- Email: [email protected]
Post-harvest physico-mechanical properties of orange peel and fruit
Journal of Food Engineering 73 (2006) 112–120 www.elsevier.com/locate/jfoodeng
Post-harvest physico-mechanical properties of orange peel and fruit Krishna K. Singh *, B. Sreenivasula Reddy Central Institute of Agricultural Engineering, Nabi Bagh, Berasia Road, Bhopal 462 038, India Received 31 May 2004; accepted 13 January 2005 Available online 13 March 2005
Abstract The post-harvest physico-mechanical properties data of fruits and vegetables are important in adoption and design of various handling, packaging, storage and transportation systems. Physico-mechanical properties namely, orange peel tensile strength and cutting energy and fruit color, weight loss, bioyield point, firmness, puncture force and cutting energy were determined with respect to storage period under ambient and refrigerated conditions. Peel tensile strength, modulus of elasticity and cutting energy decreased with storage period in both ambient and refrigerated conditions. The color index of orange followed a fourth-order polynomial equation during storage. At the end of 17 days storage, the fruit cumulative weight losses in ambient and refrigerated conditions were 19.4% and 7.3%, respectively. Bioyield point, firmness, puncture force and cutting energy of orange fruits decreased with respect to number of days of storage. The firmness of orange fruit was significantly higher in stem-calyx axis in vertical position than that in horizontal position. 2005 Published by Elsevier Ltd. Keywords: Citrus; Color; Peel; Physico-mechanical properties; Weight loss; Firmness
1. Introduction The mechanical harvesting of fruits causes damage from branches and other fruits as fruit falls from the tree and drops on the ground. These damages are in the form of splits, punctures and bruises. Further damage is caused when it is raked, picked up, loaded and transported to distant places by trucks. Generally, it takes several days in transportation from one place to another that causes various changes in physico-mechanical properties of fruits. The post-harvest mechanical properties data of fruits and vegetables are important in adoption and design of various handling, packaging, storage and transportation systems. The fruit compression test simulates the condition of static loading that fruit can withstand in mechan*
Corresponding author. Tel.: +91 7552733226x298; fax: +91 7552734016. E-mail address: [email protected] (K.K. Singh). 0260-8774/$ - see front matter 2005 Published by Elsevier Ltd. doi:10.1016/j.jfoodeng.2005.01.010
ical handling and storage. The most common practice to determine the fruit ripeness in field situation is pressing with ball of the thumb. Force deformation characteristics of fruits beyond the elastic limit may be important to simulate the destruction that occurs in bruising. Elastic modulus or YoungÕs modulus is often used by engineers as an index of product firmness. Puncture tests are also measures of firmness of fruits and vegetables to estimate harvest maturity or post-harvest evaluation of firmness. Research has been carried out for several years to determine the resistance of fruits and vegetables to compression force. Witz (1954) reported resistance to bruising of potatoes to puncture by using a plunger. Studies on bruises to apples resulting from dropping and from application of pressure was reported by Gaston and Levin (1951). Ahmed, Martin, and Fluck (1973) reported shear stress data of peel pieces collected at the time of harvest. Kaufmann (1970) measured the effect of water potential
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
and temperature on the extensibility of citrus peel. Gyasi, Friedly, and Chen (1981) determined PoissonÕs ratio for citrus fruit peel and pulp. Fidelibus, Teixeira, and Davies (2002) determined the gibberellic acid (GA3) treatment effect on mechanical properties of pre-harvest orange peel and whole fruit. The properties such as color and firmness of orange that differentiate individual units of a product are important to determine the degree of acceptability of the product to the buyer (Guzel, Alizade, & Sinn, 1994). Fruit softening is often used as a criterion for estimating the feasibility of their storage or shelf life (Kader, 1992; Polderdijk, Tijskens, Robberts, & Van der Valk, 1993; Blankenship, Parker, & Unrath, 1997). Color is considered to be one of the most important external factors of fruit quality, as the appearance of the fruit greatly influences consumers. Fruit and vegetable yellowing is often a result of the disappearance of chlorophylls which allows the yellow orange xanthophylls and carotenes to become more visible (Shewfelt & Prussia, 1993). The relationship between color and level of maturation has been widely studied in tomatoes (Choi, Lee, Han, & Bun, 1995), peaches, and nectarines (Mitchell, 1987; Luchsinger & Walsh, 1993). Along the same line, Mercado-Silva, Benito-Bautista, and Garcia-Velasco (1998) identified L , a , and hue values as being the best parameters for differentiating the different stages of the maturation of guava. In citrus, Jimenez-Cuesta, Cuquerella, and Martinez-Javega (1981) proposed the use of the formula 1000a /(L b ) as ‘‘Color Index’’ for recording the process of orange degreening. In most fruits, their firmness diminishes as the degree of maturation increases due to the action of pectic enzymes during fruit maturation (Muramatsu, Kiyohide, & Tatsushi, 1996). Miller (1987) determined stress index, modulus of elasticity, and rupture force of freeze-damaged and non-damaged fruit. Sarig and Nahir (1973) reported the initial and permanent deformations of a creep test of citrus fruit to indicate firmness. Churchill, Sumner, and Whitney (1980) determined the influence of harvest date on the physical strength properties (burst and puncture) of whole fruit and tensile strength of peel pieces of three orange varieties. Singh (1971) studied optimum storage temperature, storage life and keeping quality of mandarins and sweet lemon. During storage the loss of moisture from the peel is continuously replenished by the movement of the moisture from the pulp. If this loss due to combined effect of respiration and transpiration goes on unchecked, the fruit shrivels up and becomes unmarketable. There is a dearth of information on post-harvest physico-mechanical properties changes of orange peel and fruit under ambient and refrigerated storage conditions which are helpful to decide handling, packaging, storage, and transportation systems to be adopted and their designs. The objective of this paper is to report
113
changes in basic physical and mechanical properties of orange peel and whole fruit under ambient and refrigerated fruit storage conditions.
2. Materials and methods Orange (Variety: Nagpur Mandarin) fruits were procured from experimental orchard of National Research Center for Citrus, Nagpur, India. Random samples were drawn from a freshly harvested lot of citrus at the time of harvest. Fruits were divided into two lots each consisting of 150 fruits. One lot of fruits was taken into ventilated corrugated fiberboard box and kept in an ambient conditions of 28 C and 58% RH. Another lot of fruits was kept in refrigerator at a temperature of 7 C and 78% RH. Post-harvest physico-mechanical properties of orange peel and fruits were determined with respect to the storage period in both ambient and refrigerated conditions. 2.1. Peel moisture content About 5 g of peel sample was taken in to an aluminum container at the time of experimentation. The samples were dried in hot air oven at 80 C for 24 h. Peel moisture content was calculated on dry weight basis. The average values of three replications are reported. 2.2. Peel tensile test The peel tensile strength test was used to evaluate the behavior of the orange peel under applied tensile loads. Clamps were made to hold a section of orange peel for determining peel strength. Peel pieces were carefully dissected from the equator of five randomly selected fruits. Immediately after peel removal, peel thickness was measured using vernier calipers (accuracy 0.01 g), and peel strips of 15 mm (polar) and 60 mm (equatorial) were attached to Instron Testing Machine (Model: 4400, Instron Limited, England) clamps. One clamp was fixed to the base of the machine, while the other was attached to a load cell rated at a maximum of 5000 N. Strips were subjected to axial tensile loading in an equatorial direction, with a crosshead speed of 10 mm/min until rupture. Rupture force was taken as the maximum peak force required to rupture the peel as shown in Fig. 1. Tensile strength (rt) was calculated with dividing the peak rupture force by the cross-sectional area (thickness · width) of the initial specimen. Modulus of elasticity (E) was calculated as the slope of the initial linear portion of a stress/strain curve of Fig. 1. Rupture force, tensile strength and modulus of elasticity were measured for 10 days from harvest in both ambient and refrigerated conditions. The average values obtained from 10 replications are reported.
