Influence of ultrasound on the functional characteristics of indigenous varieties of mango (Mangifera indica L.)

Ultrasonics - Sonochemistry 64 (2020) 104987

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Influence of ultrasound on the functional characteristics of indigenous varieties of mango (Mangifera indica L.)

T

Tahir Mahmood Qureshia, , Muhammad Nadeemb, Farzana Makenb, Anum Tayyabab, Hamid Majeeda, Masooma Munirc ⁎

a

Department of Food Sciences, Cholistan University of Veterinary & Animal Sciences, Bahawalpur, Pakistan Institute of Food Science and Nutrition, University of Sargodha, Pakistan c Food Science Research Institute, National Agricultural Research Centre, Islamabad, Pakistan b

ARTICLE INFO

ABSTRACT

Keywords: Mango varieties Ultrasonic treatment Chemical characteristics Antioxidant potential

The present study was conducted to evaluate the effect of ultrasonic (US) treatment on chemical characteristics and antioxidant potential of pulps obtained from eight mango varieties indigenous to Pakistan. There was a significant (p < 0.05) effect of varieties and US treatment on chemical characteristics i.e. pH, acidity, TSS, vitamin C contents, total sugars (%), reducing sugars (%) and non-reducing sugars (%). Microstructure evaluation of pulp from all mango varieties showed deshaped middle lamella and cell wall of cells after 8 min of US treatment. At 4 min of US treatment as per shaped cell wall and middle lamella, the chemical characteristics and antioxidant potential were higher. The total phenolics (TP), flavonoids (TF) and total antioxidant activity (TAA) of pulp from most varieties increased significantly (p < 0.05) after US treatment for 4 min but decreased successively after each treatment i.e. 8 and 12 min. The maximum value (314.17 μg AAE/mL pulp) of DPPH was shown by pulp from Dosehri and the minimum (158.67 μg AAE/mL pulp) was found in pulp from Langra before US treatment. The DPPH values of pulp from most of the varieties increased significantly (p < 0.05) after US treatment for 4 min but decreased successively after each treatment but pulp from Langra showed increasing trend after 8 min of US treatment which decreased after 12 min of treatment. The total anthocyanin (TA) values of pulp from Chaunsa, Dosehri, Sindhri, Gulab Khas and Langra increased abruptly after US treatment for 4 min but decreased successively after subsequent treatment. The pulp from Desi, Anwar Ratol, Gulab Khas and Langra showed an abrupt decrease in TA after 8 min of US treatment. An increasing trend of values of total carotenoids (TC) was shown by pulp from all mango varieties after 4 min of US treatment but decreasing trend was observed with subsequent increase in time of US treatment.

1. Introduction Fruit juices may be susceptible to physical, chemical and microbiological changes under thermal conditions due to presence of thermally sensitive compounds [1]. It has been investigated in previous studies that ultrasound application may retain ascorbic acid contents and anthocyanins and also inactivates enzymes (polyphenol oxidase and peroxidase) which may cause browning in juices [2,3]. Similarly, in other studies, it was observed that ultrasonic (US) treatment has the ability to enhance the extraction of phenolic compounds from mango peel, avocado, apple, jussara (Euterpe edulis M.) and blueberry (Vaccinium myrtillus) through acoustic cavitation produced in the solvent [46]. Moreover, it has been suggested that US treatment might be a promising aid in food processing and preservation [7,8].

⁎

Mango (Mangifera indica L., Anacardiaceae family) is known as the ‘King of fruits’ which is grown in tropical and sub-tropical regions in the world. Mango is the most commonly consumed fruit in many countries because of its sweet taste and nutritional value. Pakistan is among the top few mango producing countries in the world. Local industry is involved in the preservation of mango pulp in order to be used during off season for making its nectars and ready to drink juices. As nutritional quality and antioxidant potential of fruits depend on different geographical locations [9,10], it was interested to study the antioxidant potential of pulp from different mango varieties grown in Pakistan. So far, no comprehensive study has been carried out regarding aforementioned aspect of mango varieties present in Pakistan. Moreover, no scientific literature was also available concerning influence of US treatment on antioxidant potential of pulp from

Corresponding author. E-mail address: [email protected] (T.M. Qureshi).

https://doi.org/10.1016/j.ultsonch.2020.104987 Received 27 December 2019; Received in revised form 20 January 2020; Accepted 21 January 2020 Available online 25 January 2020 1350-4177/ © 2020 Elsevier B.V. All rights reserved.

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Fig. 1. Photographs of mango cultivars used in the present study.

prominent mango varieties indigenous to Pakistan. Hence, in view of the above aspects, the present study was designed to evaluate the effect of ultrasound on the antioxidant potential of pulp from prominent mango varieties used in the present study.

(St. Louis, MO). All other chemicals used were of analytical grade. 2.2. Geographical locations of selected indigenous mango varieties Mango is the second largest fruit crop of Pakistan due to its suitable climate and soil for cultivation. Punjab province produces 70% mangoes of total production whereas Sindh produces 24% and only 1% is contributed by Khyber Pakhtunkhwa (KPK) (https://dailytimes.com. pk/7670/east-or-west-pakistani-mangoes-are-the-best/). The 'Sindhri' mango is a large oval shaped mango and is considered the Queen of Mangoes due to its unique taste. It is grown in Sindhri, the biggest area and a town located in Mirpur Khas which is a district of Sindh province whose geographical coordinates are 25° 32′ 0″ North, 69° 0′ 0″ East. Sindhri is also grown in other cities of Sindh, i.e. Umerkot and

2. Materials and methods 2.1. Procurement of materials and chemicals Eight prominent mango varieties such as Chaunsa, Dosehri, Sunehri, Desi, Anwar Ratol, Sindhri, Gulab Khas (locally known as Gulabo) and Langra (Fig. 1) at their optimum maturity were collected from the market at Sargodha, Pakistan. DPPH (2, 2-diphenyl-1-picrylhydrazyl) and other standards were purchased from Sigma-Aldrich Chemical Co. 2

