 mg/100 ml), and pH 5.89 (Figure 1). The
The degree of esterification (DE) of pomelo peel pectin ranged
values of moisture, ash, protein, and fat were nearly in accordance with
from 61.19 to 70.79% (Table 1). According to DE, our results showed
the results of raw carrots reported by Sharma et al. (2012). Beta-
that the both samples pH 1.5 and 2.0 produced high methoxyl pectin.
carotene and vitamin C contents observed in our studies were much
Methacanon et al. (2014) also found high-methoxyl pectin from pomelo
higher than those reported by Sharma et al. (2012). These variations
peel (59.4–70.7%). These values were lower than those reported by
might be due to origin of the samples.
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araca and marolo jams increased during storage. This might be attributed to the reduction in moisture content (Damiani et al., 2012). The pH values for all jam samples ranged from 2.62 to 3.34. This finding was in accordance with the results observed for apple jam (2.71–4.60, Muhammad, Durrani, Zeb, Ayub, & Ullah, 2008), apricot jam (3.21–3.54, Touati et al., 2014), and roselle jam 2.59–3.74 (Ashaye & Adeleke, 2009). pH values decreased throughout the storage period, observe for apple jam (Muhammad et al., 2008), apricot jam (3.21– 3.54, Touati et al., 2014), and roselle jam (2.59–3.74, Ashaye & FIGURE 1
Adeleke, 2009). The rate of decrease in pH was higher in jam prepared
Chemical composition of raw carrot
with pomelo peel pectin than in jam prepared with commercial pectin. The decrease in pH value may be attributed to hydrolysis of pectin
3.3 | Physicochemical properties of carrot jam during storage
(Sogi & Singh, 2001), formation of free acid (Muhammad et al., 2008), and compositional variation (Souad, Jamal, & Olorunnisola, 2012). Values of titrable acidity and total soluble solids (TSS) of prepared
Various physicochemical compositions of carrot jam during storage are shown in Table 2. Moisture and ash content of all carrot jam varied from 28.63 to 31.19% and 0.37 to 0.78%, respectively. The moisture contents of jams prepared using commercial pectin and pomelo pectin were similar. Data regarding changes in ash content of carrot jams during storage revealed that time and pectin concentration did not affect the ash content. Similar finding was observed by Damiani et al. (2012), who did not find any changes in the ash content during storage for a mixed araca and marolo jam. The fat contents of produced jams were in the range between 1 and 2%. Similar results were reported by Pavlova et al. (2013), who found fat contents of 0.90 and 0.97% for raspberry jam and peach jam, respectively. The protein contents of for-
jam samples were 0.160–0.352% and 65.40–69.308 Brix, respectively, over the storage period. Titrable acidity values were higher than that of apple jam (0.21–0.64%, Muhammad et al., 2008) and lower than that of apricot jam (0.82%, Touati et al., 2014). Titrable acidity values increased with increasing storage time. This is mainly due to breakdown of pectin into pectinic acid (Muhammad et al., 2008). TSS values were in agreement with Ferreira et al. (2004), who observed values between 59.2 and 75.18 Brix for quince jams. TSS values of jams decreased, except for jam prepared with high concentration of pomelo peel pectin. Increase in TSS values might be due to breakdown of polysaccharide into monosaccharide and oligosaccharides and fermentation of sugar (Wisal, Mashwani, & Noor, 2014).
mulated jams were within a range of 0.65–1.01%, which was nearly in accordance with the protein contents of raspberry jam (1.76%) and peach jam (1.82%) reported by Pavlova et al. (2013). Protein content of the jam decreased with increasing the storage time, except in jam formu-
3.4 | Bioactive compound levels of carrot jam during storage
lated with 1% commercial pectin. Previous study by Pavlova et al. (2013)
Table 3 reveals the bioactive compound retention of carrot jam during
showed that protein content of raspberry jam decreased during storage.
