FormalPara Highlights
  • Aloe vera (AV) and modified atmosphere packaging (MAP) treatments reduced the storage losses and decay ratio during cold storage in pear.

  • AV and MAP treatments maintained the fruit quality and bioactive compounds content of pear during cold storage.

  • AV and MAP treatments have a significant effect on extending the post-harvest life of pear.

Introduction

Pear ripens rapidly in the post-harvest period due to its climacteric characteristic, followed by significant quality losses with a decrease in flesh firmness, water, flavor and nutrients and their interiors tend to brown. This shortens the shelf life of pear fruit and causes significant economic losses (Huang et al. 2022). Techniques such as low temperature (Xu et al. 2020), modified atmosphere packaging (Wang et al. 2020), melatonin (Zheng et al. 2019), 1‑methylcyclopropene (Latt et al. 2023), boric acid (Kaur and Kaur 2019), methyl salicylate (Zhang et al. 2020a), acibenzolar-S-methyl (Huang et al. 2022), carbon dioxide (Wang et al. 2021), candida oleophila (Nie et al. 2019), and Wickerhamomyces anomalus (Zhang et al. 2020b) are used to delay ripening in pears by slowing down respiration and pigment degradation, maintain storage quality, and control post-harvest rot.

Edible coating applied to the surface of the fruit, providing a partial barrier to water molecules and gas movement, thus reducing water loss and changing the micro atmosphere around the fruit (Zhang et al. 2023), is an environmentally friendly and health-friendly coating applied to many fruit species to prevent post-harvest losses. These are applications that do not pose any risks. Aloe vera (AV) gel application is a frequently used technique for this purpose. Previous studies have shown that AV application found to be effective in preserving post-harvest fruit quality in fruit species such as sweet cherry (Martínez-Romero et al. 2006), nectarine (Ahmed et al. 2009), pomegranate (Martínez-Romero et al. 2013), kiwifruit (Benítez et al. 2013), grapes (Shweta et al. 2014), raspberry (Hassanpour 2015), plum (Avcı et al. 2023), peach (Guillén et al. 2013), blueberry (Vieira et al. 2016), papaya (Mendy et al. 2019), cherry laurel (Ozturk et al. 2019), and jujube (Islam et al. 2022).

MAP application, which can change the gas concentration around the fruit and create a suitable atmosphere to limit respiration and metabolic activity by affecting humidity rates (Mendoza et al. 2016), can provide significant advantages (Petracek et al. 2002) by reducing water loss, respiration activity, ethylene production, enzymatic reactions, physiological changes and by preserving fruit flesh firmness (Moradinezhad and Dorostkar 2021) during storage of the fruit. In previous studies, it has been demonstrated that MAP has a positive effect on maintaining fruit quality after harvest in fruit species such as kiwi (Hertog et al. 2004),sweet cherry (Aglar et al. 2017), pomegranate (Candir et al. 2018), jujube (Islam et al. 2022), cornelian cherry (Ozturk and Aglar 2019) and plum (Avcı et al. 2023). However, it has been reported that the effect is further increased with the combination of AV and MAP (Ozkaya et al. 2016).Nevertheless, there is no study on the application of AV and MAP in pear. In this study, we aimed to determine the effect of AV and MAP applications on post-harvest fruit quality in ‘Ankara’ pear cultivar.

Materials and Methods

The plant material used for this research consists of fruit harvested from the orchard established with ‘Ankara’ pear cultivar (late ripening) trees grafted on quince A rootstock in Tokat province, Turkey, in 2010 year. Fruit harvested at commercial maturity were placed in 10-kg capacity plastic boxes (Plasta¸s, Turkey) and quickly brought to GAPUTAEM Quality and Technology Laboratory with a refrigerated vehicle (12 ± 1.0 °C and 75 ± 5.0% relative humidity [RH]). The injured or damaged fruit were eliminated and excluded from evaluation. The fruit selected by considering fruit color and size were divided into four groups: 1: fruit stored without any application (control); 2: fruit stored by placing them in Xtend® modified atmosphere packaging (MAP application); 3: fruit stored after being immersed in 33% AV solution for 10 min and dried at room conditions for 20 min (AV application); 4: fruit stored in Xtend® modified atmosphere bags after being immersed in 33% AV solution for 10 min and dried at room conditions for 20 min (AV + MAP application). In fruit that were stored at 0 ± 0.5 °C and 90 ± 5% RH for 120 days, measurements and analyses were performed in three replicates on the 30th, 60th, 90th and 120th days of storage, and six fruit were used for each repetition.

