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Effect of drying methods and maltodextrin concentration on pigment content of watermelon juice powder
Journal of Food Engineering 165 (2015) 172–178
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Effect of drying methods and maltodextrin concentration on pigment content of watermelon juice powder Davinder Pal Singh Oberoi, Dalbir Singh Sogi ⇑ Department of Food Science and Technology, Guru Nanak Dev University, Amritsar 143 005, India
a r t i c l e
i n f o
Article history: Received 23 April 2015 Received in revised form 11 June 2015 Accepted 17 June 2015 Available online 18 June 2015 Keywords: Watermelon Spray drying Freeze drying Lycopene Maltodextrin
a b s t r a c t The effect of spray/freeze drying and maltodextrin concentration (3%, 5%, 7% and 10%) on pigment retention of watermelon juice powder from three cultivars was investigated. Incorporation of maltodextrin in watermelon juice yielded freely flowable powder. The spray dried powder has less moisture content, low water activity, high dissolution value and less reducing sugar content as compared to freeze dried powder. Lycopene of fresh watermelon juice was 4.58–6.53 mg/100 g on wet basis (wb) which was increased up to 56.4 mg/100 g (wb) in spray dried powder and 62.3 mg/100 g (wb) in freeze dried powder. Variation in instrumental color parameters with maltodextrin levels and dryers revealed that the freeze dried powder have lower ‘L’ value, higher ‘a’ value, higher ‘b’ value, lower ‘hue angle’ and high ‘chroma’ values as compared to spray dried powder. In spray drying lycopene loss was influenced by high air temperature and intensive exposure to oxygen causing degradation of lycopene. The freeze dried powder retained more pigment but powder had high water activity, limited shelf life, low flowability and hygroscopic in nature. Good correlation between colorimetric values and lycopene content was observed in spray dried powder. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction Watermelon (Citrullus lanatus Thunb) accounts for 18.32% of the world area devoted to vegetable production in 2012 (FAO, 2014). The color in the watermelon juice is red (Huor et al., 1980) due to the presence of lycopene that has potential to act as bio-color and anticancer drug. Lycopene has been shown to protect important biomolecules such as lipids, low-density lipoproteins and DNA against oxidative damage resulting in prevention of cancers, atherogenesis, and cell proliferation (Agarwal and Rao, 2000; Weisburger, 2002; Arab et al., 2002). Watermelon as one of underutilized fruits is harvested in summer months and is liked by consumer due to its delicate flavor and attractive color (Tressler and Joslyn, 1971). Watermelon juice is vulnerable to microbial and enzymatic deterioration due to high water activity. Drying is widely used to extend the shelf life of food products. The decrease in moisture content causes the reduction of the mass, volume, enzymatic and microbial activity (Karim and Hawlader, 2005; Kaya et al., 2007). Spray and freeze drying are the common techniques employed for the dehydration of fruit juices. The sticky behavior of sugar and acid rich materials is
attributed to low molecular weight sugars such as fructose, glucose, sucrose and organic acids such as citric, malic and tartaric acid which contributes more than 90% of solids in fruit juices (Dolinsky et al., 2000; Adhikari et al., 2004). Due to this sticky behavior of juices, it is difficult to dry them under normal conditions. Maltodextrin, consisting of b-D-glucose units is added to fruit juices to reduce stickiness and improving product stability (Reineccius, 1991; Bhandari et al., 1993; Silva et al., 2006). The present investigation was undertaken to study the effect of drying methods and maltodextrin concentration on physico-chemical properties and lycopene content of watermelon juice powder. 2. Material and methods 2.1. Material Watermelons of ‘Namdhari-95’ and ‘Namdhari-450’ varieties were procured from the farm located in Kapurthala (India) and of ‘Sugar Baby’ variety were obtained from Department of Vegetables, Punjab Agricultural University, Ludhiana (India). 2.2. Preparation of powder
⇑ Corresponding author. E-mail addresses: [email protected] (D.P.S. Oberoi), [email protected] (D.S. Sogi). http://dx.doi.org/10.1016/j.jfoodeng.2015.06.024 0260-8774/Ó 2015 Elsevier Ltd. All rights reserved.
Watermelons were cut into quarters, deseeded, peeled and passed through screw juice extractor (Kalsi Industries, Ludhiana,
D.P.S. Oberoi, D.S. Sogi / Journal of Food Engineering 165 (2015) 172–178
India) to obtain juice. The watermelon juice was passed through 40 lm sieve and then through 15 lm sieve to remove the fibrous matter. Maltodextrin (3%, 5%, 7% and 10%) was added in the juice and spray dried (ADL 31, Yamato Scientific Co. Ltd., Tokyo, Japan). Atomization of the juice was done using two fluid nozzle in which one part contain juice and other one contain compressed hot air. The spray dryer was operated at 125 °C inlet temperature, 70 °C outlet temperature, 0.25 kg/cm2 air pressure, 6.5 m3/min aspiration rate, 4 ml/min pump speed and 3 g/min feed rate. The powder was packed in air tight polyethylene pouches and stored at 4 °C in dark. In second drying method, the watermelon juice was passed through the 40 microns sieve, mixed with maltodextrin (3%, 5%, 7% and 10%), frozen in a chiller (Heto, Vedback, Denmark), dried in a freeze drier (Heto, Vedback, Denmark), packed in air tight polyethylene pouches and kept at 20 °C. 2.3. Physico-chemical properties The moisture content was determined in a vacuum oven (Narang Scientific Pvt Ltd., New Delhi, India) at 60 ± 2 °C and 100 mm Hg pressure for 24 h (AOAC, 1990). Titrable acidity (as anhydrous citric acid) was determined using a pH meter (LI120, Elico, Hyderabad, India). The water activity was determined using water activity analyzer (Aqua Lab 4TE, Decagon devices, USA). For the dissolution test, 50 mg of powder sample was placed in a test tube. 1 ml of distilled water at room temperature was added and mixing was performed using vortex. The time (s) to fully reconstitute the powders was recorded (Quek et al., 2007). Reducing and total sugars were determined according to Lane and Eynon method (Ranganna, 1986). Non-reducing sugar was calculated from difference of total sugars and reducing sugars. 2.4. Lycopene and total carotenoids Sample (2 g) was extracted with acetone in a pestle and mortar till residues became colorless. Pigment was transferred into petroleum ether phase in a separating funnel, passed through sodium sulphate and evaporated under vacuum. Lycopene content was determined by HPLC (Waters, Milford, MA, USA) fitted with a photodiode array detector using YMC Carotenoids (5 lm) column, methanol: ethanol: Tetrahydrofuran (15:4:1) mobile phase, 1 ml/min flow rate and 470 nm wavelength. Lycopene (Sigma Chemical Co, St. Louis, Missouri, U.S.A.) was used as standard. The total carotenoids were determined by measuring the absorbance at 452 nm on spectrophotometer (Shimadzu, Kyoto, Japan) using beta carotene (Sigma Chemical Co, St. Louis, Missouri, USA) as standard. 2.5. Visual color analysis Visual color was measured using a Hunter Color Lab (Hunter Associate Laboratory, Reston, USA) in terms of L (lightness), a (redness (+) and greenness ()) and b (yellowness (+) and blueness ()). The instrument was calibrated with a standard black tile and then standard white tile (L = 90.55, a = 0.71, b = 0.39). A sample handling dish was charged with samples, placed on the analyzing port and noted the L, a, b values. The hue angle (h° = tan1 b/a) represents the maximum degree of redness at 0°, yellowness at 90°, greenness at 180° and blueness at 270° (Patras et al., 2011). The chroma p (C = a2 + b2) indicates the color intensity or saturation of sample. 2.6. Statistical analysis Two-way analysis of variance was applied on the data of physico-chemical, lycopene, total carotenoids and Hunter color
