Effect of AVG (Aminoethoxyvinylglycine) Treatment and Maturity Stages on Physico-mechanical and Chemical Properties of Plum (cv. Giant) Fruit

Volume07-2019
Advances in Agricultural Science 07 (2019), 02: 88-99

Effect of AVG (Aminoethoxyvinylglycine) Treatment and Maturity Stages on Physico-mechanical and Chemical Properties of Plum (cv. Giant) Fruit

Ebubekir ALTUNTAS 1*, Burhan OZTURK 2 and Onur SARACOGLU 3

Department of Biosystems Engineering, Faculty of Agriculture, University of Gaziosmanpasa, 60240, Tasliciftlik, Tokat, Turkey.
Department of Horticulture, Faculty of Agriculture, University of Ordu, 52000, Ordu, Turkey.
Department of Horticulture, Faculty of Agriculture, University of Gaziosmanpasa, 60240, Tasliciftlik, Tokat, Turkey.

ABSTRACT

AVG (Aminoethoxyvinylglycine) has been widely used in plum and improved the quality of fruit. And also, AVG treatment has been delayed fruit maturity and decreased the preharvest fruit drop by inhibiting ethylene that cause to accelerate the maturation at period before harvest.The effect of AVG treatment and harvest periods on physical, chemical and mechanical properties of plum (cv. Giant) fruit was determined. The geometric mean diameter was lower in the after full blooming 143 days (13 August harvest date) than after full blooming 150 days (20 August harvest date). The surface area and porosity of plum fruit were higher in in the after full blooming 150 days (20 August) than the after full blooming 143 days (13 August harvest date).  L*, b*,  C* and h colour characteristics with harvesting dates, b* values decreased with harvesting date changes; whereas, L*, a*, b* and C* colour characteristics of plum fruit decreased for 200 mg L-1 AVG treatment with harvesting date, respectively. In general, the friction coefficients of plum fruit for laminate friction surface were found lower than the other friction surfaces such as galvanized steel, plywood and chipboard). Generally, the rupture force, deformation and absorbed energy of plum fruit decreased for 100 mg L-1 AVG treatment for after full blooming 143 and 150 days (13 August and 20 August harvesting dates) along Z- axial axis for compression tests. The force required to initiate plum fruit rupture on the X-axis decreased as AVG doses increased from 0 to 200 mg L-1. The results indicated that the rupture force along all three axes is highly dependent on harvesting date over the AVG doses ranges investigated. Chemical characteristics of plum fruit [SSC, Soluble solid content, TA,  titratable acidity, pH changed from 12.17 to 10.80 (11.26% decrease); from 3.543 to 3.637 (2.82% increase); from 1.441 to 1.146 (20.48% decrease) for after full blooming 143 days (13 August harvesting date) with AVG dose increase from 0 mg L-1 to 200 mg L-1, respectively. For this reason, post-harvest technological applications of the plum fruit must be designed while taking these criteria into consideration such as physical, mechanical and chemical properties of plum fruit.

Keywords: Aminoethoxyvinylglycine, Geometric mean diameter, Colour, Rupture force


How to Cite: ALTUNTAS, E., OZTURK, B., & SARACOGLU, O. (2019). The Effect of AVG (Aminoethoxyvinylglycine) Treatment and Maturity Stages on Physico-mechanical and Chemical Properties of Plum (cv. Giant) Fruit. Advances in Agricultural Science, 7(2), 88-99. 

1. Introduction

The use of growth regulatory substances in modern farming to improve fruit quality and efficiency has become widespread. Plant growth regulators have been evaluated among factors causing changes of the physical, mechanical, chemical and bioactive compounds in fruit (Shin et al. 2008). AVG has been used heavily to improve the quality of fruit, decrease preharvest fruit drop, delay fruit harvest and protect the fruit firmness by inhibiting ethylene that cause to accelerate the maturation at period before harvest (Greene and Schupp, 2004; Yuan and Carbaugh, 2007). In addition to the control of vegetative growth and regulation of flowering, size, shape, colour development and postharvest quality have been manipulated with use of AVG (Autio and Bramlage, 1982; Greene, 2006).