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Sanghar, as well as some areas in Punjab. The 'Chaunsa' mango is extensively grown in South Punjab, i.e. Multan and Rahim Yar Khan. It is also called as King of mangoes due to its unique sweetness, wonderful fragrance and succulent flesh with minimum fiber contents. The geographical coordinates of Rahim Yar Khan are 28° 25′ 0″ North, 70° 18′ 0″ East whereas Multan is situated at 30° 11′ 44″ North, 71° 28′ 31″ East. Besides Multan and Rahim Yar Khan, Chaunsa is also grown in Muzzafargarh and Bahawalpur. Dosehri and Anwar Ratol are extensively grown in Jalalpur Pirwala, a city situated about 90 km away towards south from Multan. Dosehri (long and oval shaped) flavor is sweet and aromatic but Anwar Ratol (small sized) is extremely sweet mango variety. Anwar Ratol is also grown in Shujabad which is located about 45 km in south from Multan. Anwar Ratol and Dosehri are also produced in Mirpur Khas. Langra variety has fiber-less flesh and naturally very sugary and soft. It is grown in Mirpur Khas as well as in Rahim Yar Khan. The Desi mango variety (small and cheaply sold) is not as popular as the commercial ones like Chaunsa, Sindhri and Dosehri because growers are fast switching over to economically profitable mango varieties. It is also grown in Mirpur Khas as well as in Rahim Yar Khan. Gulab Khas has reddish-yellow color, honeyed fragrance and sweet taste. It is grown in Mirpur Khas. Sunehri is also grown in Mirpur Khas.

12 min) was placed on glass slide and covered with cover slip with no bubbles. The same method was adapted for the samples without US treatment. The prepared slides were examined under 40X and images were taken to evaluate the proper sonication time for well homogenized mango pulp sample having excellent antioxidant potential. 2.7. Determination of total phenolics (TP), total flavonoids (TF) and total antioxidant activity (TAA) The TP were determined by following spectrophotometric method [13] and the results were expressed as µg gallic acid equivalent (GAE)/ mL pulp. The TF were also determined by the spectrophotometric method as described by Jia et al. [14]. The results were expressed both as µg of (+)-Catechin equivalent (CE)/100 mL and µg Quercetin equivalent (QE)/mL pulp. The total antioxidant activity (TAA) was determined by the method of Prieto et al. [15] and the results were expressed as µg ascorbic acid equivalent (AAE)/100 mL pulp. 2.8. Determination of DPPH radical scavenging activity and reducing power (RP) Mango varieties were assessed for their DPPH free radical scavenging activity by the method of Yi et al. [16] with some minor modifications and the results were expressed as μg ascorbic acid equivalent (AAE)/mL pulp. The RP was determined by the method as described by Hegazy and Ibrahium [17] and the results were expressed as μg ascorbic acid equivalent (AAE)/100 mL pulp.

2.3. Physical analysis of mango fruits As part of preliminary data, physical analysis of all selected mango fruits was carried out. In order to get reproducible results, 20 mango fruits (from each variety) were randomly selected to measure physical characteristics such as fruit weight (g), seed weight (%), peel weight (%), pulp weight (%), width (mm), volume (L) and Length (cm). A digital calibrated analytical balance was used for physical measurements whereas volume was calculated through displacement method. Further, pulp to seed ratio was also calculated.

2.9. Determination of total carotenoids (TC) and total anthocyanins (TA) Mango pulp from all varieties was also assessed for its total carotenoids using following equation as reported by Hsieh and Ko [18]:

DW = (4.69 × A 440.5

2.4. Ultrasonic treatment of mango pulp

1.96 × A663.6

4.74 × A646.6 ) × V / S

where DW is carotenoids (mg/g), A440.5, A663.6 and A646.6 were the absorbance at 440.5, 663.6, 646.6 nm, V is supernatant volume (mL), S is Sample weight (g). The supernatants of all the samples were prepared after centrifugation at 3000 g for 10 min. The total anthocyanins contents were also calculated using the following equation by following the procedure as described by Aadil et al. [19]:

Ultrasonic (US) treatment of mango pulp was carried according to the method as described by Jabbar et al. [11]. After sorting, washing and slicing of mango fruits, pulp from 20 mango fruits from each variety was extracted and mixed evenly with the help of a domestic blender. Out of the blended mixture of pulp, two equal parts (150 mL each) were taken. One part was given US treatment (24 kHz frequency, amplitude level of 80% (525 W power), pulse duration 5 sec on and 5 sec off, 25 °C) using ultrasonic processor (UP400S, Hielscher Ultrasonics GmbH Hielscher USA, Inc.) with 0.5-inch probe (inserted up to 2 in. inside the sample). The other part (150 mL) was considered as control which was not given any US treatment. The temperature was maintained by using an automatic control system. The US treatment was given for 4, 8 and 12 min. The US treatment for all the samples was performed in duplicate.

Total anthocyanins(mg/L) = (Abs × Mw × DF × 1000)/ × 1 where Abs = (Abs520 − Abs700)pH = 1.0 (Abs520 − Abs700)pH = 4.5, MW = Molecular weight, DF = dilution factor, 1 = path length (1 cm), pigment contents were calculated as malvidin-3-O-glucoside using an extinction coefficient of 28 000 L/mol/cm and a molecular weight of 493.2 g/mol, 1000 = conversion from g to mg. 2.10. Statistical analysis

2.5. Chemical analysis of mango pulp

The statistical analysis was conducted using two way ANOVA at a significance level of p ≤ 0.05, and significant differences between mean values were determined by Tukey pairwise comparison test. The statistical analysis was performed by using Statistix 8.1 software (Analytical Software, Tallahassee, FL, USA).

The total soluble solids (TSS), titratable acidity, total sugars, reducing and non-reducing sugars and vitamin C contents of the extracted pulp (as described in section 2.4) were determined by AOAC method [12]. The TSS (%) to acidity ratio was also calculated. 2.6. Microstructure evaluation of mango pulp after sonication using compound microscope

3. Results 3.1. Physical properties of mango varieties

Ultrasonically treated fresh mango pulp samples from some selected varieties (Fig. 2) were taken in order to judge the homogeneity of mango tissues using compound microscope with green permissible channel (OPTIKA, Microscope, Italy, 4083.B3, Optikam B3 Digital Camera) equipped with Image focus. A small drop of homogenized mango pulp treated under variable sonication time periods (4, 8 and

The results regarding physical characteristics of mango varieties are shown in Table 1. The variety Sindhri excelled in terms of average fruit weight (407.6 g) followed by Sunehri (260.4), Chaunsa (255.9 g), Langra (251.1 g) and Gulab Khas (236.8.20 g). The minimum fruit weight and pulp weight was recorded in Desi and Anwar Ratol. The 3

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Fig. 2. Light microscopic images of Anwar Ratol mango pulp A1 – A4 (A1- control, A3 – A4 ultrasonication treated for 4, 8 & 12 min), Chonsa mango pulp B1 – B4 (B1- control, B3 – B4 ultrasonication treated for 4, 8 & 12 min), Dusehri mango pulp C1 – C4 (C1- control, C3 – C4 ultrasonication treated for 4, 8 & 12 min) and Desi mango pulp D1 – D4 (D1- Control, D3 – D4 ultrasonication treated for 4, 8 & 12 min).

maximum width, volume, length, quantity of pulp (73.28%) and pulp to seed (edible/non-edible) ratio (4.83) were found in Sindhri. The considerable quantity of pulp was found in Chaunsa, Dusehri and Sunehri. Some varieties had low peel weight whereas some contained high quantity of peel. The Chaunsa had the maximum length among all varieties. The minimum width, volume and length were observed in variety Anwar Ratol.