114
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
Fig. 1. A typical curve for peel tensile test obtained from Instron Testing Machine (crosshead speed: 10 mm/min).
2.3. Peel cutting test Peel pieces were carefully dissected from the equator of five randomly selected fruits. Peel pieces of about 20 · 40 mm were placed upon a Texture Analyzer (model:TAXT2i, Stable Microsystems, England) HDP/ BSK blade set. A blade set knife of the Texture Analyzer attached to the probe carrier was used to cut the peel pieces. The load cell was calibrated to 250 N and the cutting was done at a speed of 1 mm/s. As the cutter blade applied force on peel to cut, there was about 6 mm settling before the cutting begun. Peak cutting force was considered as the first peak force in N recorded as shown in Fig. 2. The peel cutting energy was taken as area under force–deformation curve as shown in Fig. 2. The average values of 10 replications each day for 10 days storage period both in ambient and refrigerated conditions are reported. 2.4. Fruit color The color change of orange fruit was measured using LabScanXE spectrocolorimeter (Model No. LX16244, Hunter Associates Laboratory, Virginia) in terms of CIE ÔL Õ (lightness), Ôa Õ (redness and greenness) and Ôb Õ (yellowness and blueness). Sensor was standardized with a white tile and black tile to measure the color. Five fruits each refrigerated and ambient conditions were numbered for identification and marked equatorially on the peel surface to divide into five equal parts. Fruit color of five different marked sections of each fruit was measured by placing over the 8 mm aperture of sample measurement port of the colorimeter. The change in
Fig. 2. A typical force–deformation curve for peel cutting with HDP/ BSK blade cutter (cutting speed: 1 mm/s).
color of same samples was measured up to 17 days at the interval of 3 days. Color was expressed in L , a , b Hunter parameters and color index (CI) was calculated using the following formula (Jimenez-Cuesta et al., 1981). CI ¼
1000a L b
ð1Þ
The average L , a and b values of each five fruits both in ambient and refrigerated conditions for 17 days were used to calculate color index. 2.5. Weight loss For determining weight loss in fruit during storage, 10 fruits in each experimental lot were numbered and kept in ambient and refrigerated conditions. Weight of the fruit was measured with respect to storage period with electronic balance (model 6315, Osaw Industrial Products Private Limited, India) having least count of 0.01 g. The loss in weight was expressed as percentage of the original fresh weight of the fruit. The average data of 10 fruits for 17 days storage period in both ambient and refrigerated conditions was used. 2.6. Fruit compression test Orange fruit was set upon a flat base plate of Texture Analyzer. Probe carrier was fixed with a 65 mm diameter flat plate and brought in contact with the fruit. A 250 N load cell was used. Compression force was applied at a speed of 1 mm/s to compress the fruit for 10 mm from the contact point. The bioyield point was considered as the force under the prescribed conditions,
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
115
Fig. 4. A typical force–deformation curve for puncture resistance of orange (5 mm diameter solid cylindrical probe, speed: 1 mm/s).
Fig. 3. A typical force–deformation curve for orange under compression (probe speed: 1 mm/s).
required to cause permanent deformation indicated by the peak force before a sudden drop as shown in a force–deformation curve (Fig. 3). The firmness was expressed as the force in kN required to compress the fruit to 10 mm distance. Fruit compression tests were performed in two orientations viz., stem-calyx axis in horizontal and vertical directions. The average values of 10 replications for 10 days storage in both ambient and refrigerated conditions are reported. 2.7. Puncture resistance For measurement of puncture resistance the Texture Analyzer was fitted with a 5 mm cylindrical probe to the probe carrier. Orange was placed upon a flat plate and ensured that the stem calyx axis was parallel to the flat plate. The test was carried out at the probe speed of 1 mm/s. The maximum force required to make the puncture on the fruit surface was taken from the force–deformation curve as shown in Fig. 4. The puncture resistance was measured with 10 fruits (replications) and average values are reported for both ambient and refrigerated conditions for 10 days storage period.
Fig. 5. A typical force distance curve for whole orange fruit cutting with a HDP/BSK Blade cutter (probe speed: 1 mm/s).
were taken as the maximum peak force applied while flevado and albedo sections of the fruit cutting respectively. The total fruit cutting energy was considered as the total area under the force–deformation curve as shown in Fig. 5. The average values of 10 fruits (replications) in each ambient and refrigerated conditions for 10 days are reported.
2.8. Fruit cutting test 3. Results and discussion Blade set knife of the Texture Analyzer was attached to probe carrier. Orange fruit was positioned, stem-calyx horizontally upon a HDP/BSK Blade set. Cutter speed of 1 mm/s was used with 250 N load cell. The load against depth of cut was recorded continuously. Sample data generated by a fruit cutting test is shown in Fig. 5. Peak fruit cutting force and albedo peak cutting force
3.1. Peel moisture content Initial moisture content of orange peel was 292% drybasis (db). It was observed to be 252.8% and 281.3% db, respectively, under ambient and refrigerated conditions at the end of 10 days of storage. The peel
116
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
3.3. Peel cutting test
moisture loss in ambient and refrigerated conditions after 10 days storage was observed as 13% and 3.7%, respectively. The rate of peel moisture loss was 3.6 times higher in ambient condition than that in refrigerated condition.
Peak cutting force and cutting energy for peel are presented in Table 2. Peak cutting force and peel cutting energy decreased from 79.5 to 63.2 N and 240.7 to 115.7 J in ambient condition. The Peak cutting force and peel cutting energy decreased from 79.5 to 66.3 N and 240.7 to 165.3 J respectively under refrigerated condition. However, the decrease in peak cutting force with storage period was non-significant at P > 0.05 in both ambient as well as in refrigerated conditions. But decrease in peel cutting energy with storage period was significant at P 6 0.05 in both of the cases, ambient as well as refrigerated conditions. The peak cutting force and peel cutting energy under refrigerated condition were consistently higher than that under ambient condition but the difference were statistically non-significant at P > 0.05 in both of the cases (Table 2).
3.2. Peel tensile test Peel rupture force (Frt), tensile strength (rt) and modulus of elasticity (E) generally decreased with storage period under both refrigerated and ambient storage conditions (Table 1). However, the decrease in all the parameters with storage period was statistically nonsignificant at 5% probability level. The slight decrease in rupture force, tensile strength and modulus of elasticity with storage period might be due to drying effect and softening of peel tissues that reduced the turbidity. The comparison of properties between refrigerated and ambient storage conditions revealed that rupture force, tensile strength and modulus of elasticity were consistently higher in refrigerated conditions than that in ambient condition but the difference was statistically non-significant at P > 0.05 (Table 1).
3.4. Fruit color The change in color index (CI) with respect to storage period under ambient as well as refrigerated conditions
Table 1 Peak rupture force (Frt), tensile strength (rt) and modulus of elasticity (E) of orange peel in ambient and refrigerated conditions with respect to the storage period (crosshead speed: 10 mm/min) Number of days in storage
1 3 7 10
Ambient condition
Refrigerated condition
Frt, N
rt, MPa
E, MPa
Frt, N
rt, MPa
E, MPa
1
2
3
4
5
6
15.6(2.5) 12.8(3.4) 11.5(3.8) 10.8(2.5)
0.173(0.031) 0.146(0.061) 0.139(0.051) 0.125(0.03)
1.57(0.54) 1.48(0.58) 1.27(0.32) 1.11(0.19)
15.6(2.5) 13.7(4.3) 13.1(1.3) 12.7(2.1)
0.173(0.031) 0.156(0.054) 0.147(0.019) 0.138(0.027)
1.57(0.54) 1.48(0.51) 1.36(0.37) 1.03(0.15)
Note: • The numerical value in the parenthesis is standard deviation. • ANOVA indicated non-significant effect of storage period on all the parameters shown in the columns from 1 to 6 at P > 0.05. • The t-test indicated non-significant difference between the columns 1 and 4, 2 and 5, and 3 and 6 at P > 0.05.