The maturity level, colour, size and mechanical defect,  firmness  are  some  of  the  importance  factors  considered  for  plum fruit marketing. To  design  and  improve  of  relevant  machines  and  facilities  used  in harvesting,  separating,  conveying,  storing,  handling,  processing,  packaging systems and estimating the cooling and heating loads of plum fruit, there is a need to know  the  various  physical  and  mechanical  properties. The mechanical behaviour under quasi-static compression loading of agricultural materials should be known to determination of the fruit quality in harvesting, transporting, processing storage, and the design of machines and devices used in the harvest and posthervest production processing. The harvested agricultural products have been damaged by the mechanical harvesting methods with exert load and breaking stress (Kuna-Broniowska et al. 2012). Compression orientation and speed affect the amount of force applied to post-harvest applications for plum fruit (Pérez-Vicente et al. 2002).

Processing of plum fruit to fruit juice and marmalade consists of a mechanical treatment of the plum fruit. This mechanical treatment is eventually related to the external forces exerted on each plum fruit (Kilickan and Guner, 2008). The coefficients of friction of the plum fruit against the various surfaces are necessary in designing of conveying, transporting and storing structures.

Several researchers have investigated the physical, mechanical behaviour under compression loading and chemical properties of some fruit such as mango (Mangifera indica L.), (Jha et al. 2006), orange (Citrus cinensis L.) (Topuz et al. 2005), cactus pear (Opuntia ficus india L.) (Kabas et al. 2006), kiwifruit (Razavi and Parvar, 2007), cherry tomato varieties (Kabas and Ozmerzi, 2008); oil fruit (Kilickan and Guner 2008); pear cultivars (Pyrus communis L.) (Ozturk et al. 2009); pomegranate peel and fruit (Ekrami-Rad et al. 2011) and persimmon (Diospyros kaki Thunb.) (Altuntas et al. 2011), medlar (Altuntas et al. 2013a), cherry laurel (Altuntas et al. 2018a), respectively.

Technical information and data in the scientific literature with regards to the effects of aminoethoxyvinylglycine (AVG) treatments on the physical, mechanical behaviour and chemical properties of plum fruit are insufficient. Thus, the objective of this study is to examine of the effects of AVG treatments and harvest periods on physical, chemical and mechanical properties of plum (cv. Giant) fruit.

2. Materials and methods

The plum fruit were harvested, on two harvest dates (13 August and 20 August), manually from Tokat city, located in Mid-Black Sea Transition Climate Belt region, during the harvest season on days after full blooming 143 and 150 days for Giant plum, 13 August and 20 August 2013, respectively., Then, they were transferred in polyethlene bags to the laboratory. To determine the plum fruit’s size, 100 fruit were randomly selected as cleaned, removed from foreign matters and undamaged fruit. AVG was applied 2 weeks before estimated harvest time. An ethylene inhibitor AVG was applied in ReTain formulation (ValentBioSciences Corp., Libertyville, IL) at three doses of   0 mg L-1 (control) , 100 mg L-1 and 200 mg L-1, respectively. The control trees (nontreatment of AVG) were treated only with water (pH = 6.48) + “Sylgard 309” surfactant.

The physical (geometric) properties of plum fruit, such as three principal length, width and thickness dimensions were measured by using a digital vernier caliper with an accuracy of 0.01 mm. For fruit mass, the digital electronic balance precision balance (0.01 g resolution) was used. The geometric mean diameter (Dg), sphericity (Φ), and surface area (S) of plum fruit were calculated using the equations explained by Mohsenin (1980; Altuntas et al. 2018b).