3.2. Chemical properties of mango varieties The results regarding chemical characteristics of pulp from mango varieties after US treatment are presented in Tables 2 and 3. There was a significant (p < 0.05) effect of varieties and US treatment on chemical characteristics i.e. pH, acidity, TSS, vitamin C contents, total sugars (%), reducing sugars (%) and non-reducing sugars (%). The 4

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Table 1 Physical characteristics of mango varieties. Varieties

Fruit weight (g)

Seed weight (%)

Peel (%)

Chaunsa Dosehri Sunehri Desi Anwar Ratol Sindhri Gulab Khas Langra

255.9 164.2 260.4 169.9 148.0 407.6 236.8 251.1

18.96 ± 2.17B 17.64 ± 3.37B 16.52 ± 3.25B 25.1 ± 2.65A 23.81 ± 5.28A 15.4 ± 1.753B 17.69 ± 2.983B 15.71 ± 3.092B

11.86 14.86 15.48 15.53 15.94 11.32 20.39 18.61

± ± ± ± ± ± ± ±

17.70B 17.61C 27.47B 24.33C 20.45C 41.50A 24.25B 32.65B

± ± ± ± ± ± ± ±

2.40CD 3.28BCD 2.20BC 1.62BC 3.665B 2.618D 4.443A 3.006AB

Pulp (%)

Pulp:Seed

Width (mm)

Volume (L)

Length (mm)

69.18 67.51 68 ± 59.37 60.25 73.28 61.92 65.68

3.71 3.97 4.30 2.39 2.70 4.83 3.66 4.42

67.53 ± 4.73BC 70.99 ± 9.93AB 66.11 ± 5.44BC 70.22 ± 14.84AB 60.1 ± 3.02C 76.99 ± 4.84A 62.71 ± 4.09BC 66.63 ± 4.69BC

243.6 154.6 254.5 164.7 144.2 322.9 186.2 256.3

193.40 ± 1.30A 97.2 ± 7.40A 94.50 ± 5.30A 89.50 ± 4.90A 69.00 ± 2.26A 143.50 ± 9.50A 94.20 ± 5.50A 103.60 ± 5.10A

± 4.33AB ± 5.64ABC 5.01ABC ± 3.68BD ± 8.37D ± 3.79A ± 6.65CD ± 4.86BCD

± ± ± ± ± ± ± ±

0.62ABC 0.90AB 1.07AB 0.34D 0.87CD 0.73A 1.06BC 1.36AB

± ± ± ± ± ± ± ±

4.81B 19.59C 63.55B 25.46C 28.43C 61.40A 29.70C 41.08B

Means with different letters in the same column show significant (p < 0.05) differences.

Table 2 Influence of ultrasonic (US) treatment on chemical characteristics (pH, acidity, total soluble solids (TSS) and vitamin C) of pulp from mango varieties. Varieties

US (min)

pH

Acidity (%)

TSS

Chaunsa

0 4 8 12

4.80 4.71 4.62 4.58

± ± ± ±

Dosehri

0 4 8 12

4.78 4.68 4.61 4.56

Sunehri

0 4 8 12

Desi

Vitamin C (mg/100 g)