the period of storage. b-carotene is a potent precursor of vitamin A
On the contrary, Damiani et al. (2012) reported that protein contents of
that has several positive health effects, such as improving retinol
T A B LE 2
Effect of pectin concentrations on physico-chemical properties of carrot jam during storage Quality Parameters
Sample
Period of storage pH
Raw carrot – 1
2
3
4
Titrable acidity (%) TSS (8Brix)
5.89 6 0.01 2.99 6 0.01
0th day
A
90th day
B
0th day
A
90th day
B
0th day
A
90th day
B
0th day
A
90th day
B
0.064 6 0.00 0.192 6 0.00
d
b
2.62 6 0.01c
A
3.12 6 0.01b
A
2.83 6 0.00b
A
3.06 6 0.00c
A
2.93 6 0.00a
A
3.34 6 0.01a
A
2.83 6 0.02b
A
Moisture (%)
4.85 6 0.07
90.55 6 0.17
a
67.30 6 1.41
A
65.75 6 0.07c
A
67.30 6 1.27a
A
66.80 6 0.00b
B
67.15 6 0.21a
A
65.40 6 0.28c
A
66.30 6 0.28a
A
69.30 6 0.00a
A
a
A
0.352 6 0.04a
A
0.160 6 0.04a
A
0.224 6 0.04b
A
0.160 6 0.04a
A
0.288 6 0.05ab
B
0.160 6 0.05a
A
0.256 6 0.00ab
A
Fat (%)
30.24 6 0.08
Ash (%)
0.20 6 0.01 bc
1.5 0 6 0.71
A
0.90 6 0.14 0.70 6 0.14
a
A
1.33 6 0.60a
A
1.50 6 0.71a
A
1.00 6 0.00a
A
1.50 6 0.71a
A
1.68 6 0.11a
A
2.00 6 0.00a
A
1.78 6 0.00a
A
31.17 6 3.26a
A
30.58 6 0.03ab
A
29.13 6 0.14a
A
29.57 6 0.47c
A
28.99 6 0.30a
A
31.19 6 0.24b
A
28.63 6 1.05a
B
Protein (%) 0.67 6 0.05 0.65 6 0.00d
a
A
0.71 6 0.17a
A
0.40 6 0.00b
A
0.37 6 0.01b
0.70 6 0.06a 1.01 6 0.00a
A
0.79 6 0.12a
0.40 6 0.00b
A
0.90 6 0.00c
0.41 6 0.04b
B
0.78 6 0.03a
A
0.74 6 0.02a
A
0.88 6 0.00a 0.92 6 0.00b 0.79 6 0.12a
1 5 jam containing 1% commercial pectin, 2 5 jam containing 1% pomelo pectin, 3 5 jam containing 1.5% commercial pectin, 4 5 jam containing 1.5% pomelo pectin. A–B Means followed by different superscript alphabets in each column are significantly different among storage time (p < .05). a–b Means followed by different superscript alphabets in each column are significantly different among pectin concentration (p < .05).
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T A B LE 3
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Effect of pectin concentrations on b-carotene, vitamin C, and total phenol content of carrot jam during storage
Sample
Period of storage
Raw carrot
–
1
b-carotene (mg/100 g) 0.044.5 6 0.71 B
0th day
0.061.0 6 0.00c
B
0.0435 6 0.71a
A
0.067.0 6 1.41ab
B
0.0435 6 0.71a
A
0.0655 6 0.71b
B
0.044.5 6 0.71a
A
0.068.0 6 0.00a
B
0th day
A
90th day
A
0th day
A
90th day
B
81.73 6 3.27 a
B
32.3 6 3.04a
88.18 6 0.13a
145.38 6 1.63a
A
49.5 6 3.04a
A
90th day
4
55.9 6 6.08
A
B
0th day
3
0.0445 6 0.71
Total phenol (mg/g)
79.45 6 3.04 a
A
90th day 2
Vitamin C (mg/100 g)
83.27 6 9.25a
A
30.1 6 6.08a
131.25 6 18.91a
A
53.8 6 3.04a
B
36.6 6 3.040a
90.39 6 1.08a
136.25 6 5.30a
A
55.8 6 5.87a
84.33 6 0.13a
A
32.3 6 3.04a
141.74 6 19.58a
A
Sample 1, sample 2, sample 3, and sample 4 abbreviations are given in Table 2. A–B Means followed by different superscript alphabets in each column are significantly different among storage time (p < .05). a–b Means followed by different superscript alphabets in each column are significantly different among pectin concentration (p < .05).