The physical (volumetric) properties such as fruit density (rf) a fruit is determined by the toluene (C7H8) displacement method and the bulk density (rb) of plum fruit was determined by hectoliter standard weight method (Altuntas et al. 2018a). The porosity was determined from fruit and bulk density values explained by Mohsenin (1980).  The initial moisture content of plum fruit was determined using the standard hot-air oven method at 105 ± 1°C for 24 h (Brusewitz, 1975).

The colour characteristics [(L*, a*, b*)], of skin of plum fruit were measured by a chromamater (Minolta, model CR-3000, Tokyo, Japan). Values of  L*, a* and b* were used to define a three-dimensional colour space and interpreted as follows: L* indicates lightness, with values ranging from 0 (completely opaque or ’black’) to 100 (completely transparent or ’white’); a positive a* value indicates redness on the hue circle (-a* =greenness) and a positive b* value indicates yellowness (-b*=blueness). The hue angle (h) expresses the colour nuance and values are defined as follows: red-purple: 0 ; yellow: 90 ; bluish green: 180; blue: 270. The chroma (C*) is a  measure of chromaticity, which defines the purity  or saturation of the colour. The  chroma  value  and the hue angle were following equations : (McGuire, 1992).

Colour characteristics of plum fruit sample was measured and computed as the mean of each treatment according to the method of McGuire (1992); Jha et al. (2006).

A biological materials test device (Sundoo, SH–2, 500 N, China; Instruction Manual for Materials Testing Machines) was used to determine the mechanical behaviour of the plum fruit tested. This device has three main components: a moving platform, a driving unit and a data acquisition (load cell, PC card and software) system (Altuntas and Yildiz 2016). fruitMechanical measurements of plum fruit were measured using by 73 mm diameter plate with biological materials test device ().  Force and time curves of plum fruit were recorded and to rupture force of plum fruit along three axial forces (Fx, Fy and Fz) were measured (Figure 1). The plum fruit sample was placed on the moving platform and loaded at 1.06 mm s-1 compression speed and pressed with a plate fixed on the load cell until the plum fruit ruptured. And also, deformation was measured as mm using by measuring ruler stand of the  biological materials test device. Absorbed energy along three axial axes (Ex, Ey, Ez) was obtained from the following equation:

where, is the rupture force and D  is the deformation at rupture point.

 Three replications were made for each harvest date of plum fruit as using 15 samples (Braga et al., 1999). Friction coefficients of plum fruit samples, tangent value of the angle of slope, were determined for different surfaces (chipboard, galvanized steel, plywood, laminate and rubber) (Altuntas et al., 2011).

For each harvesting date and AVG doses (0 mg L-1 (control) , 100 mg L-1 and 200 mg L-1), SSC (Soluble

Figure 1. Presentation of the three perpendicular dimensions of plum fruit the and three axial forces (Fx, Fy and Fz ); mechanical measurements of plum fruit sample by biological materials test device.

 

solid content), TA (titratable acidity) and pH of plum fruit were determined by the method of the AOAC (Association of Official Analytical Chemists, 1984; Barrett et al., 2007). Statistical analyses for the experiment results were conducted with SPSS 13.0 software based on a randomized complete plot design.

3. Results and discussion

3.1 Physical properties

The physical properties of plum fruit affected by AVG doses and harvest dates are given in Table 1. The effect AVG doses for each harvest date on the geometric mean diameters of plum fruit was statistically significant (p<0.01), while the sphericity was not statistically significant with AVG doses for each harvest date changes. The geometric mean diameter was lower on the after full blooming 143 days (13 August) than after full blooming 150 days (20 August harvest date), while, the surface area of plum fruit was higher in the after full blooming 150 days (20 August) than after full blooming 143 days (13 August harvest date) (Table 1).

 

Table 1.  Physical properties of plum fruit at the different AVG doses and harvest dates.