Table 2 Peak cutting force and cutting energy of orange peel in ambient and refrigerated storage conditions with respect to the storage period (HDP/BSK blade cutter, cutting speed: 1 mm/s) Number of days in storage
Ambient condition Peak cutting force, N
1 3 7 10
Refrigerated condition Peel cutting energy, J
Peak cutting force, N
Peel cutting energy, J
1
2
3
4
79.5(8.3) 72.6(8.2) 68.9(8.2) 63.2(19.6)
240.7(65.1) 201.7(70.6) 176.8(28.0) 115.7(42.4)
79.5(8.3) 77.2(13.5) 71.7(6.4) 66.3(19.7)
240.7(65.1) 225.5(43.4) 185.8(32.8) 165.3(27.6)
Note: • The numerical value in the parenthesis is standard deviation. • ANOVA indicated non-significant effect of storage period on peak cutting force (columns 1 and 3) under ambient and refrigerated conditions at P > 0.05. • ANOVA indicated significant effect of storage period on peel cutting energy (columns 2 and 4) at P 6 0.05. • The t-test indicated non-significant difference between columns 1 and 3 and 2 and 4 at P > 0.05.
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
CI ¼ 0:0003t4 þ 0:0061t3 þ 0:008t2 þ 0:0851t 7:5537 ðR2 ¼ 0:99Þ
ð2Þ
Refrigerated condition: 4
3
2
CI ¼ 0:0006t þ 0:0216t 0:2095t þ 0:8462t 6:9163 ðR2 ¼ 0:99Þ
ð3Þ
where CI is the color index, t the storage period, days and R is the correlation coefficient. The change in fruit color during storage under refrigerated condition was less than that under ambient condition. The polynomial curves indicated that loss of chlorophyll associated with the change in color from green to yellow, appeared to follow change in color index. Similar trend was also reported for Lanelate and Valencia varieties of oranges by Olmo, Nadas, and Garcia (2000). At the end of 17 days storage the fruit stored under ambient condition turned light yellow where as refrigerated fruit remained pale green color. 3.5. Weight loss The percentage cumulative weight loss of orange during storage under ambient and refrigerated conditions for 17 days of storage is presented in Fig. 7. The weight loss increased with increase in storage period under both ambient as well as refrigerated conditions and these followed second-order polynomial regression equations (Eqs. (4) and (5)). Use of various substances in respiration can result in loss of food reserves in the tissue. At
Ambient (28°C and 58% RH) 20
Refrigerated (7°C and 78% RH)
15
10
5
0 0
3
6
9
12
15
18
Storage period, days Fig. 7. Weight loss of orange during storage under ambient and refrigerated conditions.
the end of 17 days storage, the cumulative loss of weight in ambient and refrigerated storage conditions were 19.4% and 7.3%, respectively. The fruit stored under ambient condition lost the weight almost three times more than that stored in refrigerated condition. The higher weight loss in fruit stored under ambient condition may be attributed to the high rate of change in soluble sugar concentration due to the monosaccharides being used in the respiration process during storage at higher temperatures. The trend in weight loss of orange fruits with storage period is in agreement with previous studies (Martinez-Javega, Cuquerella, Del Ris, & Matoes, 1989; Singh, 1971). Ambient condition: WL ¼ 0:0157t2 þ 0:9011t 0:2497 ðR2 ¼ 0:99Þ
ð4Þ
Refrigerated condition:
4
Color Index (1000 a)* /L* b*
25
Fruit weight loss, %
is shown in Fig. 6. The color index of orange during storage under ambient and refrigerated conditions was strongly correlated with storage period following fourth-order polynomial equations (Eqs. (2) and (3)). Ambient condition:
117
WL ¼ 0:0116t2 þ 0:238t 0:0426
2
0 0
3
6
9
12
15
18
ðR2 ¼ 0:99Þ
ð5Þ
where WL is the cumulative weight loss during storage, %, t the storage period, days and R is the correlation coefficient.
-2
3.6. Fruit compression test
-4
-6
-8
Ambient (28ºC and 58% RH) Refrigerated (7ºC and 78% RH)
-10
Storage period, days Fig. 6. Color index of orange fruit during storage in ambient and refrigerated conditions.
The firmness values of orange slowly decreased during the post-harvest storage under both ambient and refrigerated conditions (Table 3) and followed second degree polynomial relationship (Eqs. (6) and (7)). The decrease in firmness of orange fruit has strong relationship with storage period and the trend is in agreement with the results reported by Olmo et al. (2000) for Lanelate and Valencia oranges. The decrease in firmness was more pronounced under ambient condition than that
118
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
Table 3 Bioyield point (BYP) and firmness (F) ratio of orange fruit in horizontal and vertical orientations under compression in ambient and refrigerated storage conditions with respect to the storage period (65 mm diameter flat probe, probe speed: 1 mm/s) Number of days in storage
1 3 7 10
Fruit compression (Horizontal orientation)
Fruit compression (Vertical orientation)
Ambient
Ambient
Refrigerated
Refrigerated
BYP, N
Firmness, N
BYP, N
Firmness, N
BYP, N
Firmness, N
BYP, N
Firmness, N
1
2
3
4
5
6
7
8
134.8(13.9) 117.0(16.9) 107.7(12.3) 98.9(8.9)
44.9(17.9) 36.2(7.6) 28.0(4.8) 21.9(4.1)
134.8(13.9) 129.3(25.5) 111.1(20.6) 103.9(20.9)
44.9(17.9) 36.9(7.3) 33.5(3.9) 28.9(7.4)
153.3(4.4) 144.9(6.5) 139.9(29.3) 138.3(14.9)
54.2(9.6) 39.3(14.6) 34.3(9.5) 33.5(10.4)
153.3(4.4) 146.5(9.2) 142.8(14.1) 141.0(16.9)
54.2(9.6) 44.7(6.4) 39.8(12.9) 36.4(17.1)
Note: • The numerical value in the parenthesis is standard deviation. • ANOVA indicated significant effect of storage period on the values shown in columns 2 and 6 and non-significant effect on the values shown in columns 1, 3, 4, 5, 7, and 8. • The t-test indicated non-significant difference between columns 1 and 3, 2 and 4, and 5 and 7 P > 0.05, and significant difference between columns 2 and 6, 3 and 7, 4 and 8, and 6 and 8 at P 6 0.05.
under refrigerated condition. This might be because at low temperatures, fruit ripens slowly because of a metabolic delay, consequently, fruit softening is also delayed. Higher temperature promotes fruit transpiration and ripening, a fast decrease in firmness being one of the more representative signs of these processes. Ambient condition: F ¼ 0:0398t3 þ 0:905t2 8:031t þ 55:96
ðR2 ¼ 1Þ ð6Þ
Refrigerated condition: F ¼ 0:0436t3 þ 0:9798t2 7:8209t þ 56:981 ðR2 ¼ 1Þ
ness with increase in storage period was significant at P 6 0.05. The firmness under refrigerated condition was slightly higher than that under ambient condition. When the firmness was compared between horizontal and vertical orientations, it was observed that the firmness was significantly higher in later case for both ambient and refrigerated conditions. The similar trends were also reported by Miller (1987) and Churchill et al. (1980) for orange. Thus it can be inferred that fruit offers more resistance to the applied force in vertical orientation than that in horizontal orientation. 3.7. Puncture resistance
ð7Þ where F is the fruit firmness, N and t is the storage duration, days. Table 3 shows the effect of storage period on bio-yield point and firmness of orange, in horizontal and vertical orientations, stored under ambient and refrigerated conditions. In horizontal orientation, the bio-yield point decreased from 134.8 to 98.9 N and 134.8 to 103.9 N under both ambient and refrigerated conditions, respectively with increase in storage period. Similarly, in vertical orientation, bio-yield point decreased from 153.3 to 138.3 N and 153.3 to 141.0 N under ambient and refrigerated conditions, respectively. The bio-yield point of orange stored under refrigerated condition was observed to be slightly higher than that fruit stored under ambient condition in both of the cases horizontal as well as vertical orientations. The bio-yield point in vertical orientation was significantly higher than that in horizontal orientation under both ambient and refrigerated conditions (Table 3). In horizontal orientation, firmness decreased from 44.9 to 21.9 N and 44.9 to 28.9 N under ambient and refrigerated conditions respectively with increase in storage period from 1st to 10th day. The decrease in firm-
Peel puncture force of orange in both refrigerated and ambient conditions is presented in Table 4. Peel puncture force slightly decreased from 16.8 N to 14.7 N and 16.8 to 15.3 N with storage period under ambient and refrigerated conditions, respectively though the decrease was non-significant in both of the cases at Table 4 Puncture force of orange fruit under ambient and refrigerated storage conditions with respect to the storage period (5 mm diameter solid cylindrical probe, probe speed: 1 mm/s) Number of days in storage
Average puncture force, N
1
2
1 3 7 10
16.8(2.1) 15.5(3.6) 14.9(3.5) 14.7(2.5)
16.8(2.1) 16.7(1.5) 15.6(1.8) 15.3(3.3)
Ambient condition
Refrigerated condition
Note: • The numerical value in the parenthesis is standard deviation. • ANOVA indicated non-significant effect of storage period on average puncture force in columns 1 and 2 at P > 0.05. • The t-test indicated significant difference between columns. 1 and 2 at P 6 0.05.