0.02B 0.01C-E 0.03FG 0.02G

0.26 0.34 0.39 0.44

± ± ± ±

0.07MN 0.02 K-N 0.07 J-M 0.08H-L

17.00 18.11 18.58 18.32

± ± ± ±

0.05G-K 0.08C-F 0.58B-D 0.03B-E

8.80 ± 0.56P 14.29 ± 0.51KL 14.44 ± 0.35KL 13.29 ± 0.49LM

± ± ± ±

0.03BC 0.05D-F 0.02FG 0.01G

0.32 0.43 0.52 0.41

± ± ± ±

0.06 K-N 0.04H-L 0.06E-J 0.04I-M

16.03 16.66 16.44 16.43

± ± ± ±

0.06LM 0.15H-L 0.04 J-L 0.06 J-L

11.20 ± 0.63M-O 11.66 ± 0.38MN 11.58 ± 0.20MN 9.32 ± 0.38 N-P

3.18 3.02 2.97 2.91

± ± ± ±

0.03P 0.03Q 0.02QR 0.03R

1.36 1.47 1.66 1.53

± ± ± ±

0.14C 0.08BC 0.04A 0.07AB

15.26 16.61 16.75 16.22

± ± ± ±

0.15MN 0.29I-L 0.43H-L 0.12 K-M

52.27 78.33 80.78 67.22

0 4 8 12

4.94 4.83 4.75 4.68

± ± ± ±

0.04A 0.03B 0.04B-D 0.02D-F

0.19 0.29 0.45 0.32

± ± ± ±

0.01N 0.06L-N 0.01G-L 0.06 K-N

17.06 18.30 18.55 17.80

± ± ± ±

0.06G-K 0.10B-E 0.05B-D 0.54D-G

8.43 9.55 8.87 8.86

Anwar Ratol

0 4 8 12

4.42 4.37 4.32 4.26

± ± ± ±

0.02H-J 0.02I-K 0.03KL 0.01L

0.45 0.61 0.75 0.62

± ± ± ±

0.02G-L 0.08D-G 0.02D 0.04D-F

17.96 19.60 19.20 18.95

± ± ± ±

0.15D-G 0.17A 0.57AB 0.06A-C

14.81 16.65 18.17 17.33

Sindhri

0 4 8 12

4.17 4.04 3.94 3.87

± ± ± ±

0.02M 0.02N 0.04O 0.03O

0.45 0.66 0.68 0.62

± ± ± ±

0.03G-L 0.01DE 0.02DE 0.04D-F

12.95 13.82 14.92 14.41

± ± ± ±

0.15P 0.07OP 0.06N 0.69NO

9.30 ± 0.02 N-P 22.15 ± 0.13E 21.40 ± 0.62EF 18.71 ± 1.15GH

Gulab Khas

0 4 8 12

4.41 4.36 4.32 4.28

± ± ± ±

0.02H-J 0.02JK 0.03KL 0.02L

0.26 0.48 0.48 0.51

± ± ± ±

0.06MN 0.03F-K 0.05F-K 0.01E-J

15.93 16.72 17.62 17.26

± ± ± ±

0.13LM 0.16H-L 0.55D-H 0.53F-J

16.65 19.43 18.20 13.33

Langra

0 4 8 12

4.64 4.57 4.47 4.45

± ± ± ±

0.02E-G 0.03G 0.03H 0.04HI

0.51 0.56 0.61 0.65

± ± ± ±

0.02E-J 0.01E-I 0.02D-H 0.02DE

15.96 16.70 17.47 16.79

± ± ± ±

0.15LM 0.17H-L 0.51E-I 0.14H-L

9.52 ± 0.02 N-P 16.52 ± 0.02H-K 15.99 ± 0.10I-K 15.04 ± 0.58 J-L

± ± ± ±

± ± ± ±

2.33D 2.19B 1.24A 0.68C

0.45P 0.04 N-P 0.02OP 0.04OP

± ± ± ±

± ± ± ±

0.02KL 0.02H-K 0.03G-I 0.55G-J

0.02H-K 0.72FG 0.20G-I 0.02LM

Means with different letters in the same column show significant (p < 0.05) differences.

lowest pH (3.18) was found in the pulp (without US treatment) from Sunehri whereas pulp from Desi showed the highest (4.94) value. In general, it was observed that pH of pulp from most of mango varieties decreased significantly (p < 0.05) after 4 min of US treatment but further treatment changed the values non-significantly. The pulp from Sindhri and Gulab Khas showed significant (p < 0.05) increase in acidity after US treatment. Even though the pulp from other varieties showed decreasing trend after successive US treatment but that variation was not significant. The minimum TSS (12.95%) was observed in pulp (without US treatment) from Sindhri whereas the maximum (17.96%) was found in pulp (without US treatment) from Anwar Ratol. Generally, there was a significant (p < 0.05) increase in TSS of pulp from Chaunsa, Sunehri, Desi and Anwar Ratol after 4 min of US treatment but further increase in US treatment time did not have significant effect on TSS contents. The rest of the varieties also showed increasing

trend of TSS after subsequent US treatment but that increment was nonsignificant (p < 0.05). Regarding vitamin C contents, pulp from Chaunsa, Sunehri, Sindhri, Gulab Khas and Langra showed significant (p < 0.05) increasing trend after US treatment for 4 min but afterwards, non-significant (p < 0.05) variations were observed in the contents. The maximum vitamin C contents (52.27 mg/100 g) were found in pulp from Sunehri whilst minimum (8.43 mg/100 g) were observed in pulp from Desi before US treatment. The contents of vitamin C increased significantly (p < 0.05) in pulp from Chaunsa, Sunehri, Sindhri, Gulab Khas and Langra after 4 min of US treatment whereas other varieties showed non-significant increase in contents after same treatment. After 8 and 12 min of US treatment to pulp from all varieties, variations in vitamin C contents were non-significant (p < 0.05). Total sugars (%) of pulp from all varieties except Sunehri showed 5

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Table 3 Influence of ultrasonic (US) treatment on chemical characteristics (Total sugars, reducing sugars, non-reducing sugars) of pulp from mango varieties. Varieties

US (min)

Total sugars (%)

Reducing sugars (%)

Non reducing Sugars (%)

Chaunsa

0 4 8 12

18.74 20.42 21.41 20.56

± ± ± ±

0.28G 0.38DE 0.39B-D 0.30DE

6.60 8.63 8.44 8.80

± ± ± ±

0.20DE 0.15C 0.66CD 0.02C

12.14 11.79 12.97 11.75

± ± ± ±

0.41E-G 0.25E-G 0.43DE 0.30E-G

Dosehri

0 4 8 12

16.44 17.03 18.43 18.74

± ± ± ±

0.32HI 0.43H 0.24G 0.28G

5.30 5.83 5.88 5.73

± ± ± ±

0.02E-H 0.07EF 0.12EF 0.06E-G

11.14 11.20 12.55 13.01

± ± ± ±

0.46E-G 0.36E-G 0.12EF 0.23DE

Sunehri

0 4 8 12

10.71 12.25 12.61 12.19

± ± ± ±

0.09L 0.12K 1.33K 0.09K

3.40 3.80 3.96 5.85

± ± ± ±

0.02H 0.08GH 0.03F-H 1.34EF

7.31 8.44 8.65 6.34

Desi

0 4 8 12

20.24 21.65 22.57 21.43

± ± ± ±

0.13E 0.60A-C 0.05A 0.03B-D

5.42 5.73 5.95 5.88

± ± ± ±

0.02E-G 0.11E-G 0.02EF 0.10EF

14.81 15.92 16.61 15.55

± ± ± ±

0.11CD 0.69BC 0.03A-C 0.13BC

Anwar Ratol

0 4 8 12

18.75 19.95 20.90 20.23

± ± ± ±

0.02G 0.02EF 0.03C-E 0.02E

8.28 8.53 8.87 8.63

± ± ± ±

0.02CD 0.09CD 0.09C 0.25C

10.46 11.41 12.03 11.59

± ± ± ±

0.03F-H 0.10E-G 0.10E-G 0.23E-G

Sindhri

0 4 8 12

19.02 20.22 21.74 20.31

± ± ± ±

0.02FG 0.04E 0.02A-C 0.02E

11.20 13.06 14.06 13.40

Gulab Khas

0 4 8 12

9.26 ± 0.15M 13.01 ± 0.02JK 14.02 ± 0.02J 15.73 ± 0.02I

4.76 4.94 5.34 5.45

± ± ± ±

0.02E-H 0.05E-H 0.03E-H 0.02E-G

4.50 ± 0.14L 8.07 ± 0.07I-K 8.68 ± 0.02H-J 10.28 ± 0.02G-I

Langra

0 4 8 12

20.52 22.15 21.64 20.91

3.41 3.80 4.53 3.78

± ± ± ±

0.02H 0.08GH 0.02F-H 0.02GH

17.09 18.35 17.11 17.13

± ± ± ±

0.34DE 0.03AB 0.59A-C 0.02C-E

± ± ± ±

0.02B 0.02AB 0.59A 0.02A

7.81 7.15 7.68 6.91

± ± ± ±

± ± ± ±

0.11JK 0.07H-K 1.36H-J 2.34KL

0.02JK 0.02JK 0.58JK 0.02JK

± ± ± ±

0.32AB 0.06A 0.58AB 0.02AB

Means with different letters in the same column show significant (p < 0.05) differences.

