*3.3. Tray Damage*

For packaging to protect the product, the material must absorb the mechanical shock event to mitigate the event from transferring to the product. After drop testing, the trays were graded based on the level of damage observed using the scale outlined in Section 2.5. The MF trays from the 30 cm and 50 cm drops were graded as good condition. Regardless of drop height, the MF trays showed occasional small tears (<25 cm) and minor creasing. The EPS trays from both the 30 cm and 50 cm drops experience heavy damage, and were graded as poor condition. Figure 11 illustrates the type of damage experienced by the EPS trays as result of the drop testing. This absorption of shock will often damage the packaging materials, especially at refrigerated conditions where the materials, specifically plastics, are more brittle than fiber-based trays [33]. However, although the EPS trays were

damaged, the apple bruising was not as prevalent as the MF tray material. This indicates that the EPS tray material, although more susceptible to fracturing due to the storage conditions, absorbed more impact energy during the drop testing as compared to MF. For all of the drop tests, both with the MF and EPS trays, no damage was observed to any of the corrugated containers used.

**Figure 9.** Example of acceleration vs. time curve during impact response from each of the experimental treatments.

**Figure 10.** Impact acceleration from the free-fall drop events of apples by tray location packaged using MF and EPS trays from 30 and 50 cm drop height (mean ± SD, *n* = 2). Different letters indicate statistically significant differences at *p* < 0.05. Bars with no common letters are significantly different (*p* < 0.05).

**Figure 11.** Example of tray damage, (**a**) EPS and (**b**) MF.

#### **4. Conclusions**

Examined in this research project were two packaging tray materials, molded fiber and expanded polystyrene, commonly used to transport whole apples. To evaluate the protective nature of these trays, packaged product systems were subjected to mechanical drops by free-fall, promoting bruise damage and reducing fruit quality. This study indicates the EPS trays decreased the bruise susceptibility of whole apples compared to the MF trays, regardless of drop height. This was confirmed in both bruise analysis performed on the individual apples as well as comparing the impact accelerations of the apples packaged in these two configurations. The apples packaged using EPS trays experienced significantly less impact acceleration as those packaged inside MF trays, indicating the EPS trays mitigated the shock, thus reducing the severity and level of bruising to the apples. Fruit damage was more prevalent to the middle layers of the packages, noting additional cushioning material may be desirable to reduce bruising in those areas. Based on the data from this study, although both materials prevent direct fruit-to-fruit contact during handling, they do not provide the same level of performance in reducing bruise damage. Therefore, it is imperative to select a packaging material, which can decrease the likelihood of bruising to the apple as a result of mechanical forces experienced during transport and handling. Results from this study would be of great benefit to apple growers and packaging engineers who are seeking to reduce or minimize the effects of bruising to apples during transport.

**Author Contributions:** Conceptualization, K.D.; methodology, K.D., I.S. and M.H.; validation, K.D., I.S. and M.H.; formal analysis, I.S., M.H.; investigation, K.D., I.S. and M.H.; writing—original draft preparation, K.D.; writing—review and editing, K.D., I.S. and M.H.; visualization, I.S., M.H.; supervision, K.D.; project administration, K.D.; funding acquisition, K.D. All authors have read and agreed to the published version of the manuscript.

**Funding:** This project was supported financially by the Sponsored Research Services of Rochester Institute of Technology (Rochester, NY, USA). The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest.