Weight Loss

At the beginning of the cold storage, initial weights (Wi) of the fruit were determined by a digital scale with a precision of 0.01 g (Radwag, Poland). Then, on day 10, 20 and 30 of cold storage, the final weights (Wf) were determined. The weight loss that occurred in fruit was based on the weight at the beginning of each measurement period and determined as a percentage through the equation given below (Eq. 1):

$$WL=\frac{Wi-Wf}{Wi}\times 100$$
(1)

Decay Rate

Before cold storage, the fruit (about 0.5 kg of fruit) were counted in each replication and the total number of fruit (TF) was determined. Then, during each measurement period, the decayed fruit (DF) in each replication were determined. If the development of mycelium on shell occurred, the fruit were considered rotten. Finally, with the following equation (Eq. 2), the decay rate (DR, %) was detected:

$$DR=\frac{TF-DF}{TF}\times 100$$
(2)

Fruit Firmness

Five fruit from each replication were used to determine firmness. The fruit skin was cut at two different points (on the cheeks) along the equatorial part of the fruit and the firmness was determined by using an Effegi penetrometer (FT–327; McCormick, WA, USA) with a 7.9-mm penetrating tip. Firmness was expressed in kilograms.

Soluble Solids Content (SSC), Titratable Acidity (TA) and pH

Five fruit in each replication were washed with distilled water. Fruit were homogenized by a blender (Promix HR2653, Philips, Turkey) and the homogenate was filtered through cheesecloth to obtain juice filtrate. SSC was determined with a digital refractometer (Atago PAL‑1, USA) and recorded as a percentage (%). pH was determined with a pH meter. For TA measurement, 10 mL of distilled water was added to 10 mL of juice. Then, 0.1 N sodium hydroxide (NaOH) was added until the solution’s pH reached 8.2. Based on the amount of NaOH consumed in titration, TA was determined and expressed as g malic acid kg−1. For vitamin C measurement, 0.5 mL juice was added to 5 mL of 0.5% oxalic acid (Ozturk et al. 2019).

Total Phenolics and Antioxidant Capacity

During each measurement period, five fruit taken from each replication were first washed with distilled water. The fruit were homogenized by a blender (Promix HR2653 Philips, Turkey). About 30 mL of homogenate was taken and placed into a 50-ml falcon tube. The prepared tubes were kept at −20 C until the time of analyses. Before the analyses, the frozen samples were dissolved under room temperature (21 °C). Pulp and juice were separated from each other by a centrifuge at 12,000 × g at 4 °C for 35 min. The resultant filtrate was used to determine the content of total phenolics and antioxidant capacity. Spectrophotometric measurements for total phenolics and antioxidant capacity were performed using a UV-Vis spectrophotometer (Shimadzu, Kyoto, Japan) at 734 nm wavelength (Ozturk et al. 2019).

Organic Acids

Extraction of organic acids in fresh and dried samples was carried out with the modification of the method reported by Bevilacqua and Califano (1989). A volume of 10 g of sample was taken into centrifuge tubes and then 10 mL of 0.009 N H2SO4 was added to the samples and homogenized. The samples were mixed for 1 h and centrifuged at 14,000 rpm for 15 min. The liquid remaining at the top of the centrifuge tube was filtered through filter paper, then passed through a 0.45-μm membrane filter and finally through the SEP-PAK C18 cartridge. It was injected into the high-performance liquid chromatography (HPLC) (Agilent HPLC 1100 series G 1322 A, Germany) device and the separations were performed on the appropriate column (Aminex HPX—87 H, 300 mm × 7.8 mm). Organic acids were determined at wavelengths of 214 and 280 nm. As mobile phase, 0.009 N H2SO4 solution was used.

Specific Phenolic Compounds

These were analyzed as follows: Homogeneously selected fresh fruit samples were weighed as 1 g and extracted with methyl alcohol (5 mL) in a test tube for 6 h. The extract was analyzed by HPLC (Perkin-Elmer series 200, Norwalk, USA). The HPLC system was equipped with a UV detector (Series 200, UV/Vis detector) and quaternary solvent dispensing system (Series 200, analytical pump) and used at 280 nm. Analytes were separated by a Phenomenex Kromasil (Phenomenex, Torrance, USA) 100A C18 (250 mm × 4.60 mm, 5 μm) column. The clone temperature was maintained at 26 °C using a water bath (Wisebath, WB-22, Daihan Scientific, Seoul, Korea). The mobile phase was formed from water and acetonitrile (A) containing 2.5% formic acid (B). The mobile phase flow rate was maintained at 1 mL/min and 20 μL of the sample was injected and expressed in g 100 g−1 in light of the results of the peak areas obtained.