ultrasonication cell wavy shape could be seen (Fig. 2B4, C4 and D4). In conclusion ultrasonication after 12 min treatment in all mango pulps completely deshaped the middle lamella and cell wall that suggests its suitability for homogenous pulp preparation.

increasing trend after 4 min of US treatment but afterwards, non-significant variations were observed in the contents (Table 3). The significant quantities of total sugars (%) were observed in pulp from Chaunsa (18.74%), Anwar Ratol (18.75%), Sindhri (19.02%) and Langra (20.52%). The maximum contents (11.20%) of reducing sugars were found in pulp from Sindhri whereas minimum (~3.40%) were observed in Sunehri and Langra before US treatment (Table 3). The reducing sugars in pulp from Chaunsa and Dosehri were significantly (p < 0.05) increased after 4 min of US treatment and further successive treatment did not show significant variations. The pulp from other varieties showed increasing trend of reducing sugars after US treatment but that increment was non-significant. The contents of non-reducing sugars increased non-significantly in pulp from all varieties except Gulab Khas after successive US treatment (Table 3). The maximum contents (17.09%) of non-reducing sugars were found in pulp from Langra whereas minimum (4.50%) were observed in Gulab Khas before US treatment.

3.4. Effect of ultrasound on TP, TF and TAA of mango pulp There was a significant (p < 0.05) effect of varieties and US treatment on TP, TF and TAA of pulp from mango. Regarding TP, the maximum value (898.6 μg GAE/mL pulp) was shown by pulp from Desi and the minimum (153.4 μg GAE/mL pulp) were found in pulp from Gulab Khas before US treatment. The TP of pulp from most varieties increased significantly (p < 0.05) after US treatment for 4 min but decreased successively after each treatment i.e. 8 and 12 min. Concerning TF (Catechin equivalent), the maximum value (463.4 μg CE/100 mL pulp) was shown by pulp from Desi and the minimum (75.4 μg CE/100 mL pulp) were found in pulp from Dosehri before US treatment. The TF (Catechin equivalent) of pulp from Chaunsa, Sindhri, Gulab Khas and Langra increased significantly (p < 0.05) after US treatment for 4 min but decreased successively after each treatment but pulp from Dosehri, Sunehri, Desi and Anwar Ratol showed decreasing trend after 8 min of US treatment and non-significant effect after 12 min of treatment. Similarly, TF (Quercetin equivalent), the maximum value (1450.0 μg QE/mL pulp) was shown by pulp from Desi and the minimum (156.7 μg QE/mL pulp) were found in pulp from Dosehri before US treatment. The TF (Quercetin equivalent) of pulp from Chaunsa, Sindhri, Gulab Khas and Langra increased significantly (p < 0.05) after US treatment for 4 min and decreased successively after each treatment but pulp from Dosehri, Sunehri, Desi and Anwar Ratol showed decreasing trend after 8 min of US treatment and non-

3.3. Microstructural changes in mango pulp upon US treatment The mango pulps of Anwar Ratol, Chaunsa, Dusehri and Desi were examined using light microscopy in order to optimize the effective ultrasonication work time required for homogenous mango pulp preparation having uniform dispersity (Fig. 2). US treatment in all types of mango pulp is showing rapid shape change in cells of pulp from well structure (round and wavy) to small sized wavy shape compared to control as shown in Fig. 2(A1–A4) for Anwar Ratol. At 4 & 8 min US treatment pulp cells size became narrow with little bit cell shape but at 12 min treatment cells became shapeless due to removal of cell wall (Fig. 2A4). However, in case of Chaunsa, Dusehri and Desi after 12 min 6

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Table 4 Influence of ultrasonic (US) treatment on total antioxidant activity (TAA), total flavonoids (TF) and total phenolics (TP) of pulp from mango varieties. Varieties

US (min)