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parameters of watermelon powder. The difference between the means was compared by Honestly Significant Difference (HSD) values using Tukey’s Test (Daniel, 1991) analyzed at p 6 0.05. Linear regression was applied to determine the relationship between the lycopene and hunter color values. The goodness of linear fit was evaluated by coefficient of determination (R2), adjusted R2, p-values and root mean square error computed using Minitab-15 (Mini Tab Inc., Coventry, U.K.) software. 3. Results and discussion 3.1. Physico-chemical properties of watermelon juice Moisture content of watermelon juice of cultivars ‘Namdhari-95’, ‘Namdhari-450’, ‘Sugar baby’ was in the range of 90.3–93.1 g/100 g whereas the total soluble solids of juice were 5.1–8.9 g/100 g. The acidity of juice obtained from three cultivars was in the range of 0.02–0.04 g/100 g. The reducing sugars of watermelon juice of three cultivars were in the range of 2.9– 3.7 g/100 g whereas the total sugars varied from 4.9–5.3 g/100 g respectively. Chahal and Saini (1999) analyzed bottled Indo-American hybrid watermelon juice and reported 6.4– 9.0 g/100 g soluble solids, 0.05–0.08 g/100 g acidity, 5.52 g/100 g reducing sugars and 7.76 g/100 g total sugars. Quek et al. (2007) reported 12.1°B total soluble solids, 5.5 g/100 ml glucose, 6.8 g/100 ml fructose and 1.2 g/100 ml sucrose of watermelon (Sugar baby) juice. The soluble solids content of the watermelon are comparable with previous studies of Chahal and Saini (1999) but lower than Quek et al. (2007). 3.2. Physico-chemical properties of watermelon juice powder 3.2.1. Moisture content Moisture content of spray dried watermelon juice powder was decreased with increase in maltodextrin from 3% to 10% (Table 1). In spray drying of powder, the water content of feed had an effect on the final moisture content of powder produced (Abadio et al., 2004). The low moisture content of powder at higher maltodextrin was due to increase in total solids of the feed prior to spray drying and thus reduced the amount of water for evaporation. According to Adhikari et al. (2004), the addition of maltodextrin resulted into lower moisture diffusivity and decrease water flux of sugar drops dried in spray dryer. Quek et al. (2007) concluded that by increasing the maltodextrin (3–5%) and temperature (145, 155, 165 and 175 °C), the moisture content of spray dried watermelon powder significantly (p 6 0.05) decreased. Statistical analysis revealed that the moisture content of freeze dried powder decreased significantly (p 6 0.05) with increase in maltodextrin level (Table 2). The freeze dried powder showed higher moisture as compared to spray dried powder because drying was accomplished through sublimation. Among the cultivars, moisture content of powder obtained by spray drying and freeze drying was significantly (p 6 0.05) different (see Table 3). 3.2.2. Water activity Tukey’s multiple comparison showed that water activity significantly (p 6 0.05) varied with the level of maltodextrin as well as type of cultivars used in the study. Water activity of spray dried powder decreased with increase in maltodextrin from 3% to 10% (Table 1). Quek et al. (2007) found the same pattern of water activity of spray dried watermelon powder with change in maltodextrin from 3% to 5%. The water activity of freeze dried powder was more than of spray dried powder, indicating more free available water for biological reactions and thus limited shelf life. Freeze dried powder exhibited inverse relation between the moisture and water activity which might due to high percentage of amorphous sugars
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Table 1 Physico-chemical analysis of spray dried watermelon powder during processing (n = 3). Parameters
Maltodextrin concentration (%)
‘Namdhari-95’
‘Namdhari-450’
‘Sugar Baby’
Moisture (% db) 3 5 7 10
3.39ar ± 0.11 3.25br ± 0.22 2.60cr ± 0.09 2.24dr ± 0.15
4.54aq ± 0.13 4.14bq ± 0.19 3.22cq ± 0.22 2.87dq ± 0.25
5.46ap ± 0.18 4.93bp ± 0.16 4.18cp ± 0.08 3.90dp ± 0.20
3 5 7 10
0.276aq ± 0.01 0.248br ± 0.05 0.166cr ± 0.09 0.153dr ± 0.10
0.287ap ± 0.02 0.266bq ± 0.08 0.234cq ± 0.11 0.214dq ± 0.08
0.289ap ± 0.05 0.271bp ± 0.05 0.241cp ± 0.07 0.232dp ± 0.05
3 5 7 10
9.4c ± 0.98 13.2b ± 1.5 14.1b ± 1.9 16.5a ± 2.3
11.3d ± 2.9 13.5c ± 0.56 15.4b ± 1.5 22a ± 1.2
3 5 7 10
48.23bq ± 0.89 67.89ap ± 1.02 72.20ap ± 0.75 75.24ap ± 0.24
34.08br ± 0.15 37.98bq ± 0.23 44.30bq ± 0.56 51.61aq ± 0.99
58.04bp ± 0.14 65.36ap ± 0.49 70.07ap ± 1.11 73.31ap ± 0.78
3 5 7 10
42.15cq ± 0.54 58.97bp ± 1.82 62.15bp ± 2.10 70.24ap ± 1.56
30.08cr ± 1.23 36.48bq ± 0.97 38.75bq ± 1.45 47.15aq ± 1.21
52.57dp ± 0.84 60.52cp ± 2.54 64.83bp ± 1.39 71.95ap ± 2.87
3 5 7 10
6.04 ± 0.31 8.89 ± 0.19 10.06 ± 1.91 5.00 ± 1.09
4.01 ± 0.12 1.50 ± 0.11 5.54 ± 0.34 4.46 ± 0.41
5.46 ± 0.36 4.84 ± 0.32 5.24 ± 0.29 1.36 ± 0.12
Water activity (aw)
Dissolution (s) 10.5c ± 2.1 12.5b ± 2.3 13.4b ± 1.8 21.2a ± 1.8
Total sugars (% db)
Reducing sugars (% db)
Non-Reducing sugars (% db)
Values with different superscripts are significantly (p < 0.05) different in column – a, b, c, d and in rows – p, q, r using Tukey’s Multiple comparison test.
Table 2 Physico-chemical analysis of freeze dried watermelon powder during processing (n = 3). Parameters
Maltodextrin concentration (%)
‘Namdhari-95’
‘Namdhari-450’
‘Sugar Baby’
Moisture (% db) 3 5 7 10
5.54ar ± 0.58 5.24br ± 0.39 4.77cr ± 0.09 4.43dr ± 0.05
7.00ap ± 0.17 6.60bp ± 0.08 6.20cp ± 0.02 5.86dp ± 0.19
6.66aq ± 0.16 6.26bq ± 0.24 5.86cq ± 0.08 5.50dq ± 0.28
3 5 7 10
0.333dr ± 0.12 0.349cr ± 0.14 0.368br ± 0.11 0.403ar ± 0.15
0.359dq ± 0.11 0.364cq ± 0.14 0.391bq ± 0.19 0.432aq ± 0.18
0.376dp ± 0.25 0.395cp ± 0.13 0.404bp ± 0.19 0.439ap ± 0.15
3 5 7 10
10.5 ± 0.12 11.2 ± 1.7 12.5 ± 0.9 12.9 ± 0.3
11.0 ± 0.7 12.5 ± 0.2 13.1 ± 0.64 15.8 ± 0.21
3 5 7 10
53.75cp ± 0.89 65.80bp ± 1.15 69.44ap ± 0.55 72.66aq ± 0.13
49.05dq ± 0.75 53.62cq ± 0.23 60.13bq ± 0.56 67.14ar ± 0.99
54.11dp ± 0.14 64.04cp ± 0.49 72.47bp ± 1.11 78.08ap ± 0.78
3 5 7 10
47.18dq ± 0.54 58.00cp ± 1.82 63.57bq ± 2.10 70.70aq ± 1.56
43.76dr ± 0.39 50.17cq ± 0.97 55.28br ± 1.45 61.70ar ± 1.21
46.87dp ± 0.84 57.67cp ± 2.54 67.39bp ± 1.39 75.24ap ± 1.87
3 5 7 10
6.57 ± 0.39 7.80 ± 0.67 5.87 ± 0.19 1.96 ± 0.85
5.29 ± 0.25 3.45 ± 0.49 4.85 ± 1.03 5.24 ± 0.92
7.34 ± 0.55 6.37 ± 0.21 5.07 ± 0.53 2.85 ± 0.68
Water activity (aw)
Dissolution (s) 10.7 ± 1.1 11.9 ± 1.6 12.9 ± 1.8 21.6 ± 2.1
Total sugars (% db)
Reducing sugars (% db)
Non-Reducing sugars (% db)
Values with different superscripts are significantly (p < 0.05) different in column – a, b, c, d and in rows – p, q, r using Tukey’s Multiple comparison test.
having high hygroscopicity and absorbs more free water (Carlos et al., 2005). Arya et al. (1985) concluded that freeze dried watermelon powder was stable in the water activity range of 0.22–0.25
aw whereas caking started when water activity value increased beyond 0.33. Therefore, the spray dried powder had greater shelf life compared to freeze dried powder.
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D.P.S. Oberoi, D.S. Sogi / Journal of Food Engineering 165 (2015) 172–178 Table 3 Color analysis of spray dried watermelon powder during processing (n = 3). Parameter
Maltodextrin concentration (%)
‘Namdhari-95’
‘Namdhari-450’
‘Sugar Baby’
3 5 7 10
71.77b ± 0.25 72.45b ± 0.09 89.16a ± 0.10 94.15a ± 0.04
53.52b ± 0.03 77.78a ± 0.02 78.45a ± 0.06 79.56a ± 0.07
62.77d ± 0.03 76.57c ± 0.03 85.95b ± 0.08 93.81a ± 0.04
3 5 7 10
12.12a ± 0.15 8.41b ± 0.16 2.59c ± 0.14 0.68d ± 0.15
18.07a ± 0.05 8.05b ± 0.05 5.45c ± 0.06 2.35d ± 0.24
10.14a ± 0.09 5.86b ± 0.07 3.19c ± 0.07 0.45d ± 0.03
3 5 7 10
11.12aq ± 0.10 9.851bq ± 0.08 6.58cq ± 0.06 4.72dp ± 0.06
10.13aq ± 0.03 8.75bq ± 0.10 7.09cq ± 0.04 5.41dp ± 0.04
13.11ap ± 0.04 12.82ap ± 0.06 10.22bp ± 0.04 5.78cp ± 0.04
3 5 7 10
42.52dq ± 0.18 49.51cq ± 0.26 68.21bp ± 0.11 81.96ap ± 0.08
29.24dr ± 0.22 47.36cq ± 0.31 52.43br ± 0.17 66.51aq ± 0.09
52.23dp ± 0.03 65.42cp ± 0.13 72.66bp ± 0.06 85.55ap ± 0.11
3 5 7 10
16.45a ± 0.19 12.95b ± 0.08 6.98c ± 0.07 4.57d ± 0.04
20.72a ± 0.18 11.89b ± 0.12 8.94c ± 0.03 5.89d ± 0.07
16.57a ± 0.06 14.09b ± 0.04 10.72c ± 0.07 5.79d ± 0.02
‘L’
‘a’
‘b’
Hue (°)
Chroma
Values with different superscripts are significantly (p < 0.05) different in column – a, b, c, d and in rows – p, q, r using Tukey’s Multiple comparison test.