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
119
Table 5 Peak cutting force, albedo peak cutting force and cutting energy in ambient and refrigerated storage conditions of whole orange fruit with respect to the storage period (HDP/BSK Blade set, cutting speed: 1 mm/s) Number of days in storage
1 3 7 10
Ambient condition
Refrigerated condition
Peak cutting force, N
Albedo peak cutting force, N
Fruit cutting energy, J
Peak cutting force, N
Albedo peak cutting force, N
Fruit cutting energy, J
1
2
3
4
5
6
85.7(8.5) 81.1(10.6) 69.0(8.8) 59.6(19.3)
80.8(13.4) 73.2(4.4) 68.3(3.9) 58.7(4.4)
2983.4(777.2) 2755.4(306.5) 2430.4(308.6) 2143.5(37.5)
85.7(8.5) 84.2(14.8) 79.9(16.2) 71.6(12.1)
80.8(13.4) 78.7(18.2) 78.3(31.6) 63.7(10.6)
2983.4(777.2) 2760.3(383.8) 2711.5(248.4) 2389.5(234.1)
Note: • The numerical value in the parenthesis is standard deviation. • ANOVA indicated significant effect of storage period on the values shown in columns 1 and 2 at P 6 0.05 and non-significant effect on the values shown in columns 3, 4, 5, and 6 at P > 0.05. • The t-test indicated non-significant difference between columns 1 and 4, 2 and 5, and 3 and 6 at P > 0.05.
P > 0.05. The rupture force was observed to be higher in orange stored under refrigerated condition than that under ambient condition. 3.8. Fruit cutting test Peak cutting force, albedo peak cutting force and fruit cutting energy are presented in Table 5. The peak cutting force, albedo peak cutting force and cutting energy of whole fruit decreased with the storage period in both ambient as well as refrigerated storage conditions. However, the decrease in cutting energy of whole fruit was non-significant at P > 0.05. The peak cutting force and fruit cutting energy under refrigerated condition were consistently higher than that under ambient condition but the difference was statistically non-significant at P > 0.05 in both of the cases.
Acknowledgement The authors thank Director, Central Institute of Agricultural Engineering, Bhopal and Head, Agro Processing Division for providing all necessary facilities to carry out this research work. The authors also thank Dr. A.C. Varshney, Dr. S.D. Deshpande, Dr. Sunita Singh, Er. S. Mangraj and Dr. S.P. Singh of this institute for their help and support during the experimentation.
References Ahmed, E. M., Martin, F. G., & Fluck, R. C. (1973). Damaging stresses to fresh and irradiated citrus fruit. Journal of Food Science, 38, 230–233. Blankenship, S. M., Parker, M., & Unrath, C. R. (1997). Use of maturity indices for predicting post-storage firmness of Fuji apples. Horticulture Science, 32(5), 909–910.
Choi, K., Lee, G., Han, Y. J., & Bun, J. M. (1995). Tomato maturity evaluation using color image analysis. Transactions of ASAE, 38(1), 171–176. Churchill, D. B., Sumner, H. R., & Whitney, J. D. (1980). Peel Strength properties of three orange varieties. Transactions of the ASAE, 23(1), 173–176. Fidelibus, M. W., Teixeira, A. A., & Davies, F. S. (2002). Mechanical properties of orange peel and fruit treated pre-harvest with Gibberellic acid. Transactions of the ASAE, 45(4), 1057–1062. Gaston, H. P., & Levin, J. H. (1951). How to reduce apple bruising. Michigan State College Special Bulletin, 374. Guzel, E., Alizade, H. H. A., & Sinn, H. (1994). Optical properties of W. Navel and Hamlin oranges regarding mechanical harvesting and sorting. AMA, 25(1), 57–63. Gyasi, S. R., Friedly, B., & Chen, P. (1981). Elastic and viscoelastic PoissonÕs ratio determination for selected citrus fruits. Transactions of the ASAE, 24(3), 747–750. Jimenez-Cuesta, M., Cuquerella, J., & Martinez-Javega, J. M. (1981). Determination of color index for citrus degreening. Proceedings of the International Society of Citriculture, 2, 750–753. Kader, A. A. (1992). An overview. In A. A. Kader (Ed.), Post-harvest technology of horticultural crops (pp. 15–20). University of California, Division of Agriculture and Natural Resources Publication. Kaufmann, M. R. (1970). Extensibility of pericarp tissue in growing citrus fruits. Plant Physiology, 46(6), 778–781. Luchsinger, L. E., & Walsh, C. S. (1993). Changes in ethylene rate and ground color in peaches (CV. Red Haven and Marqueen) and nectarines (cv. Fantasia) during maturation and ripening. Acta Horticulture, 343, 70–72. Martinez-Javega, J. M., Cuquerella, J., Del Ris, M. A., Matoes, M. (1989). Coating treatments in postharvest behavior of oranges. IIR Commisions C2/D1, D2/3. Technical innovations in freezing and refrigeration of fruits and vegetables. University of California Publication 51-55. Mercado-Silva, E., Benito-Bautista, P., & Garcia-Velasco, M. A. (1998). Fruit development, harvest index, and ripening changes of guavas produced in Central Mexico. Postharvet Biology and Technology, 13, 143–150. Miller, W. M. (1987). Physical properties data for postharvest handling of Florida citrus. Applied Engineering in Agriculture, 3(1), 123–128. Mitchell, F. G. (1987). Preparing peaches and nectarines for export marketing. The Orchardist of New Zealand, 60, 150–152. Muramatsu, N., Kiyohide, K., & Tatsushi, O. (1996). Relationship between texture and cell wall polysaccharides of fruit flesh in various species of citrus. Horticulture Science, 31(1), 114–116.
120
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
Olmo, M., Nadas, A., & Garcia, J. M. (2000). Nondestructive methods to evaluate maturity level of oranges. Journal of Food Science, 65(2), 365–369. Polderdijk, U., Tijskens, L. M. M., Robberts, J. E., & Van der Valk, H. C. P. (1993). Predictive model of keeping quality of tomatoes. Postharvest Biology and Technology, 2, 179–185. Sarig, Y., & Nahir, D. (1973). Deformation characteristics of Valencia oranges as an indicator of firmness. Horticultural Science, 8(5), 391–392.
Shewfelt, R. L., & Prussia, S. E. (1993). Postharvest handling: A system approach. San Diego: Academic Press. Singh, K. (1971). Storage behaviour of sweet oranges and mandarins. Indian Council of Agriculture Research. Technical Bulletin (Agriculture Series), 35. Witz, R. L. (1954). Measuring the resistance of potatoes to bruising. Agricultural Engineering, 34(4), 241–244.