AVG doses
  0 mg L-1 100 mg L-1 200 mg L-1
Harvest dates

13 August (After full blooming 143 days)

Physical properties
Length (L; mm) 60.03 a(0.50)* 58.94 b (0.64) 57.01 b (0.50)
Width (W; mm) 48.20 a(0.38) 42.97 b (2.01) 44.14 b (0.35)
Thickness ( T; mm) 46.61 a(0.35) 45.45 b (0.66) 45.51 b (0.41)
Geometric mean diameter (GMD; mm) 50.83 a(0.34) 47.96 b (1.42) 48.36 b (0.33)
Sphericity (Sp) 0.855 ns (0.001) 0.812 ns (0.021) 0.849 ns (0.005)
Fruit mass (Mf ; g) 73.78 a(1.84) 64.31 b (2.14) 61.17 b (1.20)
Bulk density (ρb; kg/m3) 655.98 a† (1.79) 615.34 b (2.72) 615.62 b (3.87)
Fruit density (ρf ; kg/m3) 925.29 b† (33.07) 918.71 b (22.83) 1081.48 a (29.89)
Porosity, (P;%) 31.93 b(1.83) 34.25 b (1.55) 45.36 a (0.81)
Surface area (Sa ; cm2) 81.23 a(1.06) 73.53 b (3.36) 73.55 b (0.99)
 

20 August (After full blooming 150 days)

 
Length (L; mm) 60.45 a(0.38)* 60.14 b (0.39) 60.75 b (0.69)
Width (W; mm) 48.61 a(0.50) 46.51 b (0.45) 48.24 b (0.60)
Thickness (T; mm) 47.09 a(0.38) 46.32 b (0.37) 47.01 b (0.45)
Geometric mean diameter (GMD; mm) 51.94 a(0.34) 50.40 b (0.37) 51.43 b (0.52)
Sphericity (Sp) 0.859 ns (0.001) 0.838 ns (0.002) 0.847 ns (0.005)
Fruit mass (Mf ; g) 75.16 a(1.82) 70.27 b (1.39) 74.88 b (2.20)
Bulk density (ρb; kg/m3) 660.75ns (6.05) 633.91ns (10.51) 651.78ns (7.39)
Fruit density (ρf ; kg/m3) 1068.87ns (33.37) 1077.13 ns(27.72) 1080.92ns (15.38)
Porosity, (P; %) 37.95 ns (2.19) 40.72 ns (0.87) 39.59ns (0.89)
Surface area (Sa ; cm2) 84.81 a(1.12) 79.87 b (1.17) 82.26 b (1.70)

*: SEM (standard error of the mean)         ns: not significant

† : Values in the same line followed by the same letter are not significant different  (p<0.05);

‡ : Values in the same line  followed by the same letter are not significant different (p<0.01);

 

Table 2.  Colour characteristics of plum fruit by affected AVG doses and harvest dates

  AVG doses
Harvest dates 0 mg L-1 100 mg L-1 200 mg L-1
13 August (After full blooming 143 days)
Colour characteristics
L* 58.60 ns (3.48)* 66.78 ns (1.29) 65.05 ns (1.54)
a* -2.15 ns (0.36) 0.22 ns (0.76) -1.64 ns (0.26)
b* 31.98 ns (1.190) 31.47 ns (0.988) 33.09 ns (0.001)
Chroma, C* 32.06 ns (1.19) 31.52 ns (0.99) 33.13 ns (1.58)
Hue, h -1.504 b†  (0.011) 0.516 a (0.152) -1.520 a (0.009)
20 August (After full blooming 150 days)

 

L* 65.62 a† (1.37)* 65.79 a (1.77) 60.87 ns (1.47)
a* -2.68 ns (0.54) -3.34 ns  (0.56) -2.18 ns (0.73)
b* 35.74 ns (0.01) 34.34 ns  (1.25) 28.48 ns (4.87)
Chroma, C* 35.86 ns (0.86) 34.53 ns  (1.20) 28.60 ns (4.88)
Hue, h -1.496 ns (0.014) -1.471 ns (0.019) -1.004 ns (0.484)