3.2.3. Dissolution test Dissolution test gives speed of reconstitution of dried powder into water. Dissolution value of spray and freeze dried powder increased with level of maltodextrin (Tables 1 and 2). The results showed that there was inverse relationship between dissolution and moisture content of powders. At low maltodextrin, products contain high moisture content and these powders has higher tendency of agglomeration which helped to increase the reconstitution of powder (Masters, 1991). Quek et al. (2007) found that the dissolution value of spray dried watermelon powder was in the range of 17–30 s with change in temperature from 145 to 175 °C. Non-significant (p > 0.05) change was observed in dissolution value among the cultivars and change in maltodextrin concentration in freeze dried powder. Freeze dried powder showed less range of dissolution value due to high moisture content of powder and has high reconstitution capacity. The dissolution value in present study varied from 9.4 to 22 s which was lower than values reported in literature.
3.2.4. Sugars The total sugars in spray dried watermelon powder were found to increase up to 75.24%, 51.61% and 73.31% dry basis (db) respectively in the ‘Namdhari-95’, Namdhari-450’, ‘Sugar baby’ cultivars with change in maltodextrin from 3% to 10% (Table 1). The sugar content of freeze dried powder values were also increased up to 72.66%, 67.14% and 78.08% db respectively for three cultivars (Table 2). Statistical analysis revealed that total sugars of ‘Namdhari-450’ variety were significantly (p 6 0.05) different from other two cultivars whereas 3% maltodextrin level showed significantly lower total sugar than other levels. With increase in maltodextrin, the reducing sugars in spray dried and freeze dried watermelon powder were found to increase. The HSD test showed that among the cultivars significant (p 6 0.05) change was observed in ‘Namdhari-450’ only. Non significant results were obtained in non reducing sugars of spray/freeze dried watermelon powder. Increase in sugars content of powder was due to increase of solids and maltodextrin concentration.
3.3. Pigment content of watermelon juice powder The pigment analysis of watermelon juice of ‘Namdhari-95’, ‘Namdhari-450’ and ‘Sugar baby’ cultivars showed lycopene values of 85.21, 91.97 and 64.50 mg/100 ml respectively on dry basis (db) without maltodextrin prior to drying whereas the total carotenoids in fresh watermelon juice were 87.88, 102.81 and 71.83 mg/100 ml on db in respective three cultivars. The processing of watermelon juice by spray drying showed that lycopene content and total carotenoids were significantly (p 6 0.05) decreased with increase in maltodextrin level (Fig. 1). There was significant loss of lycopene (32.1–76.8%) during spray drying due to heating at high temperature and exposure to oxygen. The decrease of lycopene in spray drying was due to an actual degradation of lycopene rather than progressive conversion from the all-trans lycopene to cis form (Goula and Adamopoulos, 2005). Goula et al. (2006) concluded that in spray drying process, the product was converted in form of droplets and hence larger surface area exposed to air enhances lycopene oxidation. Oxidation is undesirable because it leads to lycopene degradation and a concomitant loss of its health related properties (Rodriguez-Amaya and Kimura, 2004). Quek et al. (2007) found the lycopene content of spray dried watermelon powder decreased from 95.4 to 72.5 mg/100 g with change in temperature from 145 to 175 °C. Cole and Kapur (1957) observed 25% apparent lycopene loss in the presence of oxygen when heating the tomato pulp at 100 °C for 2 h. Increase of maltodextrin also affects the pigment content due to dilution of pigment (Quek et al., 2007). Spray drying with maltodextrin helps in microencapsulation of lycopene in a solid form. There was 5.1–7.5 times increase in lycopene in spray dried watermelon powder as compared to watermelon juice. Gomes et al. (2014) found the increase of 2.16 times in lycopene of spray dried watermelon powder using 8% maltodextrin. Quek et al. (2007) microencapsulated lycopene obtaining increase of 16.7 times using 5% maltodextrin as wall material. The average lycopene content and total carotenoid of freeze dried powder was decreased with increase in maltodextrin level (Fig. 1). However, Tukey’s multiple comparison test showed non-significant (p P 0.05) change in lycopene and total
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70
p
'Namdhari-95' p
a
b q
a
60
q
50
c
40 30 20 10 0 5
7
50 40 30 20 10 3
'Namdhari-450' p
60
r
b
50
s
c
40
d
30 20
0 3
5
80
7
5
7
10
7
10
7
10
'Namdhari-450'
80 q
a
10
70 60 50 40 30 20 10 0
10
3
'Sugar baby'
5
'Sugar baby'
80
70
70
60
p
50
q a
a
r
s
b
30
c
20 10
Pigment Content, mg/100g
Pigment Content, mg/100g
60
10
Pigment Content, mg/100g
Pigment Content, mg/100g
80
40
70
0 3
70
'Namdhari-95'
80 Pigment Content, mg/100g
Pigment Content, mg/100g
80
60 50 40 30 20 10
0
0 3
5
7
10
Maltodextrin level (%)
(a)
3
5
Maltodextrin level (%)
(b)
Fig. 1. Lycopene and total carotenoids content on moisture and maltodextrin free basis (a) spray dried and (b) freeze dried watermelon powder of different watermelon cultivars. Unfilled bar-Lycopene; filled bar – Total Carotenoids (Values with different superscripts are significantly (p < 0.05) different a, b, c, d for lycopene and p, q, r, s for total carotenoids using Tukey’s Multiple comparison test).
carotenoids of freeze dried powder with increase in maltodextrin level but significant (p 6 0.05) among the cultivars. It was observed that there was 24.99–30.88% lycopene loss in watermelon during freeze drying. The retention of lycopene in freeze dried powder was higher due to minimal processing of watermelon juice. In freeze drying effect of high temperature and oxidation was absent resulting in lower degradation of lycopene. Freeze drying resulted in 9–9.5 times concentration of lycopene as compared to fresh watermelon juice. Chiu et al. (2007) microencapsulated lycopene extract from tomato pulp waste by freeze drying using gelatin and poly (c-glutamic acid) as coating material and found 23.5% lycopene loss during freeze drying. 3.4. Visual color values The ‘L’ values for spray dried watermelon powder were increased with increase in maltodextrin concentration. The Tukey’s multiple comparison test showed that ‘L’ values of ‘Sugar
baby’ cultivar were significantly (p 6 0.05) different at all levels of maltodextrin (Table 3). The high concentration of maltodextrin resulted in whiteness of the powder. The ‘a’ and ‘b’ values of spray dried powder were significantly (p 6 0.05) decreased with change with maltodextrin. The ‘b’ values of ‘Sugar baby’ were found to be significantly (p 6 0.05) different from other cultivars. With high level of maltodextrin, the watermelon powder lost its red–orange color (Quek et al., 2007). The hue angle of spray dried powder was significantly (p 6 0.05) increased with maltodextrin and higher values showed decrease in redness of powder due to destruction of pigment during drying of juice. The chroma values of spray dried powder were significantly (p 6 0.05) decreased with maltodextrin. The present results were consistent with previous studies (Quek et al., 2007). The ‘L’ value of freeze dried powder was significantly (p 6 0.05) increased with change in maltodextrin concentration from 3% to 10% (Table 4). The statistical analysis showed that there was significant (p 6 0.05) change in ‘a’ value at 10% maltodextrin in all
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D.P.S. Oberoi, D.S. Sogi / Journal of Food Engineering 165 (2015) 172–178 Table 4 Color analysis of freeze dried watermelon powder during processing (n = 3). Parameter
Maltodextrin concentration (%)
‘Namdhari-95’
‘Namdhari-450’
‘Sugar Baby’
3 5 7 10
55.53dp ± 0.249 57.93cp ± 0.88 58.66bp ± 0.12 59.45ap ± 1.04
50.43dr ± 1.13 55.16cq ± 0.52 56.19bq ± 0.96 56.87aq ± 0.67
52.46dq ± 0.53 55.32cq ± 0.83 56.76bq ± 0.28 57.68aq ± 0.34
3 5 7 10
17.98aq ± 0.25 17.25bq ± 0.19 17.15bq ± 0.15 16.81cq ± 0.05
19.53ap ± 0.05 18.46bp ± 0.09 18.21cp ± 0.19 18.09cp ± 0.14
15.34ar ± 0.19 14.88br ± 0.06 14.23cr ± 0.11 13.52dr ± 0.19
3 5 7 10
8.29q ± 0.19 7.99q ± 0.18 7.83p ± 0.06 7.75p ± 0.06
6.5r ± 0.13 6.43r ± 0.15 6.29q ± 0.24 6.11q ± 0.32
8.79p ± 0.45 8.43p ± 0.36 8.24p ± 0.19 8.39p ± 0.24
3 5 7 10
24.74cq ± 0.23 24.7cq ± 0.18 24.56bq ± 0.14 24.74aq ± 0.11
18.36br ± 0.13 19.19ar ± 0.17 19.03ar ± 0.21 18.65ar ± 0.09
29.81bp ± 0.12 29.50bp ± 0.18 30.07bp ± 0.11 31.79ap ± 0.15
3 5 7 10
19.79aq ± 0.31 19.01bq ± 0.24 18.85bp ± 0.15 18.51bp ± 0.10
20.58ap ± 0.09 19.54bp ± 0.19 19.26cp ± 0.18 19.09cp ± 0.22
17.67ar ± 0.11 17.10br ± 0.25 16.44cq ± 0.29 15.91dq ± 0.14
‘L’
‘a’
‘b’
Hue (°)
Chroma
Values with different superscripts are significantly (p < 0.05) different in column – a, b, c, d and in rows – p, q, r using Tukey’s Multiple comparison test.
