Citation: Afolabi, A.S.; Choi, I.-L.; Lee, J.H.; Kwon, Y.B.; Yoon, H.S.; Kang, H.-M. Effect of Pre-Storage CO 2 Treatment and Modified Atmosphere Packaging on Sweet Pepper Chilling Injury. Plants 2023, 12, 671. https://doi.org/10.3390/ plants12030671 Academic Editors: Georgia Ouzounidou and Miltiadis V. Christopoulos Received: 26 December 2022 Revised: 27 January 2023 Accepted: 30 January 2023 Published: 3 February 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). plants Article Effect of Pre-Storage CO 2 Treatment and Modified Atmosphere Packaging on Sweet Pepper Chilling Injury Abiodun Samuel Afolabi 1 , In-Lee Choi 2 , Joo Hwan Lee 1 , Yong Beom Kwon 1 , Hyuk Sung Yoon 3 and Ho-Min Kang 1,2, * 1 Interdisciplinary Program in Smart Agriculture, Kangwon National University, Chuncheon 24341, Republic of Korea 2 Agricultural and Life Science Research Institute, Kangwon National University, Chuncheon 24341, Republic of Korea 3 Waksman Institute of Microbiology, Rutgers the State University of New Jersey, Piscataway, NJ 08854, USA * Correspondence: hominkang@kangwon.ac.kr; Tel.: +82-33-250-6425; Fax: +82-33-259-5562 Abstract: The effect of 10% CO 2 pre-storage treatment for 12, 24, and 48 h alongside modified atmosphere packaging (MAP) on chilling injury was determined in this study. This study found significant interactions between chilling injuries and cell membrane damage indicators. The results show that chilling injuries can be somewhat reduced by the use of CO 2 treatment for sweet peppers. It was noticed that the fruit’s respiration rate increased as the treatment duration increased immediately after the treatments, while the resultant did not affect the ethylene production rate, electrolyte leakage, or malondialdehyde. Similarly, after cold storage and on the final day, no really significant differences were shown in all those parameters except for the weight loss rate, chilling injury, calyx browning, and firmness, which were at the poorest state in the control group. Of all the treatments in this study, MAP appeared to be the best treatment, and preference may be given to the 24 h treatment of pretreated fruits. Weight loss, firmness, calyx browning, and chilling injury were maintained best in MAP due to the presence of CO 2 and high humidity. Keywords: calyx browning; electrolyte leakage; ethylene production rate; malondialdehyde; respiration rate 1. Introduction One of the many tropical and subtropical horticultural products with a low tolerance to chilling injury is the sweet pepper (Capsicum annum). Injury is more common at tempera- tures lower than 7 ◦ C, with typical symptoms including surface pitting, calyx browning, seed browning, and shriveling caused by water loss [1]. Babellahi [2] estimated that this accounts for 25–35% of total production losses. Extreme measures have been taken over the past two decades to resist this, and a number of physical and chemical treatments have succeeded. Modified atmosphere packaging (MAP) is one of them [3]. In this method, the presence of more CO 2 and the reduction of O 2 were found to protect the fruits from damage. However, there has been a lot of contentious conjecture made about peppers in this condition. For instance, a study attributed a reduced chilling injury to the CO 2 content in MAP conditions [3]. Another study determined that sweet peppers have a maximum tolerance level of 5% CO 2 in this condition [4,5], despite another study claiming that up to 20% CO 2 could reduce chilling injury rates. Meanwhile, Mathooko [6] showed that a high concentration of 60% CO 2 in cucumbers causes other types of stress that increase the ethylene production rate and putrescine level, which conversely accumulate in fruits and are attributed to chilling injuries. Therefore, the inability to regulate CO 2 content within the MAP may be something to worry about. Another factor impeding commercial acceptance is the decay and off-flavor development associated with some of the films [7]. Plants 2023, 12, 671. https://doi.org/10.3390/plants12030671 https://www.mdpi.com/journal/plants