*: SEM (standard error of the mean)

† : Values in the same line  followed by the same letter are not significant different  (p<0.05);

ns: not significant

 

The effect AVG doses for each harvest date on the fruit  mass  and  surface  area  of  plum  fruit  were statistically significant (p<0.01). The bulk density increases of 7.27%, 30.18% and 58.73% observed from the first harvesting date (13 August) to the second harvesting date (20 August) of plum fruit for 0 mg L-1 (control), 100 mg L-1 and 200 mg L-1 treatments, the fruit density increases of 15.52% and 17.24% occurred from 0 mg L-1 to 200 mg L-1 treatments, respectively (Table 1). The effect AVG treatments on the bulk density, fruit density and porosity of plum fruit for the after full blooming 143 days (13 August harves date) were statistically significant as p<0.05, p<0.05 and p<0.01, respectively, while, the effect of AVG treatments on the bulk density, fruit density and porosity of plum fruit for the after full blooming 150 days (20 August harvest date) were not statistically significant.

Esehaghbeygi  et al. (2013) reported that the differences among most physical properties of the plum varieties (Ghandi, Gatretala, and Black) were found to be statistically significant. The values for length, width, and thickness ranged from 28.05 to 36.52 mm, 26.78 to 35.46 mm, and 25.85 to 34.01 mm, respectively, for all the varieties. The values for geometric mean diameters ranged from 27.02 to 35.30 mm in all the varieties studied.

Altuntas et al. (2013b) reported that the length, width and  thickness,  geometric mean diameter and unit mass of plum fruit were found to be 56.76 mm, 46.54  mm, 46.00 mm, 49.33 mm and 70.86 g for MeJa-0, respectively. The mean length, width and thickness, geometric mean  diameter and  unit mass of plum fruit ranged from 54.48 mm to 54.40 mm, 44.37 mm to 45.67 mm, 44.24 mm to 44.96 mm, 47.26 mm to 47.96 mm and 65.10 g to 69.02 g with an increase  MeJA dose from 1120 mg L-1 to 2240 mg  L-1, respectively.

Ozturk et al. (2013) reported that the size dimensions of apple fruit were higher in 300 mg L-1 treatment compared with those of 0 mg L-1 and 100 mg L-1 treatments. As AVG doses increased, the length, width, thickness and fruit mass linearly increased. Ozkan et al. (2012) reported that the length, width, thickness, geometric mean diameter of Braeburn apple fruit were obtained as 65.43, 73.65, 71.20 and 69.68 mm (NAA, 20 mg L-1); 67.02, 74.99, 73.04 and 71.26 mm (AVG, 500 mg L-1); 63.60, 73.61, 71.24 and 69.03 mm (control), respectively. According to these results, our results related the length, width, thickness and geometric mean diameter for plum fruit are lower than reported for Braeburn apple (Ozkan et al. 2012). And also, our results related the length, width, thickness and geometric mean diameter were similar to that reported for plum fruit by Altuntas et al. (2013b).

 

3.2 Colour characteristics

Plum fruit skin colour characteristics were presented In Table 2. The effect of AVG treatment and harvesting dates on the L*, a*, b* and C* colour characteristics of plum fruit were not significant (p>0.05), while, h values of plum fruit was statistically significant (p<0.05). While plum fruit L*, b*, and C* colour characteristics for 0 mg L-1 AVG treatment increased with harvesting dates from the after full blooming 143 days (13 August) to the after full blooming 150 days (20 August harvest dates), a* and hue values decreased with harvesting date changes. For 100 mg L-1 AVG treatment, plum fruit L*, a* and h colour characteristics decreased with harvesting period, b* and C* values increased with harvesting date changes, whereas, skin of plum fruit  L*, a* and h colour characteristics decreased with harvesting period for 200 mg L-1 AVG treatment, respectively. L*, b* and C* values increased with the increase from first harvesting date (the after full blooming 143 days)  to the second harvesting date (the after full blooming 150 days) for plum fruit.

