Evaluation of modified humidity and controlled-release thymol on the preservation of blueberries and blackberries

Authors: OLMEDO, GABRIELA - Orise Fellow; Plotto, Anne; Mattia, Matthew; Zhao, Wei; Hunter, Wayne; Rosskopf, Erin; Obenland, David - Dave; Bai, Jinhe

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2024
Publication Date: 10/12/2024
Citation: Olmedo, G., Plotto, A., Mattia, M.R., Zhao, W., Hunter, W.B., Rosskopf, E.N., Obenland, D.M., Bai, J. Evaluation of modified humidity and controlled-release thymol on the preservation of blueberries and blackberries. Postharvest Biology and Technology. 219:113237. 2024. https://doi.org/10.1016/j.postharvbio.2024.113237.
DOI: https://doi.org/10.1016/j.postharvbio.2024.113237

Interpretive Summary: Over the past twenty years, blueberries and blackberries have become highly valued and increasingly in demand within the small fruit industry. However, they face significant challenges such as water loss, shriveling, softening, and susceptibility to phytopathogens, which adversely affect their storage and marketability. Therefore, preserving postharvest quality is critically important for this industry. In this study, blackberries and blueberries were packed in modified humidity clamshells (LV, for low-vented), which have an opening ratio 6.43 times smaller than commercially available clamshells (COM). Additionally, the antifungal effect of thymol, an essential oil, microencapsulated in a pectin-alginate matrix as a controlled-release system was evaluated. The results showed that the relative humidity within LV clamshells remained higher and more stable than in COM clamshells, resulting in significantly lower weight loss for both fruits. Blueberry firmness, shriveling, and marketability were positively impacted by storage in LV clamshells, and the inclusion of a microencapsulated thymol sachet effectively reduced postharvest decay. Our findings suggest that these two tools could be used to extend the shelf life of blueberries, with their combination yielding optimal results. However, these strategies were ineffective for maintaining blackberry quality. Exposure to thymol resulted in more decay, and neither clamshell vent area nor thymol treatment affected blackberry firmness, shriveling, or marketability. This highlights the necessity of tailoring storage conditions, packaging design, and handling methods to each specific fruit type to ensure optimal quality preservation.

Technical Abstract: Blueberries and blackberries are highly valued and increasing in demand over the last twenty years, despite facing challenges like water loss, shriveling, softening, and vulnerability to phytopathogens, impacting their storage and marketability. Thus, postharvest quality preservation is a crucial area of interest for the small fruit industry. In this study, blackberries and blueberries were packed in modified humidity clamshells (named as LV, for low-vented), with an opening ratio 6.43 times lower than that in commercially available clamshells (COM). Also, the antifungal effect of the thymol, an essential oil, microencapsulated in a pectin-alginate matrix as a controlled-release system was assayed. Results show that relative humidity within LV clamshells remained higher and less variable than in COM clamshells, which led to significantly lower weight loss in both crops. Blueberry firmness, shriveling and marketability were positively impacted by storage in LV clamshells, and the inclusion of a microencapsulated thymol sachet successfully reduced postharvest decay. Our results indicate that these two tools could be used to extend blueberry shelf life, with their combination yielding the most optimal results. However, the same strategies were ineffective for blackberry quality maintenance. After exposure to thymol, more decay was observed, whereas firmness, shrivel and marketability were not affected either by clamshell vent area or thymol treatment. This underscores the importance of tailoring storage conditions, packaging design, and handling methods to each specific fruit type.