Pear fruit surface color was measured using a Colorimeter (Model: CR-310, Minolta, Japan), which was calibrated using a white plate (L^* = 93.90, a^* = 3.13, b^* = 3.20). Color measurements were conducted six times per sample (108 reading a day) for 14 days of analysis to obtain the changes of L^* (lightness-darkness), a^* (redness-greenness), and b^* (yellowness-blueness) subjected to different impact levels at 10 and 22°C. Total color differences (ΔE^*) (Equation 5), Chroma (Equation 6), and Hue (Equation 7) were also calculated using the equations explained by Pathare et al. (2013):

Firmness was performed by penetrating the middle region of pear fruit by using a hand penetrometer (Model: FT 327, EFFEGI, Italy) at 2 days interval of the experiment and expressed in N by following the standard procedure of OECD (2018).

According to OECD (2018), TSS °Brix of pear was measured using a hand-held refractometer and was calibrated at 20°C. For each pear sample, two longitudinal slices were taken (from two opposite sides). Each slice was squeezed longitudinally to obtain a mixture of juice from all regions. From each group, 6 readings of TSS were taken (36 readings per day).

Table 2 shows the values of BA (mean ± Sd) and BV (mean ± Sd) of selected pear fruits at different heights and storage temperatures for 14 days period. In this study, BA and BV of bruised pears were highly increased (p < 0.05) with the increase of all investigated factors like drop height, storage duration, and temperature condition. The highest drop height (60 cm, 0.647 J) increased the average value of BA from 140.6 mm² on day 2 and 243.7 mm² on day 8 to reach 283.1 mm² on day 14 on pears stored at 10°C. However, the BA was higher on pears stored at 22°C and impacted with the heights impact level (60 cm), where BA was 204.6 mm² on day 2 and 295.2 mm² on day 8 to reach 431.6 mm² on day 14 (Table 2). Same trends of results were shown on the BV of the pear fruits where high BV resulted on pear impacted with the steel ball from 60 cm height stored at ambient temperature condition followed by the one impacted from 40 and 20 cm heights at both storage conditions. In the current study, high storage temperature conditions and impact energy during storage time slightly increased BA and BV. The same findings were recorded in apples (Fadiji et al., 2016) and pomegranate (Hussein et al., 2019). Shafie et al. (2017) also revealed that BV and BA were highly influenced by drop height. Similarly, Shafie et al. (2015) found an obvious tendency between BV and storage time, impact level, and storage temperature. Besides, Komarnicki et al. (2016) found that the maximum value of BV reached 15,000 mm³ (1.5 × 10⁻⁵ m³), which corresponded to impact from the height of 32.8 cm. However, Zarifneshat et al. (2010) recorded that high temperature can reduce BV/damage of apple.

A statistical difference (p < 0.05) was found between BS and all other studied parameters such as drop height, storage temperature, and storage duration (Figure 3). The results showed that BS gradually increased with drop height at both storage temperature conditions throughout storage duration (14 days). The results also indicated that high storage temperature and drop height for 14 days storage can elevate the percentage of BS. Bruise susceptibility of pear fruit stored at 22°C reached the maximum value with 5.0 × 10⁻³ m³ J⁻¹ for 60 cm drop height followed by 2.7 × 10⁻³ and 2.2 × 10⁻³ m³ J⁻¹ for both 40 cm and 20 cm drop heights, respectively (Figure 3B). However, less BS was observed on bruised pears stored at 10°C, which was 1.9 × 10⁻³, 1.4 × 10, and 1.3 × 10⁻³ m³ J⁻¹ for high, medium, and low drop heights, respectively, on the last day of storage (Figure 3A). Celik (2017) indicated higher BS as pear subjected to an impact from 1 m heights. High storage temperature can increase the occurrence of bruising in fresh produce as enzymes are still active resulting in cell wall degradation and stiffness (Ahmadi et al., 2010). Bugaud et al. (2014) recorded a less increment in BS of bananas stored at low temperature. Al-Dairi et al. (2021b) observed a higher percentage of bruise damage on tomatoes stored at room temperature. In contrast, Bollen (2005) observed no signs of bruising on dropped apple after storing at two different storage temperatures.