function. b-carotene content of the formulated jams ranged from
commercial pectin. The vitamin C content of formulated jam did not
0.0435to 0.068 mg/100 g. These results were much lower than various
significantly change on increasing pectin concentration. However, vita-
colored jams (8–17 mg/100 g) produced using mild heat, reported by
min C content decreased throughout the storage period, which is in
Renna et al. (2013). This variation might be related to different jam
accordance with Poiana et al. (2012), who reported a decrease in vita-
processing method and cultivar. An increase of b-carotene content by
min C content from 14 to 22% in case of bilberry jam during storage.
137.07–152.80% was observed in formulated jam, as compared with
Vitamin C is very unstable, since it oxidizes easily when exposed to
raw carrot, after 90 days of storage. The increase in the concentration
heat, oxygen, and light (Onyeka, 2008). Our results show that the jam
of b-carotene could be attributed to the increase in phenol. A good
is very high in vitamin C and could be useful against vitamin C
correlation was found between total phenol and b-carotene (data not
deficiency-related aliments like scurvy (Edem & Miranda, 2011).
shown) during storage. Renna et al. (2013) found 18–184% increase in
Despite the losses in vitamin C during processing and storage, the
b-carotene content of commercial and yellow carrot jam prepared by
residual amounts were of appreciable quantities that could still meet
mild method. In addition, Miglio, Chiavaro, Visconti, Fogliano, and Pel-
the recommended daily intake (RDA) of 30 mg/65 kg body weight for
legrini (2008) found a tendency of increase in b-carotene content of
an adult man (Olson & Hodges, 1987). Total phenol content increased in formulated jam, as compared
boiling carrot. The content of vitamin C (30.1–55.9 mg/100 g) in carrot jams was
with raw carrot, after one day of processing. This might be due to the
comparable to that reported by Sulieman et al. (2013), who found 22–
enhanced phenolic or bound phenolic content from disruption of cell
52 mg/100 g vitamin C in pumpkin jams made with orange, lemon, or
structure through thermal processing (Poiana et al., 2012). All prepared
T A B LE 4
Effect of pectin concentrations on color values of carrot jam during storage Color parameters
Samples
Period of storage
2
3
4
a*
48.21 6 1.19
Raw carrot 1
L*
31.78 6 0.52
18.54 6 3.33a
0th day
A
90th day
A
0th day
A
90th day
A
0th day
A
90th day
A
0th day
A
90th day
A
b* 45.28 6 0.51
–
31.49 6 5.35a
–
15.23 6 1.19ab
A
17.87 6 1.96b
–
13.63 6 2.11a
A
6.44 6 1.53a
A
9.11 6 0.18b
A
A
25.52 6 7.74a
A
21.46 6 1.27a
A
28.16 6 6.02a
A
6.85 6 1.03a
A
10.41 6 0.04b
A
7.04 6 0.66
a
B
09.38 6 0.23b
A
08.31 6 0.69
A
21.36 6 1.63a 30.67 6 4.48
A
a
B
22.89 6 2.25a
A
26.90 6 5.03
B
a
a
DE
13.36 6 0.35
19.59 6 3.70
9.01 6 2.59b
b
A
21.30 6 1.29b
–
15.99 6 0.10
a
A
16.78 6 0.22b
–
17.32 6 1.28
a
Sample 1, sample 2, sample 3, and sample 4 abbreviations are given in Table 2. A–B Means followed by different superscript alphabets in each column are significantly different among storage time (p < .05). a–b Means followed by different superscript alphabets in each column are significantly different among pectin concentration (p < .05).
a
11.24 6 3.21ab
4.42 6 2.55b
A
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ET AL.