Ozturk et al. (2013) reported that L*, C* and h values of skin of apple were 53.08, 41.66 and 57.58 (AVG-0); 54.29, 40.57 and 59.45 (AVG-1); 53.95, 40.42 and 58.48 (AVG-2); 54.89, 41.17 and 59.29 (AVG-3), respectively. The colour characteristics for skin apple generally increased in magnitude with an increase in AVG doses. Hue angle values for both skin and flesh apple fruit increased as AVG doses increased from 0 mg L-1 to 500 mg L-1. Ozturk et al. (2015) reported that all AVG treatments, except for 100 mg L-1, had higher L* values than the control treatment in 2011. 400 and 500 mg L-1 AVG treatments significantly increased the hue angles of the second year. Such an increase in hue angle was more distinctive in 500 mg L-1 AVG treatment. Ozturk et al. (2012) reported that L* value decreased from 28.02 to 21.84 in the control, from 30.45 to 21.49 with 100 mg L−1 AVG and from 30.51 to 21.99 with 200 mg L−1 AVG for plum fruit (Prunus salicina Lindell cv. ‘Black Amber’. In addition, the decrease in h value during storage for 100 mg L−1 AVG (from 32.37 to 23.21) was higher compared with the decrease in the control and 200 mg L−1 AVG treatments. The highest C* value (14.21) at the end of storage was obtained with the 100 mg L−1  AVG treatment, and the lowest value (9.15) was observed in the control. According to these results, our results related L* for plum fruit are higher than reported for Braeburn apple (Ozturk et al. (2013). And also, our results related L* for plum fruit (cv. Giant) are higher than reported for Prunus salicina Lindell cv. ‘Black Amber’ plum fruit (Ozturk et al. (2014).

 

3.3 Mechanical properties

The mechanical characteristics such as rupture force, deformation and absorbed energy along three perpendicular dimensions of plum fruit as affected by AVG treatment and harvesting dates are given in Figure 2. The  effects of AVG  treatments  on rupture force, deformation and absorbed energy of plum fruit were statistically significant (p<0.01); whereas, the  effect  of  harvesting  dates at rupture force, deformation and absorbed energy of plum fruit was  not significant  (p>0.05). The effect of compression axes on rupture force of plum fruit were not significant; whereas, compression axes at the deformation and absorbed energy of plum fruit was statistically significant (p<0.01), respectively. The force required to initiate plum fruit rupture on the X-axis decreased as AVG doses increased from 0 to 200 mg L-1. The results indicated that the rupture force along all three axes is highly dependent on harvesting dates over the AVG doses ranges investigated.

Deformation of plum fruit (Dx, Dy, Dz) along X-, Y-, and Z- axis compressed using with circular plate varied from 27.8 to 20.68 mm, from 23.5 to 19.0 mm, and from 21.6 to 18.7 for 13 August harvesting date (after full blooming 143 days) , respectively; whereas, deformation varied from 26.5 to   20.3 mm, from 21.8 to 15.5 mm, and from 22.8 to 18.7 mm for 20 August harvesting date (after full blooming 150 days)  with AVG dose increase from 0 mg L-1 to 200 mg L-1, respectively. Generally, the rupture force, deformation and absorbed energy of plum fruit decreased by AVG treatments and harvesting dates along X-, Y-, and Z- three axial axes for compression tests.

Altuntas et al. (2013b) reported that rupture force punctured using with cylindrical and needle probe along X- axis for medlar fruit decreased (with 90.2% and 93.1% decreases) from physiological maturity to ripening period, respectively. Altuntas et al. (2013) reported that the force required initiating plum fruit rupture on the X-axis decreased as MeJA doses increased from 0 to 2240 mg L-1. The results indicated that the rupture force along all three axes is highly dependent on harvesting time over the MeJA doses ranges investigated. Greater force was required to rupture plum fruit with low AVG 0 values being tested for each loading orientation. According to these results, our results related the the rupture force for plum fruit were similar to that reported for plum fruit by Altuntas et al. (2013b).