Table 5 Statistical parameters of linear regression of lycopene content of watermelon powder with colorimeter measurements. Adjusted R2 (%)
Intercept p-value
Slope p-value
Root mean squared error
p-value of the overall model
Spray dried watermelon powder ‘a’ 88.7 ‘b’ 99.7 ‘L’ 87.6 ‘a b’ 85.8 ‘a/b’ 91 ‘b/a’ 87.7 ‘(a/b)2’ 74.4 ‘1000a/(b + L)’ 94.8 ‘Hue’ 97.7 ‘Chroma’ 95.1
83.1 99.6 81.5 78.6 86.5 81.5 61.7 92.2 96.5 92.0
0.013* 0.012* 0.025* 0.012* 0.019* 0.004** 0.017* 0.008** 0.003** 0.027*
0.045* 0.001** 0.064ns 0.074ns 0.046* 0.064ns 0.137ns 0.026* 0.012* 0.027*
0.028 0.027 0.007 0.040 0.025 0.029 0.043 0.034 0.019 0.021
0.045* 0.001** 0.064ns 0.074ns 0.046* 0.064ns 0.137ns 0.026* 0.012* 0.027*
Freeze dried watermelon powder ‘a’ 86.9 ‘b’ 94.1 ‘L’ 95.3 ‘a b’ 89.3 ‘a/b’ 79 ‘b/a’ 37.7 ‘(a/b)2’ 84.4 ‘1000a/(b + L)’ 3.6 ‘Hue’ 42.6 ‘Chroma’ 89.2
80.4 91.1 92.9 84 68.6 6.5 77.2 0.0 13.9 83.8
0.007** 0.009** 0.001** 0.002** 0.501ns 0.052ns 0.038* 0.451ns 0.062ns 0.007**
0.068 ns 0.030* 0.024* 0.055ns 0.111ns 0.386ns 0.079ns 0.811ns 0.347ns 0.056ns
0.020 0.006 0.005 0.080 0.002 0.003 0.004 0.027 0.004 0.002
0.068 ns 0.030* 0.024* 0.055 ns 0.111 ns 0.386 ns 0.079 ns 0.811 ns 0.347 ns 0.056 ns
Hunter color values
** *
R2 (%)
Data significant at p 6 0.01. Data significant at p 6 0.05; ns: non-significant; R2: coefficient of determination.
varieties and among the cultivars the ‘a’ value was significantly (p 6 0.05) different. Non significant (p P 0.05) change was observed in ‘b’ value of freeze dried powder with change in maltodextrin. The hue angle of freeze dried powder was significantly different at 3% maltodextrin as it has inverse relationship with ‘a’ value. The HSD test showed that the hue values of freeze dried powder were significantly (p 6 0.05) different among the cultivars. Slight change was observed in chroma values of freeze dried powder with maltodextrin (see Table 4). The freeze dried powder showed lower whiteness (‘L’ value), higher redness (‘a’ value), higher yellowness (‘b’ value), lower hue angle and high chroma values as compared to spray dried powder. In spray drying product has the form of droplets, the
larger surface exposed to air enhances lycopene oxidation and loss is faster as compared to freeze drying (Goula et al., 2006). Therefore, the spray dried powder lost its redness and showed lower ‘a’ value. Que et al. (2008) concluded that freeze drying resulted in higher ‘a’ and ‘b’ value compared with pumpkin flours prepared by hot air drying. 3.5. Correlation between lycopene and colorimetric values The linear regression between the lycopene content and colorimetric parameters of watermelon juice powder was evaluated. Values of correlation between lycopene and color parameters were higher in spray dried powder (74.4–99.7%) than freeze dried
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powder (3.6–95.3%) (Table 5). The intercept p-values of spray dried powder were found to be significant for all colorimetric values. The p-values of correlation of spray dried powder were found to be significant (p 6 0.05) for ‘a’, ‘b’, ‘a/b’, ‘1000a/(b + L)’, hue and chroma color values. Good agreement between experimental and predicted data was observed which was confirmed by lower value of root mean square error (0.007–0.043). Quek et al. (2007) found the correlation coefficient between lycopene and hue content of spray dried watermelon powder in the range of 0.946. Purkayastha et al. (2011) found the good agreement between the experimental and predicted data for thin layer convective drying of blanched tomato slices confirmed by lower root mean square error values (0.002–0.010). The p-values of correlation of freeze dried powder were found to be significant at p 6 0.05 only for ‘L’ and ‘b’ whereas intercept p-values were significant for ‘a’, ‘b’, ‘a b’, ‘(a/b)2’ and chroma values. Lower values of root mean square error (0.002–0.080) indicates the validity of the model. This data indicated that as the lycopene degradation occurred with drying of watermelon juice, the visual colorimetric parameters of the product got affected. 4. Conclusion Watermelon powder was produced using different drying techniques and maltodextrin concentration. Maltodextrin was an effective drying aid helped in reducing stickiness and altered the physicochemical properties of watermelon powder. With increase in maltodextrin concentration, the moisture content of the spray and freeze dried powder decreased while time for reconstitution and sugar content increased. The freeze dried powder contained higher water activity, low flowability and was highly hygroscopic in nature. The visual color analysis showed that watermelon powder lost its redness with increase in maltodextrin above 5% in spray drying. The lycopene loss in watermelon powder was higher in spray drying as compared to freeze drying due to effect of high temperature and large surface area expose to air which results into degradation of lycopene into colorless form by oxidation process. 5. Practical application Large amount of watermelon crops gets wasted every year due to high moisture content and limited processing. Application of spray drying technique produces product with concentrated pigment and longer shelf life. Maltodextrin was added to juice to obtain free flowing powder with better reconstitution property. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.jfoodeng.2015.06. 024. References Abadio, F.D.B., Domingues, A.M., Borges, S.V., Oliveira, V.M., 2004. Physical properties of powdered pineapple (Ananas comosus) juice-effect of maltodextrin concentration and atomization speed. J. Food Eng. 64, 285–287.