Statistical Analysis

The normality of the data was confirmed by the Kolmogorov–Smirnov test and the homogeneity of variances by the Levene’s test. (P > 0.05). Therefore, the Pearson correlation test was performed. Data were analyzed by two-way ANOVA with SAS Version 9.1 (SAS Institute Inc., Cary, NC, USA) software. When the F test was significant, means were compared with Tukey’s range test.

Results and Discussion

Weight Loss, Decay Ratio and Fruit Firmness

The weight loss that occurs as a result of water evaporation through transpiration in fruit (Kader and Yahia 2011) and increases in proportion to storage time (Ozturk et al. 2021) causes significant economic damage (Sandhya 2010). It can be reduced by the use of MAP and AV coating (Ozturk et al. 2020), which delay the degradation of the cell wall in fruit (Wang et al. 2019) and cause reduced respiration in fruit. There were differences between the applications in terms of weight loss, which increased in parallel with the storage time. The lowest weight loss at the end of the cold storage was obtained in the MAP application with 1.01%, and the highest weight loss was obtained in the control application with 3.13%. AV applications had the highest weight loss after control. There was no difference between the control and AV applications on the 30th day of cold storage, but the difference between applications was significant in other measurement days (Table 1). AV application reduced weight loss during cold storage in fruit species including apple (Ergun and Satici 2012), papaya (Sharmin et al. 2015), sweet cherry (Huyuklu 2014) plum (Díaz-Mula et al. 2012), jujube (Gün 2017; Islam et al. 2022), grape (Valverde et al. 2005) and peach (Hazrati et al. 2017). Avcı (2016) suggested that MAP and AV applications reduced weight loss in black amber plum cultivar due to their effectiveness in reducing respiration rate, and Kablan et al. (2008) reported that the loss of carbon atoms in the respiration cycle can lead to weight loss.

Table 1 The effect of Aloe vera (AV) and modified atmosphere packaging (MAP) applications on weight loss, decay ratio and fruit firmness during cold storage in pear

MAP and AV applications have the potential to control disease severity in fruit by preventing fungal rot in the fruit and reducing fruit softening during cold storage. The fruit decay ratio was lower in fruits treated with MAP and AV. At the end of the cold storage, the highest decay ratio was obtained in the control application with 90%, and the lowest decay ratio was obtained in the MAP + AV and AV applications with 40%. MAP was not effective in decay ratio on the 30th day of the cold storage, but it was lower with MAP + AV and AV applications. There were significant differences between applications on the 60th and 90th days of the cold storage; the lowest decay ratio was recorded with MAP + AV applications (Table 1). Martínez-Romero et al. (2006) reported that AV application in sweet cherry slowed down the darkening of the fruit stem and fruit rot compared to the control application, while Valverde et al. (2005) reported that spoilage was faster in control fruit and the storage life of the control group was limited to only 7 days. Singh et al. (2011) determined that fruit browning and quality losses in strawberries were lower with 33% AV application, and Ergun and Satici (2012) claimed that AV application caused lower decay damage in apples, but this varied depending on the cultivar. Zapata et al. (2012) reported that 25% AV application reduced the decay ratio in peach, sweet cherry and nectarine, and Ates et al. (2022) determined that the decay ratio was lower with 33 and 66% AV application in ‘Bluecrop’ blueberry cultivar.