Post-harvest physico-mechanical properties of orange peel and fruit Krishna K. Singh *, B. Sreenivasula Reddy Central Institute of Agricultural Engineering, Nabi Bagh, Berasia Road, Bhopal 462 038, India Received 31 May 2004; accepted 13 January 2005 Available online 13 March 2005
Abstract The post-harvest physico-mechanical properties data of fruits and vegetables are important in adoption and design of various handling, packaging, storage and transportation systems. Physico-mechanical properties namely, orange peel tensile strength and cutting energy and fruit color, weight loss, bioyield point, firmness, puncture force and cutting energy were determined with respect to storage period under ambient and refrigerated conditions. Peel tensile strength, modulus of elasticity and cutting energy decreased with storage period in both ambient and refrigerated conditions. The color index of orange followed a fourth-order polynomial equation during storage. At the end of 17 days storage, the fruit cumulative weight losses in ambient and refrigerated conditions were 19.4% and 7.3%, respectively. Bioyield point, firmness, puncture force and cutting energy of orange fruits decreased with respect to number of days of storage. The firmness of orange fruit was significantly higher in stem-calyx axis in vertical position than that in horizontal position. 2005 Published by Elsevier Ltd. Keywords: Citrus; Color; Peel; Physico-mechanical properties; Weight loss; Firmness
1. Introduction The mechanical harvesting of fruits causes damage from branches and other fruits as fruit falls from the tree and drops on the ground. These damages are in the form of splits, punctures and bruises. Further damage is caused when it is raked, picked up, loaded and transported to distant places by trucks. Generally, it takes several days in transportation from one place to another that causes various changes in physico-mechanical properties of fruits. The post-harvest mechanical properties data of fruits and vegetables are important in adoption and design of various handling, packaging, storage and transportation systems. The fruit compression test simulates the condition of static loading that fruit can withstand in mechan*
Corresponding author. Tel.: +91 7552733226x298; fax: +91 7552734016. E-mail address: [email protected] (K.K. Singh). 0260-8774/$ - see front matter 2005 Published by Elsevier Ltd. doi:10.1016/j.jfoodeng.2005.01.010
ical handling and storage. The most common practice to determine the fruit ripeness in field situation is pressing with ball of the thumb. Force deformation characteristics of fruits beyond the elastic limit may be important to simulate the destruction that occurs in bruising. Elastic modulus or YoungÕs modulus is often used by engineers as an index of product firmness. Puncture tests are also measures of firmness of fruits and vegetables to estimate harvest maturity or post-harvest evaluation of firmness. Research has been carried out for several years to determine the resistance of fruits and vegetables to compression force. Witz (1954) reported resistance to bruising of potatoes to puncture by using a plunger. Studies on bruises to apples resulting from dropping and from application of pressure was reported by Gaston and Levin (1951). Ahmed, Martin, and Fluck (1973) reported shear stress data of peel pieces collected at the time of harvest. Kaufmann (1970) measured the effect of water potential
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
and temperature on the extensibility of citrus peel. Gyasi, Friedly, and Chen (1981) determined PoissonÕs ratio for citrus fruit peel and pulp. Fidelibus, Teixeira, and Davies (2002) determined the gibberellic acid (GA3) treatment effect on mechanical properties of pre-harvest orange peel and whole fruit. The properties such as color and firmness of orange that differentiate individual units of a product are important to determine the degree of acceptability of the product to the buyer (Guzel, Alizade, & Sinn, 1994). Fruit softening is often used as a criterion for estimating the feasibility of their storage or shelf life (Kader, 1992; Polderdijk, Tijskens, Robberts, & Van der Valk, 1993; Blankenship, Parker, & Unrath, 1997). Color is considered to be one of the most important external factors of fruit quality, as the appearance of the fruit greatly influences consumers. Fruit and vegetable yellowing is often a result of the disappearance of chlorophylls which allows the yellow orange xanthophylls and carotenes to become more visible (Shewfelt & Prussia, 1993). The relationship between color and level of maturation has been widely studied in tomatoes (Choi, Lee, Han, & Bun, 1995), peaches, and nectarines (Mitchell, 1987; Luchsinger & Walsh, 1993). Along the same line, Mercado-Silva, Benito-Bautista, and Garcia-Velasco (1998) identified L , a , and hue values as being the best parameters for differentiating the different stages of the maturation of guava. In citrus, Jimenez-Cuesta, Cuquerella, and Martinez-Javega (1981) proposed the use of the formula 1000a /(L b ) as ‘‘Color Index’’ for recording the process of orange degreening. In most fruits, their firmness diminishes as the degree of maturation increases due to the action of pectic enzymes during fruit maturation (Muramatsu, Kiyohide, & Tatsushi, 1996). Miller (1987) determined stress index, modulus of elasticity, and rupture force of freeze-damaged and non-damaged fruit. Sarig and Nahir (1973) reported the initial and permanent deformations of a creep test of citrus fruit to indicate firmness. Churchill, Sumner, and Whitney (1980) determined the influence of harvest date on the physical strength properties (burst and puncture) of whole fruit and tensile strength of peel pieces of three orange varieties. Singh (1971) studied optimum storage temperature, storage life and keeping quality of mandarins and sweet lemon. During storage the loss of moisture from the peel is continuously replenished by the movement of the moisture from the pulp. If this loss due to combined effect of respiration and transpiration goes on unchecked, the fruit shrivels up and becomes unmarketable. There is a dearth of information on post-harvest physico-mechanical properties changes of orange peel and fruit under ambient and refrigerated storage conditions which are helpful to decide handling, packaging, storage, and transportation systems to be adopted and their designs. The objective of this paper is to report
113
changes in basic physical and mechanical properties of orange peel and whole fruit under ambient and refrigerated fruit storage conditions.
2. Materials and methods Orange (Variety: Nagpur Mandarin) fruits were procured from experimental orchard of National Research Center for Citrus, Nagpur, India. Random samples were drawn from a freshly harvested lot of citrus at the time of harvest. Fruits were divided into two lots each consisting of 150 fruits. One lot of fruits was taken into ventilated corrugated fiberboard box and kept in an ambient conditions of 28 C and 58% RH. Another lot of fruits was kept in refrigerator at a temperature of 7 C and 78% RH. Post-harvest physico-mechanical properties of orange peel and fruits were determined with respect to the storage period in both ambient and refrigerated conditions. 2.1. Peel moisture content About 5 g of peel sample was taken in to an aluminum container at the time of experimentation. The samples were dried in hot air oven at 80 C for 24 h. Peel moisture content was calculated on dry weight basis. The average values of three replications are reported. 2.2. Peel tensile test The peel tensile strength test was used to evaluate the behavior of the orange peel under applied tensile loads. Clamps were made to hold a section of orange peel for determining peel strength. Peel pieces were carefully dissected from the equator of five randomly selected fruits. Immediately after peel removal, peel thickness was measured using vernier calipers (accuracy 0.01 g), and peel strips of 15 mm (polar) and 60 mm (equatorial) were attached to Instron Testing Machine (Model: 4400, Instron Limited, England) clamps. One clamp was fixed to the base of the machine, while the other was attached to a load cell rated at a maximum of 5000 N. Strips were subjected to axial tensile loading in an equatorial direction, with a crosshead speed of 10 mm/min until rupture. Rupture force was taken as the maximum peak force required to rupture the peel as shown in Fig. 1. Tensile strength (rt) was calculated with dividing the peak rupture force by the cross-sectional area (thickness · width) of the initial specimen. Modulus of elasticity (E) was calculated as the slope of the initial linear portion of a stress/strain curve of Fig. 1. Rupture force, tensile strength and modulus of elasticity were measured for 10 days from harvest in both ambient and refrigerated conditions. The average values obtained from 10 replications are reported.
114
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
Fig. 1. A typical curve for peel tensile test obtained from Instron Testing Machine (crosshead speed: 10 mm/min).