Adhikari, B., Howes, T., Bhandari, B.R., Troung, V., 2004. Effect of addition of maltodextrin on drying kinetics and stickiness of sugar and acid rich foods during convective drying: experiments and modeling. J. Food Eng. 62, 53–68. Agarwal, S., Rao, A.V., 2000. Carotenoids and chronic diseases. Drug Metab. Drug Inter. 17, 189–210. AOAC, 1990. Official Methods of Analysis of the Association of Official Analytical Chemists, 16th ed. The Association of Official Analytical Chemists Inc, Arlington, VA. Arab, L., Steck-Scott, S., Fleishauer, A.T., 2002. Lycopene and the lung. Exp. Bio. Med. 227, 894–899. Arya, S.S., Premavalli, K.S., Siddiah, C.H., Sharma, T.R., 1985. Storage behaviour of freeze dried watermelon juice powder. Int. J. Food Sci. Technol. 20 (3), 351–357. Bhandari, B.R., Snoussi, A., Dumoulin, E.D., Lebert, A., 1993. Spray drying of concentrated fruit juices. Dry. Technol. 11 (5), 1081–1092. Carlos, L.A., Resende, J.D., Cal-Vidal, J., 2005. Reduction from higroscopicidade of powders liofilizados by induction from crystallization em solutions-model of sugars constituents of fruits. Braz. J. Food Technol. 8 (2), 163–173. Chahal, G.S., Saini, S.P.S., 1999. Storability of juice from new hybrid watermelon variety. Indian Food Packer 51, 12–18. Chiu, Y.T., Chiu, C.P., Chien, J.T., Ho, G.H., Yang, J., Chen, B.H., 2007. Encapsulation of lycopene extract from tomato pulp waste with gelatin and poly (c-glutamic acid) as carrier. J. Agric. Food Chem. 55, 5123–5130. Cole, E.R., Kapur, N.S., 1957. The stability of lycopene II. Oxidation during heating of tomato pulp. J. Sci. Food Agric. 8, 366–368. Daniel, W.W., 1991. Biostatistics: a Foundation for Analysis in the Health Sciences, 5th ed. John Wiley and Sons Inc., New York. Dolinsky, A., Maletskaya, K., Snezhkin, Y., 2000. Fruit and vegetable powders production technology on the basis of spray and convective drying methods. Dry. Technol. 18 (3), 747–758. FAO., 2014. Food and Agriculture Organisation of United Nation., (assessed .02.14). Gomes, F.S., Cabral, L.M.C., Couri, S., 2014. Lycopene content and antioxidant capacity of watermelon powder. Acta. Hort. 1040, 105–110. Goula, A.M., Adamopoulos, K.G., 2005. Stability of lycopene during spray drying of tomato pulp. LWT-Food Sci. Technol. 38, 479–487. Goula, A.M., Adamopoulos, K.G., Chatzitakis, P.C., Nikas, V.A., 2006. Prediction of lycopene degradation during a drying process of tomato pulp. J. Food Eng. 74 (1), 37–46. Huor, S.S., Ahmed, E.M., Rao, P.V., Cornel, J.A., 1980. Formulation and sensory evaluation of fruit punch containing watermelon juice. J. Food Sci. 45, 809–813. Karim, M., Hawlader, M., 2005. Mathematical modeling and experimental investigation of tropical fruits drying. Int. J. Heat Mass Transfer 48, 4914–4925. Kaya, A., Aydin, O., Dincer, I., 2007. Numerical modeling of forced-convection drying of cylindrical moist objects. Numer. Heat Transfer Part A 51, 843–854. Masters, K., 1991. Spray Drying Handbook. Longman Scientific and Technical, United Kingdom, 365–638. Patras, A., Brunton, N.P., Tiwari, B.K., Butler, F., 2011. Stability and degradation kinetics of bioactive compounds and colour in strawberry jam during storage. Food Bioprocess. Technol. 4, 1245–1252. Purkayastha, M.D., Nath, A., Deka, B.C., Mahanta, C.L., 2011. Thin layer drying of tomato slices. J. Food Sci. Technol. 50, 654. Que, F., Mao, L., Fang, X., Tao, W.U., 2008. Comparison of hot air drying and freeze drying on the physicochemical properties and antioxidant activities of pumpkin (Cucurbita moschata Duch.) flours. Int. J. Food Sci. Technol. 43, 1195–1201. Quek, A.Y., Chok, N.K., Swedlund, P., 2007. The physicochemical properties of spray dried watermelon powders. Chem. Eng. Process. 46, 386–392. Ranganna, S., 1986. Handbook of Analysis and Quality Control for Fruits and Vegetable Products, second ed. Tata Mc-Graw hill, India, 12–15, 88–90, 105– 106. Rodriguez-Amaya, D.B., Kimura, M., 2004. Harvest Plus Handbook for Carotenoid Analysis. International Food Policy Research Institute and International Center for Tropical Agriculture, Washington. Reineccius, G.A., 1991. Carbohydrates for flavor encapsulation. Food Technol. 46 (3), 144–152. Silva, M.A., Sobral, P.J.A., Kieckbusch, T.G., 2006. State diagrams of freeze dried camu camu (myrciaria dubia (hbk) mc vaug) with and without maltodextrin addition. J. Food Eng. 77 (3), 426–432. Tressler, D.K., Joslyn, M.A., 1971. Fruit and Vegetable Juice Processing Technology, second ed. The AVI pub. Co., Inc., Westport, CT. Weisburger, J.H., 2002. Lycopene and tomato products in health promotion. Exper. Bio. Med. 227, 924–927.
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Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng
Effect of drying methods and maltodextrin concentration on pigment content of watermelon juice powder Davinder Pal Singh Oberoi, Dalbir Singh Sogi ⇑ Department of Food Science and Technology, Guru Nanak Dev University, Amritsar 143 005, India
a r t i c l e
i n f o
Article history: Received 23 April 2015 Received in revised form 11 June 2015 Accepted 17 June 2015 Available online 18 June 2015 Keywords: Watermelon Spray drying Freeze drying Lycopene Maltodextrin
a b s t r a c t The effect of spray/freeze drying and maltodextrin concentration (3%, 5%, 7% and 10%) on pigment retention of watermelon juice powder from three cultivars was investigated. Incorporation of maltodextrin in watermelon juice yielded freely flowable powder. The spray dried powder has less moisture content, low water activity, high dissolution value and less reducing sugar content as compared to freeze dried powder. Lycopene of fresh watermelon juice was 4.58–6.53 mg/100 g on wet basis (wb) which was increased up to 56.4 mg/100 g (wb) in spray dried powder and 62.3 mg/100 g (wb) in freeze dried powder. Variation in instrumental color parameters with maltodextrin levels and dryers revealed that the freeze dried powder have lower ‘L’ value, higher ‘a’ value, higher ‘b’ value, lower ‘hue angle’ and high ‘chroma’ values as compared to spray dried powder. In spray drying lycopene loss was influenced by high air temperature and intensive exposure to oxygen causing degradation of lycopene. The freeze dried powder retained more pigment but powder had high water activity, limited shelf life, low flowability and hygroscopic in nature. Good correlation between colorimetric values and lycopene content was observed in spray dried powder. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction Watermelon (Citrullus lanatus Thunb) accounts for 18.32% of the world area devoted to vegetable production in 2012 (FAO, 2014). The color in the watermelon juice is red (Huor et al., 1980) due to the presence of lycopene that has potential to act as bio-color and anticancer drug. Lycopene has been shown to protect important biomolecules such as lipids, low-density lipoproteins and DNA against oxidative damage resulting in prevention of cancers, atherogenesis, and cell proliferation (Agarwal and Rao, 2000; Weisburger, 2002; Arab et al., 2002). Watermelon as one of underutilized fruits is harvested in summer months and is liked by consumer due to its delicate flavor and attractive color (Tressler and Joslyn, 1971). Watermelon juice is vulnerable to microbial and enzymatic deterioration due to high water activity. Drying is widely used to extend the shelf life of food products. The decrease in moisture content causes the reduction of the mass, volume, enzymatic and microbial activity (Karim and Hawlader, 2005; Kaya et al., 2007). Spray and freeze drying are the common techniques employed for the dehydration of fruit juices. The sticky behavior of sugar and acid rich materials is
attributed to low molecular weight sugars such as fructose, glucose, sucrose and organic acids such as citric, malic and tartaric acid which contributes more than 90% of solids in fruit juices (Dolinsky et al., 2000; Adhikari et al., 2004). Due to this sticky behavior of juices, it is difficult to dry them under normal conditions. Maltodextrin, consisting of b-D-glucose units is added to fruit juices to reduce stickiness and improving product stability (Reineccius, 1991; Bhandari et al., 1993; Silva et al., 2006). The present investigation was undertaken to study the effect of drying methods and maltodextrin concentration on physico-chemical properties and lycopene content of watermelon juice powder. 2. Material and methods 2.1. Material Watermelons of ‘Namdhari-95’ and ‘Namdhari-450’ varieties were procured from the farm located in Kapurthala (India) and of ‘Sugar Baby’ variety were obtained from Department of Vegetables, Punjab Agricultural University, Ludhiana (India). 2.2. Preparation of powder
⇑ Corresponding author. E-mail addresses: [email protected] (D.P.S. Oberoi), [email protected] (D.S. Sogi). http://dx.doi.org/10.1016/j.jfoodeng.2015.06.024 0260-8774/Ó 2015 Elsevier Ltd. All rights reserved.