The measurements of CIE L^*, a^*, and b^* color coordinates were reported. In terms of storage days, the trend of all color values was similar in all treated pears. L^* value was varied significantly (p < 0.05) with storage temperature, drop height, and storage duration. Alteration in lightness (L^* value) increased with the increase of drop height (impact energy), temperature condition, and days of storage (Figure 4). The L^* value of all bruised pears increased significantly, particularly, for 60 cm drop height bruised pears at 10 and 22°C, where the percentage of L^* increment reached 27.7% (Figure 4B) and 25.9% (Figure 4A) on the last day of storage, respectively. However, the lowest percentage of increment on L^* was observed for 20 cm drop height (24.7%) bruised pears stored at 10°C. This was due to the conversion of pear surface color from green to more yellow color. Moreover, the lightness L^* of bruised pears exposed to different impact energy levels (drop heights) at both storage conditions showed a strong relationship with the BS (R² _{20 cm,10°C}: 0.8204, R² _{40 cm,10°C}: 0.7161, R² _{60 cm,10°C}: 0.9058, R² _{20 cm,22°C}: 0.9038, R² _{40 cm,22°C}: 0.8899, R² _{60 cm,22°C}: 0.9444) (Figure 5).

The redness (a^*) increased in all treated samples. The a^* value was significantly differed (p < 0.05) with storage period and storage temperature condition, while no statistical significance (p > 0.05) was observed in the a^* value of bruised pear with respect to drop height. Table 3 shows a rapid increase in a^* value on bruised pear stored at 22°C compared to bruised pears stored at 10°C after 14 days of storage. The highest change of a^* value was observed on bruised pears impacted with a steel ball from the medium height (40 cm) stored at 22°C, which increased from −9.66 on day 0 to reach 3.39 on day 14 followed by bruised pear impacted from low (20 cm) and high (60 cm) drop height that reached 3.38 and 3.02, respectively. At 10°C storage condition, stored pears recorded less change in a^*, which altered from −9.66 to reach −0.03, −0.49, and 0.40 on the last day of storage for 20, 40, and 60 cm height bruised pears, respectively. Generally, a^* value was maintained on bruised pears stored at 10°C. The change of redness is attributed to green color loss on bruised pears during storage (Bodner and Scampicchio, 2020). Similarly, Gao et al. (2021) recorded no significant changes on the a^* value of impacted kiwifruit during storage. As observed, higher BS indicated more redness (a^*) value per treatment as shown in Figure 6.

With storage time and temperature, an increasing trend in the color attribute of b^* was statistically (p < 0.05) observed. The impact of drop height on the b^* value of bruised pear fruit was also significant (p < 0.05). The b^* value was increasing gradually at both temperature conditions during storage (Figure 7). The results showed that the highest impact (60 cm 0.647 J) bruised pears provided the largest percentage of b^* increment (32.9%) after 14 days of storage at room temperature (Figure 7B). This was followed by bruised pears subjected to an impact from 40 cm (0.4316 J) and 20 cm (0.215 J) drop heights, where the b^* value increased by 29.1 and 28.32%, respectively (Figure 7B). Storage at 10°C increased b^* value by 28 and 31.46% for low (20 cm) and high (60 cm) impact bruised pears, respectively (Figure 7A). Generally, the b^* value increased gradually during the whole 14 days due to the conversion of the green surface color of pear to yellow. As shown in Figure 8, b^* value of pear fruit increased with the increase on BS (R² _{20 cm,10°C}: 0.9034, R² _{40 cm,10°C}: 0.9173, R² _{60 cm,10°C}: 0.8795, R² _{20 cm,22°C}: 0.9087, R² _{40 cm,22°C}: 0.8822, R² _{60 cm,22°C}: 0.9105) (Figure 8).