2.3. Peel cutting test Peel pieces were carefully dissected from the equator of five randomly selected fruits. Peel pieces of about 20 · 40 mm were placed upon a Texture Analyzer (model:TAXT2i, Stable Microsystems, England) HDP/ BSK blade set. A blade set knife of the Texture Analyzer attached to the probe carrier was used to cut the peel pieces. The load cell was calibrated to 250 N and the cutting was done at a speed of 1 mm/s. As the cutter blade applied force on peel to cut, there was about 6 mm settling before the cutting begun. Peak cutting force was considered as the first peak force in N recorded as shown in Fig. 2. The peel cutting energy was taken as area under force–deformation curve as shown in Fig. 2. The average values of 10 replications each day for 10 days storage period both in ambient and refrigerated conditions are reported. 2.4. Fruit color The color change of orange fruit was measured using LabScanXE spectrocolorimeter (Model No. LX16244, Hunter Associates Laboratory, Virginia) in terms of CIE ÔL Õ (lightness), Ôa Õ (redness and greenness) and Ôb Õ (yellowness and blueness). Sensor was standardized with a white tile and black tile to measure the color. Five fruits each refrigerated and ambient conditions were numbered for identification and marked equatorially on the peel surface to divide into five equal parts. Fruit color of five different marked sections of each fruit was measured by placing over the 8 mm aperture of sample measurement port of the colorimeter. The change in
Fig. 2. A typical force–deformation curve for peel cutting with HDP/ BSK blade cutter (cutting speed: 1 mm/s).
color of same samples was measured up to 17 days at the interval of 3 days. Color was expressed in L , a , b Hunter parameters and color index (CI) was calculated using the following formula (Jimenez-Cuesta et al., 1981). CI ¼
1000a L b
ð1Þ
The average L , a and b values of each five fruits both in ambient and refrigerated conditions for 17 days were used to calculate color index. 2.5. Weight loss For determining weight loss in fruit during storage, 10 fruits in each experimental lot were numbered and kept in ambient and refrigerated conditions. Weight of the fruit was measured with respect to storage period with electronic balance (model 6315, Osaw Industrial Products Private Limited, India) having least count of 0.01 g. The loss in weight was expressed as percentage of the original fresh weight of the fruit. The average data of 10 fruits for 17 days storage period in both ambient and refrigerated conditions was used. 2.6. Fruit compression test Orange fruit was set upon a flat base plate of Texture Analyzer. Probe carrier was fixed with a 65 mm diameter flat plate and brought in contact with the fruit. A 250 N load cell was used. Compression force was applied at a speed of 1 mm/s to compress the fruit for 10 mm from the contact point. The bioyield point was considered as the force under the prescribed conditions,
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
115
Fig. 4. A typical force–deformation curve for puncture resistance of orange (5 mm diameter solid cylindrical probe, speed: 1 mm/s).
Fig. 3. A typical force–deformation curve for orange under compression (probe speed: 1 mm/s).
required to cause permanent deformation indicated by the peak force before a sudden drop as shown in a force–deformation curve (Fig. 3). The firmness was expressed as the force in kN required to compress the fruit to 10 mm distance. Fruit compression tests were performed in two orientations viz., stem-calyx axis in horizontal and vertical directions. The average values of 10 replications for 10 days storage in both ambient and refrigerated conditions are reported. 2.7. Puncture resistance For measurement of puncture resistance the Texture Analyzer was fitted with a 5 mm cylindrical probe to the probe carrier. Orange was placed upon a flat plate and ensured that the stem calyx axis was parallel to the flat plate. The test was carried out at the probe speed of 1 mm/s. The maximum force required to make the puncture on the fruit surface was taken from the force–deformation curve as shown in Fig. 4. The puncture resistance was measured with 10 fruits (replications) and average values are reported for both ambient and refrigerated conditions for 10 days storage period.
Fig. 5. A typical force distance curve for whole orange fruit cutting with a HDP/BSK Blade cutter (probe speed: 1 mm/s).
were taken as the maximum peak force applied while flevado and albedo sections of the fruit cutting respectively. The total fruit cutting energy was considered as the total area under the force–deformation curve as shown in Fig. 5. The average values of 10 fruits (replications) in each ambient and refrigerated conditions for 10 days are reported.
2.8. Fruit cutting test 3. Results and discussion Blade set knife of the Texture Analyzer was attached to probe carrier. Orange fruit was positioned, stem-calyx horizontally upon a HDP/BSK Blade set. Cutter speed of 1 mm/s was used with 250 N load cell. The load against depth of cut was recorded continuously. Sample data generated by a fruit cutting test is shown in Fig. 5. Peak fruit cutting force and albedo peak cutting force
3.1. Peel moisture content Initial moisture content of orange peel was 292% drybasis (db). It was observed to be 252.8% and 281.3% db, respectively, under ambient and refrigerated conditions at the end of 10 days of storage. The peel
116
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
3.3. Peel cutting test
moisture loss in ambient and refrigerated conditions after 10 days storage was observed as 13% and 3.7%, respectively. The rate of peel moisture loss was 3.6 times higher in ambient condition than that in refrigerated condition.
Peak cutting force and cutting energy for peel are presented in Table 2. Peak cutting force and peel cutting energy decreased from 79.5 to 63.2 N and 240.7 to 115.7 J in ambient condition. The Peak cutting force and peel cutting energy decreased from 79.5 to 66.3 N and 240.7 to 165.3 J respectively under refrigerated condition. However, the decrease in peak cutting force with storage period was non-significant at P > 0.05 in both ambient as well as in refrigerated conditions. But decrease in peel cutting energy with storage period was significant at P 6 0.05 in both of the cases, ambient as well as refrigerated conditions. The peak cutting force and peel cutting energy under refrigerated condition were consistently higher than that under ambient condition but the difference were statistically non-significant at P > 0.05 in both of the cases (Table 2).
3.2. Peel tensile test Peel rupture force (Frt), tensile strength (rt) and modulus of elasticity (E) generally decreased with storage period under both refrigerated and ambient storage conditions (Table 1). However, the decrease in all the parameters with storage period was statistically nonsignificant at 5% probability level. The slight decrease in rupture force, tensile strength and modulus of elasticity with storage period might be due to drying effect and softening of peel tissues that reduced the turbidity. The comparison of properties between refrigerated and ambient storage conditions revealed that rupture force, tensile strength and modulus of elasticity were consistently higher in refrigerated conditions than that in ambient condition but the difference was statistically non-significant at P > 0.05 (Table 1).
3.4. Fruit color The change in color index (CI) with respect to storage period under ambient as well as refrigerated conditions
Table 1 Peak rupture force (Frt), tensile strength (rt) and modulus of elasticity (E) of orange peel in ambient and refrigerated conditions with respect to the storage period (crosshead speed: 10 mm/min) Number of days in storage
1 3 7 10
Ambient condition
Refrigerated condition
Frt, N
rt, MPa
E, MPa
Frt, N
rt, MPa
E, MPa
1
2
3
4
5
6
15.6(2.5) 12.8(3.4) 11.5(3.8) 10.8(2.5)
0.173(0.031) 0.146(0.061) 0.139(0.051) 0.125(0.03)
1.57(0.54) 1.48(0.58) 1.27(0.32) 1.11(0.19)
15.6(2.5) 13.7(4.3) 13.1(1.3) 12.7(2.1)
0.173(0.031) 0.156(0.054) 0.147(0.019) 0.138(0.027)
1.57(0.54) 1.48(0.51) 1.36(0.37) 1.03(0.15)
Note: • The numerical value in the parenthesis is standard deviation. • ANOVA indicated non-significant effect of storage period on all the parameters shown in the columns from 1 to 6 at P > 0.05. • The t-test indicated non-significant difference between the columns 1 and 4, 2 and 5, and 3 and 6 at P > 0.05.