TAA1

TF (cat)2

TF (quer)3

TP4

Chaunsa

0 4 8 12

200.8 223.6 229.8 196.3

± ± ± ±

15.80F-I 5.20DE 8.20DE 4.10G-I

104.8 ± 1.60N-Q 207.0 ± 16.20GH 134.2 ± 7.40K-N 99.6 ± 4.80O-R

254.7 595.3 352.7 237.3

± ± ± ±

5.33N-Q 54.00GH 24.67 K-N 16.00O-R

644.7 986.0 608.6 476.6

± ± ± ±

97.00IJ 2.57C 1.71JK 2.86LM

Dosehri

0 4 8 12

166.8 220.4 188.5 185.8

± ± ± ±

1.20 K 1.40D-F 0.70H-J 1.00I-K

75.4 86.0 68.4 74.6

156.7 192.0 133.3 154.0

± ± ± ±

4.67QR 8.00P-R 2.67R 3.33QR

726.6 778.0 531.1 531.4

± ± ± ±

20.86GH 8.29FG 10.00KL 2.29KL

Sunehri

0 4 8 12

182.5 195.4 171.7 168.0

± ± ± ±

1.70I-K 0.60G-I 0.70JK 1.20JK

125.6 274.6 169.8 175.8

± ± ± ±

6.40K-O 3.40EF 12.20IJ 7.00HI

324.0 820.7 471.3 491.3

± ± ± ±

21.33 K-O 11.33EF 40.67IJ 23.33HI

716.6 ± 6.86G-I 1078.0 ± 37.43B 1007.4 ± 7.43BC 657.7 ± 6.29H-J

Desi

0 4 8 12

195.2 369.7 290.5 290.5

± ± ± ±

3.00G-I 6.70A 7.50B 7.50B

463.4 567.6 229.6 302.0

± ± ± ±

10.20B 12.80A 2.80G 3.20E

1450.0 ± 34.00B 1797.3 ± 42.67A 670.7 ± 9.33G 912.0 ± 10.67E

898.6 ± 5.43D 1160.9 ± 11.71A 844.9 ± 2.00D-F 891.7 ± 11.71DE

Anwar Ratol

0 4 8 12

200.2 349.2 290.3 208.9

± ± ± ±

2.20F-I 4.40A 3.10B 8.90E-H

156.4 179.8 173.6 177.4

± ± ± ±

0.40I-K 3.00HI 8.00IJ 6.60HI

426.7 504.7 484.0 496.7

± ± ± ±

1.33I-K 10.00HI 26.67IJ 22.00HI

330.6 447.7 433.1 326.9

± ± ± ±

5.43N 10.57M 6.29M 1.71N

Sindhari

0 4 8 12

196.5 256.8 187.6 173.3

± ± ± ±

2.66G-I 0.40C 4.20I-K 14.70JK

130.6 143.2 126.8 118.4

± ± ± ±

3.40J-L 2.00K-O 0.40K-O 2.00L-O

340.7 382.7 328.0 300.0

± ± ± ±

11.3K-O 6.67J-L 1.33K-O 6.67L-O

275.4 312.3 225.4 236.0

± ± ± ±

7.43N-P 3.71NO 0.29PQ 31.43OP

Gulab Khas

0 4 8 12

184.5 197.3 195.0 184.7

± ± ± ±

1.70I-K 0.70G-I 7.80G-I 0.10I-K

128.4 137.4 110.2 105.2

± ± ± ±

0.40K-O 0.20K-M 7.40M-P 2.00N-Q

333.3 363.3 272.7 256.0

± ± ± ±

1.33K-O 0.67K-M 24.67M-P 6.67NO-Q

153.4 300.3 260.0 257.7

± ± ± ±

21.43Q 9.43N-P 8.00N-P 1.14N-P

Langra

0 4 8 12

215.9 239.7 209.6 167.3

± ± ± ±

9.30E-G 16.30CD 5.60 K 5.90E-H

367.2 424.8 303.6 263.2

± ± ± ±

13.20D 41.20C 11.20E 2.00F

1129.3 ± 44.00D 1321.3 ± 137.33C 917.3 ± 37.33E 782.7 ± 6.67F

810.7 850.9 817.1 827.1

± ± ± ±

69.64F 5.71D-F 12.00EF 0.86D-F

± ± ± ±

1.40QR 2.40P-R 0.80R 1.00QR

Means with different letters in the same column show significant (p < 0.05) differences. 1 Total antioxidant activity (µg ascorbic acid equivalent/100 g pulp). 2 Total flavonoids (µg catechin equivalent/100 g pulp). 3 Total flavonoids (µg quercetin equivalent/g pulp). 4 Total phenolics (µg gallic acid equivalent/g pulp).

significant effect after 12 min of treatment. Table 4 shows the results of TAA (μg AAE/100 mL pulp). In this study, the minimum value (166.8 μg AAE/100 mL pulp) of TAA was observed in pulp from Dosheri whereas the maximum (215.9 μg AAE/ 100 mL pulp) was shown by pulp from Langra before US treatment. It was observed that TAA of pulp from most of mango varieties increased significantly (p < 0.05) after US treatment for 4 min but decreased successively after subsequent treatment. The pulp from Dosehri caused increasing trend of TAA after subsequent US treatment.

The RP of pulp from almost all the mango varieties increased significantly (p < 0.05) after US treatment for 4 min but decreased successively after subsequent treatment. 3.6. Effect of ultrasound on TC and TA of mango pulp There was a significant (p < 0.05) effect of varieties and US treatment on TC and TA of pulp from mango. The results concerning TC and TA are presented in Table 5. An increasing trend of values of TC was shown by pulp from all mango varieties after 4 min of US treatment but decreasing trend was observed with subsequent increase in time of US treatment. The maximum value (3.42 mg/100 g pulp) of TC was shown by pulp from Chaunsa and the minimum (0.84 mg/100 g pulp) were found in pulp from Gulab Khas before US treatment. Concerning TA, the maximum value (37.95 mg/L pulp) was shown by pulp from Dosehri and the minimum (3.12 mg/L pulp) were found in pulp from Chaunsa before US treatment. The TA values of pulp from Chaunsa, Dosehri, Sindhri, Gulab Khas and Langra increased abruptly after US treatment for 4 min but decreased successively after subsequent treatment. The pulp from Desi, Anwar Ratol, Gulab Khas and Langra showed an abrupt decrease in TA after 8 min of US treatment.

3.5. Effect of ultrasound on DPPH radical scavenging activity and RP of mango pulp There was a significant (p < 0.05) effect of varieties and US treatment on DPPH and RP of pulp from mango. The results concerning DPPH and RP are presented in Table 5. The maximum value (314.17 μg AAE/mL pulp) of DPPH was shown by pulp from Dosehri and the minimum (158.67 μg AAE/mL pulp) were found in pulp from Langra before US treatment. The DPPH of pulp from most of mango varieties increased significantly (p < 0.05) after US treatment for 4 min and decreased successively after each treatment but pulp‘from Langra showed increasing trend after 8 min of US treatment and decreased after 12 min of treatment. Regarding RP, the maximum value (312.40 μg AAE/100 mL pulp) was shown by pulp from Langra and the minimum (85.4 μg AAE/ 100 mL pulp) were found in pulp from Gulab Khas before US treatment.

4. Discussion The present study was aimed to investigate the antioxidant potential of pulps from mango varieties indigenous to Pakistan after US 7

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Table 5 Influence of ultrasonic (US) treatment on reducing power (RP), DPPH radical scavenging activity (DPPH), total anthocyanins (TA) and total carotenoids (TC) of pulp from mango varieties. Varieties

US (min)