Watermelons were cut into quarters, deseeded, peeled and passed through screw juice extractor (Kalsi Industries, Ludhiana,
D.P.S. Oberoi, D.S. Sogi / Journal of Food Engineering 165 (2015) 172–178
India) to obtain juice. The watermelon juice was passed through 40 lm sieve and then through 15 lm sieve to remove the fibrous matter. Maltodextrin (3%, 5%, 7% and 10%) was added in the juice and spray dried (ADL 31, Yamato Scientific Co. Ltd., Tokyo, Japan). Atomization of the juice was done using two fluid nozzle in which one part contain juice and other one contain compressed hot air. The spray dryer was operated at 125 °C inlet temperature, 70 °C outlet temperature, 0.25 kg/cm2 air pressure, 6.5 m3/min aspiration rate, 4 ml/min pump speed and 3 g/min feed rate. The powder was packed in air tight polyethylene pouches and stored at 4 °C in dark. In second drying method, the watermelon juice was passed through the 40 microns sieve, mixed with maltodextrin (3%, 5%, 7% and 10%), frozen in a chiller (Heto, Vedback, Denmark), dried in a freeze drier (Heto, Vedback, Denmark), packed in air tight polyethylene pouches and kept at 20 °C. 2.3. Physico-chemical properties The moisture content was determined in a vacuum oven (Narang Scientific Pvt Ltd., New Delhi, India) at 60 ± 2 °C and 100 mm Hg pressure for 24 h (AOAC, 1990). Titrable acidity (as anhydrous citric acid) was determined using a pH meter (LI120, Elico, Hyderabad, India). The water activity was determined using water activity analyzer (Aqua Lab 4TE, Decagon devices, USA). For the dissolution test, 50 mg of powder sample was placed in a test tube. 1 ml of distilled water at room temperature was added and mixing was performed using vortex. The time (s) to fully reconstitute the powders was recorded (Quek et al., 2007). Reducing and total sugars were determined according to Lane and Eynon method (Ranganna, 1986). Non-reducing sugar was calculated from difference of total sugars and reducing sugars. 2.4. Lycopene and total carotenoids Sample (2 g) was extracted with acetone in a pestle and mortar till residues became colorless. Pigment was transferred into petroleum ether phase in a separating funnel, passed through sodium sulphate and evaporated under vacuum. Lycopene content was determined by HPLC (Waters, Milford, MA, USA) fitted with a photodiode array detector using YMC Carotenoids (5 lm) column, methanol: ethanol: Tetrahydrofuran (15:4:1) mobile phase, 1 ml/min flow rate and 470 nm wavelength. Lycopene (Sigma Chemical Co, St. Louis, Missouri, U.S.A.) was used as standard. The total carotenoids were determined by measuring the absorbance at 452 nm on spectrophotometer (Shimadzu, Kyoto, Japan) using beta carotene (Sigma Chemical Co, St. Louis, Missouri, USA) as standard. 2.5. Visual color analysis Visual color was measured using a Hunter Color Lab (Hunter Associate Laboratory, Reston, USA) in terms of L (lightness), a (redness (+) and greenness ()) and b (yellowness (+) and blueness ()). The instrument was calibrated with a standard black tile and then standard white tile (L = 90.55, a = 0.71, b = 0.39). A sample handling dish was charged with samples, placed on the analyzing port and noted the L, a, b values. The hue angle (h° = tan1 b/a) represents the maximum degree of redness at 0°, yellowness at 90°, greenness at 180° and blueness at 270° (Patras et al., 2011). The chroma p (C = a2 + b2) indicates the color intensity or saturation of sample. 2.6. Statistical analysis Two-way analysis of variance was applied on the data of physico-chemical, lycopene, total carotenoids and Hunter color
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parameters of watermelon powder. The difference between the means was compared by Honestly Significant Difference (HSD) values using Tukey’s Test (Daniel, 1991) analyzed at p 6 0.05. Linear regression was applied to determine the relationship between the lycopene and hunter color values. The goodness of linear fit was evaluated by coefficient of determination (R2), adjusted R2, p-values and root mean square error computed using Minitab-15 (Mini Tab Inc., Coventry, U.K.) software. 3. Results and discussion 3.1. Physico-chemical properties of watermelon juice Moisture content of watermelon juice of cultivars ‘Namdhari-95’, ‘Namdhari-450’, ‘Sugar baby’ was in the range of 90.3–93.1 g/100 g whereas the total soluble solids of juice were 5.1–8.9 g/100 g. The acidity of juice obtained from three cultivars was in the range of 0.02–0.04 g/100 g. The reducing sugars of watermelon juice of three cultivars were in the range of 2.9– 3.7 g/100 g whereas the total sugars varied from 4.9–5.3 g/100 g respectively. Chahal and Saini (1999) analyzed bottled Indo-American hybrid watermelon juice and reported 6.4– 9.0 g/100 g soluble solids, 0.05–0.08 g/100 g acidity, 5.52 g/100 g reducing sugars and 7.76 g/100 g total sugars. Quek et al. (2007) reported 12.1°B total soluble solids, 5.5 g/100 ml glucose, 6.8 g/100 ml fructose and 1.2 g/100 ml sucrose of watermelon (Sugar baby) juice. The soluble solids content of the watermelon are comparable with previous studies of Chahal and Saini (1999) but lower than Quek et al. (2007). 3.2. Physico-chemical properties of watermelon juice powder 3.2.1. Moisture content Moisture content of spray dried watermelon juice powder was decreased with increase in maltodextrin from 3% to 10% (Table 1). In spray drying of powder, the water content of feed had an effect on the final moisture content of powder produced (Abadio et al., 2004). The low moisture content of powder at higher maltodextrin was due to increase in total solids of the feed prior to spray drying and thus reduced the amount of water for evaporation. According to Adhikari et al. (2004), the addition of maltodextrin resulted into lower moisture diffusivity and decrease water flux of sugar drops dried in spray dryer. Quek et al. (2007) concluded that by increasing the maltodextrin (3–5%) and temperature (145, 155, 165 and 175 °C), the moisture content of spray dried watermelon powder significantly (p 6 0.05) decreased. Statistical analysis revealed that the moisture content of freeze dried powder decreased significantly (p 6 0.05) with increase in maltodextrin level (Table 2). The freeze dried powder showed higher moisture as compared to spray dried powder because drying was accomplished through sublimation. Among the cultivars, moisture content of powder obtained by spray drying and freeze drying was significantly (p 6 0.05) different (see Table 3). 3.2.2. Water activity Tukey’s multiple comparison showed that water activity significantly (p 6 0.05) varied with the level of maltodextrin as well as type of cultivars used in the study. Water activity of spray dried powder decreased with increase in maltodextrin from 3% to 10% (Table 1). Quek et al. (2007) found the same pattern of water activity of spray dried watermelon powder with change in maltodextrin from 3% to 5%. The water activity of freeze dried powder was more than of spray dried powder, indicating more free available water for biological reactions and thus limited shelf life. Freeze dried powder exhibited inverse relation between the moisture and water activity which might due to high percentage of amorphous sugars
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Table 1 Physico-chemical analysis of spray dried watermelon powder during processing (n = 3). Parameters
Maltodextrin concentration (%)
‘Namdhari-95’
‘Namdhari-450’
‘Sugar Baby’
Moisture (% db) 3 5 7 10
3.39ar ± 0.11 3.25br ± 0.22 2.60cr ± 0.09 2.24dr ± 0.15
4.54aq ± 0.13 4.14bq ± 0.19 3.22cq ± 0.22 2.87dq ± 0.25
5.46ap ± 0.18 4.93bp ± 0.16 4.18cp ± 0.08 3.90dp ± 0.20
3 5 7 10
0.276aq ± 0.01 0.248br ± 0.05 0.166cr ± 0.09 0.153dr ± 0.10
0.287ap ± 0.02 0.266bq ± 0.08 0.234cq ± 0.11 0.214dq ± 0.08
0.289ap ± 0.05 0.271bp ± 0.05 0.241cp ± 0.07 0.232dp ± 0.05
3 5 7 10
9.4c ± 0.98 13.2b ± 1.5 14.1b ± 1.9 16.5a ± 2.3
11.3d ± 2.9 13.5c ± 0.56 15.4b ± 1.5 22a ± 1.2
3 5 7 10
48.23bq ± 0.89 67.89ap ± 1.02 72.20ap ± 0.75 75.24ap ± 0.24
34.08br ± 0.15 37.98bq ± 0.23 44.30bq ± 0.56 51.61aq ± 0.99
58.04bp ± 0.14 65.36ap ± 0.49 70.07ap ± 1.11 73.31ap ± 0.78
3 5 7 10
42.15cq ± 0.54 58.97bp ± 1.82 62.15bp ± 2.10 70.24ap ± 1.56
30.08cr ± 1.23 36.48bq ± 0.97 38.75bq ± 1.45 47.15aq ± 1.21
52.57dp ± 0.84 60.52cp ± 2.54 64.83bp ± 1.39 71.95ap ± 2.87
3 5 7 10
6.04 ± 0.31 8.89 ± 0.19 10.06 ± 1.91 5.00 ± 1.09
4.01 ± 0.12 1.50 ± 0.11 5.54 ± 0.34 4.46 ± 0.41
5.46 ± 0.36 4.84 ± 0.32 5.24 ± 0.29 1.36 ± 0.12
Water activity (aw)
Dissolution (s) 10.5c ± 2.1 12.5b ± 2.3 13.4b ± 1.8 21.2a ± 1.8
Total sugars (% db)
Reducing sugars (% db)
Non-Reducing sugars (% db)
Values with different superscripts are significantly (p < 0.05) different in column – a, b, c, d and in rows – p, q, r using Tukey’s Multiple comparison test.
Table 2 Physico-chemical analysis of freeze dried watermelon powder during processing (n = 3). Parameters
Maltodextrin concentration (%)
‘Namdhari-95’
‘Namdhari-450’
‘Sugar Baby’
Moisture (% db) 3 5 7 10
5.54ar ± 0.58 5.24br ± 0.39 4.77cr ± 0.09 4.43dr ± 0.05
7.00ap ± 0.17 6.60bp ± 0.08 6.20cp ± 0.02 5.86dp ± 0.19
6.66aq ± 0.16 6.26bq ± 0.24 5.86cq ± 0.08 5.50dq ± 0.28
3 5 7 10
0.333dr ± 0.12 0.349cr ± 0.14 0.368br ± 0.11 0.403ar ± 0.15
0.359dq ± 0.11 0.364cq ± 0.14 0.391bq ± 0.19 0.432aq ± 0.18
0.376dp ± 0.25 0.395cp ± 0.13 0.404bp ± 0.19 0.439ap ± 0.15
3 5 7 10
10.5 ± 0.12 11.2 ± 1.7 12.5 ± 0.9 12.9 ± 0.3
11.0 ± 0.7 12.5 ± 0.2 13.1 ± 0.64 15.8 ± 0.21
3 5 7 10
53.75cp ± 0.89 65.80bp ± 1.15 69.44ap ± 0.55 72.66aq ± 0.13
49.05dq ± 0.75 53.62cq ± 0.23 60.13bq ± 0.56 67.14ar ± 0.99
54.11dp ± 0.14 64.04cp ± 0.49 72.47bp ± 1.11 78.08ap ± 0.78
3 5 7 10
47.18dq ± 0.54 58.00cp ± 1.82 63.57bq ± 2.10 70.70aq ± 1.56
43.76dr ± 0.39 50.17cq ± 0.97 55.28br ± 1.45 61.70ar ± 1.21
46.87dp ± 0.84 57.67cp ± 2.54 67.39bp ± 1.39 75.24ap ± 1.87
3 5 7 10
6.57 ± 0.39 7.80 ± 0.67 5.87 ± 0.19 1.96 ± 0.85
5.29 ± 0.25 3.45 ± 0.49 4.85 ± 1.03 5.24 ± 0.92
7.34 ± 0.55 6.37 ± 0.21 5.07 ± 0.53 2.85 ± 0.68
Water activity (aw)
Dissolution (s) 10.7 ± 1.1 11.9 ± 1.6 12.9 ± 1.8 21.6 ± 2.1
Total sugars (% db)
Reducing sugars (% db)
Non-Reducing sugars (% db)
Values with different superscripts are significantly (p < 0.05) different in column – a, b, c, d and in rows – p, q, r using Tukey’s Multiple comparison test.
having high hygroscopicity and absorbs more free water (Carlos et al., 2005). Arya et al. (1985) concluded that freeze dried watermelon powder was stable in the water activity range of 0.22–0.25
aw whereas caking started when water activity value increased beyond 0.33. Therefore, the spray dried powder had greater shelf life compared to freeze dried powder.