The effects of AVG treatment and harvesting period on the static friction coefficient for the different friction surfaces such as rubber, plywood, laminate and galvanized steel were given in Figure 3.

The effect of AVG treatment on the friction coefficients of against for rubber and plywood friction surfaces were statistically significant (p<0.05, p<0.01), whereas, the effects of AVG treatment on the friction coefficients against for

Figure 2. Mechanical behaviour of plum fruit affected by AVG treatment and harvesting dates.

 

Figure 3. Friction coefficients of plum fruit affected by AVG treatment and harvesting dates.

 

Table 3.  Chemical characteristics (TA, SSC and pH) and moisture content of plum fruit as affected by AVG and harvesting dates

Harvest periods AVG doses
13 August(After full blooming 143 days) 0 mg L-1 100 mg L-1 200 mg L-1
Chemical characteristics
TA; g/100 g 1.441 a‡ (0.051)* 1.220 b (0.002) 1.146 c (0.002)
SSC; % 12.17 a‡ (0.05) 11.47 b (0.02) 10.80 c (0.04)
pH 3.543 b‡ (0.002) 3.523 c (0.002) 3.637 a (0.005)
Moisture content (Mc; %) 86.82 b† (0.29) 86.94 b (0.10) 87.54 a (0.10)
20 August (After full blooming 150 days)
TA; g/100 g 1.057 ns (0.050)* 1.007 ns (0.003) 1.051 ns (0.009)
SSC; % 12.43 a‡ (0.02) 11.53 c (0.02) 12.10 b (0.01)
pH 3.710 ns (0.050) 3.713 ns (0.005) 3.753 ns (0.006)
Moisture content (Mc; %) 86.51 b† (0.15) 87.06 a (0.22) 86.70 a (0.15)

*: SEM (standard error of the mean)

† :Values in the same line followed by the same letter are not significant different  (p<0.05);

‡:Values in the same line followed by the same letter are not significant different (p<0.01);

ns : not significant

 

laminate and galvanized steel friction surfaces were not significant. The effect of harvesting dates on the friction coefficients of against for rubber, laminate and galvanized steel friction surfaces were not significant, whereas, the effect of harvesting period on the friction coefficient against for plywood friction surface was statistically significant (p<0.01), respectively. In general, the friction coefficients for galvanized steel, laminate, plywood and chipboard friction surfaces increased with harvesting dates of plum fruit. This is a result of the increasing adhesion between the friction surface and softened plum fruit according to physiological maturity of fruit. Esehaghbeygi  et al. (2013) reported that the friction coefficients ranged from 0.105 to 0.169 for plums on galvanized surface, from 0.131 to 0.194 on rubber, from 0.155 to 0.181 on plywood, and from 0.09 to 0.137 on fiberglass. Altuntas et al. (2013a) reported that the static coefficients of friction of medlar fruit during physiological maturity and ripening period were higher for rubber than the other surfaces. According to these results, our results related the the rupture force for plum fruit were similar to that reported for medlar fruit by Altuntas et al. (2013a).