Total color change (ΔE^*) was calculated to record the changes in bruised pear color difference (Figures 9A,B). Total color differences (ΔE^*) that increased significantly (p < 0.05) varied with drop height, storage temperature condition, and storage duration. The ΔE^* value was higher (21.23) in pear impacted at a drop height of 60 cm and stored at 22°C (Figure 9B), while the lowest value (17.12) was recorded in pear fruit stored at 10°C and impacted at a drop height of 20 cm (Figure 9A) during the whole days of the experiment. Bruising is one of the factors that cause fruit discoloration (Bodner and Scampicchio, 2020). Pathare and Al-Dairi (2021) also observed the same findings where the total color change of tomato was highly affected by storage temperature and duration as well as drop impact. Bodner and Scampicchio (2020) recorded that the total color change value for bruised pear fruit was high, suggesting the effect of bruising in accelerating the ripening process. As reported by Al-Dairi and Pathare (2021), storage at ambient temperature can accelerate the color change of fresh produce than storage at 10°C. In this study, the difference between chroma and all studied factors (drop impact, storage condition, and storage duration) was generally significant (p < 0.05; Figures 9C,D). The highest drop height and storage at 22°C showed a great effect on chroma of bruised pear fruits (26.9%) followed by medium (23.5%) and low drop height impact (Figure 9D). Storge at 10°C showed less change with 19.4, 19.7, and 23.8% impacted at 20, 40, and 60 cm drop heights, respectively (Figure 9C). Regarding hue value (color purity), there was a significant (p < 0.05) influence of both storage duration and temperature with no pronounced significance (p > 0.05) with drop height (Table 3). This study showed that hue value was decreasing slowly at both storage temperature but then increased rapidly on day 10 at 22°C storage temperature to reach 1.50 and 1.48 on day 14 after it was −1.3 on day 0 for high and medium bruised fruit due to change of a^* value from (–) to (+) value during storage. Dobrzanski and Rybezynski (2002) recorded that color characteristics of bruised apples were significantly affected by bruise damage.

Drop height, storage temperature, and storage duration statistically (p < 0.05) affect the firmness of bruised pear fruit (Figure 10). In this study, as drop height increased, the firmness of pear fruit tended to reduce by 89.2, 91.8, and 92.7% for low, medium, and high drop impact stored at 22°C, respectively. On the last day of storage, the firmness of pears stored at 10°C reduced by 80.4, 84.1, and 84.61% for low, medium, and high impact. The percentage of reduction can show that a high impact level can reduce the firm state of pear fruits in the last day of storage. Azadbakht et al. (2019) found that the firmness of pear was reduced with the increase of bruise and force level for the long storage duration. Similar findings were reported on pomegranate (Hussein et al., 2020a) and apple (Van Zeebroeck et al., 2007). Also, Li et al. (2012) confirmed that bruising is another parameter that led to a decline in the firm state due to the increment of polygalacturonase activity included on pear. For storage time and temperature conditions, firmness was decreasing dramatically during the period of storage at both storage temperatures particularly at 22°C due to continued ripening of the pear. As stated by Zhou et al. (2007), firmness reduction was observed on pears at different storage temperature conditions and it was highly reduced at ambient temperature storage conditions, where the softening rate is increased. For 14 days storage at both storage condition, the firmness of bruised pears impacted at different drop height correlates strongly with BS (R² _{20 cm,10°C}: 0.8422, R² _{40 cm,10°C}: 0.9696, R² _{60 cm,10°C}: 0.9309, R² _{20 cm,22°C}: 0.9064, R² _{40 cm,22°C}: 0.7885, R² _{60 cm,22°C}: 0.7317) (Figure 11).

The statistics showed a significant (p < 0.05) effect of both temperature and storage duration on the TSS of pear fruit. At the same time, no interaction (p > 0.05) was found between the TSS of pear and drop height. TSS value was ranging between 12.13 and 15.40 °Brix on pear stored at 22°C compared to TSS value of pears stored at 10°C that was ranging between 12.13 and 14.80 °Brix (Table 4). The highest content of TSS was shown on day 10 of storage on pear impacted from medium (40 cm) drop height at 22°C. Also, there was a gradual decline and increase in TSS content of pear stored at 10°C (Table 4). The study agreed with the findings of Hussein et al. (2020b), who obtained no significant impact between TSS content and impact bruising in pomegranate. Montero et al. (2009) found that the TSS content of tangerines was highly reduced by impact bruise. Another finding was revealed by Maia et al. (2011) who reported that the total soluble content of bananas showed an increase after subjected to bruise damage. This was attributed to the conservation of starch to total soluble sugars during the ripening process under respiration resulted in high sugar content (Al-Dairi et al., 2021c; Gao et al., 2021), particularly at room temperature.