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D.P.S. Oberoi, D.S. Sogi / Journal of Food Engineering 165 (2015) 172–178 Table 3 Color analysis of spray dried watermelon powder during processing (n = 3). Parameter
Maltodextrin concentration (%)
‘Namdhari-95’
‘Namdhari-450’
‘Sugar Baby’
3 5 7 10
71.77b ± 0.25 72.45b ± 0.09 89.16a ± 0.10 94.15a ± 0.04
53.52b ± 0.03 77.78a ± 0.02 78.45a ± 0.06 79.56a ± 0.07
62.77d ± 0.03 76.57c ± 0.03 85.95b ± 0.08 93.81a ± 0.04
3 5 7 10
12.12a ± 0.15 8.41b ± 0.16 2.59c ± 0.14 0.68d ± 0.15
18.07a ± 0.05 8.05b ± 0.05 5.45c ± 0.06 2.35d ± 0.24
10.14a ± 0.09 5.86b ± 0.07 3.19c ± 0.07 0.45d ± 0.03
3 5 7 10
11.12aq ± 0.10 9.851bq ± 0.08 6.58cq ± 0.06 4.72dp ± 0.06
10.13aq ± 0.03 8.75bq ± 0.10 7.09cq ± 0.04 5.41dp ± 0.04
13.11ap ± 0.04 12.82ap ± 0.06 10.22bp ± 0.04 5.78cp ± 0.04
3 5 7 10
42.52dq ± 0.18 49.51cq ± 0.26 68.21bp ± 0.11 81.96ap ± 0.08
29.24dr ± 0.22 47.36cq ± 0.31 52.43br ± 0.17 66.51aq ± 0.09
52.23dp ± 0.03 65.42cp ± 0.13 72.66bp ± 0.06 85.55ap ± 0.11
3 5 7 10
16.45a ± 0.19 12.95b ± 0.08 6.98c ± 0.07 4.57d ± 0.04
20.72a ± 0.18 11.89b ± 0.12 8.94c ± 0.03 5.89d ± 0.07
16.57a ± 0.06 14.09b ± 0.04 10.72c ± 0.07 5.79d ± 0.02
‘L’
‘a’
‘b’
Hue (°)
Chroma
Values with different superscripts are significantly (p < 0.05) different in column – a, b, c, d and in rows – p, q, r using Tukey’s Multiple comparison test.
3.2.3. Dissolution test Dissolution test gives speed of reconstitution of dried powder into water. Dissolution value of spray and freeze dried powder increased with level of maltodextrin (Tables 1 and 2). The results showed that there was inverse relationship between dissolution and moisture content of powders. At low maltodextrin, products contain high moisture content and these powders has higher tendency of agglomeration which helped to increase the reconstitution of powder (Masters, 1991). Quek et al. (2007) found that the dissolution value of spray dried watermelon powder was in the range of 17–30 s with change in temperature from 145 to 175 °C. Non-significant (p > 0.05) change was observed in dissolution value among the cultivars and change in maltodextrin concentration in freeze dried powder. Freeze dried powder showed less range of dissolution value due to high moisture content of powder and has high reconstitution capacity. The dissolution value in present study varied from 9.4 to 22 s which was lower than values reported in literature.
3.2.4. Sugars The total sugars in spray dried watermelon powder were found to increase up to 75.24%, 51.61% and 73.31% dry basis (db) respectively in the ‘Namdhari-95’, Namdhari-450’, ‘Sugar baby’ cultivars with change in maltodextrin from 3% to 10% (Table 1). The sugar content of freeze dried powder values were also increased up to 72.66%, 67.14% and 78.08% db respectively for three cultivars (Table 2). Statistical analysis revealed that total sugars of ‘Namdhari-450’ variety were significantly (p 6 0.05) different from other two cultivars whereas 3% maltodextrin level showed significantly lower total sugar than other levels. With increase in maltodextrin, the reducing sugars in spray dried and freeze dried watermelon powder were found to increase. The HSD test showed that among the cultivars significant (p 6 0.05) change was observed in ‘Namdhari-450’ only. Non significant results were obtained in non reducing sugars of spray/freeze dried watermelon powder. Increase in sugars content of powder was due to increase of solids and maltodextrin concentration.
3.3. Pigment content of watermelon juice powder The pigment analysis of watermelon juice of ‘Namdhari-95’, ‘Namdhari-450’ and ‘Sugar baby’ cultivars showed lycopene values of 85.21, 91.97 and 64.50 mg/100 ml respectively on dry basis (db) without maltodextrin prior to drying whereas the total carotenoids in fresh watermelon juice were 87.88, 102.81 and 71.83 mg/100 ml on db in respective three cultivars. The processing of watermelon juice by spray drying showed that lycopene content and total carotenoids were significantly (p 6 0.05) decreased with increase in maltodextrin level (Fig. 1). There was significant loss of lycopene (32.1–76.8%) during spray drying due to heating at high temperature and exposure to oxygen. The decrease of lycopene in spray drying was due to an actual degradation of lycopene rather than progressive conversion from the all-trans lycopene to cis form (Goula and Adamopoulos, 2005). Goula et al. (2006) concluded that in spray drying process, the product was converted in form of droplets and hence larger surface area exposed to air enhances lycopene oxidation. Oxidation is undesirable because it leads to lycopene degradation and a concomitant loss of its health related properties (Rodriguez-Amaya and Kimura, 2004). Quek et al. (2007) found the lycopene content of spray dried watermelon powder decreased from 95.4 to 72.5 mg/100 g with change in temperature from 145 to 175 °C. Cole and Kapur (1957) observed 25% apparent lycopene loss in the presence of oxygen when heating the tomato pulp at 100 °C for 2 h. Increase of maltodextrin also affects the pigment content due to dilution of pigment (Quek et al., 2007). Spray drying with maltodextrin helps in microencapsulation of lycopene in a solid form. There was 5.1–7.5 times increase in lycopene in spray dried watermelon powder as compared to watermelon juice. Gomes et al. (2014) found the increase of 2.16 times in lycopene of spray dried watermelon powder using 8% maltodextrin. Quek et al. (2007) microencapsulated lycopene obtaining increase of 16.7 times using 5% maltodextrin as wall material. The average lycopene content and total carotenoid of freeze dried powder was decreased with increase in maltodextrin level (Fig. 1). However, Tukey’s multiple comparison test showed non-significant (p P 0.05) change in lycopene and total
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70
p
'Namdhari-95' p
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40 30 20 10 0 5
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0 3
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80
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'Namdhari-450'
80 q
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'Sugar baby'
5
'Sugar baby'
80
70
70
60
p
50
q a
a
r
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Pigment Content, mg/100g
Pigment Content, mg/100g
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Pigment Content, mg/100g
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'Namdhari-95'
80 Pigment Content, mg/100g
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80
60 50 40 30 20 10
0
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Maltodextrin level (%)
(a)
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Fig. 1. Lycopene and total carotenoids content on moisture and maltodextrin free basis (a) spray dried and (b) freeze dried watermelon powder of different watermelon cultivars. Unfilled bar-Lycopene; filled bar – Total Carotenoids (Values with different superscripts are significantly (p < 0.05) different a, b, c, d for lycopene and p, q, r, s for total carotenoids using Tukey’s Multiple comparison test).