Table 2 Peak cutting force and cutting energy of orange peel in ambient and refrigerated storage conditions with respect to the storage period (HDP/BSK blade cutter, cutting speed: 1 mm/s) Number of days in storage
Ambient condition Peak cutting force, N
1 3 7 10
Refrigerated condition Peel cutting energy, J
Peak cutting force, N
Peel cutting energy, J
1
2
3
4
79.5(8.3) 72.6(8.2) 68.9(8.2) 63.2(19.6)
240.7(65.1) 201.7(70.6) 176.8(28.0) 115.7(42.4)
79.5(8.3) 77.2(13.5) 71.7(6.4) 66.3(19.7)
240.7(65.1) 225.5(43.4) 185.8(32.8) 165.3(27.6)
Note: • The numerical value in the parenthesis is standard deviation. • ANOVA indicated non-significant effect of storage period on peak cutting force (columns 1 and 3) under ambient and refrigerated conditions at P > 0.05. • ANOVA indicated significant effect of storage period on peel cutting energy (columns 2 and 4) at P 6 0.05. • The t-test indicated non-significant difference between columns 1 and 3 and 2 and 4 at P > 0.05.
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
CI ¼ 0:0003t4 þ 0:0061t3 þ 0:008t2 þ 0:0851t 7:5537 ðR2 ¼ 0:99Þ
ð2Þ
Refrigerated condition: 4
3
2
CI ¼ 0:0006t þ 0:0216t 0:2095t þ 0:8462t 6:9163 ðR2 ¼ 0:99Þ
ð3Þ
where CI is the color index, t the storage period, days and R is the correlation coefficient. The change in fruit color during storage under refrigerated condition was less than that under ambient condition. The polynomial curves indicated that loss of chlorophyll associated with the change in color from green to yellow, appeared to follow change in color index. Similar trend was also reported for Lanelate and Valencia varieties of oranges by Olmo, Nadas, and Garcia (2000). At the end of 17 days storage the fruit stored under ambient condition turned light yellow where as refrigerated fruit remained pale green color. 3.5. Weight loss The percentage cumulative weight loss of orange during storage under ambient and refrigerated conditions for 17 days of storage is presented in Fig. 7. The weight loss increased with increase in storage period under both ambient as well as refrigerated conditions and these followed second-order polynomial regression equations (Eqs. (4) and (5)). Use of various substances in respiration can result in loss of food reserves in the tissue. At
Ambient (28°C and 58% RH) 20
Refrigerated (7°C and 78% RH)
15
10
5
0 0
3
6
9
12
15
18
Storage period, days Fig. 7. Weight loss of orange during storage under ambient and refrigerated conditions.
the end of 17 days storage, the cumulative loss of weight in ambient and refrigerated storage conditions were 19.4% and 7.3%, respectively. The fruit stored under ambient condition lost the weight almost three times more than that stored in refrigerated condition. The higher weight loss in fruit stored under ambient condition may be attributed to the high rate of change in soluble sugar concentration due to the monosaccharides being used in the respiration process during storage at higher temperatures. The trend in weight loss of orange fruits with storage period is in agreement with previous studies (Martinez-Javega, Cuquerella, Del Ris, & Matoes, 1989; Singh, 1971). Ambient condition: WL ¼ 0:0157t2 þ 0:9011t 0:2497 ðR2 ¼ 0:99Þ
ð4Þ
Refrigerated condition:
4
Color Index (1000 a)* /L* b*
25
Fruit weight loss, %
is shown in Fig. 6. The color index of orange during storage under ambient and refrigerated conditions was strongly correlated with storage period following fourth-order polynomial equations (Eqs. (2) and (3)). Ambient condition:
117
WL ¼ 0:0116t2 þ 0:238t 0:0426
2
0 0
3
6
9
12
15
18
ðR2 ¼ 0:99Þ
ð5Þ
where WL is the cumulative weight loss during storage, %, t the storage period, days and R is the correlation coefficient.
-2
3.6. Fruit compression test
-4
-6
-8
Ambient (28ºC and 58% RH) Refrigerated (7ºC and 78% RH)
-10
Storage period, days Fig. 6. Color index of orange fruit during storage in ambient and refrigerated conditions.
The firmness values of orange slowly decreased during the post-harvest storage under both ambient and refrigerated conditions (Table 3) and followed second degree polynomial relationship (Eqs. (6) and (7)). The decrease in firmness of orange fruit has strong relationship with storage period and the trend is in agreement with the results reported by Olmo et al. (2000) for Lanelate and Valencia oranges. The decrease in firmness was more pronounced under ambient condition than that
118
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
Table 3 Bioyield point (BYP) and firmness (F) ratio of orange fruit in horizontal and vertical orientations under compression in ambient and refrigerated storage conditions with respect to the storage period (65 mm diameter flat probe, probe speed: 1 mm/s) Number of days in storage
1 3 7 10
Fruit compression (Horizontal orientation)
Fruit compression (Vertical orientation)
Ambient
Ambient
Refrigerated
Refrigerated
BYP, N
Firmness, N
BYP, N
Firmness, N
BYP, N
Firmness, N
BYP, N
Firmness, N
1
2
3
4
5
6
7
8
134.8(13.9) 117.0(16.9) 107.7(12.3) 98.9(8.9)
44.9(17.9) 36.2(7.6) 28.0(4.8) 21.9(4.1)
134.8(13.9) 129.3(25.5) 111.1(20.6) 103.9(20.9)
44.9(17.9) 36.9(7.3) 33.5(3.9) 28.9(7.4)
153.3(4.4) 144.9(6.5) 139.9(29.3) 138.3(14.9)
54.2(9.6) 39.3(14.6) 34.3(9.5) 33.5(10.4)
153.3(4.4) 146.5(9.2) 142.8(14.1) 141.0(16.9)
54.2(9.6) 44.7(6.4) 39.8(12.9) 36.4(17.1)
Note: • The numerical value in the parenthesis is standard deviation. • ANOVA indicated significant effect of storage period on the values shown in columns 2 and 6 and non-significant effect on the values shown in columns 1, 3, 4, 5, 7, and 8. • The t-test indicated non-significant difference between columns 1 and 3, 2 and 4, and 5 and 7 P > 0.05, and significant difference between columns 2 and 6, 3 and 7, 4 and 8, and 6 and 8 at P 6 0.05.
under refrigerated condition. This might be because at low temperatures, fruit ripens slowly because of a metabolic delay, consequently, fruit softening is also delayed. Higher temperature promotes fruit transpiration and ripening, a fast decrease in firmness being one of the more representative signs of these processes. Ambient condition: F ¼ 0:0398t3 þ 0:905t2 8:031t þ 55:96
ðR2 ¼ 1Þ ð6Þ
Refrigerated condition: F ¼ 0:0436t3 þ 0:9798t2 7:8209t þ 56:981 ðR2 ¼ 1Þ
ness with increase in storage period was significant at P 6 0.05. The firmness under refrigerated condition was slightly higher than that under ambient condition. When the firmness was compared between horizontal and vertical orientations, it was observed that the firmness was significantly higher in later case for both ambient and refrigerated conditions. The similar trends were also reported by Miller (1987) and Churchill et al. (1980) for orange. Thus it can be inferred that fruit offers more resistance to the applied force in vertical orientation than that in horizontal orientation. 3.7. Puncture resistance
ð7Þ where F is the fruit firmness, N and t is the storage duration, days. Table 3 shows the effect of storage period on bio-yield point and firmness of orange, in horizontal and vertical orientations, stored under ambient and refrigerated conditions. In horizontal orientation, the bio-yield point decreased from 134.8 to 98.9 N and 134.8 to 103.9 N under both ambient and refrigerated conditions, respectively with increase in storage period. Similarly, in vertical orientation, bio-yield point decreased from 153.3 to 138.3 N and 153.3 to 141.0 N under ambient and refrigerated conditions, respectively. The bio-yield point of orange stored under refrigerated condition was observed to be slightly higher than that fruit stored under ambient condition in both of the cases horizontal as well as vertical orientations. The bio-yield point in vertical orientation was significantly higher than that in horizontal orientation under both ambient and refrigerated conditions (Table 3). In horizontal orientation, firmness decreased from 44.9 to 21.9 N and 44.9 to 28.9 N under ambient and refrigerated conditions respectively with increase in storage period from 1st to 10th day. The decrease in firm-
Peel puncture force of orange in both refrigerated and ambient conditions is presented in Table 4. Peel puncture force slightly decreased from 16.8 N to 14.7 N and 16.8 to 15.3 N with storage period under ambient and refrigerated conditions, respectively though the decrease was non-significant in both of the cases at Table 4 Puncture force of orange fruit under ambient and refrigerated storage conditions with respect to the storage period (5 mm diameter solid cylindrical probe, probe speed: 1 mm/s) Number of days in storage
Average puncture force, N
1
2
1 3 7 10
16.8(2.1) 15.5(3.6) 14.9(3.5) 14.7(2.5)
16.8(2.1) 16.7(1.5) 15.6(1.8) 15.3(3.3)
Ambient condition
Refrigerated condition
Note: • The numerical value in the parenthesis is standard deviation. • ANOVA indicated non-significant effect of storage period on average puncture force in columns 1 and 2 at P > 0.05. • The t-test indicated significant difference between columns. 1 and 2 at P 6 0.05.
