Effects of an ice pack and sulfur generating pad treatment for home delivery on the quality of 'Duke' blueberry fruits

Abstract

This study focused on the improvement of blueberry delivery service using pre-cooled ice and $SO_2$ pads to prevent an increase in the fruit temperature as well as decay. To maintain the fruit quality during low temperature storage, the effect of a $SO_2$ pad and modified atmosphere packaging was also examined. Harvested blueberries were precooled at $15^{\circ}C$, sorted, and packaged. And the fruits were placed in a similar environment as that for the parcel service. Part of the fruits were stored at $0^{\circ}C$ for long term storage. The air temperature in the delivery box increased along with an increase in the simulated delivery time regardless of the treatment. However, the rate of temperature increase was lower in the ice pad treatment. No significant difference was not found after 48 h. The oxygen concentration in the box ranged between 10.5 - 14.5% in the ice pad treatment, which was higher than that of the untreated control (7.5 - 11.9%) whereas the $CO_2$ concentration was lower in the ice pad treatment. No differences were found in the occurrence of off-flavor, decay, and sensory quality loss during the 48 hours of the parcel service simulation. The combined treatment of the $SO_2$ pad and modified atmosphere packaging (MAP) using a perforated film increased the shelf-life of the blueberry fruits, the overall quality such as firmness, and the soluble solid content was not different between the treatments except for the decay incidence. No decayed fruit was found in the combined treatment. However, the percentage of decayed fruit in the control was 25% on day 15 of storage and 75% on day 33 of storage, respectively.

Fig. 1. Photos of blueberry parcel delivery service. Ice-pack treatment (A), inserting blueberry fruit box (B), and fnal styrofoam packaging (C).

Fig. 2. Firmness of blueberry fruits according to the different temperature. a, b: Means ± SE (n = 3) at each days followed by the different letters are significantly different by Duncan’s multiple test (p ≤ 0.05).

Fig. 3. Changes of ambient temperature (A), untreated control (B), icepack treatment (C).

Fig. 4. Changes of ambient humidity (A), untreated control (B), icepack treatment (C).

Fig. 5. The changes of Hunter L, a, b value (A, B, C) of blueberry fruits according to time and icepack usage at ambient temperature. * Means ± SE (n = 3) were compared by t-test (p ≤ 0.05).

Fig. 6. Quality changes of firmness (A), sweetness (B) during storage according to time and icepack usage at ambient temperature. Vertical bars represent the standard errors of means (n = 3).

Fig. 7. Carbon dioxide (A) and ethylene production (B) of blueberry fruits according to the different temperature. a, b: Means ± SE (n = 3) at each days followed by the different letters are significantly different by Duncan’s multiple test (p ≤ 0.05).

Fig. 8. Photos of control (A) and SO2 pad (B) after 45 days storage at 0℃.

Fig. 9. Mechanical injury after harvest and during storage of ‘Duke’ blueberry fruits.

Table 1. Comparison of internal gas composition in delivery box during simulated parcel service.

Table 2. Comparison of quality in delivery box during simulated parcel service.

Table 3. Effect of SO₂ pad on the blueberry fruit quality during storage at 0℃.