carotenoids of freeze dried powder with increase in maltodextrin level but significant (p 6 0.05) among the cultivars. It was observed that there was 24.99–30.88% lycopene loss in watermelon during freeze drying. The retention of lycopene in freeze dried powder was higher due to minimal processing of watermelon juice. In freeze drying effect of high temperature and oxidation was absent resulting in lower degradation of lycopene. Freeze drying resulted in 9–9.5 times concentration of lycopene as compared to fresh watermelon juice. Chiu et al. (2007) microencapsulated lycopene extract from tomato pulp waste by freeze drying using gelatin and poly (c-glutamic acid) as coating material and found 23.5% lycopene loss during freeze drying. 3.4. Visual color values The ‘L’ values for spray dried watermelon powder were increased with increase in maltodextrin concentration. The Tukey’s multiple comparison test showed that ‘L’ values of ‘Sugar
baby’ cultivar were significantly (p 6 0.05) different at all levels of maltodextrin (Table 3). The high concentration of maltodextrin resulted in whiteness of the powder. The ‘a’ and ‘b’ values of spray dried powder were significantly (p 6 0.05) decreased with change with maltodextrin. The ‘b’ values of ‘Sugar baby’ were found to be significantly (p 6 0.05) different from other cultivars. With high level of maltodextrin, the watermelon powder lost its red–orange color (Quek et al., 2007). The hue angle of spray dried powder was significantly (p 6 0.05) increased with maltodextrin and higher values showed decrease in redness of powder due to destruction of pigment during drying of juice. The chroma values of spray dried powder were significantly (p 6 0.05) decreased with maltodextrin. The present results were consistent with previous studies (Quek et al., 2007). The ‘L’ value of freeze dried powder was significantly (p 6 0.05) increased with change in maltodextrin concentration from 3% to 10% (Table 4). The statistical analysis showed that there was significant (p 6 0.05) change in ‘a’ value at 10% maltodextrin in all
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D.P.S. Oberoi, D.S. Sogi / Journal of Food Engineering 165 (2015) 172–178 Table 4 Color analysis of freeze dried watermelon powder during processing (n = 3). Parameter
Maltodextrin concentration (%)
‘Namdhari-95’
‘Namdhari-450’
‘Sugar Baby’
3 5 7 10
55.53dp ± 0.249 57.93cp ± 0.88 58.66bp ± 0.12 59.45ap ± 1.04
50.43dr ± 1.13 55.16cq ± 0.52 56.19bq ± 0.96 56.87aq ± 0.67
52.46dq ± 0.53 55.32cq ± 0.83 56.76bq ± 0.28 57.68aq ± 0.34
3 5 7 10
17.98aq ± 0.25 17.25bq ± 0.19 17.15bq ± 0.15 16.81cq ± 0.05
19.53ap ± 0.05 18.46bp ± 0.09 18.21cp ± 0.19 18.09cp ± 0.14
15.34ar ± 0.19 14.88br ± 0.06 14.23cr ± 0.11 13.52dr ± 0.19
3 5 7 10
8.29q ± 0.19 7.99q ± 0.18 7.83p ± 0.06 7.75p ± 0.06
6.5r ± 0.13 6.43r ± 0.15 6.29q ± 0.24 6.11q ± 0.32
8.79p ± 0.45 8.43p ± 0.36 8.24p ± 0.19 8.39p ± 0.24
3 5 7 10
24.74cq ± 0.23 24.7cq ± 0.18 24.56bq ± 0.14 24.74aq ± 0.11
18.36br ± 0.13 19.19ar ± 0.17 19.03ar ± 0.21 18.65ar ± 0.09
29.81bp ± 0.12 29.50bp ± 0.18 30.07bp ± 0.11 31.79ap ± 0.15
3 5 7 10
19.79aq ± 0.31 19.01bq ± 0.24 18.85bp ± 0.15 18.51bp ± 0.10
20.58ap ± 0.09 19.54bp ± 0.19 19.26cp ± 0.18 19.09cp ± 0.22
17.67ar ± 0.11 17.10br ± 0.25 16.44cq ± 0.29 15.91dq ± 0.14
‘L’
‘a’
‘b’
Hue (°)
Chroma
Values with different superscripts are significantly (p < 0.05) different in column – a, b, c, d and in rows – p, q, r using Tukey’s Multiple comparison test.
Table 5 Statistical parameters of linear regression of lycopene content of watermelon powder with colorimeter measurements. Adjusted R2 (%)
Intercept p-value
Slope p-value
Root mean squared error
p-value of the overall model
Spray dried watermelon powder ‘a’ 88.7 ‘b’ 99.7 ‘L’ 87.6 ‘a b’ 85.8 ‘a/b’ 91 ‘b/a’ 87.7 ‘(a/b)2’ 74.4 ‘1000a/(b + L)’ 94.8 ‘Hue’ 97.7 ‘Chroma’ 95.1
83.1 99.6 81.5 78.6 86.5 81.5 61.7 92.2 96.5 92.0
0.013* 0.012* 0.025* 0.012* 0.019* 0.004** 0.017* 0.008** 0.003** 0.027*
0.045* 0.001** 0.064ns 0.074ns 0.046* 0.064ns 0.137ns 0.026* 0.012* 0.027*
0.028 0.027 0.007 0.040 0.025 0.029 0.043 0.034 0.019 0.021
0.045* 0.001** 0.064ns 0.074ns 0.046* 0.064ns 0.137ns 0.026* 0.012* 0.027*
Freeze dried watermelon powder ‘a’ 86.9 ‘b’ 94.1 ‘L’ 95.3 ‘a b’ 89.3 ‘a/b’ 79 ‘b/a’ 37.7 ‘(a/b)2’ 84.4 ‘1000a/(b + L)’ 3.6 ‘Hue’ 42.6 ‘Chroma’ 89.2
80.4 91.1 92.9 84 68.6 6.5 77.2 0.0 13.9 83.8
0.007** 0.009** 0.001** 0.002** 0.501ns 0.052ns 0.038* 0.451ns 0.062ns 0.007**
0.068 ns 0.030* 0.024* 0.055ns 0.111ns 0.386ns 0.079ns 0.811ns 0.347ns 0.056ns
0.020 0.006 0.005 0.080 0.002 0.003 0.004 0.027 0.004 0.002
0.068 ns 0.030* 0.024* 0.055 ns 0.111 ns 0.386 ns 0.079 ns 0.811 ns 0.347 ns 0.056 ns
Hunter color values
** *
R2 (%)
Data significant at p 6 0.01. Data significant at p 6 0.05; ns: non-significant; R2: coefficient of determination.
varieties and among the cultivars the ‘a’ value was significantly (p 6 0.05) different. Non significant (p P 0.05) change was observed in ‘b’ value of freeze dried powder with change in maltodextrin. The hue angle of freeze dried powder was significantly different at 3% maltodextrin as it has inverse relationship with ‘a’ value. The HSD test showed that the hue values of freeze dried powder were significantly (p 6 0.05) different among the cultivars. Slight change was observed in chroma values of freeze dried powder with maltodextrin (see Table 4). The freeze dried powder showed lower whiteness (‘L’ value), higher redness (‘a’ value), higher yellowness (‘b’ value), lower hue angle and high chroma values as compared to spray dried powder. In spray drying product has the form of droplets, the
larger surface exposed to air enhances lycopene oxidation and loss is faster as compared to freeze drying (Goula et al., 2006). Therefore, the spray dried powder lost its redness and showed lower ‘a’ value. Que et al. (2008) concluded that freeze drying resulted in higher ‘a’ and ‘b’ value compared with pumpkin flours prepared by hot air drying. 3.5. Correlation between lycopene and colorimetric values The linear regression between the lycopene content and colorimetric parameters of watermelon juice powder was evaluated. Values of correlation between lycopene and color parameters were higher in spray dried powder (74.4–99.7%) than freeze dried
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powder (3.6–95.3%) (Table 5). The intercept p-values of spray dried powder were found to be significant for all colorimetric values. The p-values of correlation of spray dried powder were found to be significant (p 6 0.05) for ‘a’, ‘b’, ‘a/b’, ‘1000a/(b + L)’, hue and chroma color values. Good agreement between experimental and predicted data was observed which was confirmed by lower value of root mean square error (0.007–0.043). Quek et al. (2007) found the correlation coefficient between lycopene and hue content of spray dried watermelon powder in the range of 0.946. Purkayastha et al. (2011) found the good agreement between the experimental and predicted data for thin layer convective drying of blanched tomato slices confirmed by lower root mean square error values (0.002–0.010). The p-values of correlation of freeze dried powder were found to be significant at p 6 0.05 only for ‘L’ and ‘b’ whereas intercept p-values were significant for ‘a’, ‘b’, ‘a b’, ‘(a/b)2’ and chroma values. Lower values of root mean square error (0.002–0.080) indicates the validity of the model. This data indicated that as the lycopene degradation occurred with drying of watermelon juice, the visual colorimetric parameters of the product got affected. 4. Conclusion Watermelon powder was produced using different drying techniques and maltodextrin concentration. Maltodextrin was an effective drying aid helped in reducing stickiness and altered the physicochemical properties of watermelon powder. With increase in maltodextrin concentration, the moisture content of the spray and freeze dried powder decreased while time for reconstitution and sugar content increased. The freeze dried powder contained higher water activity, low flowability and was highly hygroscopic in nature. The visual color analysis showed that watermelon powder lost its redness with increase in maltodextrin above 5% in spray drying. The lycopene loss in watermelon powder was higher in spray drying as compared to freeze drying due to effect of high temperature and large surface area expose to air which results into degradation of lycopene into colorless form by oxidation process. 5. Practical application Large amount of watermelon crops gets wasted every year due to high moisture content and limited processing. Application of spray drying technique produces product with concentrated pigment and longer shelf life. Maltodextrin was added to juice to obtain free flowing powder with better reconstitution property. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.jfoodeng.2015.06. 024. References Abadio, F.D.B., Domingues, A.M., Borges, S.V., Oliveira, V.M., 2004. Physical properties of powdered pineapple (Ananas comosus) juice-effect of maltodextrin concentration and atomization speed. J. Food Eng. 64, 285–287.
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