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jams contained 83.27–145.38 mg/g total phenol. This finding was sup-
pomelo peel pectin. Colorimetric measurements of both jams yielded
ported by Renna et al. (2013), who found approximately 90–130 mg/g
similar results, and pectin concentration caused no significant differen-
of phenol in carrot jam prepared using mild and common method. The
ces in appearance, flavor, and texture of the prepared jams. Jam made
phenol content was much lower than those of strawberry jam (578.26
with pomelo pectin was slightly more acceptable to the panelists than
mg/g), cherry jam (543.94 mg/g), apricot jam (514.86 mg/g), and fig jam
jam prepared with commercial pectin. However, the sensory evaluation
(291.42 mg/g), reported by Rababah et al.(2011). Total phenol content
scores were not significantly different for jams prepared with commer-
in all jam samples increased after 90 days, though pectin concentration
cial and pomelo pectin.
did not significantly affect the phenolic content. Contradictory results was observed by Rababah et al. (2011) who revealed that phenolic con-
4 | CONCLUSIONS
tent decreased in fruit jam during storage. Poiana et al. (2012) also demonstrated that the phenolic content could be decreased by increas-
Pectin was extracted from pomelo peel and the effects of pectin con-
ing the low-methoxyl pectin concentration in bilberry jam. Higher total
centration on physico-chemical, bioactive compounds, color, and sen-
phenol content might be related to b-carotene. Highly correlation was
sory attributes of carrot jam during storage were studied. The results
found between total phenol and b-carotene (data not shown).
showed that pectin yield (16.07–16.74%), ash content (5.50–5.69%),
3.5 | Color stability of carrot jam during storage
70.79%), and AUA content (84.29–85.57%) were similar for the two
equivalent weight (540.04–711.33), degree of esterification (61.19–
The color attributes and changes in color values of carrot jam during storage are shown in Table 4. The Hunter color parameters, L*, a*, b*, and DE have been widely used to measure the color component. L*, a*, and b* values decreased after jam preparation, relative to the values of raw carrot. L* values increased, whereas a* and b* values decreased, during the storage period. Pectin concentration did not affect L* and DE values. Color loss was comparatively lower in jam prepared with pomelo pectin than that made with commercial pectin, and the color
samples under pH conditions of 1.5 and 2. The retention of bioactive compounds, color stability, as well as physico-chemical properties were related to pectin type and concentration throughout the storage period. This study revealed that pomelo peel is a good source of pectin, and subsequently, carrot jam might be produced using extracted pomelo peel pectin. Our results will provide an additional boost to the economic sector through new value-added products and sources of natural antioxidants.
change decreased with an increase in the pectin concentration and storage time. Variation in the L*, a*, b*, and DE values may be due to
R EF ER E N CE S
the changes in total phenol content. Phenols have been associated
Afshar, M. A., & Naser, M. (2008). Nutritive value of some agroindustrial by-products for ruminants - A review. World Journal of Zoology, 3, 40–46.
with color change, particularly lightness, in a reported by Mondy and Gosselin (1988).
AOAC. (2000). Association of official analytical chemistry (pp. 12–14). Washington DC: Author.
3.6 | Sensory evaluation of jam Impact of pectin concentrations on sensory characteristics of carrot jam are shown in Table 5. The sensory profile of carrot jam was evaluated in terms of appearance, flavor, texture, and overall acceptability after 90 days of storage period. Almost all sensory evaluation scores for jam prepared with pomelo peel pectin were same or slightly higher than those of jam prepared with commercial pectin. Appearance depended on the color: the maximum score (7.0) for appearance was recorded for jams consisting of high concentrations of commercial and Sensory evaluation scores of carrot jam with different pectin concentrations stored for 90 days
T A B LE 5
Sample Appearance 1
6.87 6 1.06
N.S
Flavor 6.13 6 0.74
N.S
Texture N.S
5.93 6 1.16
Overall acceptability N.S
6.13 6 1.36
2
6.73 6 1.01
6.53 6 0.83
6.60 6 1.06
7.20 6 1.15
3
7 .00 6 1.13
6.67 6 1.11
6.47 6 1.36
6.93 6 1.03
4
7.07 6 0.96
6.60 6 1.18
6.53 6 1.19
7.00 6 1.06
Sample 1, sample 2, sample 3, and sample 4 abbreviations are given in Table 2. NS, not significant at (p < .05).
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How to cite this article: Roy MC, Alam M, Saeid A, et al. Extraction and characterization of pectin from pomelo peel and its impact on nutritional properties of carrot jam during storage. J Food Process Preserv. 2017;e13411. https://doi.org/10.1111/ jfpp.13411
