Objective
To investigate postharvest quality and pitting-disorder incidence in Georgia-grown cucumbers stored at different temperatures.
Materials and Methods
Plant material: Cucumbers used for this research were sourced from the Corbett Brothers’ packinghouse (Echols County, GA) and sorted to ensure uniform quality.
Experimental design: The sorted cucumbers were stored in four different storage conditions. Storage conditions temperatures were 41 °F, 45 °F, 50 °F, or 55 °F, all at 90% relative humidity.
In each storage condition, three replicates of 10 cucumbers were evaluated across four storage durations. At each storage duration (3, 6, 9, and 12 days), cucumbers were transferred to ambient conditions (68 °F and 85% relative humidity) 24 hr before evaluation (the +1 indicated in the tables).
Quality Assessments
Weight loss: The weight of the stored cucumbers was measured before storage and on the day of evaluation, as the initial and final weights, respectively. Weight loss was calculated by subtracting the final weight from the initial weight, dividing by the initial weight, and expressing the result as a percentage.
Firmness: Firmness was measured using a texture analyzer (TA.XTplus by Texture Technologies, Hamilton, MA, USA). The compression probe had a diameter of 8 mm and a penetration depth of 10 mm, with a test speed of 5 mm/s. Firmness was expressed in Newtons (N). Measurements were taken at the center of each cucumber, excluding the peel.
Pitting: Pitting incidence was assessed by visual inspection. Visual inspection involved examining each cucumber for pitting damage and recording the number of affected samples out of 10 cucumbers per replicate.
Color: Cucumber skin color was measured using a chromameter (Model CR-400 by Konika Minolta, Tokyo, Japan), calibrated against a standard white plate. Results were expressed as Hunter color L values (100 = white and 0 = black) and a values (−a and +a values represent greenness and redness). For each sample, reflectance was measured at three different points on the sample surface (skin), and the mean value was calculated.
Statistical Analysis
Data were analyzed using one-way analysis of variance (ANOVA), and means were separated using the emmeans package (R version 4.4.3) to determine differences among the treatments.
Pitting incidence was analyzed through the Kruskal-Wallis test, and p-values for post hoc multiple comparisons were adjusted using the Benjamini–Hochberg method.
Results and Discussion
Across evaluation days, cucumber samples stored at 45 °F consistently showed the lowest weight loss. The results indicate that cucumber samples stored at 45 °F had the lowest weight loss, except for storage duration 12+1, where samples stored at 55 °F had lower weight loss than other storage temperatures. From day 6+1 to day 12+1, cucumbers stored at 50 °F showed the highest numerical weight loss.
| Treatments | Weight loss (%) by days of storage | |||
|---|---|---|---|---|
| 3+1 | 6+1 | 9+1 | 12+1 | |
| 55 °F | 0.77a | 0.97b | 1.32ab | 1.68c |
| 50 °F | 0.77a | 1.26a | 1.58a | 2.18a |
| 45 °F | 0.58b | 0.92b | 1.09c | 1.75bc |
| 41 °F | 0.71ab | 0.84b | 1.24bc | 2.03ab |
| Note. Levels not connected by the same letter differ significantly. | ||||
Table 2 shows that the storage temperatures studied did not affect cucumber firmness, except for day 6+1, where the samples stored at 55 °F had significantly lower firmness readings than those stored at other temperatures.
| Treatments | Firmness (%) by days of storage | |||
|---|---|---|---|---|
| 3+1 | 6+1 | 9+1 | 12+1 | |
| 55 °F | 48.5a | 42.8b | 43.7a | 43.0a |
| 50 °F | 48.5a | 48.6a | 47.1a | 40.6a |
| 45 °F | 47.2a | 47.7a | 46.5a | 42.6a |
| 41 °F | 50.6a | 48.5a | 45.4a | 44.1a |
| Note. Levels not connected by the same letter differ significantly. Firmness is measured in Newtons. | ||||
Table 3 shows the pitting incidence on cucumbers across storage days. There was no observed pitting on the cucumbers for storage durations 3+1 and 6+1 in all the storage temperatures studied. For storage durations 9+1 and 12+1, there was a significant difference in the pitting observed among storage temperatures, with 41 °F showing higher pitting incidence than other temperatures.
| Treatments | Pitting (mean rank) by days of storage | |||
|---|---|---|---|---|
| 3+1 | 6+1 | 9+1 | 12+1 | |
| 55 °F | – | – | 5.0b | 4.5b |
| 50 °F | – | – | 5.0b | 4.5b |
| 45 °F | – | – | 5.0b | 6.0b |
| 41 °F | – | – | 11.0a | 11.0a |
| Note. Levels not connected by the same letter differ significantly. – means no pitting was observed. | ||||
Apart from firmness, color is another important postharvest quality parameter that affects cucumber marketability. The Hunter color values L and a (Table 4) were measured with a chromameter. Across the storage days, there was no significant difference in L values, which represent the whiteness of the cucumber peel. The Hunter color -a values, which represent the greenness, also did not show any significant difference among the storage temperatures across the storage days, except for day 3+1, where cucumbers stored at 41 °F appeared greener than the ones stored at 50 °F.
| HCV | Treatments | Color by days of storage | |||
|---|---|---|---|---|---|
| 3+1 | 6+1 | 9+1 | 12+1 | ||
| L value | 55 °F | 30.8a | 31.3a | 32.40a | 31.8a |
| 50 °F | 29.9a | 31.1a | 32.00a | 31.4a | |
| 45 °F | 30.7a | 31.6a | 32.3a | 31.6a | |
| 41 °F | 30.7a | 31.3a | 31.9a | 32.7a | |
| a value | 55 °F | -7.02ab | -7.87a | -8.60a | -8.18a |
| 50 °F | -6.10b | -7.83a | -8.44a | -7.90a | |
| 45 °F | -7.04ab | -8.08a | -8.94a | -8.15a | |
| 41 °F | -7.76a | -7.73a | -7.95a | -9.40a | |
| Note. Levels not connected by the same letter differ significantly. HCV = Hunter color values: L values are measured along a scale where 100 = white and 0 = black; negative a values represent greenness and positive a values represent redness. | |||||
Overall, storage temperature significantly affected weight loss in cucumber samples, with fruit stored at 45 °F showing the lowest weight loss. This trend was consistently observed from storage days 3+1 through 9+1. Also, storing the cucumbers under 41 °F caused higher pitting incidence compared to other conditions. Therefore, in packinghouse operations, storing cucumbers at 45 °F would be preferable, as this temperature minimizes weight loss with no effect on other postharvest quality parameters measured. Also, the study suggests that 41 °F is not recommended for storing cucumbers as it induces pitting incidence, especially after prolonged storage (9+ days).
Stored Cucumber Samples Across the Different Days of Storage Treatments.