RP1

DPPH2

Chaunsa

0 4 8 12

132.8 514.0 212.3 207.0

± ± ± ±

12.80QR 10.80C 10.40O 18.20O

204.83 304.17 255.50 244.33

± ± ± ±

10.00O 10.50E-G 16.67 K-M 10.34MN

03.12 16.13 13.29 12.29

± ± ± ±

0.14PQ 0.80G-J 0.24 J-L 0.24KL

03.42 03.97 03.72 01.50

± ± ± ±

0.35B-E 0.31AB 0.12A-C 0.36G-J

Dosehri

0 4 8 12

286.8 468.4 353.6 309.4

± ± ± ±

10.60JK 12.40D 10.80E 10.80G-I

314.17 355.17 348.58 345.17

± ± ± ±

10.50DE 10.67A 10.25AB 10.50AB

37.95 66.75 45.98 31.90

± ± ± ±

1.87D 1.81A 1.69B 1.75E

03.34 03.70 01.69 01.65

± ± ± ±

0.17B-E 0.27A-C 0.22G-J 0.54G-J

Sunehri

0 4 8 12

118.0 349.8 270.8 273.4

± ± ± ±

10.20RS 10.20E 12.80KL 11.40KL

259.92 326.67 303.08 283.33

± ± ± ±

15.92 J-L 13.17C 10.58E-G 12.50I

07.43 17.65 15.75 16.37

± ± ± ±

0.91N 0.77GH 0.50H-J 0.54G-I

02.21 02.70 02.56 02.45

± ± ± ±

0.35D-I 0.53B-G 0.95C-I 0.10C-I

Desi

0 4 8 12

235.2 600.6 551.6 330.2

± ± ± ±

10.80N 10.60A 10.20B 11.80F

241.67 325.83 262.17 252.08

± ± ± ±

17.83N 10.83CD 14.00J-L 10.42L-N

07.95 41.56 18.88 18.88

± ± ± ±

0.51N 1.18C 0.87G 0.47G

01.58 04.92 03.55 03.18

± ± ± ±

0.59G-J 0.90A 0.89B-D 0.06B-F

Anwar Ratol

0 4 8 12

261.4 300.4 253.6 197.8

± ± ± ±

10.60LM 10.40H-J 10.20M 10.40O

206.25 347.25 343.18 310.58

± ± ± ±

10.92O 10.25AB 10.33B 12.42EF

08.49 27.38 14.37 16.35

± ± ± ±

0.83MN 0.59F 0.70I-K 1.11G-I

01.22 02.56 02.23 02.20

± ± ± ±

0.10IJ 0.06C-I 0.53D-I 0.31D-I

Sindhari

0 4 8 12

127.4 333.2 149.6 131.8

± ± ± ±

10.40Q-S 12.40F 10.80P 10.60QR

264.67 290.67 271.08 269.75

± ± ± ±

10.83JK 10.83HI 10.25 J 10.42 J

08.09 40.25 30.54 11.28

± ± ± ±

0.26N 1.41CD 0.72E 0.72LM

01.64 03.77 03.62 03.09

± ± ± ±

0.18G-J 0.03A-C 0.26A-C 0.81B-F

Gulab Khas

0 4 8 12

85.4 ± 10.60 T 141.0 ± 12.20PQ 115.2 ± 10.40S 111.2 ± 14.00S

293.18 340.11 345.25 324.50

± ± ± ±

10.83G-I 10.35B 14.58B 15.00AB

06.51 48.24 25.47 04.38

± ± ± ±

0.58NO 1.32B 0.62F 0.33OP

00.84 01.87 01.85 01.29

± ± ± ±

0.05 J 0.05F-J 0.06F-J 0.04H-J

Langra

0 4 8 12

312.4 324.7 295.6 274.8

158.67 300.68 323.25 134.58

± ± ± ±

14.83P 10.83F-H 10.92CD 10.25Q

07.04 15.99 01.33 02.06

± ± ± ±

0.53NO 0.56G-J 0.28Q 0.21PQ

02.19 02.67 02.61 02.42

± ± ± ±

0.03E-J 0.55B-G 0.40C-H 0.09C-I

± ± ± ±

10.80GH 16.66FG 12.80IJ 18.00KL

TA3

TC4

Means with different letters in the same column show significant (p < 0.05) differences. 1 Reducing power (μg ascorbic acid equivalent/100 g pulp). 2 2, 2-diphenyl-1-picrylhydrazyl radical (DPPH) (μg ascorbic acid equivalent/g pulp). 3 Total anthocyanins (mg /L). 4 Total carotenoids (mg/100 g pulp).

treatment at different timing (4, 8 and 12 min). The key findings shown in the previous section have been summarized below:

after US treatment. In the present study, increased TSS of mango pulp after US treatment might be due to release of more soluble solids from the ruptured cells. The fact of increased contents of total sugars and TSS were also depicted in blueberry juice after US treatment by Zou and Hou [23]. Microstructure evaluation of pulp from all mango varieties showed deshaped middle lamella and cell wall of cells after 8 min of US treatment. At 4 min US treatment as per shaped cell wall and middle lamella, the chemical characteristics and antioxidant potential was higher. These results were in agreement to the findings of Rimkeeree and Charoenrein [24] who reported similar cell deshape (middle lamella & cell wall) when observed under compound microscope. Similarly, retention of antioxidant potential as well as chemical characteristics upon thermal ultrasonication and high pressure homogenization treatment of mango pulps confirmed conserved morphology of mango pulp cells even after treatment [25,26]. Li et al. [27] investigated eleven Chinese mango cultivars and observed vitamin C in the range 5–35 mg/100 g pulp which was in agreement with the results (without US treatment) obtained in the present study. But Manthey et al. [28] found vitamin C in the range 11.5–134.5 mg/100 g pulp in different mango cultivars grown in Mexico, Peru, Ecuador and Brazil. At high power levels of US treatment, degradation of some bioactive components may occur. For example, in a study it was observed that ascorbic acid contents of watermelon juice decreased significantly at higher amplitude levels and processing time

• Regarding chemical characteristics i.e. pH, acidity, TSS, vitamin C • •

contents, total sugars (%), reducing sugars (%) and non-reducing sugars (%), there was significant effect of varieties and US treatment. Microstructure evaluation of pulp from all mango varieties showed deshaped middle lamella and cell wall of cells after 8 min treatment. At 4 min US treatment as per shaped cell wall and middle lamella the chemical characteristics and antioxidant potential was higher. In general, all parameters concerning antioxidant potential showed an increasing trend after 4 min of US treatment but decreased successively with the increase in subsequent treatment for more time.

The probable mechanisms for the observed effects of ultrasonic treatments have been given below: The range of pH, TSS and vitamin C contents of pulp (without US treatment) from most of the investigated mango varieties were in accordance with the results (pH − 4.13 to 5.25; TSS − 15.48 to 22.81; vitamin C − 6.85 to 25.50 mg/100 g) of mango varieties from France and Bangladesh [20,21]. Similar results of acidity were observed by Afifa et al. [20]. The decreasing trend of pH after US treatment might be due to release of more organic acids from the ruptured cells. Muzaffar et al. [22] also found increased acidity values and decreased pH values 8