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
119
Table 5 Peak cutting force, albedo peak cutting force and cutting energy in ambient and refrigerated storage conditions of whole orange fruit with respect to the storage period (HDP/BSK Blade set, cutting speed: 1 mm/s) Number of days in storage
1 3 7 10
Ambient condition
Refrigerated condition
Peak cutting force, N
Albedo peak cutting force, N
Fruit cutting energy, J
Peak cutting force, N
Albedo peak cutting force, N
Fruit cutting energy, J
1
2
3
4
5
6
85.7(8.5) 81.1(10.6) 69.0(8.8) 59.6(19.3)
80.8(13.4) 73.2(4.4) 68.3(3.9) 58.7(4.4)
2983.4(777.2) 2755.4(306.5) 2430.4(308.6) 2143.5(37.5)
85.7(8.5) 84.2(14.8) 79.9(16.2) 71.6(12.1)
80.8(13.4) 78.7(18.2) 78.3(31.6) 63.7(10.6)
2983.4(777.2) 2760.3(383.8) 2711.5(248.4) 2389.5(234.1)
Note: • The numerical value in the parenthesis is standard deviation. • ANOVA indicated significant effect of storage period on the values shown in columns 1 and 2 at P 6 0.05 and non-significant effect on the values shown in columns 3, 4, 5, and 6 at P > 0.05. • The t-test indicated non-significant difference between columns 1 and 4, 2 and 5, and 3 and 6 at P > 0.05.
P > 0.05. The rupture force was observed to be higher in orange stored under refrigerated condition than that under ambient condition. 3.8. Fruit cutting test Peak cutting force, albedo peak cutting force and fruit cutting energy are presented in Table 5. The peak cutting force, albedo peak cutting force and cutting energy of whole fruit decreased with the storage period in both ambient as well as refrigerated storage conditions. However, the decrease in cutting energy of whole fruit was non-significant at P > 0.05. The peak cutting force and fruit cutting energy under refrigerated condition were consistently higher than that under ambient condition but the difference was statistically non-significant at P > 0.05 in both of the cases.
Acknowledgement The authors thank Director, Central Institute of Agricultural Engineering, Bhopal and Head, Agro Processing Division for providing all necessary facilities to carry out this research work. The authors also thank Dr. A.C. Varshney, Dr. S.D. Deshpande, Dr. Sunita Singh, Er. S. Mangraj and Dr. S.P. Singh of this institute for their help and support during the experimentation.
References Ahmed, E. M., Martin, F. G., & Fluck, R. C. (1973). Damaging stresses to fresh and irradiated citrus fruit. Journal of Food Science, 38, 230–233. Blankenship, S. M., Parker, M., & Unrath, C. R. (1997). Use of maturity indices for predicting post-storage firmness of Fuji apples. Horticulture Science, 32(5), 909–910.
Choi, K., Lee, G., Han, Y. J., & Bun, J. M. (1995). Tomato maturity evaluation using color image analysis. Transactions of ASAE, 38(1), 171–176. Churchill, D. B., Sumner, H. R., & Whitney, J. D. (1980). Peel Strength properties of three orange varieties. Transactions of the ASAE, 23(1), 173–176. Fidelibus, M. W., Teixeira, A. A., & Davies, F. S. (2002). Mechanical properties of orange peel and fruit treated pre-harvest with Gibberellic acid. Transactions of the ASAE, 45(4), 1057–1062. Gaston, H. P., & Levin, J. H. (1951). How to reduce apple bruising. Michigan State College Special Bulletin, 374. Guzel, E., Alizade, H. H. A., & Sinn, H. (1994). Optical properties of W. Navel and Hamlin oranges regarding mechanical harvesting and sorting. AMA, 25(1), 57–63. Gyasi, S. R., Friedly, B., & Chen, P. (1981). Elastic and viscoelastic PoissonÕs ratio determination for selected citrus fruits. Transactions of the ASAE, 24(3), 747–750. Jimenez-Cuesta, M., Cuquerella, J., & Martinez-Javega, J. M. (1981). Determination of color index for citrus degreening. Proceedings of the International Society of Citriculture, 2, 750–753. Kader, A. A. (1992). An overview. In A. A. Kader (Ed.), Post-harvest technology of horticultural crops (pp. 15–20). University of California, Division of Agriculture and Natural Resources Publication. Kaufmann, M. R. (1970). Extensibility of pericarp tissue in growing citrus fruits. Plant Physiology, 46(6), 778–781. Luchsinger, L. E., & Walsh, C. S. (1993). Changes in ethylene rate and ground color in peaches (CV. Red Haven and Marqueen) and nectarines (cv. Fantasia) during maturation and ripening. Acta Horticulture, 343, 70–72. Martinez-Javega, J. M., Cuquerella, J., Del Ris, M. A., Matoes, M. (1989). Coating treatments in postharvest behavior of oranges. IIR Commisions C2/D1, D2/3. Technical innovations in freezing and refrigeration of fruits and vegetables. University of California Publication 51-55. Mercado-Silva, E., Benito-Bautista, P., & Garcia-Velasco, M. A. (1998). Fruit development, harvest index, and ripening changes of guavas produced in Central Mexico. Postharvet Biology and Technology, 13, 143–150. Miller, W. M. (1987). Physical properties data for postharvest handling of Florida citrus. Applied Engineering in Agriculture, 3(1), 123–128. Mitchell, F. G. (1987). Preparing peaches and nectarines for export marketing. The Orchardist of New Zealand, 60, 150–152. Muramatsu, N., Kiyohide, K., & Tatsushi, O. (1996). Relationship between texture and cell wall polysaccharides of fruit flesh in various species of citrus. Horticulture Science, 31(1), 114–116.
120
K.K. Singh, B.S. Reddy / Journal of Food Engineering 73 (2006) 112–120
Olmo, M., Nadas, A., & Garcia, J. M. (2000). Nondestructive methods to evaluate maturity level of oranges. Journal of Food Science, 65(2), 365–369. Polderdijk, U., Tijskens, L. M. M., Robberts, J. E., & Van der Valk, H. C. P. (1993). Predictive model of keeping quality of tomatoes. Postharvest Biology and Technology, 2, 179–185. Sarig, Y., & Nahir, D. (1973). Deformation characteristics of Valencia oranges as an indicator of firmness. Horticultural Science, 8(5), 391–392.
Shewfelt, R. L., & Prussia, S. E. (1993). Postharvest handling: A system approach. San Diego: Academic Press. Singh, K. (1971). Storage behaviour of sweet oranges and mandarins. Indian Council of Agriculture Research. Technical Bulletin (Agriculture Series), 35. Witz, R. L. (1954). Measuring the resistance of potatoes to bruising. Agricultural Engineering, 34(4), 241–244.