Fruit softening, which increases with ripening and occurs as a result of structural changes in the pectin matrix leading to loss of cell wall structure (Posé et al. 2015), is an important problem that affects the post-harvest life of the fruit and the marketing process. However, MAP and AV applications can reduce fruit softening by reducing the respiration rate and water loss in post-harvest storage. The fruit flesh firmness decreased with increasing cold storage time. However, the fruit flesh firmness values were higher in fruit treated with MAP and AV. There was no difference between the treatments on the 30th and 90th days of cold storage, and the fruit firmness values were higher in the fruit treated with AV + MAP on the 60th day. At the end of the cold storage, the control treatment fruit had significantly lower fruit flesh firmness values than the other treatments. The effect of AV + MAP applications on fruit flesh firmness was higher compared to AV applications (Table 1). Ergun and Satici (2012) emphasized that 1%, 5%, 10% AV gel applications did not differ significantly from control applications in preserving fruit flesh firmness during cold storage in ‘Red Chief’ and ‘Granny Smith’ apple cultivars. Khan et al. (2008) stated that the decrease in fruit flesh firmness is directly proportional to ethylene synthesis and that this effect occurs when ethylene increases the enzyme activity that hydrolyzes the cell wall, and MAP applications can be slowed down the fruit softening by reducing O2 concentration and preventing ethylene synthesis. Previous studies reported that fruit softening was lower with AV application in fruit species such as pear (Jawandha et al. 2017), cherry laurel (Ozturk et al. 2020), cornelian cherry (Ozturk and Aglar 2019) and jujube (Islam et al. 2022).

Soluble Solids Content (SSC), Titratable Acidity (TA) and pH

SSC and TA are significant quality characteristics that determine the storage period of the fruit (Mahto and Das 2013). During post-harvest storage, the acid metabolism converts starch and acid into sugar, causing TA to decrease and total water-soluble dry matter to increase (Duan et al. 2011). The SSC and pH ratios increased in proportion to the storage time, while the TA ratio decreased. The changes in SSC, TA and pH ratios were lower in fruit treated with MAP and AV. On the 30th and 60th days of the cold storage, the control fruit had higher SSC values compared to AV and MAP applications. On the 30th day, the fruit of control and AV treatments had similar SSC values, and the SSC content was lower in MAP-treated fruit. At the end of the cold storage, the lowest SSC values were recorded with control fruit, followed by MAP application. In the same period, there was no difference between AV and AV + MAP applications. However, the fluctuations occurred in SSC values during cold storage (Table 2). In all applications, TA values decreased during cold storage. The lowest TA value was recorded with the control application during storage; there was generally no difference between the other applications. It was determined that the titratable acid content of fruits treated with MAP + AV was higher than those treated with AV and MAP only on the 30th day of the cold storage. The pH value generally increased in all applications during cold storage. MAP and MAP + AV applications had the highest pH values on the 30th day of storage, but AV application had a significantly higher pH content on the 60th day (Table 2). The increases and decreases in the SSC content during cold storage are based on events such as the transformation of sugar into CO2 and H2O in parallel with the increase in respiration rate, the transformation of starch into sugar, the increase in the dry matter content in parallel with the decrease in the amount of water in the fruit and the disintegration of polysaccharides in the cell wall (Martinez-Romero et al. 2006; Dang et al. 2010; Díaz-Mula et al. 2012; Vieira et al. 2016). Ozturk and Aglar (2019) reported that MAP and AV applications in cranberry fruit increased SSC compared to the control. Ozturk et al. (2018) conducted a study of pre-harvest aminoethoxyvinylglycine (AVG) and post-harvest 20% AV in ‘Piraziz’ apples and only post-harvest AV application, and found that the SSC content first increased and then decreased during cold storage and shelf life in all applications, but AVG + AV application was more effective in preserving the SSC content. Hazrati et al. (2017) reported that AV-applied peach fruit had lower SSC content, while Valero et al. (2014) found that AV application did not have a significant effect on SSC values in peach and sweet cherry. Khan et al. (2013) reported MAP application maintained SSC compared to control fruit. Hazrati et al. (2017) found that TA content in AV applied peach fruit was lower than the control fruit, and Ates et al. (2022) reported that TA content of the blueberry fruit treated with 33 and 66% was higher. However, Islam et al. (2022) suggested that TA content in AV-applied jujube was lower than control fruit.

Table 2 The effect of Aloe vera (AV) and modified atmosphere packaging (MAP) applications on soluble solids content (SSC), titratable acidity (TA) and pH during cold storage in pear