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[29]. Similarly, in a calcium-added orange juice, the ascorbic acid content decreased with sonication in a time-dependent manner [30]. Our results concerning decrement of vitamin C after exposure of ultrasonic treatment for longer period might be due to degradation of vitamin C. Such kind of degradation might be due to excessive cavitation and cell disruption after longer exposure to US treatment. This might be the reason of decreasing trend concerning vitamin C contents after exposure of US treatment for more than 8 min. The TP contents of all the investigated varieties in the present study ranged from 15.34 to 89.86 mg/100 g which were slightly lower than TP from mango cultivars from France (100 mg/100 g), China (141.36 mg GAE/100 g) and Mexico (130 mg GAE/100 g) [21,27,28]. Li et al. [27] investigated eleven Chinese mango cultivars and observed TP in the range ~ 18–140 mg/100 g pulp which were in agreement with the results obtained in the present study for most of mango cultivars. Similar results were obtained by Manthey et al. [28] who investigated different mango cultivars grown in Mexico, Peru, Ecuador and Brazil and found TP in the range 19.5–130.8 mg/100 g pulp. In a study, it was observed that US treatment caused damage in cells, thereby enhanced liberation of phenolic compounds [31]. Our results were in accordance with the results of Codevilla et al. [32] who observed increased contents of TP after 5 min US treatment of goldenberry extracts compared to 15 min treatment. Similarly, in another study, the results revealed that TP of Avacado extracts increased after US treatment until 15 min but started to decrease after extending time of treatment [5]. Similar results were obtained by Muzaffar et al. [22] who observed decreased contents of TP in cherry (Prunus avium) extracts after exposure of US for a long time. At high power levels of US treatment, degradation of phenolic contents of watermelon juice occurred at higher amplitude levels and processing time [29]. Such kind of degradation might be due to excessive cavitation and cell disruption after longer exposure to US treatment. This might be the reason of decreasing trend concerning phenolic contents after exposure of US treatment for more than 8 min. In a previous study, it was found that US treatment enhanced TF of carrot-grape juice blend [33]. Similarly, it has also been reported that TF of juices from Litchi, watermelon, black jamun, carambula [34] and carrot [11] increased after US treatment which were in accordance to the results obtained in the present study. Jokić et al. [35] observed the increased contents of flavonoids in fig extracts from different varieties after US treatment. Our results were also in accordance with the results obtained by Qiao et al. [36] who reported degradation of flavonoids after longer exposure of US treatment to citrus fruit juice. Such kind of degradation might be due to excessive cavitation and cell disruption after longer exposure to US treatment. This might be the reason of decreasing trend concerning flavonoids after exposure of US treatment for more than 8 min. Regarding antioxidant activity, our results were in accordance to the results of Codevilla et al. [32] who observed increased antioxidant activity after 5 min of US treatment of goldenberry extracts compared to 15 min treatment. The increased antioxidant activity might be due to generation of hydroxyl radicals through hydroxylation of food components by US [37] but on longer exposure of sonication, high level of hydroxyl radicals may be generated in the extract which ultimately influences antioxidant activity in negative manner. This might be the reason of decreasing trend of antioxidant activity after exposure of US treatment for more than 8 min. Our results concerning DPPH radical scavenging activity were in consistent with the results of Khan et al. [38] who observed increased antioxidant activity through DPPH assay after US treatment of orange peel extracts. Similar results were obtained by Maghsoudlou et al. [39]. Muzaffar et al. [22] also observed decreased antioxidant activity related to DPPH (% inhibition) in cherry (Prunus avium) extracts after exposure of US for a long time. Similarly, enhancement of polyphenols and increase in DPPH, superoxide, and hydroxyl radicals scavenging activities were also observed in the sonicated blueberry juice Zou and

Hou [23]. The DPPH radical scavenging assay actually measures the hydrogen donating capacity of phenolic acids and other antioxidants to the stable free radical DPPH, thereby forming diphenyl picrylhydrazine [40]. In this way, phenolic and ascorbic acids in the juice samples are the major contributor to scavenge free radicals. This was confirmed due to the results obtained in the present study whereby an increase in DPPH values was observed after US treatment. The more the antioxidants (phenolic and flavonoid compounds) released after US treatment, the more DPPH radical scavenging activity would be observed in the sample extracts. By quickly reducing reactive oxygen species (ROS) including free radicals, phenolic compounds are able to protect the biomolecules [38]. The hydroxy groups present in the structures of flavonoids have the ability to donate hydrogen to DPPH free radicals, leading to termination of free radical chain reaction [41]. In this way, contribution of more hydroxy groups from the phenolic and flavonoid compounds may increase the radical scavenging activity. This might be the reason of increased DPPH radical scavenging activity after 4 min of US treatment in the present study. Moreover, total anthocyanins and total carotenoids may cause an increase in DPPH values after 4 min of treatment. It might be assumed that vitamin C, phenolic and flavonoid compounds contribute to the total antioxidant activity of any extract which was manifested in our results of mango varieties after US treatment. It has been reported that anthocyanin degradation increased with increase in amplitude and time of exposure of US treatment of jamun juice [42]. This might be the reason of decreasing trend of anthocyanins after exposure of US treatment for more than 8 min. Li et al. [27] observed TC in eleven Chinese mango cultivars in the range 0.70–2.5 mg/ 100 g pulp which were in agreement with the results obtained in the present study. The US treatment of Chokanan mango juice [43] and carrot juice [11] enhanced TC contents which were concurrent with the results obtained in the present study. But shearing effect of sonication after longer exposure may cause isomerization of carotenoids [43], leading to decreased levels of carotenoids which were observed in the present study. The assessment of reducing power of an extract may serve a good indicator of its potential antioxidant activity. The reductive ability (Fe3+ to Fe2+) of an extract indicates the presence of antioxidant compounds in it. The antioxidants (phenolic and flavonoid compounds) in the sample extract are responsible for the reduction of the ferricyanide complex to ferrocyanide complex in the assay [44]. The hydroxy groups in the structure of flavonoids may cause reduction of iron (Fe3+ to Fe2+) [45]. In addition, the flavonoids show their reducing power by donating electrons to reactive DPPH free radicals, thus converting them into more stable non-reactive compound, leading to termination of the free radical chain reaction [46]. Owing to the liberation of more phenolic and flavonoid compounds from the pulp after ultrasonic application, the reducing power of extracts might be increased which was confirmed by our results due to the increased reducing power of our samples after ultrasonic application. Even though the increase in reducing power was not significant but anyhow, increasing trend was noticed in all our samples. 5. Conclusions It was concluded from the present study that there was significant effect of varieties and US treatment on chemical characteristics i.e. pH, acidity, TSS, vitamin C contents, total sugars (%), reducing sugars (%) and non-reducing sugars (%). Microstructure evaluation of pulp from all mango varieties showed deshaped middle lamella and cell wall of cells after 8 min treatment. In general, all parameters concerning antioxidant potential showed an increasing trend after 4 min of US treatment but decreased successively with the increase in subsequent treatment for more time. Therefore, on the basis of our results, it may be suggested that US treatment of mango pulp or juice or nectar would be a promising novel 9

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technology to be implemented on a pilot scale at the industry to improve the functional quality.

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