 

3.4 Chemical properties

The effects of AVG treatment and harvesting dates on chemical properties (TA, SSC, and pH) were presented in Table 3. The effect of AVG treatment on SSC, pH, TA of plum was statistically significant (p>0.01), whereas, the effect of harvesting period on SSC, TA and pH and of plum was statistically significant (p>0.01, p>0.01, p>0.05), respectively. SSC, pH and TA chemical characteristics values of plum fruit changed from 12.17 to 10.80 (11.26% decrease); from 3.54 to 3.64 ((2.82% increase); from 1.441 to 1.146 (20.48% decrease) for 13 August harvesting date (after full blooming 143 days) with AVG dose increase from 0 mg L-1 to 200 mg L-1, respectively. SSC, pH and TA values of plum fruit were 12.43%, 3.710 and 1.06 g 100 g-1 (AVG-0), 11.53%, 3.713 and 1.007 g 100 g-1 (AVG-1), 12.10%, 3.753 and 1.051 g 100 g-1 (AVG-2) for 20 August (after full blooming 150 days), respectively. Ozturk et al. (2013) reported that SSC, pH, TA of apple increased with increasing doses of AVG decreased. The lowest and highest pH and TSS values were obtained from AVG-3 as 2.69-13.6% and AVG-0 dose as 2.87-15.44%, respectively. The effect of the AVG treatment on SSC, pH, TA and starch index of apple were statistically significant (p<0.05). Karaman et al. (2013) reported that the lowest and highest pH values for ‘Fortune’ plum fruit were obtained from control (3.21) and 200 mg L–1 AVG treatments (3.27) at the end of the storage. Similar results were obtained with the 100 and 200 mg/L AVG treatments in all analysis periods. Ozkan et al. (2016) reported that soluble solids content (SSC) of AVGtreated fruit was found to be lower than those of NAA-treated and control fruit, whereas titratable acidity of AVG-treated fruit was found to be higher at all harvest dates of 2010 and 2011. Yildiz et al. (2018) reported that SSC values of ‘Sweetheart’ cherries significantly decreased with 200 mg L–1AVG treatment in all analysis dates but decreased with 100 mg L–1 AVG treatment on 21 and 28th of June. Altuntas et al. (2013a) reported that, pH and SSC of medlar fruit varied from 4.01 to 4.70 and 17.8 to 15.5% at physiological maturity and overripe period, respectively. According to these results, our results related SSC and pH for plum fruit are lower than reported for medlar fruit (Altuntas et al., 2013b).

 

4. Conclusion

The physical, mechanical and chemical properties are highly dependent on AVG doses and harvest periods.

-The geometric mean diameter was lower on first harvesting period than the second harvesting period, while, the surface area of plum fruit was higher in the second harvesting period than first harvesting period. The bulk density increases of 7.27% to 58.73% observed from 13 August (after full blooming 143 days) to 20 August (after full blooming 150 days) of plum fruit from 0 mg L-1 (control) to 200 mg L-1 treatments, the fruit density increases of 15.52% and 17.24% occurred from 0 mg L-1 to 200 mg L-1 treatments, respectively.

L*, b*, and C* colour characteristics of plum fruit for 0 mg L-1 AVG treatment increased with harvesting period from the first harvesting period to second harvesting period, whereas a* and hue values decreased with harvesting period changes. L*, b* and C* values increased with the increase from 13 August (after full blooming 143 days) to 20 August (after full blooming 150 days) harvest dates for plum fruit.

-The force required to initiate plum fruit rupture on the X-axis decreased as AVG doses increased from 0 to 200 mg L-1. The results indicated that the rupture force along all three axes is highly dependent on harvesting time over the AVG doses ranges investigated. In general, the rupture force, deformation and absorbed energy of plum fruit decreased by AVG treatments and harvesting period along X-, Y-, and Z three axial axes for compression tests. Generally, the static friction coefficients for galvanized steel, laminate, plywood and chipboard friction surfaces increased with harvesting period of plum fruit. This is a result of the increasing adhesion between the friction surface and softened plum fruit according to physiological maturity of fruit.

-For chemical properties as SSC and TA decrease of 11.26% and 20.48%, whereas, pH incerases of 2.82% for 13 August harvesting date (after full blooming 143 days) with AVG dose increase from 0 mg L-1 to 200 mg L-1, respectively. The engineering properties of plum fruit should be considered to design the postharvest treatments, systems and processing.

 

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