Total Phenolics and Total Antioxidant Capacity

Total phenolics content increased in all treatments on the 30th day of the cold storage, and then it decreased at later times. AV + MAP and MAP applications significantly maintained the total phenolic content compared to the control, but the total phenol content in the AV application gave similar statistical results to the control application. At the end of the cold storage, the lowest total phenolic content was measured in the control application and the highest content was measured in the MAP + AV application. Total antioxidant content increased in applications other than MAP application on the 30th day of the cold storage, but it increased in MAP and AV applications on the 60th day, and total antioxidant content decreased in control and MAP + AV applications. In the measurements made on the 90th and 120th days of the cold, the antioxidant content decreased in all applications and the lowest values were measured in the control application at the end of the cold storage (Table 3). Previous studies have shown that total phenolic loss was lower in fruits treated with an edible coating (Rasouli et al. 2019) and MAP (Aglar et al. 2017). The effect of the edible coating applications on total phenolics during cold storage is explained by the limitation of cellular division in the fruit peel (Ali et al. 2019) and the slowing down of oxidation and degradation in phenolic compounds by the edible coating applications (Ouyang et al. 2019). The effect of MAP application is due to the change in the gas composition around the fruit (Aglar et al. 2017). However, Carrilo-Lopez et al. (2000) and Guan and Dou (2010) reported that MAP and AV applications inhibited ethylene synthesis and reduced the accumulation of phenolic compounds and anthocyanins.

Table 3 The effect of Aloe vera (AV) and modified atmosphere packaging (MAP) applications on total phenolic compounds and antioxidant capacity during cold storage in pear

Organic Acids and Specific Phenolic Compounds

Organic acids, which enable the digestion of nutrients and stimulate blood circulation and whose type and content may vary depending on the fruit species, are important fruit quality parameters and decrease as maturity increases (Kiralan and Gundogdu 2021). The amount of organic acids, one of the main substrates required for respiration, decreases as the respiration rate increases. The organic acid that was found in the highest amount in pear was malic acid, followed by succinic, formic, adipic and shikimic acids (Table 4). Gao et al. (2004) stated that malic acid is the main organic acid in different pear fruit. With increasing fruit maturity, the amount of the organic acid naturally decreased in general; however, although there were fluctuations in the amount of shikimic acid, this generally increased with the prolongation of storage time. AV and MAP applications caused changes in the amount of organic acids during cold storage; it has been determined that this effect varied depending on the type of organic acid and the cold storage time, and there are inconsistencies in the effect. At the end of the cold storage, the lowest values of all organic acids except shikimic acid were recorded in the fruit of the control application (Table 4).

Table 4 The effect of Aloe vera (AV) and modified atmosphere packaging (MAP) applications on organic acids during cold storage in pear

In the study, gallic acid, catechin, hydroxybenzoic acid, ferulic acid, naringin, q‑coumaric, coumarin and quercetin were the main individual phenolic compounds detected in ‘Ankara’ cultivar fruit. In general, the examined phenolic compound values decreased at the end of the cold storage. The highest individual phenolic content in pear fruit during the harvest period was gallic acid and the lowest was coumarin. At the end of the cold storage period, the highest gallic acid values were determined from the AV application, followed by MAP + AV and MAP applications, while the control application gave significantly lower values than the other applications. The highest naringin content was detected in the MAP application at the end of the cold storage; the difference between the other applications was similar. Catechin values were generally preserved with MAP and AV applications during cold storage compared to the control application, while hydroxybenzoic acid values were significantly higher in the MAP + AV application compared to the other applications there were the differences between the applications in terms of hydroxybenzoic acids. The effect of the treatments on ferrulic acid values at the end of the cold storage was similar, while q-coumaric acid values increased significantly with MAP application, followed by AV, MAP + AV and control applications. The difference was detected between all applications based on the examined values. There were no differences between MAP, AV and MAP + AV applications in terms of coumarin values and the control group had the lowest values. Quercetin values gave the highest results in the MAP + AV application, followed by AV and MAP applications, while the control application had the lowest values (Table 5).

Table 5 The effect of Aloe vera (AV) and modified atmosphere packaging (MAP) applications on specific phenolic compounds during cold storage in pear

Conclusion

Weight loss and decay ratio, which significantly affect the economic life of the fruit and consumer preference, were reduced by modified atmosphere packaging (MAP) and Aloe vera (AV) applications. The loss of fruit flesh firmness was delayed by MAP and MAP + AV applications. MAP and AV applications delayed ripeness in pear fruit, lower soluble solids content and higher titratable acidity values were detected in the fruit, and it was observed that the color change in the fruit was lower. The changes in the content of organic acids and individual phenolics occurred in cold storage, and the changes differed depending on the type of individual phenolics and organic acids. As a result, it was concluded that MAP and AV applications can be effectively used to delay ripeness and preserve the quality of ‘Ankara’ pear fruits during cold storage.